Classification
- Type: Synovial hinge (uniaxial)
- Degrees of freedom: 1 (flexion/extension)
- Region: Elbow complex (along with the humeroradial and proximal radioulnar articulations, all sharing a common joint capsule)
Articular Surfaces
- Trochlea of the humerus (convex, spool-shaped): A pulley-shaped surface on the distal medial humerus with a central groove flanked by medial and lateral ridges. The medial ridge extends further distally than the lateral, producing the normal valgus carrying angle. Covered with hyaline cartilage.
- Trochlear notch of the ulna (concave): A deep, C-shaped notch formed by the olecranon process posteriorly and the coronoid process anteriorly. The notch wraps nearly 180° around the trochlea, providing significant bony stability. A transverse ridge bisects the notch, fitting into the trochlear groove.
Movements and ROM
Carrying angle: In full extension with the forearm supinated, the forearm angles laterally relative to the humerus. Normal: 5–10° in males, 10–15° in females. An increased carrying angle (cubitus valgus) increases stretch on the ulnar nerve and MCL stress. A decreased angle (cubitus varus — "gunstock deformity") typically follows a malunited supracondylar fracture.
Capsular Pattern
Flexion > Extension
When the humeroulnar capsule is restricted, flexion loss exceeds extension loss. This pattern is seen in OA, post-immobilization capsulitis, and post-traumatic stiffness. It is the same proportional pattern as the tibiofemoral joint.
Resting Position
- 70° flexion, 10° supination
- Maximum capsular volume; used for joint mobilization and joint play assessment
Close-Packed Position
- Full extension with full supination
- Maximum bony congruence, capsule and ligaments at maximum tension
- Used for ligament integrity testing; do NOT mobilize in this position
End-Feels
| Movement |
Normal End-Feel |
Type |
| Flexion |
Tissue approximation (soft) |
Forearm muscles contacting the anterior arm muscles. In lean individuals, bony contact (coronoid into coronoid fossa) may produce a hard end-feel. |
| Extension |
Bony (hard) |
Olecranon process contacts the olecranon fossa of the humerus |
Abnormal end-feels: A springy end-feel in flexion or extension suggests a loose body (cartilage fragment, osteophyte) blocking motion. A capsular (firm) end-feel replacing the normal bony end-feel in extension suggests capsular contracture. An empty end-feel suggests acute fracture or infection.
Ligaments
Ulnar (Medial) Collateral Ligament (UCL/MCL)
- Attachments: Three bands — anterior band (strongest, most important): medial epicondyle → coronoid process (sublime tubercle); posterior band: medial epicondyle → olecranon; transverse band: coronoid → olecranon (does not cross the joint — provides no stability against valgus stress)
- Function: The primary restraint against valgus stress at the elbow. The anterior band is the most critical component — it is taut throughout the full ROM and is the structure damaged in "Tommy John" injuries. The posterior band contributes primarily in flexion beyond 90°.
- Injury mechanism: Repetitive valgus stress — overhead throwing (the late cocking and early acceleration phases produce enormous valgus force at the medial elbow). Also acute valgus injury from a fall on an outstretched hand. Common in baseball pitchers, javelin throwers, and other overhead athletes.
- Grade classification: Grade I — local medial tenderness, stable on valgus stress; Grade II — medial opening with firm end-feel; Grade III — significant medial opening with soft end-feel, complete rupture
- Assessment test: Valgus stress test at 20–30° flexion (slight flexion unlocks the olecranon from its fossa, isolating the UCL). Moving valgus stress test (valgus force applied while the elbow is moved from flexion to extension — pain at 70–120° indicates anterior band involvement).
- Condition link: UCL sprain, UCL insufficiency (pitcher's elbow), conditions/medial-epicondylitis
Radial (Lateral) Collateral Ligament (RCL)
- Attachments: Lateral epicondyle → annular ligament. The lateral ulnar collateral ligament (LUCL) is the most important component — it continues from the lateral epicondyle to the supinator crest of the ulna.
- Function: Primary restraint against varus stress. The LUCL is the primary restraint against posterolateral rotatory instability (PLRI) — the most common pattern of recurrent elbow instability.
- Injury mechanism: Varus force, or more commonly, elbow dislocation that tears the LUCL. PLRI results from LUCL insufficiency and produces a giving-way sensation during activities that load the extended, supinated forearm.
- Assessment test: Varus stress test at 20–30° flexion. Lateral pivot shift test (forearm supinated, valgus + axial compression during flexion from extension — reproduces the subluxation/reduction clunk of PLRI).
- Condition link: RCL sprain, posterolateral rotatory instability, conditions/lateral-epicondylitis
Annular Ligament
- Attachments: Anterior margin of the radial notch of the ulna → posterior margin of the same notch, encircling the radial head
- Function: Holds the radial head against the ulna, allowing it to rotate freely during pronation/supination while preventing lateral displacement. Part of the proximal radioulnar joint but functionally important for elbow stability.
- Injury mechanism: In children, axial traction on a pronated forearm can sublux the radial head out from under the annular ligament ("pulled elbow" or nursemaid's elbow). In adults, radial head fractures may disrupt the annular ligament.
- Condition link: Nursemaid's elbow (children), radial head subluxation
Mobilization Techniques
Hands-on instruction is required. The descriptions below provide clinical reference detail for understanding and supervised practice. They are not a substitute for instructor-led technique training. Correct hand placement, force dosage, and tissue response interpretation require hands-on coaching and feedback.
Convex-Concave Rule at the Humeroulnar Joint
The trochlea is
convex and the trochlear notch is
concave. In mobilization, we move the
concave ulna on the fixed convex humerus — concave-on-convex rule applies. The glide occurs in the
same direction as the restricted movement.
| Restricted Movement |
Glide Direction |
Reasoning |
| Flexion |
Anterior glide of the ulna |
Flexion moves the ulna anteriorly → concave on convex → same direction → anterior |
| Extension |
Posterior glide of the ulna |
Extension moves the ulna posteriorly → concave on convex → same direction → posterior |
General Contraindications (All Humeroulnar Mobilizations)
- Absolute: Joint instability (UCL/RCL/LUCL compromise), acute fracture (supracondylar, olecranon, coronoid), joint dislocation, active infection, heterotopic ossification (myositis ossificans — common after elbow trauma), acute inflammatory arthritis
- Relative: Osteoporosis (Grade I–II only), total elbow replacement, bony end-feel on extension (do not mobilize into a bony block)
- Critical caution: The elbow is highly prone to heterotopic ossification after trauma. Aggressive mobilization too early after fracture or dislocation can trigger myositis ossificans. Follow post-injury timelines carefully and maintain gentle grades.
Ulnar Distraction
Purpose: General capsular stretch and pain modulation. Opens the joint space, stretches the entire capsule. Useful as a preparatory technique before directional glides.
Patient position:
- Supine on the treatment table
- Elbow at approximately 70° flexion, 10° supination (resting position)
- Humerus supported on the table or a bolster
Hand placement:
- Stabilizing hand: Grips the distal humerus just proximal to the epicondyles, pressing it into the table/bolster
- Mobilizing hand: Grips the proximal ulna (olecranon region). The forearm rests along the clinician's forearm for control. Force directed distally along the long axis of the ulna.
Technique execution:
- Apply a slow, sustained or oscillatory traction force directed distally (away from the humerus along the ulnar shaft)
- Grade I–II: Gentle oscillatory traction for pain modulation. Appropriate for acute post-injury or post-surgical stiffness.
- Grade III: Sustained traction at end-range for capsular stretch
- Duration: 30–60 seconds per set, 3–5 sets
Indications:
- General capsular restriction following the capsular pattern (flexion > extension)
- Post-immobilization stiffness (cast removal)
- Acute elbow pain where directional glides are too provocative
- As a preparatory technique before anterior or posterior ulnar glides
Technique notes:
- Common error: Gripping too distally on the forearm — creates torque at the wrist rather than traction at the elbow.
- Reassessment: Re-test both flexion and extension PROM. Improvement in both confirms capsular involvement.
Medial-Lateral Ulnar Glide (Gapping)
Purpose: Restores medial and lateral joint play. Useful when specific medial or lateral capsular tightness is identified. Medial gapping stretches the lateral capsule; lateral gapping stretches the medial capsule.
Patient position:
- Supine on the treatment table
- Elbow at 70° flexion (resting position)
- Humerus stabilized on the table
Hand placement:
- Stabilizing hand: Grips the distal humerus firmly, stabilizing it against the table
- Mobilizing hand: Grips the proximal ulna. For medial glide: force directed medially. For lateral glide: force directed laterally.
Technique execution:
- Apply a slow, sustained or oscillatory force directed medially (to stretch lateral structures) or laterally (to stretch medial structures)
- Grade I–II: Small oscillations for pain modulation and assessment
- Grade III: Oscillations into the end-range medial or lateral resistance
- Duration: 20–30 seconds per set, 2–3 sets
Indications:
- Decreased medial or lateral joint play on accessory motion testing
- Post-immobilization stiffness with asymmetric capsular restriction
- Adjunct to distraction and AP glides for comprehensive capsular mobilization
Technique notes:
- Critical caution: Do not apply lateral gapping (valgus) if the UCL is compromised — this stresses the already-damaged ligament. Do not apply medial gapping (varus) if the RCL/LUCL is compromised.
- Reassessment: Compare medial and lateral joint play bilaterally. Symmetric improvement confirms capsular, not ligamentous, restriction.
Muscles Crossing This Joint
Flexors
Extensors
- anatomy/muscles/triceps-brachii — the primary elbow extensor; inserts on the olecranon; long head crosses the shoulder
- anatomy/muscles/anconeus — small extensor on the posterolateral elbow; stabilizes the ulna during pronation
Conditions Affecting This Joint
- conditions/osteoarthritis — primary elbow OA is uncommon but occurs in laborers and athletes with repetitive loading; follows the capsular pattern (flexion > extension)
- conditions/lateral-epicondylitis — "tennis elbow"; common extensor origin tendinopathy; pain at the lateral epicondyle with gripping and wrist extension
- conditions/medial-epicondylitis — "golfer's elbow"; common flexor origin tendinopathy; pain at the medial epicondyle with wrist flexion and gripping
- Elbow dislocation — posterior dislocation is the most common type; damages collateral ligaments, capsule, and often the coronoid process
- Olecranon bursitis — inflammation of the subcutaneous bursa over the olecranon; "student's elbow" from prolonged pressure
Clinical Notes
- The elbow is the second most commonly dislocated major joint (after the shoulder). Posterior dislocations are most common and damage the UCL, RCL, and capsule. Post-dislocation stiffness is the rule — the elbow is highly prone to capsular contracture. Early gentle mobilization (when medically cleared) prevents long-term stiffness.
- Heterotopic ossification is a major concern. The elbow is the most common site of myositis ossificans after trauma. Aggressive or premature mobilization increases the risk. If passive ROM is regressing after initial improvement, suspect HO — obtain imaging and cease mobilization.
- The carrying angle changes with pathology. Compare the carrying angle bilaterally — asymmetry suggests malunion of a previous fracture (cubitus varus from supracondylar fracture in children) or ligamentous laxity (increased valgus from UCL insufficiency).
- Bony end-feel in extension is normal. Unlike most joints where a bony end-feel suggests pathology, the humeroulnar joint normally has a hard (bony) end-feel in extension — the olecranon contacts the olecranon fossa. Do not mobilize into a normal bony block.
Key Takeaways
- Capsular pattern flexion > extension — same as the knee; distinguishes capsular restriction from mechanical block (loose body) or ligamentous injury.
- Concave-on-convex rule: the concave ulna moves on the convex trochlea, so glide is in the same direction as the restricted movement.
- The UCL (anterior band) is the primary valgus stabilizer — repetitive valgus stress in overhead athletes is the classic injury mechanism.
- The elbow is highly prone to heterotopic ossification after trauma — aggressive mobilization increases this risk; always follow post-injury timelines.
