DiagnosticTree/FrontOfArm
{
"model": "bayesian_lr_scoring",
"version": "1.0",
"region_label": "Volar Forearm Pain",
"description": "Probabilistic scoring model for pain on the volar (palm-side) forearm. Two muscles generate it locally: the palmaris longus, with its distinctive prickling, needle-like pain in the distal volar forearm and central palm; and the pronator teres, a deep volar-forearm ache that can compress the median nerve between its two heads (pronator syndrome) and mimic carpal tunnel. Two refer from a distance: the serratus anterior (side of chest to the medial arm and palm, with a respiratory component) and the triceps brachii, whose deep medial-head trigger point refers to the medial epicondyle and the inner forearm from an origin in the posterior arm. Structural and neurological differential led by the proximal median-nerve entrapments (pronator teres syndrome and its siblings, and anterior interosseous syndrome), carpal tunnel syndrome as the distal contrast, forearm fracture with Monteggia/Galeazzi, and the can't-miss forearm compartment syndrome (Dididze et al. 2023; Akhondi et al.; Brukner & Khan 2006, Ch.18).",
"thresholds": {
"early_exit_posterior": 0.55,
"early_exit_gap": 0.18,
"pairwise_trigger": 0.15
},
"muscles": {
"palmaris_longus": {
"label": "Palmaris Longus",
"prior": 0.25,
"page": "Muscle:Palmaris_Longus",
"key_trp_note": "Unique among the forearm muscles in referring a PRICKLING, needle-like sensation - fine needles in the distal volar forearm and the centre of the palm - rather than the deep aching of other myofascial referrals; this quality is the key diagnostic feature. Activated by pressing or holding a tool (screwdriver, trowel, chisel, racquet butt, angular cane) forcibly in the cupped palm. The tendon stands out at the wrist on vigorous palm-cupping - and the muscle is congenitally ABSENT in up to 20% of people, so confirm it exists before blaming it. Active trigger points commonly accompany Dupuytren's contracture; anomalous variants can themselves entrap the median nerve at the wrist.",
"subtitle": "A distinctive PRICKLING, needle-like pain in the lower (distal) front of the forearm and the centre of the palm - not a deep ache; brought on by pressing a tool handle into the cupped palm"
},
"pronator_teres": {
"label": "Pronator Teres",
"prior": 0.25,
"page": "Muscle:Hand_and_Finger_Flexors",
"key_trp_note": "A proximal volar-forearm muscle referring a deep ache along the volar forearm to the radial wrist. The median nerve passes between its two heads in most people, so a taut or hypertrophied pronator teres can compress it (pronator teres syndrome), producing median-territory paraesthesia that - unlike carpal tunnel syndrome - INCLUDES the thenar eminence (the palmar cutaneous branch leaves the median nerve proximal to the carpal tunnel but distal to the pronator teres), is worse on resisted pronation, and lacks the nocturnal predominance of carpal tunnel syndrome. A positive Tinel sign over the proximal edge of the muscle is typical. Distinguish the trigger point and pronator syndrome from true carpal tunnel syndrome and from the sibling proximal-median entrapments. Examine with the other volar forearm flexors.",
"subtitle": "A deep ache in the front of the forearm running toward the radial side of the wrist; worse on turning the palm down against resistance; often with tingling of the thumb, index, and middle fingers (a carpal-tunnel mimic that also affects the ball of the thumb)"
},
"serratus_anterior": {
"label": "Serratus Anterior",
"prior": 0.25,
"page": "Muscle:Serratus_Anterior",
"key_trp_note": "A lateral chest-wall muscle whose essential pain is at the anterolateral midchest (with an interscapular patch), spilling down the medial arm and forearm to the palm and ring finger - which is how it reaches this region. Its signature is respiratory: a 'stitch in the side' on running, air hunger, and inability to finish a sentence without pausing for breath. Activated by fast or prolonged running, push-ups, severe coughing, and the torsional stress of wrenching the body around. The trigger point sits in the midaxillary line over the fifth or sixth rib. Left-sided pain must not be called myofascial until cardiac disease has been excluded.",
"subtitle": "Pain on the SIDE of the chest (and a patch between the shoulder blades) spilling down the inner arm and forearm to the palm; a 'stitch in the side', breathlessness, or pain on taking a deep breath; brought on by hard running or wrenching the body around"
},
"triceps_brachii": {
"label": "Triceps Brachii",
"prior": 0.25,
"page": "Muscle:Triceps_Brachii",
"key_trp_note": "Enters this region through its deep medial-head trigger point (the deep, medial portion just above the medial epicondyle), which refers to the medial epicondyle and may extend along the INNER side of the forearm and to the volar surface of the fourth and fifth digits, the adjacent palm, and sometimes the middle finger. Unlike the local volar-forearm muscles, the PAIN ORIGINATES IN THE POSTERIOR ARM and is provoked by forceful or resisted ELBOW EXTENSION (and reproduced by passive elbow flexion). Often mistaken for medial epicondylitis ('golfer's elbow') - but resisted wrist flexion is negative here, and the tender point is in the triceps, not the common flexor origin. A satellite of latissimus dorsi and serratus posterior superior trigger points, which must be inactivated first for lasting relief.",
"subtitle": "A deep ache that starts in the back of the upper arm and reaches the INNER side of the forearm and the medial epicondyle (the 'funny bone' bump), sometimes the palm side of the ring and little fingers; brought on by straightening the elbow against resistance"
}
},
"questions": [
{
"id": "q_zone",
"text": "Where is the pain mainly felt, and where does it seem to start?",
"sublabel": "The origin of the whole pattern",
"type": "choice",
"answers": [
{
"id": "distal_volar_palm",
"label": "The LOWER front of the forearm and the centre of the PALM",
"sublabel": "Distal volar forearm / palm",
"lr": {
"palmaris_longus": 6.5,
"pronator_teres": 1.0,
"serratus_anterior": 0.5,
"triceps_brachii": 0.5
}
},
{
"id": "proximal_volar_to_wrist",
"label": "The front of the forearm running down toward the RADIAL wrist",
"sublabel": "Volar forearm to radial wrist",
"lr": {
"palmaris_longus": 1.0,
"pronator_teres": 6.5,
"serratus_anterior": 0.5,
"triceps_brachii": 0.5
}
},
{
"id": "side_of_chest",
"label": "The SIDE of the CHEST (and maybe between the shoulder blades), spilling down the inner arm",
"sublabel": "Lateral chest source",
"lr": {
"palmaris_longus": 0.5,
"pronator_teres": 0.5,
"serratus_anterior": 7.0,
"triceps_brachii": 0.6
}
},
{
"id": "back_of_arm_inner_forearm",
"label": "The BACK of the UPPER ARM, reaching the INNER forearm and the 'funny bone' bump",
"sublabel": "Posterior arm / inner forearm",
"lr": {
"palmaris_longus": 0.5,
"pronator_teres": 0.5,
"serratus_anterior": 0.6,
"triceps_brachii": 7.0
}
}
]
},
{
"id": "q_quality",
"text": "What is the pain like?",
"sublabel": "The prickling quality is near-unique to one muscle",
"type": "choice",
"answers": [
{
"id": "prickling",
"label": "PRICKLING or needle-like, like fine needles in the forearm and palm",
"sublabel": "Prickling / needle-like",
"lr": {
"palmaris_longus": 7.5,
"pronator_teres": 0.5,
"serratus_anterior": 0.5,
"triceps_brachii": 0.5
}
},
{
"id": "deep_ache_local",
"label": "A DEEP ACHE in the forearm or arm itself",
"sublabel": "Deep local ache",
"lr": {
"palmaris_longus": 0.6,
"pronator_teres": 4.0,
"serratus_anterior": 0.7,
"triceps_brachii": 4.0
}
},
{
"id": "referred_distance",
"label": "A spillover from an ache that really lives in the chest or upper arm",
"sublabel": "Referred from a distance",
"lr": {
"palmaris_longus": 0.5,
"pronator_teres": 0.6,
"serratus_anterior": 4.5,
"triceps_brachii": 3.0
}
}
]
},
{
"id": "q_provocation",
"text": "Which activity most reliably brings on the pain?",
"sublabel": "Choose the single strongest aggravator",
"type": "choice",
"answers": [
{
"id": "tool_in_palm",
"label": "Pressing a tool handle (or cane/racquet butt) into the cupped palm",
"sublabel": "Tool pressed in palm",
"lr": {
"palmaris_longus": 7.0,
"pronator_teres": 0.7,
"serratus_anterior": 0.5,
"triceps_brachii": 0.5
}
},
{
"id": "resisted_pronation",
"label": "Turning the palm down against resistance, or repetitive twisting (hammering, ladling, wringing cloths)",
"sublabel": "Resisted pronation",
"lr": {
"palmaris_longus": 0.8,
"pronator_teres": 6.5,
"serratus_anterior": 0.5,
"triceps_brachii": 0.6
}
},
{
"id": "resisted_elbow_extension",
"label": "Straightening the elbow against resistance (push-ups, pushing, a tennis backhand)",
"sublabel": "Resisted elbow extension",
"lr": {
"palmaris_longus": 0.6,
"pronator_teres": 0.6,
"serratus_anterior": 0.6,
"triceps_brachii": 7.0
}
},
{
"id": "running_cough_torsion",
"label": "Hard running, coughing, or wrenching the body around (turning a heavy steering wheel)",
"sublabel": "Running / cough / torsion",
"lr": {
"palmaris_longus": 0.6,
"pronator_teres": 0.6,
"serratus_anterior": 7.0,
"triceps_brachii": 0.7
}
}
]
},
{
"id": "q_median_tingle",
"text": "Is there tingling or numbness of the THUMB, INDEX, and MIDDLE fingers - INCLUDING the ball of the thumb (thenar eminence)?",
"sublabel": "Median-territory symptoms that include the thenar eminence point to a proximal (pronator-level) median compression rather than the local muscles; carpal tunnel syndrome characteristically SPARES the thenar skin",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - median-territory tingling that includes the ball of the thumb",
"lr": {
"palmaris_longus": 0.8,
"pronator_teres": 5.0,
"serratus_anterior": 0.7,
"triceps_brachii": 0.7
}
},
{
"id": "no",
"label": "No - aching/prickling pain only, or no thenar involvement",
"lr": {
"palmaris_longus": 1.1,
"pronator_teres": 0.4,
"serratus_anterior": 1.05,
"triceps_brachii": 1.05
}
}
]
},
{
"id": "q_respiratory",
"text": "Is there a 'stitch in the side', breathlessness, or pain clearly worse on taking a deep breath?",
"sublabel": "Serratus anterior signature - a respiratory symptom complex distinguishes it from the other sources",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes - a stitch in the side, breathlessness, or pain on deep breathing",
"lr": {
"palmaris_longus": 0.6,
"pronator_teres": 0.6,
"serratus_anterior": 7.0,
"triceps_brachii": 0.6
}
},
{
"id": "no",
"label": "No - breathing does not affect it",
"lr": {
"palmaris_longus": 1.05,
"pronator_teres": 1.05,
"serratus_anterior": 0.3,
"triceps_brachii": 1.05
}
}
]
},
{
"id": "q_palpation",
"text": "Where does firm palpation most precisely reproduce the familiar forearm pain?",
"sublabel": "The reproducing tender point - the most specific localiser",
"type": "choice",
"answers": [
{
"id": "mid_volar_forearm",
"label": "In the middle of the front of the forearm, over the central tendon that pops up on cupping the palm (palmaris longus)",
"sublabel": "Palmaris longus location",
"lr": {
"palmaris_longus": 7.0,
"pronator_teres": 0.6,
"serratus_anterior": 0.4,
"triceps_brachii": 0.4
}
},
{
"id": "proximal_volar_forearm",
"label": "In the upper front of the forearm just below the elbow crease (pronator teres)",
"sublabel": "Pronator teres location",
"lr": {
"palmaris_longus": 0.6,
"pronator_teres": 7.0,
"serratus_anterior": 0.4,
"triceps_brachii": 0.4
}
},
{
"id": "midaxillary_ribs",
"label": "On the side of the chest over the ribs, in line with the armpit (serratus anterior)",
"sublabel": "Serratus anterior location",
"lr": {
"palmaris_longus": 0.4,
"pronator_teres": 0.4,
"serratus_anterior": 7.0,
"triceps_brachii": 0.5
}
},
{
"id": "posterior_arm_medial",
"label": "Deep in the back of the upper arm, toward the inner side just above the 'funny bone' (triceps, medial head)",
"sublabel": "Triceps brachii location",
"lr": {
"palmaris_longus": 0.4,
"pronator_teres": 0.4,
"serratus_anterior": 0.5,
"triceps_brachii": 7.0
}
}
]
}
],
"pairwise": [
{
"id": "pw_pl_pt",
"pair": [
"palmaris_longus",
"pronator_teres"
],
"text": "Tiebreaker - Palmaris Longus vs Pronator Teres",
"question": "Is the pain a PRICKLING, needle-like sensation in the distal forearm and central palm (palmaris longus), or a DEEP ACHE in the upper forearm running to the radial wrist, often with median-finger tingling and worse on resisted pronation (pronator teres)?",
"sublabel": "The two local volar-forearm sources",
"answers": [
{
"id": "pl",
"label": "Prickling, needle-like, distal forearm/palm - palmaris longus",
"lr": {
"palmaris_longus": 6.0,
"pronator_teres": 0.4
}
},
{
"id": "pt",
"label": "Deep ache to radial wrist, median tingling, resisted pronation - pronator teres",
"lr": {
"palmaris_longus": 0.4,
"pronator_teres": 6.0
}
}
]
},
{
"id": "pw_pt_tri",
"pair": [
"pronator_teres",
"triceps_brachii"
],
"text": "Tiebreaker - Pronator Teres vs Triceps Brachii",
"question": "Does the forearm ache run to the RADIAL wrist and worsen with resisted PRONATION, often with median tingling (pronator teres)? Or does it start in the BACK OF THE UPPER ARM, reach the INNER forearm and medial epicondyle, and worsen with resisted ELBOW EXTENSION (triceps)?",
"sublabel": "Both give a deep forearm ache but from opposite sides and mechanisms",
"answers": [
{
"id": "pt",
"label": "Radial wrist, resisted pronation, median tingling - pronator teres",
"lr": {
"pronator_teres": 5.5,
"triceps_brachii": 0.4
}
},
{
"id": "tri",
"label": "Posterior arm to inner forearm, resisted elbow extension - triceps brachii",
"lr": {
"pronator_teres": 0.4,
"triceps_brachii": 5.5
}
}
]
},
{
"id": "pw_sant_tri",
"pair": [
"serratus_anterior",
"triceps_brachii"
],
"text": "Tiebreaker - Serratus Anterior vs Triceps Brachii",
"question": "Is the source a SIDE-OF-CHEST pain with a respiratory component - stitch in the side, breathlessness (serratus anterior), or a BACK-OF-THE-UPPER-ARM ache reaching the inner forearm, worse on straightening the elbow (triceps)?",
"sublabel": "Two distant referrers reaching the forearm",
"answers": [
{
"id": "sant",
"label": "Side of chest with stitch/breathlessness - serratus anterior",
"lr": {
"serratus_anterior": 5.5,
"triceps_brachii": 0.4
}
},
{
"id": "tri",
"label": "Back of upper arm to inner forearm, resisted elbow extension - triceps brachii",
"lr": {
"serratus_anterior": 0.4,
"triceps_brachii": 5.5
}
}
]
},
{
"id": "pw_pl_sant",
"pair": [
"palmaris_longus",
"serratus_anterior"
],
"text": "Tiebreaker - Palmaris Longus vs Serratus Anterior",
"question": "Is the pain a local PRICKLING in the distal forearm and palm from a forearm tender point (palmaris longus), or a SIDE-OF-CHEST/respiratory pattern spilling down the inner arm to the palm (serratus anterior)?",
"sublabel": "Local prickling source vs distant respiratory source",
"answers": [
{
"id": "pl",
"label": "Prickling, distal forearm/palm, forearm tender point - palmaris longus",
"lr": {
"palmaris_longus": 5.5,
"serratus_anterior": 0.4
}
},
{
"id": "sant",
"label": "Side of chest, stitch/breathlessness, inner-arm spillover - serratus anterior",
"lr": {
"palmaris_longus": 0.4,
"serratus_anterior": 5.5
}
}
]
}
],
"treatment_dag": {
"edges": [
{
"from": "palmaris_longus",
"to": "pronator_teres",
"type": "functional_unit",
"label": "Palmaris longus and pronator teres are adjacent volar-forearm flexors overloaded together by gripping and pronation; examine and treat together, and check the median nerve for a pronator component"
},
{
"from": "serratus_anterior",
"to": "triceps_brachii",
"type": "key_satellite",
"label": "Serratus posterior superior and latissimus dorsi drive satellite triceps trigger points; the shoulder-girdle/trunk drivers must be inactivated before the triceps will resolve"
},
{
"from": "triceps_brachii",
"to": "pronator_teres",
"type": "secondary_load",
"label": "Triceps is a posterior-arm referrer reaching the inner forearm; address it when local volar-forearm treatment gives incomplete relief"
},
{
"from": "serratus_anterior",
"to": "pronator_teres",
"type": "secondary_load",
"label": "Serratus anterior is a distant trunk referrer; treat it when local forearm treatment is incomplete and a respiratory pattern is present"
}
],
"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": "Acute forearm compartment syndrome",
"question": "Surgical emergency. Severe forearm pain OUT OF PROPORTION to the injury, worsening and unrelieved by analgesia, with PAIN ON PASSIVE STRETCH of the fingers (the earliest sign) and a tense, wood-like forearm? After a fracture, crush, reperfusion, tight cast, bleeding (anticoagulation), or strenuous exertion (kayakers, rowers, weight-trainers)? The volar compartments are most often affected and the median and ulnar nerves run within them. Pallor, pulselessness, paraesthesia, and paralysis are LATE. Confirm with compartment pressures if needed (delta-p within 30 mmHg of diastolic, or absolute >30 mmHg) but do not delay - fasciotomy within about 6 hours gives near-complete recovery; later, irreversible necrosis and Volkmann's contracture follow.",
"source": "Forearm Compartment Syndrome StatPearls (NBK556130); Brukner & Khan Ch.18"
},
{
"id": "rf-e2",
"label": "Acute coronary syndrome / cardiac ischaemia",
"question": "Left-sided or central chest pressure, tightness, or constriction radiating to the inner arm and forearm, especially with exertion, breathlessness, sweating, nausea, or a cardiac history? The left serratus anterior (and pectoral) trigger-point patterns mimic cardiac pain - and relief by trigger-point treatment does NOT exclude cardiac disease. Establish cardiac status independently and urgently when this pattern is present.",
"source": "T&S Ch.46 (serratus anterior cardiac mimicry)"
}
],
"urgent": [
{
"id": "rf-u1",
"label": "Forearm fracture with Monteggia or Galeazzi pattern",
"question": "Forearm pain, deformity, or marked tenderness after a fall or direct blow? Both bones usually break together; a single-bone forearm fracture must prompt a search for an associated joint dislocation - the Monteggia injury (ulnar fracture with radial-head dislocation at the elbow) and the Galeazzi injury (radial fracture with distal-ulnar/DRUJ dislocation at the wrist). These are usually displaced, need orthopaedic referral and internal fixation, and the dislocation is easily missed if the whole forearm (elbow AND wrist) is not imaged.",
"source": "Brukner & Khan Ch.18"
},
{
"id": "rf-u2",
"label": "Anterior interosseous nerve (AIN) syndrome",
"question": "Forearm pain with WEAKNESS but NO sensory loss - specifically difficulty bending the tip of the thumb and index finger so the patient cannot make a normal 'OK' sign (the pulps flatten and pinch instead)? The anterior interosseous nerve is the pure-motor terminal branch of the median nerve (flexor pollicis longus, flexor digitorum profundus to the index/middle, pronator quadratus). Often a transient neuritis but compression and trauma occur; needs electrodiagnostic confirmation and timely specialist assessment because motor recovery is the concern.",
"source": "Anterior Interosseous Syndrome StatPearls (NBK525956)"
},
{
"id": "rf-u3",
"label": "Pronator teres syndrome / proximal median nerve entrapment",
"question": "Volar forearm pain worse on resisted pronation, with median-territory paraesthesia that INCLUDES the thenar eminence (unlike carpal tunnel) and a positive Tinel over the proximal pronator teres? Consider the sibling entrapments: ligament of Struthers (worse on supination and elbow extension, possibly a reduced radial pulse), lacertus fibrosus (worse on resisted elbow flexion in supination), and the flexor digitorum superficialis sublimis bridge (worse on resisted middle-finger PIP flexion). Progressive motor or sensory deficit warrants nerve studies and surgical release.",
"source": "Pronator Teres Syndrome StatPearls (Dididze et al. 2023)"
},
{
"id": "rf-u4",
"label": "Forearm stress fracture",
"question": "Activity-related forearm pain that builds with loading and eases with rest, in an upper-limb sport (gymnastics, throwing, racquet sports, weight-training), with focal bony tenderness? A radius or ulnar stress fracture needs activity modification and imaging (it may be occult on early plain films); missed, it can progress to a complete fracture.",
"source": "Brukner & Khan Ch.18"
}
],
"broad_differential": [
{
"id": "bd-1",
"condition": "Carpal tunnel syndrome (median neuropathy at the wrist)",
"confidence": "common",
"mimics": "Median-territory hand symptoms and volar forearm aching - overlaps the pronator teres referral and is the chief distal contrast",
"distinguishing_feature": "Burning volar wrist/hand pain with median-distribution paraesthesia (thumb, index, middle, radial ring finger) that is characteristically NOCTURNAL and can radiate proximally up the forearm; positive Phalen and Tinel at the wrist; late thenar wasting. Crucially, the thenar SKIN is SPARED (the palmar cutaneous branch leaves the median nerve proximal to the carpal tunnel), pronation is unaffected, and night symptoms predominate - the opposite of pronator teres syndrome, where the thenar eminence is involved, pronation provokes the pain, and night symptoms are usually absent. Because the two coexist, a proximal pronator syndrome is easily missed when carpal tunnel syndrome is found - rule it out before carpal tunnel surgery.",
"action": "Phalen/Tinel at the wrist vs resisted pronation and proximal Tinel; thenar sensory testing; nerve conduction studies confirm and localise (distal latencies are normal in pure pronator syndrome). Night splinting, activity modification, injection, decompression for motor loss. Treat coexisting pronator teres and forearm-flexor trigger points.",
"source": "Pronator Teres Syndrome StatPearls; Shehab & Mirabelli 2013; Brukner & Khan Ch.19"
},
{
"id": "bd-2",
"condition": "Proximal median nerve entrapments (ligament of Struthers, lacertus fibrosus, FDS sublimis bridge)",
"confidence": "uncommon",
"mimics": "Volar forearm pain with median paraesthesia - the same picture as pronator teres syndrome, with which they are grouped",
"distinguishing_feature": "All produce forearm pain and median-digit paraesthesia, separated by the provocative posture: the ligament of Struthers is worse on forearm SUPINATION and elbow EXTENSION (and may reduce the radial pulse, as the brachial artery runs with the nerve under the ligament from a supracondylar bony spur); lacertus fibrosus (bicipital aponeurosis) is worse on resisted ELBOW FLEXION with the forearm supinated; the FDS sublimis bridge is worse on resisted FLEXION of the middle-finger PIP joint. Trigger-point referral has no fixed sensory deficit and is reproduced by muscle palpation.",
"action": "Targeted provocative testing for each site; nerve conduction studies (often normal); ultrasound or MRI can show the compressing structure. Conservative care (rest, activity modification, splinting, NSAIDs) for at least 6 weeks; surgical release of all compressive structures if motor/sensory deficit or failure of conservative treatment.",
"source": "Pronator Teres Syndrome StatPearls (Dididze et al. 2023)"
},
{
"id": "bd-3",
"condition": "Anterior interosseous nerve syndrome",
"confidence": "uncommon",
"mimics": "Forearm pain - but the hallmark is motor weakness without sensory change, distinguishing it from the muscular sources",
"distinguishing_feature": "Poorly localised forearm/cubital-fossa pain with a PURE MOTOR deficit and NO sensory loss: weakness of flexor pollicis longus and flexor digitorum profundus to the index (and middle) finger, so the patient cannot flex the distal joints to make a normal 'OK' sign (the pinch flattens - a positive pinch-grip/Froment sign), plus pronator quadratus weakness on resisted pronation with the elbow flexed. Often a transient neuritis (may follow viral illness, like a forme fruste of neuralgic amyotrophy). Trigger-point pain has full strength and no pincer deficit.",
"action": "Test FPL, FDP (index/middle), and pronator quadratus individually; the OK-sign/pinch test screens at the bedside. Nerve conduction studies and EMG confirm and localise. Many recover spontaneously over months; persistent or compressive cases are referred for decompression or tendon transfer.",
"source": "Anterior Interosseous Syndrome StatPearls (NBK525956); Pronator Teres Syndrome StatPearls"
},
{
"id": "bd-4",
"condition": "Medial epicondylitis (flexor/pronator tendinopathy, 'golfer's elbow')",
"confidence": "common",
"mimics": "Medial elbow and proximal volar forearm pain - overlaps the pronator teres origin and the triceps TrP5 medial-epicondyle referral",
"distinguishing_feature": "Tenderness localised at or just below the MEDIAL EPICONDYLE at the common flexor-pronator origin, with pain on RESISTED WRIST FLEXION and resisted forearm pronation (reverse Mills' test), especially with passive stretch of the tendon. Seen in golfers and in tennis players with heavy topspin forehands. Distinguish from a pronator teres trigger point (belly tenderness, deep forearm ache to the wrist) and from triceps TrP5 (medial-epicondyle pain that is NEGATIVE on resisted wrist flexion and reproduced from the posterior arm). The ulnar nerve may be caught in adjacent scar.",
"action": "Localise tenderness to the common flexor origin; resisted wrist flexion and pronation reproduce it. Relative rest, technique correction, eccentric loading, bracing, corticosteroid injection if refractory; treat coexisting pronator teres trigger points. Check the ulnar nerve.",
"source": "Brukner & Khan Ch.18; Hand and Finger Flexors (Ch.38)"
},
{
"id": "bd-5",
"condition": "Cervical radiculopathy (C6-C7) / brachial plexopathy / neuralgic amyotrophy",
"confidence": "uncommon",
"mimics": "Volar forearm pain with median-territory or motor symptoms referred from the neck or plexus - overlaps the proximal-median and AIN pictures",
"distinguishing_feature": "Neck pain radiating to the arm, dermatomal sensory change, reflex loss, and weakness in muscles OUTSIDE the median territory point to a root (C6-C7) or plexus lesion rather than a forearm entrapment; a positive Spurling's supports radiculopathy. Neuralgic amyotrophy (Parsonage-Turner) typically begins with severe SHOULDER pain, then patchy multi-nerve weakness (it can present as an AIN-like palsy) and usually improves over 6-12 months. Trigger-point referral and isolated forearm entrapments produce no root-level deficit. When a median muscle is abnormal, test muscles of the same myotome supplied by other nerves to exclude a proximal lesion.",
"action": "Full neurological and upper-quarter examination with Spurling's; MRI cervical spine and electrodiagnostics where root/plexus signs are present; consider neuralgic amyotrophy when severe shoulder pain precedes patchy weakness. Treat coexisting scalene/shoulder-girdle and forearm trigger points concurrently.",
"source": "Pronator Teres Syndrome StatPearls (differential); Brukner & Khan Ch.18 (referred pain)"
},
{
"id": "bd-6",
"condition": "Chronic exertional forearm compartment syndrome",
"confidence": "uncommon",
"mimics": "Activity-related volar forearm pain and tightness - overlaps the local muscular sources during loading",
"distinguishing_feature": "Aching, tightness, and sometimes paraesthesia in the flexor (volar) forearm that builds predictably with sustained gripping or repetitive loading and is RELIEVED BY REST, in rowers, kayakers/canoeists, motorcyclists, and weight-trainers (and rock climbers). Distinct from the ACUTE compartment syndrome emergency - the chronic form is exertional and reversible. Compartment-pressure testing during/after exercise confirms it. Trigger-point pain is reproduced by palpation and is not strictly load-threshold dependent.",
"action": "History of strict activity-related onset and rapid relief with rest; dynamic compartment-pressure measurement is diagnostic. Activity and technique modification first; fasciotomy for refractory cases. Address coexisting forearm-flexor trigger points.",
"source": "Brukner & Khan Ch.18; Forearm Compartment Syndrome StatPearls"
},
{
"id": "bd-7",
"condition": "Pronator quadratus / distal volar forearm strain and flexor tenosynovitis",
"confidence": "uncommon",
"mimics": "Distal volar forearm pain on gripping and rotation - overlaps the palmaris longus and pronator referral",
"distinguishing_feature": "Localised distal volar-forearm pain and tenderness from a flexor or pronator-quadratus strain or a flexor tenosynovitis, worse on resisted gripping or pronation, sometimes with crepitus or swelling along the tendons. Trigger-point pain (especially the palmaris prickling quality) is reproduced by muscle-belly palpation and lacks tendon-sheath swelling or crepitus, though they can coexist.",
"action": "Examine the flexor tendons and resisted pronation; ultrasound for tenosynovitis. Relative rest, splinting, activity modification, anti-inflammatories; treat coexisting forearm trigger points.",
"source": "Brukner & Khan Ch.18/Ch.19; Hand and Finger Flexors (Ch.38)"
}
]
}