DiagnosticTree/Olecranon
{
"schema_version": "2.1",
"region_id": "Olecranon",
"region_label": "Olecranon / Posterior Elbow Pain",
"red_flags": [
"Fluctuant swelling directly over the olecranon tip \u2014 olecranon bursitis; if with fever/erythema, septic bursitis is an emergency",
"Loss of active elbow extension or palpable gap in the triceps tendon \u2014 distal triceps rupture; urgent orthopaedic evaluation; look for flake sign on plain film",
"Pain only at terminal extension with hard end-feel, comfortable mid-range \u2014 elbow osteoarthritis with bony impingement; radiograph indicated",
"Young throwing athlete with focal olecranon tenderness \u2014 stress fracture; plain film then MRI if negative",
"Fever, warmth, erythema at the posterior elbow \u2014 septic bursitis or septic arthritis; emergency evaluation"
],
"broad_differential": [
{
"diagnosis": "Olecranon bursitis (aseptic or septic)",
"key_features": "Visible fluctuant swelling at olecranon tip; may be painless (aseptic) or painful with fever/erythema (septic); elbow ROM usually preserved; distinguish from TrP4 by presence of bursal fluid \u2014 TrP4 tenderness is deep to the aponeurosis with no fluctuance",
"reference": "Chung et al. 2025 (PMC12093526); Muscle:Triceps_Brachii differential"
},
{
"diagnosis": "Distal triceps tendon rupture / triceps tendinopathy",
"key_features": "Weakness or loss of active elbow extension; palpable gap at tendon; positive modified Campbell Thompson test for complete tear; flake sign on X-ray; TrP4 preserves full active extension strength",
"reference": "Chung et al. 2025 (PMC12093526)"
},
{
"diagnosis": "Elbow osteoarthritis (posterior compartment)",
"key_features": "Pain at terminal extension and/or maximum flexion only; comfortable mid-range; osteophytes on X-ray; stiffness; may cause ulnar neuropathy",
"reference": "Chung et al. 2025 (PMC12093526)"
},
{
"diagnosis": "C8\u2013T1 radiculopathy",
"key_features": "Objective neurological deficit (motor weakness, reflex change, dermatomal sensory loss, positive Spurling's) \u2014 must be present to diagnose; serratus posterior superior refers numbness into C8\u2013T1 distribution WITHOUT neurological deficit",
"reference": "Muscle:Serratus_Posterior differential"
}
],
"muscles": [
{
"id": "triceps_TrP4",
"label": "Triceps Brachii (distal attachment, near olecranon)",
"page": "Muscle:Triceps_Brachii",
"prior": 0.6,
"bold": true
},
{
"id": "serratus_posterior_superior",
"label": "Serratus Posterior Superior",
"page": "Muscle:Serratus_Posterior",
"prior": 0.4,
"bold": false
}
],
"questions": [
{
"id": "q1",
"text": "What is the full extent of your pain \u2014 beyond just the elbow tip?",
"type": "single",
"answers": [
{
"id": "q1a1",
"text": "Pain right at the elbow tip (olecranon) only \u2014 nothing above the elbow or down the forearm",
"likelihood_ratios": {
"triceps_TrP4": 7.5,
"serratus_posterior_superior": 0.3
}
},
{
"id": "q1a2",
"text": "Elbow tip pain plus aching in the back of the upper arm or shoulder",
"likelihood_ratios": {
"triceps_TrP4": 2.0,
"serratus_posterior_superior": 1.5
}
},
{
"id": "q1a3",
"text": "Elbow tip pain plus a deep ache under the shoulder blade that you can't quite reach, running down toward the little finger",
"likelihood_ratios": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 7.5
}
},
{
"id": "q1a4",
"text": "Elbow tip pain plus numbness or tingling down the inner forearm or into the little (5th) finger",
"likelihood_ratios": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 6.0
}
}
]
},
{
"id": "q2",
"text": "What activity or situation most reliably provokes or worsens the elbow tip pain?",
"type": "single",
"answers": [
{
"id": "q2a1",
"text": "Pushing things away, press-ups, dips, or straightening the elbow against resistance",
"likelihood_ratios": {
"triceps_TrP4": 6.5,
"serratus_posterior_superior": 0.35
}
},
{
"id": "q2a2",
"text": "Sustained postures \u2014 elbow held forward or unsupported for long periods (driving, writing, desk work)",
"likelihood_ratios": {
"triceps_TrP4": 3.0,
"serratus_posterior_superior": 2.0
}
},
{
"id": "q2a3",
"text": "History of prolonged coughing, respiratory illness, or breathing difficulties \u2014 pain started or worsened during or after",
"likelihood_ratios": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 7.0
}
},
{
"id": "q2a4",
"text": "Reaching behind yourself, carrying loads with arms extended, or sitting with shoulders elevated",
"likelihood_ratios": {
"triceps_TrP4": 0.5,
"serratus_posterior_superior": 5.5
}
}
]
},
{
"id": "q3",
"text": "Do you have any associated sensations \u2014 aching, numbness, or tingling \u2014 away from the elbow itself?",
"type": "single",
"answers": [
{
"id": "q3a1",
"text": "No radiation \u2014 the pain stays localised to the back of the elbow tip",
"likelihood_ratios": {
"triceps_TrP4": 4.5,
"serratus_posterior_superior": 0.4
}
},
{
"id": "q3a2",
"text": "Aching into the back of the upper arm, sometimes toward the back of the shoulder",
"likelihood_ratios": {
"triceps_TrP4": 2.5,
"serratus_posterior_superior": 3.0
}
},
{
"id": "q3a3",
"text": "Numbness or tingling down the inner (little-finger) side of the forearm or into the 5th digit",
"likelihood_ratios": {
"triceps_TrP4": 0.4,
"serratus_posterior_superior": 6.5
}
},
{
"id": "q3a4",
"text": "A sense of deep tenderness or fullness under the shoulder blade on the same side",
"likelihood_ratios": {
"triceps_TrP4": 0.35,
"serratus_posterior_superior": 7.0
}
}
]
},
{
"id": "q4",
"text": "Does pushing things away from you, or straightening the elbow against resistance, specifically reproduce the elbow tip pain?",
"type": "single",
"answers": [
{
"id": "q4a1",
"text": "Yes \u2014 the elbow tip specifically hurts when pushing, pressing, or extending against resistance",
"likelihood_ratios": {
"triceps_TrP4": 6.0,
"serratus_posterior_superior": 0.35
}
},
{
"id": "q4a2",
"text": "No \u2014 straightening the elbow under load does not change the pain; posture or breathing matters more",
"likelihood_ratios": {
"triceps_TrP4": 0.4,
"serratus_posterior_superior": 5.5
}
},
{
"id": "q4a3",
"text": "Unsure / pain is present with most activities regardless of elbow loading",
"likelihood_ratios": {
"triceps_TrP4": 1.0,
"serratus_posterior_superior": 1.0
}
}
]
},
{
"id": "q5",
"text": "Where is the most tender spot when you or a clinician press firmly in the area?",
"type": "single",
"answers": [
{
"id": "q5a1",
"text": "Right at the olecranon tip \u2014 deep, spot tenderness through the tendon; no swelling or fluctuance",
"likelihood_ratios": {
"triceps_TrP4": 5.5,
"serratus_posterior_superior": 0.4
}
},
{
"id": "q5a2",
"text": "Deep under the shoulder blade \u2014 tenderness only accessible when the arm is swung well forward",
"likelihood_ratios": {
"triceps_TrP4": 0.3,
"serratus_posterior_superior": 7.0
}
},
{
"id": "q5a3",
"text": "In the back of the upper arm muscle belly, somewhere above the elbow",
"likelihood_ratios": {
"triceps_TrP4": 3.5,
"serratus_posterior_superior": 2.0
}
},
{
"id": "q5a4",
"text": "Not well localised \u2014 pain felt but hard to pinpoint on palpation",
"likelihood_ratios": {
"triceps_TrP4": 1.2,
"serratus_posterior_superior": 1.2
}
}
]
}
],
"treatment_dag": {
"triceps_TrP4": [],
"serratus_posterior_superior": [
"triceps_TrP4"
]
}
}