DiagnosticTree/Antecubital
{
"region": "Antecubital",
"start": "q_thumb_zone",
"redflags": {
"emergency": [
{
"id": "rf_sepsis",
"label": "Bacteraemia / systemic sepsis",
"question": "Fever, rigors, tachycardia, malaise, or a spreading hot tender swelling around the elbow?",
"rationale": "Systemic features with a hot, swollen elbow point to a deep infective focus seeding the bloodstream. Myofascial pain is never febrile and never produces systemic toxicity.",
"action": "Do not proceed with the algorithm. Obtain blood cultures, FBC, CRP/ESR and arrange same-day medical assessment. Antecubital pain is not a myofascial problem in the presence of sepsis."
},
{
"id": "rf_compartment",
"label": "Acute compartment syndrome of the forearm",
"question": "Severe, escalating forearm pain out of proportion to findings, pain on passive finger extension, tense swollen compartment, paraesthesia, or a recent fracture/crush/reperfusion?",
"rationale": "Pain out of proportion and pain on passive stretch of the compartment's muscles are the earliest and most reliable signs; pulselessness is a late, unreliable sign. This is a surgical emergency.",
"action": "Emergency. Do not elevate above heart level, remove constricting dressings, and refer immediately for surgical fasciotomy assessment. Time-critical to prevent muscle necrosis."
},
{
"id": "rf_septic_joint",
"label": "Septic arthritis of the elbow",
"question": "Hot, red, exquisitely tender elbow with marked pain on the slightest passive movement and an effusion, especially with fever?",
"rationale": "A septic joint refuses nearly all passive range because of intra-articular pus; the global, movement-evoked pain is unlike the position-specific pain of a muscle TrP.",
"action": "Emergency. Urgent joint aspiration before antibiotics where possible, and same-day orthopaedic/rheumatology referral. Do not inject."
},
{
"id": "rf_osteomyelitis",
"label": "Osteomyelitis",
"question": "Deep, constant, night-prominent bone pain with local warmth/swelling, fever, or a background of recent infection, open wound, or immunocompromise?",
"rationale": "Constant unremitting bone pain unrelieved by rest or position, with systemic or local infective signs, is incompatible with a mechanical myofascial source.",
"action": "Emergency/urgent. Arrange inflammatory markers, blood cultures and imaging (MRI most sensitive) and refer for specialist management."
},
{
"id": "rf_nec_fasc",
"label": "Necrotising fasciitis",
"question": "Rapidly spreading erythema, pain grossly out of proportion, skin blistering/dusky discolouration, crepitus, or rapid systemic deterioration?",
"rationale": "Pain out of proportion to visible skin change, rapid progression, and systemic toxicity are the hallmark early features. Delay is fatal.",
"action": "Emergency — resuscitate and refer for immediate surgical debridement. Do not delay for imaging."
}
],
"urgent": [
{
"id": "rf_stress_fracture",
"label": "Stress fracture",
"question": "Localised bony tenderness with a history of repetitive loading or a sudden change in training/occupational load, pain worsening with activity and easing with rest?",
"rationale": "A focal point of bony (not muscular) tenderness that tracks with cumulative loading and is reproduced by bony percussion suggests a stress fracture rather than a TrP.",
"action": "Urgent. Relative rest from the provoking load and imaging (X-ray often normal early; MRI or bone scan more sensitive). Refer if confirmed or strongly suspected."
}
]
},
"nodes": {
"q_thumb_zone": {
"type": "symptom",
"question": "Is pain felt at the BASE OF THE THUMB or the dorsal web of the thumb (with or without tingling/numbness over the dorsum of the thumb)?",
"clinical_rationale": "The dorsum of the thumb CMC joint and the dorsal web are the essential (solid) referral zone of brachialis TrPs. Biceps TrPs do not refer to the thumb. This single feature is the strongest early discriminator between the two muscles of this region.",
"muscles_implicated": ["Brachialis"],
"muscles_excluded": ["Biceps Brachii"],
"yes": "q_thumb_elbow_dissoc",
"no": "q_anterior_shoulder"
},
"q_thumb_elbow_dissoc": {
"type": "examination",
"exam_type": "active_movement",
"question": "Does ACTIVE movement of the THUMB reproduce the pain while ACTIVE flexion/extension of the ELBOW does NOT?",
"clinical_rationale": "This dissociation — thumb use hurts, elbow use does not — is the characteristic clinical sign that directs attention away from the thumb and to the brachialis in the upper arm. It is the finding T&S highlight as redirecting the clinician from the thumb to the arm.",
"positive_finding": "Thumb movement painful, elbow movement painless",
"negative_finding": "Elbow movement itself is painful, or thumb movement is not differentially worse",
"muscles_implicated": ["Brachialis"],
"yes": "q_brachialis_confirm",
"no": "q_brachialis_vs_lateral"
},
"q_brachialis_confirm": {
"type": "examination",
"exam_type": "provocation",
"question": "Does PASSIVE full elbow extension increase the thumb-base / antecubital pain, AND is elbow-flexion weakness EQUAL whether the forearm is pronated or supinated?",
"landmark": "Brachialis TrPs lie in the distal half of the muscle belly; displace the biceps medially (elbow flexed 30–45°, forearm supinated) to palpate the brachialis against the humerus.",
"clinical_rationale": "Passive elbow extension stretches the brachialis and reproduces its referred pain. Because the brachialis attaches to the ulna, its strength is unaffected by forearm rotation — weakness equal in pronation and supination distinguishes it from the biceps (which is weaker in pronation).",
"positive_finding": "Passive extension increases pain; weakness equal in both forearm positions",
"negative_finding": "Weakness clearly worse in supination (suggests biceps), or passive extension does not reproduce pain",
"muscles_implicated": ["Brachialis"],
"yes": "result_brachialis",
"no": "q_anterior_shoulder"
},
"q_brachialis_vs_lateral": {
"type": "overlap",
"text": "Thumb-base referral is present but the thumb–elbow dissociation is absent and elbow movement itself is painful. Brachialis remains possible, but lateral-elbow muscles that also refer to the thumb/radial hand (supinator, brachioradialis) and lateral epicondylitis should be screened on their own pages — these lie outside the antecubital region this algorithm covers.",
"screen_these": [
"Brachialis — re-examine distal belly beneath the biceps for taut bands and spot tenderness",
"Supinator and brachioradialis — lateral elbow / radial forearm muscles (separate region)",
"Lateral epicondylitis — Mills' and Cozen's tests",
"Radial tunnel / posterior interosseous nerve — resisted middle-finger extension"
],
"wiki_page": "Muscle:Brachialis"
},
"q_anterior_shoulder": {
"type": "symptom",
"question": "Is the DOMINANT complaint a superficial ache over the ANTERIOR SHOULDER, with the antecubital discomfort only a mild downward spillover?",
"clinical_rationale": "The essential referral zone of biceps brachii TrPs is the anterior surface of the shoulder and anterior deltoid; antecubital pain is only a milder downward spillover. When the anterior shoulder dominates and the antecubital pain is secondary, biceps is the likely source — but anterior shoulder pain is itself a separate pain region (see Pain:Anterior Shoulder).",
"muscles_implicated": ["Biceps Brachii"],
"yes": "q_biceps_confirm",
"no": "q_residual_antecubital"
},
"q_biceps_confirm": {
"type": "examination",
"exam_type": "provocation",
"question": "Is elbow-flexion weakness WORSE in supination than pronation, can the patient LIE COMFORTABLY on the affected side and reach behind the waistline, AND does the Biceps-extension Test show the elbow flexing to compensate as the arm is extended?",
"landmark": "Screen each head of the biceps in the distal third with flat then pincer palpation; brachialis TrPs may sit beneath and refer to the thumb.",
"clinical_rationale": "Pronation-sensitive weakness (biceps wraps the radius in pronation), preserved comfortable side-lying and behind-back reach (distinguishing from infraspinatus), and the compensatory elbow flexion of the Biceps-extension Test together confirm a shortened, TrP-bearing biceps. The two sleep/reach positives are the T&S must-be-present features that point away from infraspinatus.",
"positive_finding": "Supination-worse weakness; can lie on affected side and reach behind back; positive Biceps-extension Test",
"negative_finding": "Cannot lie on affected side or reach behind back (screen infraspinatus); no compensatory elbow flexion",
"muscles_implicated": ["Biceps Brachii"],
"yes": "result_biceps",
"no": "q_residual_antecubital"
},
"q_residual_antecubital": {
"type": "overlap",
"text": "Neither the thumb-base brachialis pattern nor the anterior-shoulder biceps pattern is clearly established. Antecubital pain is a spillover zone for both elbow flexors, so re-examine both muscles directly, and consider that the source may lie outside the antecubital region (anterior shoulder, lateral elbow, or cervical). Review the broad differential below before concluding.",
"screen_these": [
"Brachialis — distal belly beneath the biceps; thumb-base referral; equal weakness in pronation and supination",
"Biceps brachii — distal third of both heads; anterior shoulder referral; supination-worse weakness",
"Infraspinatus — if anterior shoulder pain with inability to lie on either side and restricted behind-back reach (separate region)",
"Cervical C5/C6 — if any dermatomal sensory deficit, reflex change, or true myotomal weakness"
],
"wiki_page": "Muscle:Brachialis"
},
"result_brachialis": {
"type": "result",
"diagnosis": "Brachialis trigger points",
"confidence": "high",
"notes": "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 and occasionally the anterior deltoid. A lateral-border TrP may additionally entrap the sensory branch of the radial nerve, adding dysesthesia on the dorsum of the thumb — both components resolve with TrP inactivation.",
"treatment_hint": "Spray and stretch with the elbow gradually extended and vapocoolant swept toward the thumb; augment with postisometric relaxation. Inject (≥3.8 cm needle) only with strict avoidance of the medial (median nerve) and lateral (radial nerve) borders. Place a pillow in the elbow crook at night; avoid sustained loaded elbow flexion.",
"chapter_ref": "Travell & Simons Vol. 1, Ch. 31",
"confirmatory": [
"Pain at the base of the thumb / dorsal web at rest and with thumb use (essential zone)",
"Active thumb movement hurts; active elbow movement does not (the key dissociation)",
"Passive full elbow extension increases the thumb / antecubital pain",
"Shoulder motion unimpaired (anterior deltoid spillover does not restrict the shoulder)",
"No reflex change and no objective dermatomal sensory deficit (excludes C5–C6 radiculopathy)"
],
"satellite_trps": ["Biceps brachii", "Supinator", "Brachioradialis", "Adductor pollicis"],
"landing_page_topics": [
"Radial sensory nerve entrapment screen (almond-shaped lateral-border TrP at the musculospiral groove)",
"Distinguishing brachialis from biceps weakness (pronation vs supination strength testing)",
"Tennis-elbow co-involvement sequence (supinator primary; brachialis and biceps secondary)",
"Differentiation from de Quervain's, first CMC arthritis, carpal tunnel"
],
"wiki_page": "Muscle:Brachialis",
"related_pages": [
{ "label": "Biceps Brachii", "page": "Muscle:Biceps_Brachii" },
{ "label": "Trigger Point Injection", "page": "Concept:Trigger_Point_Injection" },
{ "label": "Perpetuating Factors", "page": "Concept:Perpetuating_Factors" }
],
"less_likely": [
{ "muscle": "Biceps Brachii", "reason": "Refers to the anterior shoulder, not the thumb; antecubital is only mild spillover" }
]
},
"result_biceps": {
"type": "result",
"diagnosis": "Biceps brachii trigger points",
"confidence": "moderate",
"notes": "Biceps TrPs refer a superficial ache to the anterior shoulder and anterior deltoid, with the antecubital space as a milder downward spillover — so biceps is rarely the cause of antecubital pain as a chief complaint. Where it is implicated, the antecubital component accompanies a dominant anterior-shoulder ache. Infraspinatus is the key TrP source most likely to drive satellite biceps TrPs and should be addressed first for durable relief.",
"treatment_hint": "Address infraspinatus first if its features are present. Spray and stretch the biceps across all three joints (lateral rotation, abduction, pronation, elbow extension); follow by spraying the brachialis and triceps to prevent reactive cramping. Inject with strict avoidance of the medial and lateral borders of the distal muscle. Carry with forearms pronated to unload the biceps; pillow in the elbow crook at night.",
"chapter_ref": "Travell & Simons Vol. 1, Ch. 30",
"confirmatory": [
"Superficial anterior shoulder aching is the essential zone (NOT deep glenohumeral joint pain, NOT mid-deltoid pain)",
"Can lie comfortably on the affected side (distinguishes from infraspinatus)",
"Can reach behind the waistline without pain (distinguishes from infraspinatus)",
"Elbow-flexion weakness worse in supination than pronation",
"Palpable midmuscle taut bands with spot tenderness; no neurological deficit"
],
"satellite_trps": ["Brachialis", "Supinator", "Triceps brachii", "Anterior deltoid", "Supraspinatus", "Upper trapezius", "Coracobrachialis"],
"landing_page_topics": [
"Biceps-extension Test technique (three-joint lengthening)",
"Distinguishing biceps shortening from elbow joint contracture",
"Bicipital tendinitis vs referred biceps TrP tenderness (Yergason's interpretation)",
"Infraspinatus as the key satellite-driving source"
],
"wiki_page": "Muscle:Biceps_Brachii",
"related_pages": [
{ "label": "Brachialis", "page": "Muscle:Brachialis" },
{ "label": "Infraspinatus", "page": "Muscle:Infraspinatus" },
{ "label": "Trigger Point Injection", "page": "Concept:Trigger_Point_Injection" }
],
"less_likely": [
{ "muscle": "Brachialis", "reason": "Refers to the thumb base with the antecubital fossa as spillover; lacks the anterior-shoulder dominance" }
]
}
},
"broad_differential": [
{ "id": "bd_distal_biceps_rupture", "confidence": "uncommon", "condition": "Distal biceps tendon rupture", "mimics": "Acute antecubital pain and weakness of supination/flexion", "distinguishing_feature": "Audible/perceived pop, palpable tendon gap or 'Popeye' deformity, marked supination weakness.", "action": "Urgent orthopaedic referral; surgical repair is time-sensitive." },
{ "id": "bd_epicondylitis", "confidence": "uncommon", "condition": "Lateral / medial epicondylitis", "mimics": "Elbow pain provoked by grip and loading", "distinguishing_feature": "Point tenderness at the epicondyle; positive Mills'/Cozen's (lateral) or resisted wrist flexion (medial). Frequently coexists with supinator/brachioradialis TrPs.", "action": "Examine the relevant forearm muscles for TrPs; myofascial source is common and first-line." },
{ "id": "bd_radial_tunnel", "confidence": "uncommon", "condition": "Radial tunnel / posterior interosseous nerve entrapment", "mimics": "Deep aching lateral to the antecubital region", "distinguishing_feature": "Pain 4–5 cm distal to the lateral epicondyle, worse on resisted middle-finger extension and supination; usually no paraesthesia.", "action": "If TrP treatment fails, refer for nerve conduction studies." },
{ "id": "bd_cubital_tunnel", "confidence": "uncommon", "condition": "Cubital tunnel syndrome (ulnar nerve)", "mimics": "Elbow pain with hand symptoms", "distinguishing_feature": "MEDIAL location; paraesthesia in the ring and little fingers; positive Tinel's at the medial epicondyle — not an anterior/antecubital pattern.", "action": "Refer for electrodiagnostic assessment; structural compression not addressed by TrP work." },
{ "id": "bd_cervical_radic", "confidence": "uncommon", "condition": "Cervical radiculopathy (C5/C6)", "mimics": "Arm pain in a C5/C6 distribution", "distinguishing_feature": "Dermatomal sensory deficit, reflex change, or true myotomal weakness — absent in pure TrP pain.", "action": "Neurological exam; image if focal deficit present. May coexist with TrPs." },
{ "id": "bd_osteoarthritis", "confidence": "uncommon", "condition": "Elbow osteoarthritis", "mimics": "Activity-related elbow ache and stiffness", "distinguishing_feature": "Restricted range in all planes, crepitus, radiographic joint-space change; pain not position-specific to a muscle.", "action": "Radiographs; joint examination before any injection in the fossa." },
{ "id": "bd_tendinopathy", "confidence": "uncommon", "condition": "Bicipital / distal tendinopathy", "mimics": "Anterior elbow or tendon pain", "distinguishing_feature": "Tenderness localised to the tendon and groove, positive Yergason's; often coexists with biceps TrPs.", "action": "Inactivate TrPs first and reassess; persistent tendon signs may warrant sheath injection." },
{ "id": "bd_tenosynovitis", "confidence": "uncommon", "condition": "Tenosynovitis (incl. de Quervain's if thumb-dominant)", "mimics": "Thumb-base or radial pain", "distinguishing_feature": "Localised tendon-sheath tenderness and swelling; positive Finkelstein's for de Quervain's — brachialis TrPs give no Finkelstein's sign.", "action": "Examine the first dorsal compartment; differentiate from brachialis referral." },
{ "id": "bd_bursitis", "confidence": "uncommon", "condition": "Aseptic (olecranon) bursitis", "mimics": "Elbow swelling and discomfort", "distinguishing_feature": "Fluctuant posterior swelling over the olecranon; not an anterior/antecubital muscle pattern. (If hot/red/febrile — treat as septic, see emergency flags.)", "action": "Aspirate if diagnosis unclear; exclude septic bursitis." },
{ "id": "bd_enthesitis", "confidence": "atypical", "condition": "Enthesitis", "mimics": "Tenderness at a tendon/ligament insertion", "distinguishing_feature": "Insertional tenderness, may be part of a spondyloarthropathy; consider if multiple entheses or other inflammatory features.", "action": "Screen for inflammatory arthropathy if multifocal." },
{ "id": "bd_periostitis", "confidence": "atypical", "condition": "Periostitis", "mimics": "Surface bone tenderness with loading", "distinguishing_feature": "Tenderness over the periosteum with repetitive loading history; bony rather than muscular tenderness.", "action": "Relative rest and imaging if persistent; overlaps with stress fracture (urgent flag)." },
{ "id": "bd_apophysitis", "confidence": "atypical", "condition": "Apophysitis", "mimics": "Traction pain at an apophysis (skeletally immature patient)", "distinguishing_feature": "Adolescent, tenderness at a traction apophysis aggravated by the attached muscle's loading.", "action": "Activity modification; imaging if diagnosis uncertain." },
{ "id": "bd_myositis_ossificans", "confidence": "rare", "condition": "Myositis ossificans", "mimics": "Persistent firm painful mass after trauma to the arm", "distinguishing_feature": "Hardening palpable mass weeks after a significant blow/haematoma; radiographic ossification within muscle.", "action": "Imaging; avoid aggressive massage/manipulation of the mass; specialist referral." },
{ "id": "bd_chondromalacia", "confidence": "rare", "condition": "Chondromalacia (articular cartilage softening)", "mimics": "Activity-related joint ache with crepitus", "distinguishing_feature": "Joint-line symptoms with crepitus on loaded movement; an articular rather than muscular source.", "action": "Joint assessment and imaging if persistent." },
{ "id": "bd_adhesive_capsulitis", "confidence": "rare", "condition": "Adhesive capsulitis", "mimics": "Painful global restriction (shoulder-origin referral)", "distinguishing_feature": "Global passive and active restriction of the shoulder capsule; an adjacent-region condition that can refer toward the arm.", "action": "Assess shoulder capsule pattern; manage as a shoulder problem." },
{ "id": "bd_impingement", "confidence": "rare", "condition": "Subacromial impingement", "mimics": "Anterior shoulder pain spilling toward the arm", "distinguishing_feature": "Painful abduction arc and positive impingement signs at the shoulder; an adjacent-region source.", "action": "Shoulder examination; treat at the shoulder if confirmed." },
{ "id": "bd_charcot", "confidence": "rare", "condition": "Charcot (neuropathic) joint", "mimics": "Swollen joint with surprisingly little pain", "distinguishing_feature": "Marked joint destruction/swelling disproportionate to the (often reduced) pain, on a background of neuropathy (e.g. diabetes).", "action": "Imaging and management of the underlying neuropathy; specialist referral." }
]
}