DiagnosticTree/BaseOfThumbAndRadialHand
{
"model": "bayesian_lr_scoring",
"version": "1.0",
"region_label": "Base-of-Thumb and Radial Hand Pain",
"description": "Probabilistic scoring model for pain at the base of the thumb and the radial side of the hand. The anchor is the brachialis, an arm muscle whose trigger points refer precisely to the base of the thumb with the telltale dissociation that thumb movement hurts while elbow movement does not. Other proximal radial referrers - supinator, brachioradialis, extensor carpi radialis longus, scaleni, subclavius, and infraspinatus - carry pain to the thumb base and radial hand by their own routes, while four local thumb muscles (opponens pollicis, adductor pollicis, first dorsal interosseous, and flexor pollicis longus) generate it at the thumb itself. Structural differential led by first carpometacarpal osteoarthritis, de Quervain's tenosynovitis, scaphoid fracture, intersection syndrome, and radial sensory nerve entrapment (Shehab & Mirabelli 2013; Dittman & Kakar 2022; Look 2023; Calotta & Dellon 2022; Forman 2005; Ng 2024).",
"thresholds": {
"early_exit_posterior": 0.55,
"early_exit_gap": 0.18,
"pairwise_trigger": 0.15
},
"muscles": {
"brachialis": {
"label": "Brachialis",
"prior": 0.107143,
"page": "Muscle:Brachialis",
"key_trp_note": "The anchor of this region and a classic diagnostic trap: an arm muscle that refers pain to the base of the thumb and dorsal thumb web, routinely mistaken for de Quervain's, first CMC arthritis, carpal tunnel, or C5-C6 radiculopathy. The cardinal dissociation is that active thumb use hurts but active elbow movement does not, and passively extending the elbow fully increases the thumb pain. A taut band in its lateral border can entrap the sensory branch of the radial nerve (an almond-shaped trigger point just proximal to the nerve's exit), adding dorsal-thumb dysesthesia. Lies deep under the biceps, which must be pushed aside to palpate it. In the tennis-elbow chain the supinator is primary and the brachialis secondary.",
"subtitle": "Pain at the base of the thumb and the dorsal thumb web coming from the upper arm; the hallmark is that ACTIVE THUMB movement hurts while ACTIVE ELBOW movement does not, and fully straightening the elbow PASSIVELY increases the pain; may add tingling/numbness on the back of the thumb"
},
"supinator": {
"label": "Supinator",
"prior": 0.107143,
"page": "Muscle:Supinator",
"key_trp_note": "Refers to the lateral epicondyle and the dorsal thumb web, and is typically the primary trigger point in the tennis-elbow chain (brachialis and biceps become secondarily involved). Provoked by resisted supination. Can entrap the deep radial / posterior interosseous nerve in the radial tunnel - watch for weakness of finger and thumb extension, which points to a nerve component rather than a pure trigger point. Examine alongside brachialis and brachioradialis when the complaint is thumb-base pain.",
"subtitle": "Pain at the lateral epicondyle and over the back of the thumb web, with the radial forearm; worse on resisted supination (turning a stiff doorknob/screwdriver); the usual primary trigger point in 'tennis elbow'"
},
"brachioradialis": {
"label": "Brachioradialis",
"prior": 0.107143,
"page": "Muscle:Brachioradialis",
"key_trp_note": "A superficial radial-forearm muscle that refers from the lateral epicondyle down the radial forearm to the base of the thumb and the thumb web. Activated by forceful, repetitive gripping (its wrist-stabilising role under a strong grip). A common overlooked contributor to both lateral elbow pain and thumb-base pain; examine with the supinator and brachialis, which share the same thumb-web target.",
"subtitle": "Pain at the lateral epicondyle running down the radial forearm to the base of the thumb and the web; worse with forceful gripping; often misdiagnosed as tennis elbow"
},
"scaleni": {
"label": "Scaleni",
"prior": 0.107143,
"page": "Muscle:Scalene",
"key_trp_note": "The scalene complex refers pain down the arm and is a key driver of satellite trigger points throughout the forearm and hand, so it seeds and perpetuates the whole radial-chain pattern. The neck must be examined whenever a base-of-thumb or radial-forearm trigger point is found, because treating the arm without addressing a scalene driver leads to recurrence. May contribute to a thoracic-outlet-type picture with a lower-trunk pattern.",
"subtitle": "Neck-origin pain spreading down the arm toward the radial forearm and hand; a key driver of satellite trigger points throughout the forearm and thumb muscles; examine the neck whenever thumb-base pain is found"
},
"opponens_pollicis": {
"label": "Opponens Pollicis",
"prior": 0.107143,
"page": "Muscle:Adductor_Pollicis_and_Opponens_Pollicis",
"key_trp_note": "An intrinsic thenar muscle that refers pain to the palmar surface of most of the thumb and, characteristically, to a discrete spot on the radial palmar aspect of the wrist that the patient localises with a fingertip. Thumb opposition (bringing the thumb pad to the little-finger pad) is weak or painful. Part of the 'weeder's thumb' picture from sustained forceful pincer grip; almost always accompanied by adductor pollicis and first dorsal interosseous trigger points. No autonomic features and no nerve entrapment.",
"subtitle": "Pain over the PALMAR surface of most of the thumb and a discrete spot on the RADIAL PALMAR side of the wrist that the patient points to with a fingertip; thumb opposition weak or painful"
},
"adductor_pollicis": {
"label": "Adductor Pollicis",
"prior": 0.107143,
"page": "Muscle:Adductor_Pollicis_and_Opponens_Pollicis",
"key_trp_note": "An intrinsic thumb-web muscle that refers aching to the radial side of the thumb and hand at the base of the thumb, with spillover to the thenar eminence and dorsal web. Thumb adduction is weak - the patient cannot hold a sheet of paper firmly between thumb and index metacarpal. A Heberden's node on the ulnar side of the thumb interphalangeal joint is closely associated and serves as a guide to the trigger point. The core of 'weeder's thumb'; treat the first dorsal interosseous (which responds first) and the proximal referrers before concluding the thenar muscles are the whole problem.",
"subtitle": "Aching on the RADIAL side of the thumb and hand at the base of the thumb, spilling into the thenar eminence and dorsal web; thumb adduction weak (cannot hold paper firmly); a Heberden's node on the ulnar side of the thumb end-joint is a guide"
},
"infraspinatus": {
"label": "Infraspinatus",
"prior": 0.071429,
"page": "Muscle:Infraspinatus",
"key_trp_note": "The principal myofascial source of deep anterior shoulder-joint pain, with spillover that radiates down the anterolateral arm to the lateral forearm and, in a minority, the radial side of the hand - which is how it enters this region. Onset is typically acute (a reach-and-twist incident the patient recalls). Behind-the-back reaching is restricted (positive Hand-to-Shoulder-Blade test). Easily mistaken for C5-C6 radiculopathy; the radial-hand pain is distant spillover, so the shoulder findings are the tell.",
"subtitle": "Deep pain in the FRONT of the shoulder joint that radiates down the front-outer arm to the lateral forearm and sometimes the radial hand; acute onset the patient can pin to an incident; behind-the-back reaching is restricted"
},
"ecrl": {
"label": "Extensor Carpi Radialis Longus",
"prior": 0.071429,
"page": "Muscle:Extensor_Carpi_Radialis",
"key_trp_note": "The proximal radial wrist extensor; refers to the lateral epicondyle and along the dorsoradial forearm to the wrist and anatomical snuffbox, reaching the radial border of the hand. Provoked by resisted wrist extension and gripping. One of the muscles listed on the thenar page as needing to be cleared first, since it refers into the thumb-web zone; examine with the brevis and the other radial-forearm referrers.",
"subtitle": "Pain at the lateral epicondyle and down the dorsoradial forearm to the wrist and the anatomical snuffbox; worse on resisted wrist extension and gripping"
},
"subclavius": {
"label": "Subclavius",
"prior": 0.071429,
"page": "Muscle:Subclavius",
"key_trp_note": "A small muscle beneath the clavicle whose referral runs down the radial side of the arm and forearm, characteristically SKIPPING the elbow and wrist, and reappears on the radial hand at the thumb, index, and middle fingers. Its shortening draws the clavicle toward the subclavian vessels, a vascular (reduced-radial-pulse) mechanism distinct from the neurological scalene pattern. Routinely overlooked because it is palpated through the pectoralis major, with which it is almost always co-active.",
"subtitle": "Front-of-shoulder pain running down the RADIAL arm and forearm, SKIPPING the elbow and wrist, reappearing on the thumb, index, and middle fingers; may reduce the radial pulse (vascular pattern); almost always with pectoralis major"
},
"first_dorsal_interosseous": {
"label": "First Dorsal Interosseous",
"prior": 0.071429,
"page": "Muscle:Interossei",
"key_trp_note": "The intrinsic muscle filling the dorsal thumb web; refers to the radial side of the index finger and deeply through the dorsum and palm, overlapping the thumb-web zone. Activated by sustained or repetitive pincer grasp and almost always co-active with the thenar muscles in 'weeder's thumb' - it typically responds to treatment first, leaving the thumb muscles as the primary problem. An index end-joint Heberden's node may guide to the trigger point.",
"subtitle": "Pain in the dorsal thumb web and down the radial side of the index finger, deep through the dorsum and palm; brought on by sustained pinch; a Heberden's node at the index end-joint is a guide; responds to treatment before the thenar muscles"
},
"flexor_pollicis_longus": {
"label": "Flexor Pollicis Longus",
"prior": 0.071429,
"page": "Muscle:Hand_and_Finger_Flexors",
"key_trp_note": "The deep radial-forearm flexor of the thumb; refers pain along the volar (palmar) surface of the thumb to its tip and beyond - the 'shoots past the fingertip' quality typical of the finger flexors, and on the palmar (not dorsal) thumb. Unlike the other forearm flexors it tends to develop independently. Palpated as deep tenderness in the radial forearm reproducing the thumb pain. Its tendon is the structure involved in trigger thumb.",
"subtitle": "Pain along the PALMAR (front) surface of the thumb out to its tip and beyond; develops independently of the other forearm flexors; brought on by forceful twisting-and-pulling thumb activity"
}
},
"questions": [
{
"id": "q_zone",
"text": "Where does the pain seem to come from?",
"sublabel": "The dominant origin of the whole pattern",
"type": "choice",
"answers": [
{
"id": "upper_arm",
"label": "The UPPER ARM, with the thumb hurting at the far end",
"sublabel": "Arm source",
"lr": {
"brachialis": 6.5,
"supinator": 1.0,
"brachioradialis": 1.0,
"scaleni": 0.8,
"opponens_pollicis": 0.5,
"adductor_pollicis": 0.5,
"infraspinatus": 1.5,
"ecrl": 0.8,
"subclavius": 0.8,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "radial_forearm_elbow",
"label": "The RADIAL FOREARM or outer elbow, running down toward the thumb",
"sublabel": "Radial forearm / elbow source",
"lr": {
"brachialis": 1.0,
"supinator": 5.0,
"brachioradialis": 5.0,
"scaleni": 0.7,
"opponens_pollicis": 0.5,
"adductor_pollicis": 0.5,
"infraspinatus": 0.6,
"ecrl": 5.0,
"subclavius": 0.7,
"first_dorsal_interosseous": 0.6,
"flexor_pollicis_longus": 2.5
}
},
{
"id": "thumb_itself",
"label": "The THUMB and base of the thumb themselves",
"sublabel": "Local thumb source",
"lr": {
"brachialis": 1.2,
"supinator": 0.7,
"brachioradialis": 0.7,
"scaleni": 0.5,
"opponens_pollicis": 5.5,
"adductor_pollicis": 5.5,
"infraspinatus": 0.4,
"ecrl": 0.6,
"subclavius": 0.6,
"first_dorsal_interosseous": 4.5,
"flexor_pollicis_longus": 4.0
}
},
{
"id": "neck",
"label": "The NECK, spreading down the arm",
"sublabel": "Neck source",
"lr": {
"brachialis": 0.6,
"supinator": 0.6,
"brachioradialis": 0.6,
"scaleni": 7.0,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.9,
"ecrl": 0.6,
"subclavius": 0.9,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.5
}
},
{
"id": "front_shoulder",
"label": "The FRONT of the shoulder, radiating down the arm",
"sublabel": "Anterior shoulder source",
"lr": {
"brachialis": 0.8,
"supinator": 0.5,
"brachioradialis": 0.5,
"scaleni": 0.8,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 6.5,
"ecrl": 0.5,
"subclavius": 3.0,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.5
}
}
]
},
{
"id": "q_thumb_surface",
"text": "On the thumb, where exactly is the pain?",
"sublabel": "Front vs back of the thumb, and where on the thumb",
"type": "choice",
"answers": [
{
"id": "dorsal_web",
"label": "Across the BACK of the thumb and the web between thumb and index finger",
"sublabel": "Dorsal thumb / web",
"lr": {
"brachialis": 5.0,
"supinator": 3.0,
"brachioradialis": 3.0,
"scaleni": 1.0,
"opponens_pollicis": 0.6,
"adductor_pollicis": 3.0,
"infraspinatus": 0.7,
"ecrl": 2.0,
"subclavius": 1.5,
"first_dorsal_interosseous": 3.5,
"flexor_pollicis_longus": 0.4
}
},
{
"id": "palmar_to_tip",
"label": "Along the FRONT (palm side) of the thumb out to its tip",
"sublabel": "Palmar thumb to tip",
"lr": {
"brachialis": 0.6,
"supinator": 0.5,
"brachioradialis": 0.5,
"scaleni": 0.7,
"opponens_pollicis": 4.0,
"adductor_pollicis": 1.0,
"infraspinatus": 0.5,
"ecrl": 0.5,
"subclavius": 0.8,
"first_dorsal_interosseous": 0.8,
"flexor_pollicis_longus": 6.5
}
},
{
"id": "radial_base",
"label": "On the RADIAL (outer) side at the base of the thumb / thenar mound",
"sublabel": "Radial base / thenar",
"lr": {
"brachialis": 2.0,
"supinator": 1.2,
"brachioradialis": 1.5,
"scaleni": 0.7,
"opponens_pollicis": 2.5,
"adductor_pollicis": 5.0,
"infraspinatus": 0.6,
"ecrl": 1.5,
"subclavius": 1.2,
"first_dorsal_interosseous": 2.0,
"flexor_pollicis_longus": 1.0
}
},
{
"id": "radial_palmar_wrist",
"label": "A discrete spot on the RADIAL side of the front of the WRIST (I can point to it)",
"sublabel": "Radial palmar wrist spot",
"lr": {
"brachialis": 0.6,
"supinator": 0.6,
"brachioradialis": 0.8,
"scaleni": 0.6,
"opponens_pollicis": 6.5,
"adductor_pollicis": 1.0,
"infraspinatus": 0.5,
"ecrl": 1.0,
"subclavius": 0.7,
"first_dorsal_interosseous": 0.7,
"flexor_pollicis_longus": 1.5
}
},
{
"id": "not_mainly_thumb",
"label": "Not mainly on the thumb - more the radial hand, wrist, or fingers",
"sublabel": "Radial hand rather than thumb",
"lr": {
"brachialis": 0.7,
"supinator": 1.2,
"brachioradialis": 1.2,
"scaleni": 1.5,
"opponens_pollicis": 0.5,
"adductor_pollicis": 0.6,
"infraspinatus": 2.0,
"ecrl": 2.5,
"subclavius": 2.0,
"first_dorsal_interosseous": 1.5,
"flexor_pollicis_longus": 0.7
}
}
]
},
{
"id": "q_brachialis_dissociation",
"text": "Does using the THUMB hurt while moving the ELBOW does not - and does fully straightening the elbow make the thumb pain worse?",
"sublabel": "The cardinal brachialis dissociation: thumb-base pain referred from the arm, worsened by passive full elbow extension",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - thumb use hurts, elbow movement is fine, and straightening the elbow worsens it",
"lr": {
"brachialis": 7.0,
"supinator": 1.0,
"brachioradialis": 1.0,
"scaleni": 0.8,
"opponens_pollicis": 0.8,
"adductor_pollicis": 0.8,
"infraspinatus": 0.8,
"ecrl": 0.8,
"subclavius": 0.8,
"first_dorsal_interosseous": 0.7,
"flexor_pollicis_longus": 0.8
}
},
{
"id": "no",
"label": "No - that specific pattern doesn't fit",
"lr": {
"brachialis": 0.3,
"supinator": 1.05,
"brachioradialis": 1.05,
"scaleni": 1.05,
"opponens_pollicis": 1.05,
"adductor_pollicis": 1.05,
"infraspinatus": 1.05,
"ecrl": 1.05,
"subclavius": 1.05,
"first_dorsal_interosseous": 1.05,
"flexor_pollicis_longus": 1.05
}
}
]
},
{
"id": "q_provocation",
"text": "Which activity most reliably brings on the pain?",
"sublabel": "Choose the single strongest aggravator",
"type": "choice",
"answers": [
{
"id": "resisted_supination",
"label": "Twisting the forearm against resistance (stiff doorknob, screwdriver, wringing a cloth)",
"sublabel": "Resisted supination",
"lr": {
"brachialis": 1.0,
"supinator": 6.5,
"brachioradialis": 1.5,
"scaleni": 0.7,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.6,
"infraspinatus": 0.6,
"ecrl": 1.0,
"subclavius": 0.6,
"first_dorsal_interosseous": 0.6,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "resisted_wrist_ext",
"label": "Cocking the wrist back or gripping with the palm down (lifting, backhand)",
"sublabel": "Resisted wrist extension",
"lr": {
"brachialis": 0.7,
"supinator": 1.2,
"brachioradialis": 2.5,
"scaleni": 0.6,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.6,
"infraspinatus": 0.6,
"ecrl": 6.0,
"subclavius": 0.6,
"first_dorsal_interosseous": 0.6,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "pincer_pinch",
"label": "Sustained fine pinch between thumb and finger (sewing, weeding, writing with pressure)",
"sublabel": "Pincer / pinch overload",
"lr": {
"brachialis": 0.7,
"supinator": 0.6,
"brachioradialis": 0.6,
"scaleni": 0.6,
"opponens_pollicis": 5.5,
"adductor_pollicis": 6.0,
"infraspinatus": 0.5,
"ecrl": 0.6,
"subclavius": 0.6,
"first_dorsal_interosseous": 5.0,
"flexor_pollicis_longus": 2.5
}
},
{
"id": "elbow_flexion_load",
"label": "Carrying or lifting with the elbow bent (groceries, a child, a power tool held up)",
"sublabel": "Loaded elbow flexion",
"lr": {
"brachialis": 6.0,
"supinator": 0.8,
"brachioradialis": 1.5,
"scaleni": 0.7,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.6,
"infraspinatus": 0.8,
"ecrl": 0.7,
"subclavius": 0.6,
"first_dorsal_interosseous": 0.5,
"flexor_pollicis_longus": 0.8
}
},
{
"id": "thumb_twist_pull",
"label": "Forceful twisting-and-pulling with the thumb (rocking and pulling out weeds, hard pinch-and-twist)",
"sublabel": "Forceful thumb twist/pull",
"lr": {
"brachialis": 0.7,
"supinator": 0.7,
"brachioradialis": 0.7,
"scaleni": 0.6,
"opponens_pollicis": 1.5,
"adductor_pollicis": 2.5,
"infraspinatus": 0.5,
"ecrl": 0.6,
"subclavius": 0.6,
"first_dorsal_interosseous": 1.2,
"flexor_pollicis_longus": 6.0
}
},
{
"id": "reach_behind_neck",
"label": "Reaching behind the back / overhead, or neck movement, or after a balance-grab incident",
"sublabel": "Shoulder reach / neck",
"lr": {
"brachialis": 0.6,
"supinator": 0.6,
"brachioradialis": 0.6,
"scaleni": 3.5,
"opponens_pollicis": 0.5,
"adductor_pollicis": 0.5,
"infraspinatus": 5.5,
"ecrl": 0.6,
"subclavius": 2.0,
"first_dorsal_interosseous": 0.5,
"flexor_pollicis_longus": 0.6
}
}
]
},
{
"id": "q_skip_radial",
"text": "Does the arm pain SKIP the elbow and wrist - present in the arm and again in the radial fingers, but not at the elbow or wrist?",
"sublabel": "The radial skip pattern of the subclavius",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - the elbow and wrist are spared while the arm and radial fingers hurt",
"lr": {
"brachialis": 0.8,
"supinator": 0.7,
"brachioradialis": 0.7,
"scaleni": 0.9,
"opponens_pollicis": 0.7,
"adductor_pollicis": 0.7,
"infraspinatus": 1.0,
"ecrl": 0.7,
"subclavius": 7.0,
"first_dorsal_interosseous": 0.7,
"flexor_pollicis_longus": 0.7
}
},
{
"id": "no",
"label": "No - the pain includes the elbow or wrist, or runs continuously",
"lr": {
"brachialis": 1.05,
"supinator": 1.05,
"brachioradialis": 1.05,
"scaleni": 1.0,
"opponens_pollicis": 1.05,
"adductor_pollicis": 1.05,
"infraspinatus": 1.0,
"ecrl": 1.05,
"subclavius": 0.3,
"first_dorsal_interosseous": 1.05,
"flexor_pollicis_longus": 1.05
}
}
]
},
{
"id": "q_radial_nerve",
"text": "Is there tingling, numbness, or altered sensation on the BACK of the thumb and its web (as well as the aching pain)?",
"sublabel": "Radial sensory component - a brachialis lateral-border taut band can entrap the radial sensory nerve; also seen in Wartenberg's syndrome",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - tingling/numbness on the dorsum of the thumb and web",
"lr": {
"brachialis": 4.5,
"supinator": 1.5,
"brachioradialis": 1.0,
"scaleni": 1.2,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.6,
"infraspinatus": 0.8,
"ecrl": 0.8,
"subclavius": 1.0,
"first_dorsal_interosseous": 0.7,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "no",
"label": "No - aching pain only, no tingling or numbness",
"lr": {
"brachialis": 0.7,
"supinator": 1.0,
"brachioradialis": 1.05,
"scaleni": 1.0,
"opponens_pollicis": 1.1,
"adductor_pollicis": 1.1,
"infraspinatus": 1.05,
"ecrl": 1.05,
"subclavius": 1.0,
"first_dorsal_interosseous": 1.05,
"flexor_pollicis_longus": 1.1
}
}
]
},
{
"id": "q_neck_driver",
"text": "Is there neck pain or tightness with the thumb/hand pain, or does pressing the side of the neck reproduce or worsen the arm pain?",
"sublabel": "Scalene driver screen - scalene trigger points seed satellite trigger points down the radial forearm and thumb",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - neck pain/tightness, or neck pressure reproduces the arm pain",
"lr": {
"brachialis": 0.8,
"supinator": 0.8,
"brachioradialis": 0.8,
"scaleni": 6.5,
"opponens_pollicis": 0.7,
"adductor_pollicis": 0.7,
"infraspinatus": 1.2,
"ecrl": 0.8,
"subclavius": 1.0,
"first_dorsal_interosseous": 0.7,
"flexor_pollicis_longus": 0.7
}
},
{
"id": "no",
"label": "No - no neck component",
"lr": {
"brachialis": 1.05,
"supinator": 1.05,
"brachioradialis": 1.05,
"scaleni": 0.3,
"opponens_pollicis": 1.05,
"adductor_pollicis": 1.05,
"infraspinatus": 1.0,
"ecrl": 1.05,
"subclavius": 1.0,
"first_dorsal_interosseous": 1.05,
"flexor_pollicis_longus": 1.05
}
}
]
},
{
"id": "q_shoulder",
"text": "Is there deep pain in the front of the shoulder, with difficulty reaching behind the back (to a back pocket or to fasten clothing)?",
"sublabel": "Infraspinatus screen - deep anterior shoulder-joint pain with restricted behind-the-back reach, radiating down to the radial hand",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - deep front-of-shoulder pain and restricted behind-the-back reaching",
"lr": {
"brachialis": 0.7,
"supinator": 0.6,
"brachioradialis": 0.6,
"scaleni": 1.0,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.6,
"infraspinatus": 7.0,
"ecrl": 0.6,
"subclavius": 1.5,
"first_dorsal_interosseous": 0.5,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "no",
"label": "No - no shoulder pain or behind-the-back restriction",
"lr": {
"brachialis": 1.05,
"supinator": 1.05,
"brachioradialis": 1.05,
"scaleni": 1.0,
"opponens_pollicis": 1.05,
"adductor_pollicis": 1.05,
"infraspinatus": 0.3,
"ecrl": 1.05,
"subclavius": 0.9,
"first_dorsal_interosseous": 1.05,
"flexor_pollicis_longus": 1.05
}
}
]
},
{
"id": "q_palpation",
"text": "Where does firm palpation most precisely reproduce the familiar thumb/hand pain?",
"sublabel": "The reproducing tender point - the most specific localiser",
"type": "choice",
"answers": [
{
"id": "deep_arm_under_biceps",
"label": "Deep in the upper arm, beneath the biceps against the bone (biceps pushed aside)",
"sublabel": "Brachialis location",
"lr": {
"brachialis": 7.0,
"supinator": 0.5,
"brachioradialis": 0.5,
"scaleni": 0.4,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.5,
"ecrl": 0.4,
"subclavius": 0.4,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.4
}
},
{
"id": "over_supinator",
"label": "Just below the outer elbow over the supinator (deep, radial, with the forearm rotated)",
"sublabel": "Supinator location",
"lr": {
"brachialis": 0.5,
"supinator": 7.0,
"brachioradialis": 1.0,
"scaleni": 0.4,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.4,
"ecrl": 1.0,
"subclavius": 0.4,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.5
}
},
{
"id": "brachioradialis_belly",
"label": "In the brachioradialis (the muscle that bunches on the upper radial forearm when you bend the elbow)",
"sublabel": "Brachioradialis location",
"lr": {
"brachialis": 0.5,
"supinator": 1.0,
"brachioradialis": 7.0,
"scaleni": 0.4,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.4,
"ecrl": 1.5,
"subclavius": 0.4,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.5
}
},
{
"id": "radial_extensor_mass",
"label": "In the radial wrist-extensor mass just below the elbow crease (ulnar to brachioradialis)",
"sublabel": "Extensor carpi radialis longus location",
"lr": {
"brachialis": 0.5,
"supinator": 1.0,
"brachioradialis": 1.5,
"scaleni": 0.4,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.4,
"ecrl": 7.0,
"subclavius": 0.4,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.5
}
},
{
"id": "thumb_web_pincer",
"label": "In the thumb web, pinched between thumb and index metacarpals",
"sublabel": "Adductor pollicis / first dorsal interosseous location",
"lr": {
"brachialis": 0.5,
"supinator": 0.4,
"brachioradialis": 0.4,
"scaleni": 0.4,
"opponens_pollicis": 1.2,
"adductor_pollicis": 6.0,
"infraspinatus": 0.4,
"ecrl": 0.4,
"subclavius": 0.4,
"first_dorsal_interosseous": 5.5,
"flexor_pollicis_longus": 0.6
}
},
{
"id": "thenar_eminence",
"label": "Across the thenar mound at the base of the thumb (flat pressure)",
"sublabel": "Opponens pollicis location",
"lr": {
"brachialis": 0.5,
"supinator": 0.4,
"brachioradialis": 0.4,
"scaleni": 0.4,
"opponens_pollicis": 6.5,
"adductor_pollicis": 1.5,
"infraspinatus": 0.4,
"ecrl": 0.4,
"subclavius": 0.4,
"first_dorsal_interosseous": 1.0,
"flexor_pollicis_longus": 0.7
}
},
{
"id": "radial_volar_forearm",
"label": "Deep in the radial volar forearm (front, thumb side) - reproduces pain to the thumb tip",
"sublabel": "Flexor pollicis longus location",
"lr": {
"brachialis": 0.5,
"supinator": 0.6,
"brachioradialis": 0.6,
"scaleni": 0.4,
"opponens_pollicis": 0.6,
"adductor_pollicis": 0.5,
"infraspinatus": 0.4,
"ecrl": 0.6,
"subclavius": 0.4,
"first_dorsal_interosseous": 0.5,
"flexor_pollicis_longus": 7.0
}
},
{
"id": "side_of_neck",
"label": "In the side of the neck (scalene muscles)",
"sublabel": "Scaleni location",
"lr": {
"brachialis": 0.5,
"supinator": 0.4,
"brachioradialis": 0.4,
"scaleni": 7.0,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.6,
"ecrl": 0.4,
"subclavius": 0.7,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.4
}
},
{
"id": "back_of_shoulder_blade",
"label": "On the shoulder blade at the back of the shoulder",
"sublabel": "Infraspinatus location",
"lr": {
"brachialis": 0.5,
"supinator": 0.4,
"brachioradialis": 0.4,
"scaleni": 0.5,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 7.0,
"ecrl": 0.4,
"subclavius": 0.6,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.4
}
},
{
"id": "beneath_clavicle",
"label": "Deep beneath the collarbone (through the chest muscle)",
"sublabel": "Subclavius location",
"lr": {
"brachialis": 0.5,
"supinator": 0.4,
"brachioradialis": 0.4,
"scaleni": 0.6,
"opponens_pollicis": 0.4,
"adductor_pollicis": 0.4,
"infraspinatus": 0.6,
"ecrl": 0.4,
"subclavius": 7.0,
"first_dorsal_interosseous": 0.4,
"flexor_pollicis_longus": 0.4
}
}
]
}
],
"pairwise": [
{
"id": "pw_opp_add",
"pair": [
"opponens_pollicis",
"adductor_pollicis"
],
"text": "Tiebreaker - Opponens Pollicis vs Adductor Pollicis",
"question": "Is the pain on the PALMAR thumb plus a radial palmar-wrist spot, or aching on the RADIAL side of the thumb base with weak thumb adduction (cannot hold paper)?",
"sublabel": "Both are thenar 'weeder's thumb' muscles - separate by surface and weakness pattern",
"answers": [
{
"id": "opp",
"label": "Palmar thumb + radial palmar-wrist spot, weak opposition - opponens pollicis",
"lr": {
"opponens_pollicis": 5.5,
"adductor_pollicis": 0.4
}
},
{
"id": "add",
"label": "Radial thumb base, weak adduction (paper test), ulnar IP-joint node - adductor pollicis",
"lr": {
"opponens_pollicis": 0.4,
"adductor_pollicis": 5.5
}
}
]
},
{
"id": "pw_brach_sup",
"pair": [
"brachialis",
"supinator"
],
"text": "Tiebreaker - Brachialis vs Supinator",
"question": "Does using the THUMB hurt while the elbow is fine (worse on passive elbow extension), or is the pain reproduced by resisted SUPINATION at the outer elbow?",
"sublabel": "Arm anchor vs the primary tennis-elbow trigger point",
"answers": [
{
"id": "brach",
"label": "Thumb-use pain, elbow fine, worse straightening the elbow - brachialis",
"lr": {
"brachialis": 6.0,
"supinator": 0.4
}
},
{
"id": "sup",
"label": "Reproduced by resisted supination at the outer elbow - supinator",
"lr": {
"brachialis": 0.4,
"supinator": 6.0
}
}
]
},
{
"id": "pw_sup_brad",
"pair": [
"supinator",
"brachioradialis"
],
"text": "Tiebreaker - Supinator vs Brachioradialis",
"question": "Is the pain reproduced by resisted SUPINATION (turning), or by forceful GRIPPING with the brachioradialis bunching on the upper radial forearm?",
"sublabel": "Both refer from the outer elbow to the thumb web",
"answers": [
{
"id": "sup",
"label": "Resisted supination - supinator",
"lr": {
"supinator": 5.5,
"brachioradialis": 0.4
}
},
{
"id": "brad",
"label": "Forceful gripping, brachioradialis belly tender - brachioradialis",
"lr": {
"supinator": 0.4,
"brachioradialis": 5.5
}
}
]
},
{
"id": "pw_brad_ecrl",
"pair": [
"brachioradialis",
"ecrl"
],
"text": "Tiebreaker - Brachioradialis vs Extensor Carpi Radialis Longus",
"question": "Is the radial-forearm pain reproduced by forceful gripping (brachioradialis), or specifically by resisted WRIST EXTENSION reaching the snuffbox (ECRL)?",
"sublabel": "Adjacent radial-forearm muscles",
"answers": [
{
"id": "brad",
"label": "Forceful gripping, upper radial forearm - brachioradialis",
"lr": {
"brachioradialis": 5.0,
"ecrl": 0.4
}
},
{
"id": "ecrl",
"label": "Resisted wrist extension, pain to wrist/snuffbox - extensor carpi radialis longus",
"lr": {
"brachioradialis": 0.4,
"ecrl": 5.0
}
}
]
},
{
"id": "pw_add_fdi",
"pair": [
"adductor_pollicis",
"first_dorsal_interosseous"
],
"text": "Tiebreaker - Adductor Pollicis vs First Dorsal Interosseous",
"question": "Is the pain mainly at the radial base of the THUMB with weak thumb adduction, or down the radial side of the INDEX finger from the thumb web?",
"sublabel": "Both palpated in the thumb web; the interosseous responds to treatment first",
"answers": [
{
"id": "add",
"label": "Radial thumb base, weak thumb adduction - adductor pollicis",
"lr": {
"adductor_pollicis": 5.0,
"first_dorsal_interosseous": 0.4
}
},
{
"id": "fdi",
"label": "Radial index finger from the web - first dorsal interosseous",
"lr": {
"adductor_pollicis": 0.4,
"first_dorsal_interosseous": 5.0
}
}
]
},
{
"id": "pw_opp_fpl",
"pair": [
"opponens_pollicis",
"flexor_pollicis_longus"
],
"text": "Tiebreaker - Opponens Pollicis vs Flexor Pollicis Longus",
"question": "Is the palmar thumb pain localised to the thenar mound and a radial wrist spot (opponens), or does it shoot along the thumb to its very tip from a deep radial-forearm point (flexor pollicis longus)?",
"sublabel": "Both give palmar thumb pain - separate by local thenar vs forearm origin and tip extension",
"answers": [
{
"id": "opp",
"label": "Thenar mound + radial palmar-wrist spot, weak opposition - opponens pollicis",
"lr": {
"opponens_pollicis": 5.0,
"flexor_pollicis_longus": 0.4
}
},
{
"id": "fpl",
"label": "Shoots to the thumb tip from a deep radial-forearm point - flexor pollicis longus",
"lr": {
"opponens_pollicis": 0.4,
"flexor_pollicis_longus": 5.0
}
}
]
}
],
"treatment_dag": {
"edges": [
{
"from": "scaleni",
"to": "brachialis",
"type": "key_satellite",
"label": "Scalene trigger points seed satellite trigger points down the radial chain; treat the neck first"
},
{
"from": "scaleni",
"to": "supinator",
"type": "key_satellite",
"label": "Scalene trigger points drive satellite forearm trigger points; address the neck driver"
},
{
"from": "supinator",
"to": "brachialis",
"type": "functional_unit",
"label": "Tennis-elbow chain: supinator is primary, brachialis and biceps become secondarily involved; examine together"
},
{
"from": "supinator",
"to": "brachioradialis",
"type": "functional_unit",
"label": "Radial-forearm referrers to the thumb web - examine supinator, brachioradialis, and ECRL together"
},
{
"from": "brachioradialis",
"to": "ecrl",
"type": "functional_unit",
"label": "Adjacent radial-forearm muscles; examine and treat together"
},
{
"from": "brachialis",
"to": "adductor_pollicis",
"type": "secondary_load",
"label": "Proximal referrers (scalene, brachialis, supinator, ECRL, brachioradialis) refer to the thumb web; treat them before the thenar muscles, whose tenderness may then resolve"
},
{
"from": "adductor_pollicis",
"to": "first_dorsal_interosseous",
"type": "functional_unit",
"label": "Weeder's-thumb intrinsics: the first dorsal interosseous is co-active and responds to treatment first, leaving the thenar muscles as the primary problem"
},
{
"from": "adductor_pollicis",
"to": "opponens_pollicis",
"type": "functional_unit",
"label": "Adductor and opponens pollicis are almost always involved together; treat in the same session"
},
{
"from": "subclavius",
"to": "brachialis",
"type": "secondary_load",
"label": "Subclavius is a deep residual radial source (co-active with pectoralis major); treat after the primary muscles"
}
],
"edge_type_labels": {
"key_satellite": "Treat first - key TrP driving satellite",
"functional_unit": "Treat concurrently in same session",
"secondary_load": "Treat after primary resolves",
"antagonist_risk": "Treat in alternating cycles - reactive activation risk"
}
},
"emergency": [
{
"id": "rf-e1",
"label": "Septic arthritis of the thumb / wrist joint or deep hand-space infection",
"question": "An acutely hot, red, swollen, exquisitely tender thumb base or wrist with severe pain on any movement, after a bite, puncture, or wound? Fever or systemic upset? Requires urgent washout and antibiotics.",
"source": "Standard joint-sepsis screen; Sanderson, Mohr & Abraham 2020"
},
{
"id": "rf-e2",
"label": "Flexor (suppurative) tenosynovitis of the thumb",
"question": "Surgical emergency. The four Kanavel signs: fusiform swelling of the whole thumb, the thumb held semi-flexed at rest, tenderness along the flexor pollicis longus sheath into the thenar/wrist, and severe pain on PASSIVE EXTENSION of the thumb. Usually follows a penetrating injury or bite. Needs urgent hand-surgery referral, IV antibiotics, and drainage.",
"source": "Standard hand-infection emergency criteria (Kanavel)"
},
{
"id": "rf-e3",
"label": "Acute scaphoid fracture with risk of avascular necrosis / neurovascular compromise",
"question": "After a fall on the outstretched hand: snuffbox swelling and tenderness, scaphoid-tubercle tenderness, and pain on axial loading of the thumb (this combination is near 100% sensitive)? A proximal-pole scaphoid fracture risks avascular necrosis and nonunion. Any dusky/pulseless thumb or progressive neurological deficit needs emergent referral.",
"source": "Shehab & Mirabelli 2013; Sanderson, Mohr & Abraham 2020"
}
],
"urgent": [
{
"id": "rf-u1",
"label": "Occult scaphoid fracture (negative initial films)",
"question": "Snuffbox tenderness after a fall on the outstretched hand but normal initial radiographs? Conventional radiography misses up to 30% of scaphoid fractures. Immobilise in a thumb spica and re-image at 10-14 days, or obtain MRI/bone scan - a missed scaphoid fracture leads to nonunion and avascular necrosis.",
"source": "Shehab & Mirabelli 2013"
},
{
"id": "rf-u2",
"label": "Base-of-thumb fracture / fracture-dislocation (Bennett, Rolando) and gamekeeper's/skier's thumb",
"question": "After trauma or a forced thumb abduction: an intra-articular fracture at the base of the thumb metacarpal (Bennett/Rolando, inherently unstable), or laxity of the thumb metacarpophalangeal joint from an ulnar collateral ligament avulsion (gamekeeper's/skier's thumb)? Both need radiographs, thumb-spica splinting, and surgical referral.",
"source": "Sanderson, Mohr & Abraham 2020"
},
{
"id": "rf-u3",
"label": "Scapholunate ligament injury / carpal instability",
"question": "Dorsoradial wrist pain after a fall, with point tenderness just distal to Lister's tubercle, a painful clunk on radial-ulnar deviation, or scapholunate widening (>3 mm, the Terry-Thomas sign) on radiographs? Untreated scapholunate dissociation progresses to advanced collapse - splint and refer.",
"source": "Dittman & Kakar 2022; Sanderson, Mohr & Abraham 2020"
},
{
"id": "rf-u4",
"label": "Posterior interosseous / radial sensory nerve entrapment",
"question": "Progressive weakness of thumb and finger extension (posterior interosseous nerve), or burning dorsoradial wrist/thumb pain with paraesthesia worsened by ulnar wrist flexion and a positive Tinel over the radial sensory nerve (Wartenberg's)? Distinguish neuropathic pain and any motor loss from a myofascial source.",
"source": "Calotta & Dellon 2022; Forman et al. 2005"
}
],
"broad_differential": [
{
"id": "bd-1",
"condition": "First carpometacarpal (thumb basal joint) osteoarthritis",
"confidence": "common",
"mimics": "Pain and tenderness at the base of the thumb with use - overlaps the brachialis, adductor pollicis, and supinator/brachioradialis referral directly",
"distinguishing_feature": "Basal-joint tenderness with crepitus and pain on the GRIND TEST (axial compression and rotation of the thumb metacarpal on the trapezium) - positive in first CMC osteoarthritis and negative in de Quervain's. Radiographs show joint-space narrowing and osteophytes; advanced disease gives a squared-off thumb base. Trigger-point pain is reproduced by muscle palpation and lacks the grind-test crepitus, though the two commonly coexist.",
"action": "Grind test and radiographs. A diagnostic lidocaine injection into the CMC joint (or, conversely, into the first extensor compartment to exclude de Quervain's) clarifies the source. Splinting, activity modification, analgesia; injection or surgery for refractory disease. Treat coexisting thumb-web and forearm trigger points, which can be the dominant pain source even when radiographic OA is present.",
"source": "Shehab & Mirabelli 2013; Dittman & Kakar 2022"
},
{
"id": "bd-2",
"condition": "De Quervain's tenosynovitis (first extensor compartment)",
"confidence": "common",
"mimics": "Radial wrist and thumb-base pain worse with thumb use - overlaps the supinator, brachioradialis, brachialis, and adductor pollicis referral",
"distinguishing_feature": "Tenderness and sometimes swelling over the radial styloid and the first extensor compartment tendons (abductor pollicis longus and extensor pollicis brevis), with a positive Finkelstein test (thumb tucked in the fist, wrist ulnarly deviated reproduces the pain) and a NEGATIVE grind test. Especially common in new mothers and after repetitive thumb use. Trigger-point pain has no focal first-compartment tendon tenderness and a negative Finkelstein.",
"action": "Finkelstein and grind tests; the diagnosis is clinical. Where CMC OA is also considered, a lidocaine block of the first extensor compartment relieving the pain confirms a tendon (not arthritic) source. Splinting, activity modification, corticosteroid injection; release if refractory.",
"source": "Shehab & Mirabelli 2013"
},
{
"id": "bd-3",
"condition": "Scaphoid fracture / nonunion and scapholunate injury",
"confidence": "uncommon",
"mimics": "Dorsoradial wrist and thumb-base pain - overlaps the ECRL, supinator, and brachioradialis referral, especially after a fall",
"distinguishing_feature": "Snuffbox swelling and tenderness, scaphoid-tubercle tenderness, and pain on axial thumb loading after a fall on the outstretched hand. Conventional radiography misses up to 30% of acute scaphoid fractures, so a tender snuffbox with normal films is treated as an occult fracture. Scapholunate injury gives tenderness just distal to Lister's tubercle and scapholunate widening (>3 mm). Trigger-point pain follows no fall and has no bony or scapholunate tenderness.",
"action": "Radiographs with scaphoid views; if negative but clinically suspicious, thumb-spica immobilisation and repeat imaging at 10-14 days, or MRI/bone scan. Refer displaced, proximal-pole, or scapholunate injuries. Maintain a high index of suspicion - missed scaphoid fractures cause avascular necrosis and nonunion.",
"source": "Shehab & Mirabelli 2013; Dittman & Kakar 2022; Forman et al. 2005"
},
{
"id": "bd-4",
"condition": "Intersection syndrome",
"confidence": "uncommon",
"mimics": "Dorsoradial forearm and wrist pain - overlaps the ECRL, supinator, and brachioradialis zone",
"distinguishing_feature": "Pain, swelling, and sometimes crepitus about 4-6 cm proximal to the wrist on the dorsoradial forearm, where the first extensor compartment muscles cross over the radial wrist extensors - more proximal than de Quervain's. Associated with repetitive wrist extension (rowing, weightlifting). Trigger-point pain is reproduced by muscle palpation and is not localised to this crossover point.",
"action": "Clinical diagnosis (the proximal location distinguishes it from de Quervain's); ultrasound or MRI if uncertain. Activity modification, splinting, NSAIDs, occasionally corticosteroid injection. Treat coexisting radial-forearm trigger points.",
"source": "Forman et al. 2005; Ng et al. 2024"
},
{
"id": "bd-5",
"condition": "Radial sensory nerve entrapment (Wartenberg's syndrome / cheiralgia paraesthetica)",
"confidence": "uncommon",
"mimics": "Dorsoradial wrist and thumb pain with sensory change - overlaps the brachialis radial-nerve component and the dorsal thumb-web referral",
"distinguishing_feature": "Burning or electric pain with paraesthesia/numbness over the dorsoradial wrist and thumb-index web, worsened by ulnar wrist flexion and by tight watch straps, with a positive Tinel over the radial sensory nerve. In up to 75% of people the lateral antebrachial cutaneous nerve overlaps the radial sensory territory, so residual pain after a radial-nerve block points to that second nerve. A brachialis lateral-border taut band can itself entrap the radial sensory nerve and produce the same dorsal-thumb dysesthesia, which resolves when the trigger point is inactivated.",
"action": "Differential diagnostic nerve blocks (radial sensory nerve, then lateral antebrachial cutaneous nerve) localise the generator; sensory nerve conduction studies before and after trigger-point treatment document a myofascial entrapment. Remove external compression, activity modification, neural gliding; treat the brachialis trigger point; surgery for refractory structural entrapment.",
"source": "Calotta & Dellon 2022"
},
{
"id": "bd-6",
"condition": "Scaphotrapeziotrapezoid (STT) joint osteoarthritis",
"confidence": "uncommon",
"mimics": "Radial wrist pain at the base of the thumb just proximal to the CMC joint - overlaps the opponens pollicis radial-palmar-wrist spot and the CMC OA zone",
"distinguishing_feature": "Tenderness localised to the STT joint (distal to the scaphoid, at the base of the thumb-index metacarpals) with radiographic STT joint-space narrowing; pain on resisted wrist movements. Often coexists with first CMC OA. Trigger-point pain is reproduced by thenar or forearm muscle palpation rather than localised to the STT joint line.",
"action": "Radiographs; localised tenderness and a diagnostic injection distinguish it from CMC OA and de Quervain's. Splinting and activity modification; injection or surgery for refractory disease.",
"source": "Look et al. 2023; Dittman & Kakar 2022"
},
{
"id": "bd-7",
"condition": "Trigger thumb / flexor pollicis longus tendon entrapment",
"confidence": "uncommon",
"mimics": "Thumb pain with catching - can be confused with flexor pollicis longus or thenar trigger-point pain",
"distinguishing_feature": "Painful catching or locking of the thumb in flexion, with a palpable nodule and tenderness at the A1 pulley over the head of the first metacarpal on the palmar side. Trigger-point pain has no mechanical locking and no A1-pulley nodule. Many cases resolve spontaneously over months.",
"action": "Clinical diagnosis. Splinting and corticosteroid injection (higher success than analgesic alone); surgical release for refractory locking. Treat coexisting thenar and forearm trigger points.",
"source": "Look et al. 2023; T&S Ch.39"
},
{
"id": "bd-8",
"condition": "Carpal tunnel syndrome / C6 radiculopathy",
"confidence": "uncommon",
"mimics": "Thumb and radial-hand pain or numbness - overlaps the brachialis (when perceived over the thenar eminence) and the proximal referrers",
"distinguishing_feature": "Carpal tunnel syndrome gives PALMAR median-distribution paraesthesia (thumb, index, middle, radial ring finger), nocturnal symptoms, and positive Phalen/Tinel; brachialis referral is to the DORSUM of the thumb without finger or nocturnal symptoms. C6 radiculopathy gives dermatomal sensory change (thumb/index), a depressed biceps/brachioradialis reflex, and myotomal weakness with a positive Spurling. Trigger-point referral produces no reflex change or true dermatomal deficit and is reproduced by muscle palpation.",
"action": "Phalen/Tinel, Spurling, full neurological examination; nerve conduction studies and cervical MRI where neurological signs are present. Treat coexisting trigger points (brachialis, supinator, scalene), which can themselves mimic carpal tunnel syndrome.",
"source": "Shehab & Mirabelli 2013; Forman et al. 2005"
},
{
"id": "bd-9",
"condition": "Thumb metacarpophalangeal (MCP) joint arthritis",
"confidence": "uncommon",
"mimics": "Pain at the base of the thumb - sits just distal to the carpometacarpal joint and is easily lumped in with basal-joint osteoarthritis or thenar trigger-point referral",
"distinguishing_feature": "Tenderness, swelling, and crepitus localised to the thumb METACARPOPHALANGEAL joint (one joint distal to the carpometacarpal/basal joint), with pain on stressing that joint rather than on the axial grind/lever tests that load the carpometacarpal joint. It may follow ulnar collateral ligament injury (gamekeeper's/skier's thumb) or accompany inflammatory arthritis. Distinguish from first carpometacarpal osteoarthritis (tenderness and grind/lever pain at the basal joint, one level proximal) and from opponens/adductor pollicis trigger-point referral (reproduced by muscle palpation, no joint-line crepitus).",
"action": "Localise the tender joint precisely (MCP vs CMC); radiographs of the thumb. Activity modification, splinting, NSAIDs; assess MCP stability for a coexisting ulnar collateral ligament injury. Refer for arthritis that fails conservative care.",
"source": "Swigart 2009; Dickson, Dickson & Farnell 2015"
},
{
"id": "bd-10",
"condition": "Crystal or inflammatory arthropathy (gout, CPPD, rheumatoid)",
"confidence": "uncommon",
"mimics": "Pain and swelling at the base of the thumb or radial wrist - can mimic an osteoarthritis flare or a thenar trigger-point source",
"distinguishing_feature": "A subacute or recurrent hot, swollen, exquisitely tender joint with rapid onset points to a crystal arthropathy (gout, calcium pyrophosphate deposition) rather than mechanical osteoarthritis; prolonged morning stiffness, symmetrical small-joint involvement, and systemic features (nodules, fatigue) suggest rheumatoid or other inflammatory arthritis. A truly hot, red, acutely swollen joint with fever must be treated as septic until proven otherwise (see the emergency screen). Trigger-point pain has no joint effusion, warmth, or systemic features and is reproduced by muscle palpation.",
"action": "Assess for warmth, effusion, and systemic features; serum urate, inflammatory markers, and joint aspiration for crystals and culture where an inflammatory or crystal cause is suspected (and urgently if septic arthritis is possible). Treat the underlying arthropathy; address any coexisting trigger points only once an active inflammatory or infective process is excluded.",
"source": "Dickson, Dickson & Farnell 2015; Swigart 2009"
}
]
}