DiagnosticTree/Antecubital

{

 "model": "bayesian_lr_scoring",
 "version": "2.0",
 "region": "Antecubital",
 "description": "Probabilistic scoring model for antecubital (anterior elbow) pain. Scope per Travell & Simons: the two muscles whose TrP referral reaches the antecubital space — Brachialis (Vol.1 Ch.31, essential zone thumb base/dorsal web, antecubital spillover) and Biceps Brachii (Vol.1 Ch.30, essential zone anterior shoulder, antecubital spillover). Both are non-bold in the regional overview; equal priors. LRs are deliberately asymmetric: pathognomonic features carry strong positive LRs when present but only mild negative LRs when absent, because a TrP's signature feature is highly specific yet NOT mandatory — gating on it would lose sensitivity for atypical presentations. High-sensitivity shared features (antecubital spillover, loaded-flexion aggravation) carry small LRs so they keep both muscles in contention without dominating the ranking.",
 "thresholds": {
   "early_exit_posterior": 0.8,
   "early_exit_gap": 0.45,
   "pairwise_trigger": 0.18
 },
 "muscles": {
   "brachialis": {
     "label": "Brachialis",
     "prior": 0.5,
     "page": "Muscle:Brachialis",
     "subtitle": "Thumb base / dorsal web pain with antecubital spillover; active thumb hurts, active elbow does not; weakness equal in pronation and supination",
     "key_trp_note": "The brachialis is the essential antecubital pain generator. Its TrPs refer to the dorsum of the thumb CMC joint and dorsal web (essential zone) with spillover to the antecubital space. Almost always co-involved with biceps brachii in elbow-flexion overload; in the tennis-elbow sequence the supinator is the primary TrP with brachialis and biceps secondary. A lateral-border TrP may entrap the radial sensory nerve, adding dorsal-thumb dysesthesia — relieved by TrP inactivation. Examine the distal belly by displacing the biceps medially."
   },
   "biceps": {
     "label": "Biceps Brachii",
     "prior": 0.5,
     "page": "Muscle:Biceps_Brachii",
     "subtitle": "Anterior-shoulder-dominant superficial ache with antecubital spillover; can lie on affected side and reach behind back; weakness worse in supination; positive Biceps-extension Test",
     "key_trp_note": "Biceps TrPs refer a superficial ache to the anterior shoulder/anterior deltoid, with antecubital pain only as mild downward spillover — so biceps is rarely the sole cause of an antecubital chief complaint. Infraspinatus is the key TrP source most likely to drive satellite biceps TrPs and should be addressed first for durable relief. As a three-joint muscle, range-of-motion testing is unreliable unless the muscle is lengthened across shoulder, elbow, and radioulnar joints together (Biceps-extension Test)."
   }
 },
 "questions": [
   {
     "id": "q_antecubital_present",
     "text": "Is pain felt in or around the antecubital space (the crease at the front of the elbow)?",
     "sublabel": "HIGH SENSITIVITY screen. Antecubital pain is a spillover zone for both elbow flexors, so a 'yes' keeps both muscles in contention rather than discriminating between them. A 'no' gently lowers both (the complaint may belong to an adjacent region — anterior shoulder, lateral elbow, or neck).",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — antecubital / anterior-elbow pain is part of the picture",
         "lr": {
           "brachialis": 1.6,
           "biceps": 1.4
         }
       },
       {
         "id": "no",
         "label": "No — no antecubital component",
         "lr": {
           "brachialis": 0.6,
           "biceps": 0.7
         }
       }
     ]
   },
   {
     "id": "q_loaded_flexion",
     "text": "Is the pain provoked by sustained or repeated elbow flexion under load — carrying with the elbow bent, holding tools at elbow height, lifting, or instrument playing?",
     "sublabel": "HIGH SENSITIVITY. Both elbow flexors are overloaded by sustained loaded flexion, so this keeps both in the race. Absence only mildly lowers both — many real TrP cases are activated by other mechanisms (overstretch, immobilisation).",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — loaded elbow flexion is an aggravator",
         "lr": {
           "brachialis": 1.8,
           "biceps": 1.7
         }
       },
       {
         "id": "no",
         "label": "No — not clearly related to loaded flexion",
         "lr": {
           "brachialis": 0.7,
           "biceps": 0.7
         }
       }
     ]
   },
   {
     "id": "q_thumb_zone",
     "text": "Is pain or deep aching felt at the BASE OF THE THUMB or the dorsal web of the thumb (with or without tingling on the dorsum of the thumb)?",
     "sublabel": "HIGH SPECIFICITY for brachialis — the dorsal thumb CMC and web are its essential referral zone, and the biceps does not refer to the thumb. PRESENT is a strong positive for brachialis. ABSENT is only a mild argument against brachialis (atypical brachialis cases may not show the full thumb pattern), so sensitivity is preserved.",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — thumb-base or dorsal-web pain present",
         "lr": {
           "brachialis": 7.0,
           "biceps": 0.6
         }
       },
       {
         "id": "no",
         "label": "No — no thumb involvement",
         "lr": {
           "brachialis": 0.55,
           "biceps": 1.4
         }
       }
     ]
   },
   {
     "id": "q_thumb_elbow_dissoc",
     "text": "Does ACTIVE movement of the THUMB reproduce the pain while ACTIVE flexion/extension of the ELBOW does NOT?",
     "sublabel": "HIGH SPECIFICITY (near-pathognomonic) for brachialis — the dissociation that redirects attention from the thumb to the arm. PRESENT is decisive for brachialis. ABSENT lowers brachialis only mildly: the dissociation is not always elicitable, and its absence must not rule brachialis out.",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — thumb movement hurts, elbow movement does not",
         "lr": {
           "brachialis": 8.0,
           "biceps": 0.5
         }
       },
       {
         "id": "no",
         "label": "No — elbow movement is painful, or thumb is not differentially worse",
         "lr": {
           "brachialis": 0.55,
           "biceps": 1.3
         }
       }
     ]
   },
   {
     "id": "q_anterior_shoulder_dominant",
     "text": "Is the DOMINANT complaint a superficial ache over the ANTERIOR SHOULDER / anterior deltoid, with antecubital discomfort only a secondary spillover?",
     "sublabel": "HIGH SPECIFICITY for biceps — the anterior shoulder is its essential referral zone, whereas antecubital is only spillover. PRESENT strongly favours biceps. ABSENT lowers biceps only mildly, since biceps can present with the antecubital spillover more prominent in some cases.",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — anterior shoulder ache dominates; antecubital is secondary",
         "lr": {
           "biceps": 7.0,
           "brachialis": 0.55
         }
       },
       {
         "id": "no",
         "label": "No — the antecubital/forearm component dominates, not the shoulder",
         "lr": {
           "biceps": 0.55,
           "brachialis": 1.5
         }
       }
     ]
   },
   {
     "id": "q_overhead_reach",
     "text": "Is there pain or weakness on raising the hand above shoulder level (reaching overhead), or snapping/grating at the front of the shoulder on arm elevation?",
     "sublabel": "HIGH SENSITIVITY for biceps — common in biceps TrP presentations (the long-head tendon and three-joint span), but not specific. Mild LRs so it supports biceps without overriding the discriminating features.",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — overhead reach is painful/weak, or anterior shoulder snapping",
         "lr": {
           "biceps": 2.2,
           "brachialis": 0.8
         }
       },
       {
         "id": "no",
         "label": "No — overhead reach is not a feature",
         "lr": {
           "biceps": 0.7,
           "brachialis": 1.1
         }
       }
     ]
   },
   {
     "id": "q_pronation_supination_weakness",
     "text": "Comparing elbow-flexion strength with the forearm SUPINATED versus PRONATED (elbow extended): how does the weakness behave?",
     "sublabel": "HIGH SPECIFICITY discriminator grounded in anatomy. The brachialis attaches to the ulna, so its strength is unaffected by forearm rotation (equal weakness both ways). The biceps wraps the radius in pronation, so it is weaker in supination-position testing. This is one of the strongest mechanical separators of the two muscles.",
     "type": "choice",
     "answers": [
       {
         "id": "equal_both",
         "label": "EQUAL weakness in both positions — pronation makes no difference",
         "sublabel": "Points to brachialis (ulnar attachment, rotation-independent)",
         "lr": {
           "brachialis": 6.0,
           "biceps": 0.4
         }
       },
       {
         "id": "worse_supinated",
         "label": "WORSE in supination — pronating the forearm reduces the weakness/pain",
         "sublabel": "Points to biceps (radius wrap unloads it in pronation)",
         "lr": {
           "brachialis": 0.4,
           "biceps": 6.0
         }
       },
       {
         "id": "not_tested_unclear",
         "label": "Not tested or unclear",
         "sublabel": "No information — leaves both unchanged",
         "lr": {
           "brachialis": 1.0,
           "biceps": 1.0
         }
       }
     ]
   },
   {
     "id": "q_passive_extension",
     "text": "Does PASSIVE full elbow extension increase the thumb-base / antecubital pain?",
     "sublabel": "SPECIFICITY support for brachialis (passive extension stretches it and reproduces its referred pain). Moderate positive LR; absence is only mildly negative because the few-degree restriction is subtle and easily missed.",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — passive elbow extension reproduces/increases the pain",
         "lr": {
           "brachialis": 3.0,
           "biceps": 1.1
         }
       },
       {
         "id": "no",
         "label": "No — passive extension does not reproduce it",
         "lr": {
           "brachialis": 0.7,
           "biceps": 1.0
         }
       }
     ]
   },
   {
     "id": "q_biceps_extension_test",
     "text": "On the Biceps-extension Test (arm abducted ~45°, elbow extended, forearm pronated, arm moved into extension without medial rotation): does the ELBOW FLEX to compensate as the arm is extended?",
     "sublabel": "HIGH SPECIFICITY for biceps — compensatory elbow flexion indicates a shortened, TrP-bearing biceps and is the purpose-built test for this three-joint muscle. PRESENT strongly favours biceps; ABSENT lowers it only mildly (the test requires correct technique and the shortening may be mild).",
     "type": "binary",
     "answers": [
       {
         "id": "yes",
         "label": "Yes — elbow flexes to compensate (positive test)",
         "lr": {
           "biceps": 6.0,
           "brachialis": 0.7
         }
       },
       {
         "id": "no",
         "label": "No / not performed — no compensatory elbow flexion",
         "lr": {
           "biceps": 0.7,
           "brachialis": 1.1
         }
       }
     ]
   },
   {
     "id": "q_sidelying_behindback",
     "text": "Can the patient lie comfortably on the AFFECTED side AND reach behind the waistline without pain?",
     "sublabel": "SPECIFICITY support that separates biceps from an infraspinatus source of anterior-shoulder pain (infraspinatus prevents both). Within this 2-muscle model it gently supports biceps when the anterior shoulder is involved, and flags infraspinatus screening when negative. Mild LRs.",
     "type": "choice",
     "answers": [
       {
         "id": "yes_both",
         "label": "Yes — can lie on the affected side and reach behind the back",
         "sublabel": "Consistent with biceps; argues against an infraspinatus source",
         "lr": {
           "biceps": 2.0,
           "brachialis": 1.0
         }
       },
       {
         "id": "no_either",
         "label": "No — cannot lie on that side and/or cannot reach behind the back",
         "sublabel": "Screen infraspinatus (separate region) — points away from a pure biceps picture",
         "lr": {
           "biceps": 0.5,
           "brachialis": 0.9
         }
       },
       {
         "id": "na",
         "label": "Not applicable — no shoulder component",
         "sublabel": "Neutral",
         "lr": {
           "biceps": 1.0,
           "brachialis": 1.0
         }
       }
     ]
   }
 ],
 "pairwise": [
   {
     "id": "pw_brachialis_biceps",
     "pair": [
       "brachialis",
       "biceps"
     ],
     "text": "Tiebreaker — Brachialis vs Biceps Brachii",
     "question": "Taking the single most distressing site of pain: is it at the THUMB BASE / dorsal web (with the antecubital fossa secondary), or over the ANTERIOR SHOULDER (with the antecubital fossa secondary)?",
     "answers": [
       {
         "id": "thumb_dominant",
         "label": "Thumb base / dorsal web is the dominant site",
         "lr": {
           "brachialis": 5.0,
           "biceps": 0.25
         }
       },
       {
         "id": "shoulder_dominant",
         "label": "Anterior shoulder is the dominant site",
         "lr": {
           "brachialis": 0.25,
           "biceps": 5.0
         }
       },
       {
         "id": "antecubital_only",
         "label": "Neither — pain is confined to the antecubital fossa itself",
         "sublabel": "Re-examine both elbow flexors directly; consider lateral-elbow and cervical sources outside this region",
         "lr": {
           "brachialis": 1.2,
           "biceps": 1.0
         }
       }
     ]
   }
 ],
 "treatment_dag": {
   "edges": [
     {
       "from": "brachialis",
       "to": "biceps",
       "type": "functional_unit",
       "label": "Brachialis and biceps brachii are synergistic elbow flexors almost always involved together — examine and treat both in the same session"
     },
     {
       "from": "biceps",
       "to": "brachialis",
       "type": "functional_unit",
       "label": "Biceps TrPs drive early secondary brachialis TrPs — treat concurrently; spray and stretch the brachialis after the biceps"
     }
   ],
   "edge_type_labels": {
     "key_satellite": "Treat first — key TrP driving satellites",
     "functional_unit": "Treat concurrently in the same session",
     "secondary_load": "Treat after primary resolves",
     "antagonist_risk": "⚠ Treat in alternating cycles — reactive activation risk"
   }
 },
 "region_label": "Antecubital (Anterior Elbow) Pain",
 "red_flags": {
   "emergency": [
     {
       "id": "rf-e1",
       "label": "Vascular compromise — brachial artery (elbow dislocation / supracondylar fracture)",
       "question": "Anterior elbow injury — a fall, posterior dislocation, or supracondylar fracture — with a COLD, PALE, or PULSELESS hand, an expanding antecubital swelling/haematoma, or new median/anterior-interosseous signs? The brachial artery runs through the fossa; B&K make assessment of distal pulses mandatory after any elbow dislocation, and an absent pulse needs EMERGENT reduction. Untreated ischaemia causes Volkmann's contracture and limb loss.",
       "source": "Brukner & Khan Ch.18 (posterior dislocation — vascular assessment)"
     },
     {
       "id": "rf-e2",
       "label": "Acute forearm compartment syndrome",
       "question": "Severe escalating forearm pain OUT OF PROPORTION to findings, pain on PASSIVE finger extension/stretch (earliest sign), and a tense, wood-like volar forearm — after a supracondylar fracture, crush, reperfusion, or tight cast? The volar compartment carrying the median and ulnar nerves is most affected; pallor, pulselessness, and paralysis are LATE. Fasciotomy within ~6 hours is limb-saving.",
       "source": "Forearm Compartment Syndrome StatPearls (NBK556130); Brukner & Khan Ch.18"
     },
     {
       "id": "rf-e3",
       "label": "Septic arthritis of the elbow",
       "question": "A hot, red, exquisitely tender elbow with marked pain on the slightest passive movement and an effusion, especially with fever? Urgent aspiration (Gram stain, culture, crystals) and drainage with antibiotics; it must be distinguished from an acute gout/CPPD flare, which can look identical — treat as infection until excluded.",
       "source": "Chung et al. 2023 (gout vs septic differentiation)"
     }
   ],
   "urgent": [
     {
       "id": "rf-u1",
       "label": "Distal biceps tendon rupture",
       "question": "Sudden anterior elbow pain (often a 'pop') during a forceful eccentric load — lifting or catching a heavy object — then weakness of elbow flexion and especially SUPINATION, antecubital bruising, and a retracted muscle belly ('reverse Popeye')? A positive HOOK TEST (the examiner cannot hook a finger under the distal biceps tendon in the fossa) confirms it. B&K: acute complete avulsions need prompt surgical reattachment, ideally within ~2–3 weeks before the tendon retracts and scars.",
       "source": "Brukner & Khan Ch.18 (tendon ruptures)"
     },
     {
       "id": "rf-u2",
       "label": "Fracture about the elbow (radial head, supracondylar, coronoid)",
       "question": "Anterior elbow pain, effusion, and restricted/painful movement after a fall on the outstretched hand? B&K: the radial head fracture is the commonest adult elbow fracture and is often subtle — the fat-pad (sail) sign on the lateral film may be the only clue; supracondylar fractures predominate in children with a high neurovascular complication rate. Inability to fully extend, a tense effusion, or focal bony tenderness warrants radiographs and orthopaedic referral; check distal neurovascular status.",
       "source": "Brukner & Khan Ch.18 (radial head / supracondylar fractures)"
     },
     {
       "id": "rf-u3",
       "label": "Pronator teres syndrome / proximal median nerve entrapment",
       "question": "Anterior forearm/elbow ache 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 antecubital sibling sites the median nerve passes: the lacertus fibrosus (worse on resisted elbow flexion in supination), the ligament of Struthers (worse on supination + elbow extension, possible reduced radial pulse), and the FDS sublimis bridge (worse on resisted middle-finger PIP flexion). Progressive deficit warrants nerve studies and release.",
       "source": "Pronator Teres Syndrome StatPearls (Dididze et al. 2023); Brukner & Khan Ch.18"
     },
     {
       "id": "rf-u4",
       "label": "Anterior interosseous nerve (AIN) syndrome",
       "question": "Anterior forearm/cubital-fossa pain with WEAKNESS but NO sensory loss — specifically an inability to flex the tips of the thumb and index finger to make a normal 'OK' sign (the pinch flattens)? The AIN is the pure-motor median branch (flexor pollicis longus, flexor digitorum profundus to index/middle, pronator quadratus), arising just distal to the fossa. Often a transient neuritis, but compression and trauma occur; needs electrodiagnostic confirmation and timely specialist review as motor recovery is the concern.",
       "source": "Anterior Interosseous Syndrome StatPearls (NBK525956)"
     },
     {
       "id": "rf-u5",
       "label": "Elbow dislocation — post-reduction instability / coronoid fracture",
       "question": "A history of elbow dislocation (often a posterolateral rotatory mechanism on a fall) with persistent anterior pain, apprehension, or a sense of instability? B&K: even after reduction an associated coronoid or radial-head fracture can cause ongoing instability — large coronoid fractures need fixation. Obtain post-reduction films, assess collateral-ligament stability, and refer for any fracture or instability.",
       "source": "Brukner & Khan Ch.18 (posterior dislocation)"
     }
   ]
 },
 "broad_differential": [
   {
     "condition": "Distal biceps tendinopathy",
     "confidence": "common",
     "mimics": "Anterior elbow pain on lifting and twisting — the chief non-emergency antecubital source and the main overlap with biceps/brachialis TrP referral",
     "distinguishing_feature": "Activity-related pain at the distal biceps insertion on the radial tuberosity, reproduced by resisted elbow flexion and resisted supination, with tendon tenderness but NO retraction and a NEGATIVE hook test (separating it from rupture). Often coexists with — and may be driven by — biceps TrP taut-band tension.",
     "action": "Resisted flexion/supination testing and hook test to exclude rupture; ultrasound for tendinosis/partial tear. Inactivate biceps TrPs first and reassess; relative rest and eccentric loading.",
     "source": "Brukner & Khan Ch.18; Chung et al. 2023 (biceps tendinopathy)"
   },
   {
     "condition": "Bicipitoradial (cubital) bursitis",
     "confidence": "uncommon",
     "mimics": "Deep anterior elbow pain and fullness — overlaps distal biceps tendinopathy",
     "distinguishing_feature": "Pain and sometimes a palpable fullness DEEP in the antecubital fossa from inflammation of the bicipitoradial bursa (between the distal biceps tendon and the radial tuberosity), worse on resisted supination/pronation as the tendon compresses the bursa; can occasionally irritate the radial nerve. Anterior — distinct from the posterior olecranon bursa.",
     "action": "Ultrasound/MRI to confirm the bursa and exclude a mass; assess for radial nerve irritation. Activity modification, NSAIDs, image-guided aspiration/corticosteroid; excision if refractory.",
     "source": "Chung et al. 2023 (anterior elbow); general elbow-bursa knowledge"
   },
   {
     "condition": "Brachialis strain / tendinopathy",
     "confidence": "uncommon",
     "mimics": "Deep anterior elbow pain — overlaps distal biceps pathology and brachialis TrP referral",
     "distinguishing_feature": "Deep anterior elbow pain from overload of the brachialis (prime elbow flexor on the floor of the fossa), worse on resisted elbow flexion with the forearm PRONATED (which favours brachialis over biceps), often after heavy/repetitive lifting or climbing. A brachialis TrP refers to the thumb base and is reproduced by deep palpation (displace the biceps medially); lateral-border overload can irritate the radial sensory nerve.",
     "action": "Resisted flexion testing in pronation; relative rest and graded loading. Treat coexisting brachialis TrPs; consider radial sensory irritation if dorsal-thumb dysesthesia appears.",
     "source": "Brukner & Khan Ch.18; Chung et al. 2023"
   },
   {
     "condition": "Elbow osteoarthritis (anterior osteophytes / intra-articular loose body)",
     "confidence": "uncommon",
     "mimics": "Activity-related elbow ache, stiffness, and end-range anterior pain",
     "distinguishing_feature": "Pain at the extremes of motion — anterior pain at maximal FLEXION from coronoid/radial-fossa osteophytes — typically sparing the mid-range, with crepitus and a flexion contracture; an osteophyte can fracture to form a LOOSE BODY causing mechanical locking, catching, or a painful block. Radiographic joint-space change is often preserved until late; pain is not position-specific to a muscle.",
     "action": "Radiographs/CT for osteophytes and loose bodies; joint examination before any injection in the fossa. NSAIDs, activity modification; arthroscopic/open debridement or loose-body removal for mechanical symptoms.",
     "source": "Chung et al. 2023 (primary osteoarthritis; intra-articular loose body)"
   },
   {
     "condition": "Gout / crystal arthropathy (CPPD) of the elbow",
     "confidence": "uncommon",
     "mimics": "Acute or recurrent anterior elbow pain and swelling — can mimic an OA flare or bursitis",
     "distinguishing_feature": "A subacute or episodic hot, swollen, exquisitely tender elbow with rapid onset — the elbow is involved in 20–30% of gout patients; CPPD is the other crystal cause. Aspiration shows negatively birefringent monosodium urate crystals. A truly hot, red, febrile joint must be treated as SEPTIC until aspiration excludes it.",
     "action": "Joint aspiration for crystals and culture (mandatory to exclude sepsis); serum urate. Acute flare: NSAIDs/colchicine/short steroid; chronic: urate-lowering therapy. Treat TrPs only once an active crystal/infective process is excluded.",
     "source": "Chung et al. 2023 (gout)"
   },
   {
     "condition": "Rheumatoid / inflammatory arthritis",
     "confidence": "uncommon",
     "mimics": "Anterior elbow pain, boggy swelling, and stiffness",
     "distinguishing_feature": "Persistent synovitic pain with boggy swelling, prolonged morning stiffness, and usually a symmetrical multi-joint pattern with systemic features (fatigue, nodules); the elbow is a common site in established RA. TrP pain lacks synovitis, effusion, and systemic features.",
     "action": "Inflammatory markers, rheumatoid serology, rheumatology referral; radiographs for erosions. Treat the underlying disease (DMARDs); address TrPs adjunctively.",
     "source": "Chung et al. 2023 (rheumatoid arthritis)"
   },
   {
     "condition": "Anterior capsule strain (hyperextension injury)",
     "confidence": "uncommon",
     "mimics": "Diffuse anterior elbow pain after a hyperextension event",
     "distinguishing_feature": "Diffuse anterior elbow pain and tenderness following hyperextension (a fall, a blocked tackle), worse on terminal extension as the anterior capsule is stretched, without focal tendon-insertion tenderness, mechanical locking, or neurological signs. Usually self-limiting.",
     "action": "Exclude fracture/dislocation and biceps rupture; relative rest, NSAIDs, graded return to extension load. Persistent end-range pain warrants imaging for occult osteochondral injury or loose body.",
     "source": "Chung et al. 2023 (anterior capsule strain)"
   },
   {
     "condition": "Proximal bicipital (long head) tendinopathy — anterior-shoulder spillover",
     "confidence": "uncommon",
     "mimics": "Anterior-shoulder/bicipital-groove pain spilling down toward the antecubital fossa",
     "distinguishing_feature": "Tenderness at the long-head tendon in the bicipital groove with a positive Yergason's/Speed's; the pain centres on the anterior shoulder and only spills toward the arm, so it presents as a shoulder problem rather than a true antecubital one. Often coexists with biceps TrPs and may be driven by their taut-band tension.",
     "action": "Examine the shoulder/groove (Yergason's, Speed's); inactivate biceps TrPs first and reassess. Persistent groove signs may warrant sheath injection at the shoulder.",
     "source": "Chung et al. 2023; Brukner & Khan Ch.18"
   },
   {
     "condition": "De Quervain's / first-dorsal-compartment tenosynovitis",
     "confidence": "uncommon",
     "mimics": "Thumb-base / radial pain — the key differential for brachialis thumb referral",
     "distinguishing_feature": "Localised tendon-sheath tenderness and swelling at the radial styloid with a positive Finkelstein's test. Because the brachialis refers to the thumb base/dorsal web, this must be separated from a brachialis TrP — which gives NO Finkelstein's sign and is reproduced by palpating the distal brachialis, not the first compartment.",
     "action": "Examine the first dorsal compartment and Finkelstein's; if negative, re-examine the brachialis for a referring TrP.",
     "source": "Brukner & Khan Ch.19; Chung et al. 2023 (anterior/forearm differential)"
   },
   {
     "condition": "Radial tunnel / posterior interosseous nerve entrapment",
     "confidence": "uncommon",
     "mimics": "Deep aching just lateral and distal to the antecubital fossa",
     "distinguishing_feature": "Pain over the mobile wad 4–5 cm distal to the lateral epicondyle, worse on resisted middle-finger extension and resisted supination, characteristically pain WITHOUT weakness or paraesthesia (contrast PIN compression syndrome, which has true extensor weakness). Relevant here because a lateral-border brachialis TrP can itself irritate the radial nerve.",
     "action": "If TrP treatment of the brachialis/supinator fails, refer for nerve conduction studies (often normal in radial tunnel).",
     "source": "Brukner & Khan Ch.18 (PIN / radial tunnel); Chung et al. 2023"
   },
   {
     "condition": "Cervical radiculopathy (C5/C6) / referred neural pain",
     "confidence": "uncommon",
     "mimics": "Anterior elbow/arm pain referred from the neck",
     "distinguishing_feature": "Neck pain radiating to the anterior arm with dermatomal sensory change (C5–C6: lateral arm/forearm, thumb), a depressed biceps/brachioradialis reflex, myotomal weakness, and a positive Spurling's points to a cervical root rather than a local antecubital lesion. Anterior elbow pain is also frequently referred from the cervical/upper-thoracic spine and periscapular soft tissues. TrPs commonly coexist and may dominate.",
     "action": "Full neurological/upper-quarter examination with Spurling's; cervical MRI and electrodiagnostics if a focal deficit is present. Treat the cervical source and coexisting scalene/shoulder-girdle and forearm TrPs concurrently.",
     "source": "Chung et al. 2023 (referred pain); Brukner & Khan Ch.18 (cervical/thoracic contribution)"
   }
 ]

}