DiagnosticTree/Olecranon
{
"model": "bayesian_lr_scoring",
"version": "1.0",
"description": "Probabilistic scoring model for posterior elbow / olecranon pain. Two muscles drawn from T&S Vol.1: Triceps Brachii (attachment TrP at the distal insertion, TrP4) and Serratus Posterior Superior (olecranon accent in spillover zone). Triceps TrP4 is the bold primary referrer (prior 0.60); serratus posterior superior is the non-bold spillover source (prior 0.40).",
"thresholds": {
"early_exit_posterior": 0.82,
"early_exit_gap": 0.25,
"pairwise_trigger": 0.15
},
"muscles": {
"triceps_TrP4": {
"label": "Triceps Brachii (distal attachment)",
"prior": 0.6,
"page": "Muscle:Triceps_Brachii",
"key_trp_note": "This is an attachment TrP \u2014 almost always secondary to a central TrP in the long, lateral, or deep medial head of triceps. Primary treatment must be directed at the responsible central TrP, not the olecranon attachment site itself. Palpate back along the induration from the olecranon toward the muscle belly to find the driver. Latissimus dorsi and serratus posterior superior are key TrP sources that can drive satellite TrPs in the triceps \u2014 always consider them when triceps TrPs recur.",
"subtitle": "Focal tender spot at the olecranon tip, deep through the tendon; worse on pushing or straightening the elbow against resistance; no bursal swelling"
},
"serratus_posterior_superior": {
"label": "Serratus Posterior Superior",
"prior": 0.4,
"page": "Muscle:Serratus_Posterior",
"key_trp_note": "Serratus posterior superior TrPs refer a wide arc: deep under the scapula (inaccessible at rest \u2014 scapula must be fully abducted to palpate) \u2192 posterior deltoid and triceps region \u2192 olecranon accent \u2192 ulnar forearm \u2192 5th digit. The olecranon pain is one stop in this wider pattern. Scalene TrPs are the primary driver of serratus posterior superior satellite TrPs \u2014 always examine the neck. Treat scalenes first if found.",
"subtitle": "Olecranon pain is part of a wide arc: deep scapular ache you cannot reach \u2192 posterior arm \u2192 elbow accent \u2192 ulnar forearm \u2192 5th digit; respiratory overload history"
}
},
"questions": [
{
"id": "q_pain_extent",
"text": "What is the full extent of the pain \u2014 beyond just the elbow tip?",
"sublabel": "Choose the description that best captures the whole pattern",
"type": "choice",
"answers": [
{
"id": "olecranon_only",
"label": "Elbow tip only \u2014 pain stays right at the back of the elbow; nothing above or below",
"sublabel": "No radiation up into the arm or down into the forearm",
"lr": {
"triceps_TrP4": 7.5,
"serratus_posterior_superior": 0.25
}
},
{
"id": "elbow_plus_upper_arm",
"label": "Elbow tip plus aching in the back of the upper arm or toward the shoulder",
"sublabel": "Pain extends proximally into the posterior arm",
"lr": {
"triceps_TrP4": 2.5,
"serratus_posterior_superior": 1.5
}
},
{
"id": "wide_arc_scapula_to_finger",
"label": "Elbow tip is part of a wide arc \u2014 deep under the shoulder blade, through the arm, down to the little finger",
"sublabel": "The scapular ache and arm referral are present alongside the elbow pain",
"lr": {
"triceps_TrP4": 0.2,
"serratus_posterior_superior": 8.0
}
},
{
"id": "elbow_plus_ulnar_forearm",
"label": "Elbow tip plus aching or numbness down the inner (little-finger) side of the forearm",
"sublabel": "Pain or numbness tracks down toward the 5th digit",
"lr": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 6.5
}
}
]
},
{
"id": "q_provocation",
"text": "What activity or situation most reliably provokes or worsens the elbow pain?",
"sublabel": "Choose the best match",
"type": "choice",
"answers": [
{
"id": "pushing_pressing",
"label": "Pushing things away, press-ups, dips, or straightening the elbow against resistance",
"sublabel": "Any activity requiring forceful elbow extension",
"lr": {
"triceps_TrP4": 7.0,
"serratus_posterior_superior": 0.3
}
},
{
"id": "sustained_forward_elbow",
"label": "Sustained postures with the elbow held forward or unsupported for long periods",
"sublabel": "Desk work, driving, writing \u2014 elbow out in front without rest",
"lr": {
"triceps_TrP4": 3.5,
"serratus_posterior_superior": 1.5
}
},
{
"id": "respiratory_or_cough",
"label": "During or after a period of prolonged coughing, respiratory illness, or breathing difficulties",
"sublabel": "Pain started or significantly worsened with a respiratory episode",
"lr": {
"triceps_TrP4": 0.25,
"serratus_posterior_superior": 8.0
}
},
{
"id": "reaching_overhead",
"label": "Reaching behind, carrying with arms extended, or sitting with shoulders elevated at a high desk",
"sublabel": "Overhead or reaching postures",
"lr": {
"triceps_TrP4": 0.5,
"serratus_posterior_superior": 5.5
}
}
]
},
{
"id": "q_elbow_loading",
"text": "Does straightening the elbow against resistance \u2014 or pushing something away \u2014 specifically reproduce the elbow tip pain?",
"sublabel": "Resisted elbow extension test",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes \u2014 elbow tip pain is specifically reproduced by pushing or resisted extension",
"lr": {
"triceps_TrP4": 6.0,
"serratus_posterior_superior": 0.3
}
},
{
"id": "no",
"label": "No \u2014 elbow loading does not change the pain; posture or breathing matters more",
"lr": {
"triceps_TrP4": 0.35,
"serratus_posterior_superior": 5.5
}
}
]
},
{
"id": "q_scapular_ache",
"text": "Is there a deep aching under the shoulder blade on the same side \u2014 an ache you cannot quite reach even when pressing on it?",
"sublabel": "The scapula covers the source; the ache is felt underneath it",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes \u2014 a deep unreachable ache under the shoulder blade is present",
"lr": {
"triceps_TrP4": 0.25,
"serratus_posterior_superior": 8.0
}
},
{
"id": "no",
"label": "No \u2014 no scapular ache; pain is at the elbow only or in the arm",
"lr": {
"triceps_TrP4": 2.5,
"serratus_posterior_superior": 0.5
}
}
]
},
{
"id": "q_digit_symptoms",
"text": "Is there any numbness, tingling, or aching into the little (5th) finger or the inner edge of the ring finger?",
"sublabel": "Referred C8\u2013T1 sensation into the ulnar digits \u2014 present in serratus posterior superior spillover",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes \u2014 numbness or aching reaches the 5th finger or ulnar ring finger",
"lr": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 7.0
}
},
{
"id": "no",
"label": "No \u2014 no finger symptoms",
"lr": {
"triceps_TrP4": 1.8,
"serratus_posterior_superior": 0.6
}
}
]
},
{
"id": "q_swelling_check",
"text": "Is there any visible swelling or a soft fluctuant lump at the tip of the elbow?",
"sublabel": "Olecranon bursitis screen \u2014 if present, this algorithm does not apply",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes \u2014 visible swelling or fluctuance at the olecranon",
"lr": {
"triceps_TrP4": 0.1,
"serratus_posterior_superior": 0.1
}
},
{
"id": "no",
"label": "No \u2014 no swelling; deep spot tenderness only",
"lr": {
"triceps_TrP4": 2.0,
"serratus_posterior_superior": 1.5
}
}
]
},
{
"id": "q_extension_strength",
"text": "Can the patient fully straighten the elbow against gravity \u2014 is elbow extension strength intact?",
"sublabel": "Distal triceps rupture screen \u2014 loss of active extension strength is a red flag",
"type": "binary",
"answers": [
{
"id": "yes",
"label": "Yes \u2014 full active extension against gravity; strength is intact",
"lr": {
"triceps_TrP4": 2.0,
"serratus_posterior_superior": 1.8
}
},
{
"id": "no",
"label": "No \u2014 cannot fully extend the elbow against gravity; weakness present",
"lr": {
"triceps_TrP4": 0.1,
"serratus_posterior_superior": 0.1
}
}
]
},
{
"id": "q_tenderness_location",
"text": "Where is the most tender spot on palpation?",
"sublabel": "Press firmly in each location to find the most exquisite point",
"type": "choice",
"answers": [
{
"id": "olecranon_tip_deep",
"label": "Right at the olecranon tip \u2014 deep, through-the-tendon spot tenderness; no fluid",
"sublabel": "Pain is deep to the skin and subcutaneous tissue, through the aponeurosis",
"lr": {
"triceps_TrP4": 6.0,
"serratus_posterior_superior": 0.35
}
},
{
"id": "under_scapula",
"label": "Deep under the shoulder blade \u2014 only accessible when the arm is swung well forward",
"sublabel": "Tenderness found only when the scapula is abducted away from the ribs",
"lr": {
"triceps_TrP4": 0.25,
"serratus_posterior_superior": 8.0
}
},
{
"id": "posterior_arm_belly",
"label": "In the back of the upper arm muscle belly \u2014 somewhere above the elbow in the triceps",
"sublabel": "A taut band or nodule in the posterior arm, not at the elbow tip itself",
"lr": {
"triceps_TrP4": 3.5,
"serratus_posterior_superior": 1.5
}
},
{
"id": "not_well_localised",
"label": "Not well localised \u2014 pain is felt but hard to pinpoint on palpation",
"lr": {
"triceps_TrP4": 1.2,
"serratus_posterior_superior": 1.2
}
}
]
}
],
"pairwise": [
{
"id": "pw_triceps_serratus",
"pair": [
"triceps_TrP4",
"serratus_posterior_superior"
],
"text": "Tiebreaker \u2014 Triceps (distal attachment) vs Serratus Posterior Superior",
"question": "Does pushing or pressing specifically reproduce the elbow tip pain, OR is the elbow pain part of a wider pattern that includes a deep scapular ache or 5th-finger numbness?",
"sublabel": "The key question: is this a local loading problem, or a wide referred pain pattern?",
"answers": [
{
"id": "loading_reproduces",
"label": "Pushing / pressing specifically reproduces the olecranon pain \u2014 local loading problem",
"lr": {
"triceps_TrP4": 6.0,
"serratus_posterior_superior": 0.25
}
},
{
"id": "wide_pattern",
"label": "Elbow pain is part of a wider pattern \u2014 scapular ache, arm referral, or 5th-finger numbness present",
"lr": {
"triceps_TrP4": 0.25,
"serratus_posterior_superior": 6.0
}
}
]
}
],
"treatment_dag": {
"edges": [
{
"from": "serratus_posterior_superior",
"to": "triceps_TrP4",
"type": "key_satellite",
"label": "Serratus posterior superior TrPs can drive satellite TrPs in the triceps \u2014 treat serratus first; triceps attachment tenderness may resolve without direct treatment"
}
],
"edge_type_labels": {
"key_satellite": "Treat first \u2014 key TrP driving satellite",
"functional_unit": "Treat concurrently in same session",
"secondary_load": "Treat after primary resolves",
"antagonist_risk": "\u26a0 Treat in alternating cycles \u2014 reactive activation risk"
}
},
"region_label": "Posterior Elbow / Olecranon Pain",
"emergency": [
{
"id": "rf-e1",
"label": "Acute compartment syndrome of the forearm or arm",
"question": "Severe pain disproportionate to the apparent injury, rapidly worsening and unrelieved by rest or elevation? Pain sharply increased by passive extension of the fingers or wrist? Forearm or arm feels tense or woody on palpation? Paraesthesia, pallor, or weakness of the hand developing? Recent crush injury, fracture, tight cast, or circumferential burn?"
},
{
"id": "rf-e2",
"label": "Septic arthritis of the elbow joint",
"question": "Acutely hot, swollen, and exquisitely tender elbow with severe restriction of ALL movements \u2014 both flexion-extension and forearm rotation? Fever, rigors, or systemically unwell? Recent bacteraemia, penetrating injury to the elbow, intravenous drug use, or immunosuppression? Note: septic arthritis restricts the whole joint; olecranon bursitis preserves elbow ROM."
},
{
"id": "rf-e3",
"label": "Cardiac ischaemia referred to the left arm and elbow",
"question": "Left-sided posterior elbow or inner arm pain in a patient with cardiac risk factors (age > 45, hypertension, diabetes, smoking, known coronary disease)? Pain associated with exertion, chest tightness, breathlessness, diaphoresis, or jaw pain? Pain unrelated to elbow movement or palpation?"
}
],
"urgent": [
{
"id": "rf-u1",
"label": "Septic olecranon bursitis",
"question": "Erythema, warmth, and tenderness localised to the olecranon bursa with fever or systemically unwell? Broken skin, puncture wound, or abrasion over the olecranon tip? Immunocompromised patient (diabetes, renal failure, corticosteroid use)? Needs aspiration, Gram stain, culture, and antibiotics \u2014 do not attempt TrP examination until infection excluded."
},
{
"id": "rf-u2",
"label": "Fracture \u2014 olecranon, radial head, or distal humerus",
"question": "Significant trauma \u2014 fall on outstretched hand, direct blow to the posterior elbow, or forced hyperextension? Point bony tenderness directly over the olecranon process, radial head, or medial/lateral epicondyle? Visible deformity or inability to bear weight through the arm? Flake sign (small avulsion fragment posterior to olecranon) on plain X-ray?"
},
{
"id": "rf-u3",
"label": "Elbow dislocation",
"question": "Significant trauma with immediate loss of elbow function? Visible posterior deformity \u2014 olecranon prominent posteriorly, loss of normal triangular relationship between epicondyles and olecranon? Neurovascular compromise of the hand (check radial pulse, median and ulnar nerve sensation)?"
},
{
"id": "rf-u4",
"label": "Distal triceps tendon rupture",
"question": "Acute posterior elbow pain immediately after an eccentric load \u2014 fall on outstretched hand, or forced elbow flexion against an actively contracting triceps? Inability to actively extend the elbow against gravity (modified Campbell Thompson test: no extension when triceps compressed in prone position)? Palpable gap or defect in the tendon just above the olecranon? Flake sign on X-ray?"
},
{
"id": "rf-u5",
"label": "Cellulitis of the posterior elbow",
"question": "Spreading erythema, warmth, and diffuse swelling of the skin AROUND the posterior elbow \u2014 not confined to the bursa alone? Tender regional lymph nodes (epitrochlear or axillary)? Fever or systemic signs? Needs antibiotic treatment \u2014 distinguish from bursitis by extent of erythema spreading beyond the bursa margin."
},
{
"id": "rf-u6",
"label": "Osteomyelitis of the olecranon",
"question": "Deep, constant bone pain over the olecranon that is present at rest and worsening, not related to elbow movement? Fever, elevated CRP or ESR, or leucocytosis? Child, immunocompromised patient, or patient with sickle cell disease or recent bacteraemia? X-ray may be normal in early osteomyelitis \u2014 MRI is the investigation of choice."
}
],
"broad_differential": [
{
"id": "bd-1",
"condition": "Olecranon bursitis \u2014 aseptic",
"confidence": "common",
"mimics": "Posterior elbow pain and swelling at the olecranon tip; easily confused with deep TrP attachment tenderness",
"distinguishing_feature": "Visible fluctuant swelling directly over the olecranon tip is the key finding \u2014 TrP4 attachment tenderness is deep to the aponeurosis with no palpable fluid and no swelling. Aseptic bursitis may be painless or only mildly tender; ROM is preserved. Causes include direct trauma, crystal deposition (gout, pseudogout), and systemic disease (RA, SLE, uraemia).",
"action": "Aspiration only when diagnosis is unclear or for symptom relief in refractory cases \u2014 routine aspiration risks introducing infection. NSAIDs, padding, and activity modification first-line. If gout suspected, check serum urate and consider urate-lowering therapy."
},
{
"id": "bd-2",
"condition": "Olecranon bursitis \u2014 septic",
"confidence": "uncommon",
"mimics": "Posterior elbow pain and localised swelling with erythema \u2014 can resemble a hot, irritable TrP presentation",
"distinguishing_feature": "Fever present in 20\u201386% of cases. Erythema and warmth extending over the bursa. Pathogen identified on bursal fluid culture (Staphylococcus aureus most common). Distinguish from septic arthritis: bursitis preserves elbow ROM; septic joint restricts all movements. MRI distinguishes bursitis from osteomyelitis or septic arthritis if uncertain.",
"action": "Urgent aspiration for Gram stain and culture. Antibiotics targeting skin flora. Surgical drainage for cases resistant to antibiotics. Do not perform TrP examination until infection is excluded."
},
{
"id": "bd-3",
"condition": "Triceps tendinopathy",
"confidence": "uncommon",
"mimics": "Insertional posterior elbow pain at the olecranon, worsened by resisted elbow extension \u2014 closely overlaps with triceps TrP4 attachment pattern",
"distinguishing_feature": "Tenderness at the triceps tendon insertion on the olecranon, reproduced by resisted extension and passive stretch (full elbow flexion). Imaging (ultrasound or MRI) shows tendon thickening, disorganised fibres, or partial tearing \u2014 TrP4 produces spot tenderness through the aponeurosis without tendon structural change. TrP4 is almost always secondary to a central TrP; tendinopathy may coexist and be driven by the same taut band tension.",
"action": "Ultrasound or MRI to confirm structural tendon change. Eccentric loading programme. Address central triceps TrPs concurrently \u2014 taut band tension at the insertion is a perpetuating factor for enthesopathy."
},
{
"id": "bd-4",
"condition": "Distal triceps tendon rupture (partial or complete)",
"confidence": "rare",
"mimics": "Acute posterior elbow pain and swelling after eccentric load \u2014 early presentation before weakness becomes obvious can resemble severe TrP activation",
"distinguishing_feature": "Loss of active elbow extension against gravity distinguishes complete rupture. Palpable gap in the tendon just proximal to the olecranon. Flake sign on plain X-ray (small avulsion fragment posterior to olecranon). Modified Campbell Thompson test: with elbow flexed 90\u00b0 in prone position, compression of triceps belly produces no extension in complete tear. MRI confirms location and extent. Most common in males and after eccentric load (fall on outstretched hand).",
"action": "Plain X-ray first (flake sign). MRI for extent. Orthopaedic referral \u2014 complete ruptures require surgical repair. Partial tears without active extension deficit may be managed conservatively with splinting."
},
{
"id": "bd-5",
"condition": "Elbow osteoarthritis \u2014 posterior compartment",
"confidence": "uncommon",
"mimics": "Posterior elbow pain, particularly in manual workers or throwing athletes \u2014 may coexist with TrP pain and be mistakenly attributed entirely to TrPs",
"distinguishing_feature": "Pain specifically at terminal extension (olecranon apex impacting the fossa) and at maximum flexion (anterior compartment); mid-range motion is relatively pain-free until advanced disease. Osteophytes at the olecranon apex and olecranon fossa on plain X-ray or CT. Joint space is generally preserved in early stages. Loose bodies may cause locking. Posteromedial capsule contracture can compress the ulnar nerve, causing 4th\u20135th finger numbness.",
"action": "Plain X-ray lateral view (anterior and posterior osteophytes, loose bodies). CT for preoperative planning. Conservative: NSAIDs, activity modification, physiotherapy. Surgical: arthroplasty (debridement, osteophyte removal) for younger patients; total elbow replacement reserved for advanced disease in older patients."
},
{
"id": "bd-6",
"condition": "Posterior impingement / valgus extension overload syndrome",
"confidence": "uncommon",
"mimics": "Posterior elbow pain in throwing athletes or racquet sports players \u2014 same population as triceps TrP overuse activation",
"distinguishing_feature": "Pain specifically at terminal extension in throwing athletes; posteromedial osteophyte of the olecranon on X-ray. Hard end-feel at terminal extension (bony block). Often associated with medial collateral ligament insufficiency \u2014 valgus laxity on stress testing. Calcification of the MCL in >50% of cases. Distinguish from TrP pain by the hard end-feel and clear throwing-arc provocation.",
"action": "Plain X-ray and CT for osteophyte size and loose bodies. Assess MCL integrity (valgus stress view, MRI arthrogram). Arthroscopic debridement of posteromedial osteophyte. MCL reconstruction if concurrent instability."
},
{
"id": "bd-7",
"condition": "Olecranon stress fracture",
"confidence": "rare",
"mimics": "Insidious posterior elbow pain in young throwing athletes \u2014 identical history to triceps TrP overuse; both worsen with throwing volume",
"distinguishing_feature": "Point tenderness directly over the olecranon process (bone, not tendon). Pain increases with valgus stress or extension loading in throwing. Plain X-ray normal in early stages \u2014 MRI is the investigation of choice (bone marrow oedema). CT confirms fracture line when MRI equivocal. Risk increased by metabolic bone disease, low bone density, or rapid increase in throwing load.",
"action": "Plain X-ray first (may be normal). MRI if clinical suspicion high. Activity restriction and throwing cessation 6\u20138 weeks minimum. Surgical fixation for complete fractures or failed conservative management."
},
{
"id": "bd-8",
"condition": "Gout / crystal arthropathy at the elbow",
"confidence": "uncommon",
"mimics": "Acute severe posterior elbow pain with swelling and redness \u2014 episodic flares can superficially resemble an acutely activated TrP in a susceptible patient",
"distinguishing_feature": "Severe episodic pain in a single joint; swelling and erythema over the elbow. Needle-shaped crystals with negative birefringence on polarising microscopy of joint fluid confirm gout. Elevated serum urate supports the diagnosis but is not diagnostic during an acute flare (urate may be normal). Tophaceous deposits around the olecranon in chronic gout. Must be distinguished from septic arthritis \u2014 joint aspiration may be required.",
"action": "Joint aspiration for crystal identification and culture (to exclude sepsis). Acute management: colchicine, NSAIDs, or short-course corticosteroids. Long-term: urate-lowering therapy (allopurinol, febuxostat) once acute episode resolved. Surgical debridement for large tophi causing mechanical problems."
}
]
}