Anatomy of elbow joint orthopedic exam
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I now have comprehensive information from Miller's Review of Orthopaedics and Firestein & Kelley's Textbook of Rheumatology. Let me compile the complete answer.
Elbow Joint - Anatomy & Orthopedic Examination
Sources: Miller's Review of Orthopaedics 9th Ed.; Firestein & Kelley's Textbook of Rheumatology
Bony Anatomy
The elbow is composed of three distinct articulations within a shared synovial cavity:
| Articulation | Bones | Function |
|---|---|---|
| Humeroulnar | Trochlea of humerus + trochlear notch of ulna | Primary hinge (flexion/extension) |
| Humeroradial (Radiocapitellar) | Capitulum of humerus + radial head | Flexion + rotation; transmits 60% of axial load in full extension |
| Proximal Radioulnar | Radial head + radial notch of ulna | Pronation/supination |
Key bony landmarks:
- Distal humerus: medial and lateral columns; articular surface angled 30° anterior to humeral shaft axis
- Medial epicondyle - attachment of common flexor tendon (FCR, FCU, palmaris longus, FDS, pronator teres)
- Lateral epicondyle - attachment of common extensor tendon (ECRB, EDC, ECU, anconeus)
- Olecranon - posterior projection of ulna forming the hinge
- Coronoid process - anterior ulna; resists posterior dislocation
- Radial head - secondary stabilizer against valgus stress
Normal Range of Motion
| Movement | Normal Range | Functional Range |
|---|---|---|
| Flexion | 0 - 150° | 30 - 130° |
| Extension | 0° (full) | 30 - 130° |
| Pronation | 0 - 80-85° | 50° |
| Supination | 0 - 80-85° | 50° |
- Valgus carrying angle: 5-10° in men; 10-15° in women
- Cubitus valgus (increased) vs. cubitus varus (decreased/"gunstock deformity")
Ligamentous Anatomy
Medial (Ulnar) Collateral Ligament (MCL/UCL) Complex
Three bundles: anterior, posterior, and transverse.
- Anterior bundle = PRIMARY restraint to valgus stress throughout functional ROM
- Origin: posterior medial epicondyle → Insertion: sublime tubercle of medial coronoid process
- Secondary restraint: radial head
- Posterior bundle = primary restraint to valgus in maximal flexion
- Transverse bundle = minimal contribution to stability
Lateral Collateral Ligament (LCL) Complex
Four components:
- Radial collateral ligament (RCL)
- Lateral ulnar collateral ligament (LUCL) - PRIMARY restraint to varus stress and external rotational stress (posterolateral rotatory instability/PLRI)
- Accessory collateral ligament
- Annular ligament - encircles radial head; maintains radioulnar articulation
Musculature
Flexors (nerve root C5-C6)
- Biceps brachii (musculocutaneous n.) - primary supinator, secondary flexor
- Brachialis (musculocutaneous n.) - primary flexor
- Brachioradialis (radial n.)
Extensors
- Triceps brachii (radial n., C7-C8) - primary extensor
- Anconeus (radial n.) - assists extension; intact anconeus may preserve some extension even after distal triceps rupture
Common Extensor Tendon (from lateral epicondyle)
- ECRB (most commonly implicated in lateral epicondylitis), ECRL, EDC, ECU, anconeus
Common Flexor-Pronator Mass (from medial epicondyle)
- FCR, FCU, palmaris longus, FDS, pronator teres
Neurovascular Anatomy
| Structure | Location | Clinical Relevance |
|---|---|---|
| Ulnar nerve | Medial - cubital tunnel (behind medial epicondyle) | Cubital tunnel syndrome; at risk in medial approaches |
| Radial nerve (divides → PIN + superficial branch) | Lateral, deep to brachioradialis | At risk in lateral epicondylitis surgery; radial tunnel syndrome |
| Median nerve | Anterior | Pronator syndrome; anterior interosseous nerve (AIN) syndrome |
| Lateral antebrachial cutaneous nerve (LABCN) | Lateral | At risk in single-incision distal biceps repair |
| Brachial artery | Anterior cubital fossa | Splits into radial + ulnar arteries at level of radial neck |
Orthopedic Examination
1. Inspection
- Carrying angle deformity (cubitus valgus/varus)
- Swelling, ecchymosis, skin changes
- Olecranon bursa prominence (bursitis)
- Skin: psoriatic plaques, rheumatoid nodules, tophi
- Muscle bulk asymmetry (biceps "Popeye" sign in distal biceps rupture)
2. Palpation
Technique: Examiner places thumb between lateral epicondyle and olecranon in the lateral para-olecranon groove; one or two fingers in the corresponding medial groove. Passively move through flexion, extension, and rotation while palpating.
Key structures to palpate:
- Medial epicondyle - tenderness = medial epicondylitis (golfer's elbow)
- Lateral epicondyle - tenderness = lateral epicondylitis (tennis elbow)
- Olecranon / olecranon bursa - fluctuance, nodules, tophi
- Radial head - rotation palpation; tenderness after radial head fracture
- Cubital tunnel - ulnar nerve tenderness/Tinel's
- Synovial swelling bulges under examiner's thumb on passive extension; synovitis most easily palpated posteriorly between olecranon and distal humerus
3. Range of Motion
- Active then passive in all planes (compare bilateral)
- Limitation of extension = synovitis/effusion (most sensitive sign)
- Mechanical block to rotation = assess for radial head fracture or loose body
4. Strength Testing
| Muscle/Motion | Nerve Root | Test |
|---|---|---|
| Elbow flexion (biceps) | C5-C6 | Resisted supinated flexion |
| Elbow flexion (brachialis) | C5-C6 | Resisted pronated flexion |
| Elbow extension (triceps) | C7-C8 | Resisted extension from 90° |
| Wrist extension | C6-C7 | Resisted dorsiflexion |
| Wrist flexion | C7-C8 | Resisted palmar flexion |
Special Tests
Lateral Elbow
| Test | Technique | Positive Sign | Diagnosis |
|---|---|---|---|
| Cozen's Test | Elbow at 90°, patient makes fist, pronates forearm, extends wrist against resistance | Pain at lateral epicondyle | Lateral epicondylitis |
| Mill's Test | Passive wrist flexion with elbow extended + forearm pronated | Pain at lateral epicondyle | Lateral epicondylitis |
| Middle Finger Extension Test | Examiner resists extension of middle finger at PIP with elbow extended | Pain at lateral epicondyle/common extensor origin | Lateral epicondylitis (ECRB) |
| Pivot Shift Test of the Elbow | Supinate forearm, apply valgus stress + axial load through elbow while moving from extension to flexion | Palpable subluxation/apprehension of radial head at ~40° flexion | LUCL injury / PLRI |
Medial Elbow
| Test | Technique | Positive Sign | Diagnosis |
|---|---|---|---|
| Valgus Stress Test | Elbow at 20-30° flexion (to unlock olecranon from fossa), apply valgus force | Medial pain or laxity > contralateral | MCL injury |
| Moving Valgus Stress Test | Stabilize humerus, apply constant valgus force, rapidly move elbow from full flexion to 30° extension | Reproduction of medial pain between 70-120° of flexion ("shear angle") | MCL insufficiency (highly sensitive in throwers) |
| Valgus Extension Overload Test | Extend elbow rapidly while applying valgus stress | Posteromedial olecranon pain | Posteromedial impingement / valgus overload syndrome |
| Milking Maneuver | Patient reaches under affected arm to pull their own thumb with elbow in flexion; examiner applies valgus stress | Medial pain/instability | MCL injury |
| Golfer's Elbow Test | Resisted wrist flexion + forearm pronation with elbow extended | Pain at medial epicondyle | Medial epicondylitis |
Nerve Tests
| Test | Technique | Positive Sign | Diagnosis |
|---|---|---|---|
| Tinel's Sign (cubital tunnel) | Tap ulnar nerve in cubital tunnel (posterior medial epicondyle) | Tingling in ring + little fingers | Cubital tunnel syndrome (ulnar neuropathy) |
| Elbow Flexion Test | Full elbow flexion + wrist extension for 60 sec | Ulnar paresthesias | Cubital tunnel syndrome |
| Tinel's Sign (radial tunnel) | Tap over radial tunnel (5 cm distal to lateral epicondyle) | Tingling/deep ache in dorsal forearm | Radial tunnel syndrome / PIN compression |
Tendon Tests
| Test | Technique | Positive Sign | Diagnosis |
|---|---|---|---|
| Hook Test | With elbow at 90° + forearm supinated, hook finger under biceps tendon from lateral side | Inability to hook cord-like structure | Distal biceps tendon rupture (100% sensitive) |
| Biceps Squeeze Test | Squeeze biceps muscle belly with elbow at 60-80° flexion | No forearm supination | Distal biceps rupture |
| Triceps Squeeze Test | Squeeze triceps with elbow at 90° | No extension | Distal triceps rupture |
| "Flake Sign" on X-ray | Bone fragment at posterior olecranon on lateral radiograph | Present | Pathognomonic for distal triceps avulsion; warrants MRI |
High-Yield Clinical Correlations
| Finding | Key Anatomy | Implication |
|---|---|---|
| MCL incompetence | Anterior bundle UCL | Valgus instability; Tommy John surgery (UCL reconstruction); ~80% of athletes return to sport at 1 year |
| LUCL incompetence | LUCL | Posterolateral rotatory instability (PLRI); diagnosed by lateral pivot-shift |
| "Terrible Triad" | Radial head + coronoid + capsule + LCL | Elbow dislocation with radial head and coronoid fractures; treat all three |
| Anteromedial coronoid fracture | Coronoid process anteromedial facet | Varus posteromedial rotatory instability |
| Distal biceps rupture | Radial tuberosity footprint (radial side) | Supination strength > flexion strength lost; abnormal Hook test |
| Lateral epicondylitis | ECRB tendon origin (degenerative tendinopathy) | Angiofibroblastic hyperplasia on histology; no inflammatory infiltrate |
| Chronic MCL incompetence | UCL + olecranon fossa | Valgus overload syndrome: posteromedial osteophytes, loose bodies, capitellar wear |
| Postoperative positioning | After LUCL repair | Immobilize in PRONATION to protect lateral repair |
References: Miller's Review of Orthopaedics 9th Edition, p. 723-740; Firestein & Kelley's Textbook of Rheumatology, p. 765
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