Classification
- Type: Synovial condyloid (functionally hinge with limited rotation)
- Degrees of freedom: 2 (flexion/extension shared with the humeroulnar joint; the radial head also rotates on the capitulum during pronation/supination)
- Region: Elbow complex (shares a common joint capsule with the humeroulnar and proximal radioulnar joints)
Articular Surfaces
- Capitulum of the humerus (convex): A rounded, almost hemispherical eminence on the anterolateral distal humerus. Smaller than the trochlea. Covered with hyaline cartilage on its anterior and inferior surfaces only — there is no cartilage posteriorly because the radial head does not contact the capitulum in full extension.
- Radial head (concave, dish-shaped): The superior surface (fovea) of the radial head is a shallow concavity that articulates with the convex capitulum. Covered with hyaline cartilage. The radial head also has a peripheral rim that articulates with the radial notch of the ulna (proximal radioulnar joint).
Movements and ROM
Load transmission: The humeroradial joint bears approximately 60% of compressive force across the elbow (the humeroulnar joint bears ~40%). This explains why radial head fractures are common with axial loading (falling on an outstretched hand) and why radial head excision alters elbow biomechanics.
Capsular Pattern
Flexion > Extension (shared with the humeroulnar joint)
The humeroradial joint shares a common capsule with the humeroulnar joint. Capsular restriction follows the same pattern.
Resting Position
- Full extension with forearm supinated
- Alternatively: 70° flexion, 35° supination (when considering the elbow complex as a whole)
Close-Packed Position
- 90° flexion with 5° supination
- Maximum radial head congruence with the capitulum
End-Feels
| Movement |
Normal End-Feel |
Type |
| Flexion |
Tissue approximation (soft) |
Same as humeroulnar — forearm muscles meet arm muscles |
| Extension |
Bony (hard) |
Shared with humeroulnar — olecranon contacts olecranon fossa |
| Pronation |
Capsular (firm) |
Ligamentous and capsular tension; may also include tissue approximation of forearm muscles |
| Supination |
Capsular (firm) |
Ligamentous and capsular tension |
Ligaments
The humeroradial joint is stabilized by the same ligaments as the humeroulnar joint (UCL, RCL, annular ligament) — see
anatomy/joints/humeroulnar for detailed ligament descriptions. The most directly relevant ligament is:
Annular Ligament
- Attachments: Anterior margin of the radial notch of the ulna → posterior margin, encircling the radial head
- Function: Maintains the radial head against the ulna during rotation (pronation/supination). Allows the radial head to spin freely within the ligament while preventing lateral displacement.
- Clinical relevance: In children under 5, axial traction on a pronated forearm (pulling a child by the hand) can sublux the radial head from under the annular ligament — "nursemaid's elbow" or "pulled elbow." Reduced by supination with slight flexion pressure.
Lateral Collateral Ligament Complex
- Function at the humeroradial joint: The RCL and LUCL resist varus stress and posterolateral rotatory instability. The LUCL specifically prevents the radial head from subluxing posterolaterally.
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 Humeroradial Joint
The capitulum is
convex and the radial head is
concave. When mobilizing the concave radius on the fixed convex humerus, the glide is in the
same direction as the restricted movement (concave-on-convex rule).
| Restricted Movement |
Glide Direction |
Reasoning |
| Flexion |
Anterior radial glide |
Concave on convex → same direction |
| Extension |
Posterior radial glide |
Concave on convex → same direction |
General Contraindications
- Same as humeroulnar joint — see anatomy/joints/humeroulnar for complete contraindication list
- Additional: Radial head fracture (even suspected — the "fat pad sign" on radiograph indicates intra-articular fracture), radial head prosthesis
Radial Head Distraction
Purpose: General pain modulation and capsular stretch at the humeroradial joint. Useful when compressive loading is painful (e.g., radial head contusion or early OA).
Patient position:
- Supine or seated
- Elbow at 70° flexion, forearm in midprone (neutral) position
- Humerus supported on the table
Hand placement:
- Stabilizing hand: Grips the distal humerus, stabilizing it against the table or bolster
- Mobilizing hand: Grips the radial head between thumb and index finger. The thumb contacts the radial head anteriorly, the index finger posteriorly. Force directed laterally (away from the ulna) and slightly distally.
Technique execution:
- Apply a slow, sustained or oscillatory traction force directed laterally and distally — separating the radial head from the capitulum
- Grade I–II: Gentle oscillatory distraction for pain modulation
- Grade III: Sustained traction for capsular stretch
- Duration: 20–30 seconds per set, 2–3 sets
Indications:
- Radial head compression tenderness (post-contusion, early OA)
- Decreased radial head mobility on accessory motion testing
- Adjunct to humeroulnar mobilization for comprehensive elbow treatment
Technique notes:
- Common error: Gripping the radial shaft distally rather than the radial head — produces forearm rotation, not humeroradial distraction.
- Palpation tip: The radial head is palpable in the "soft spot" — the triangle between the lateral epicondyle, olecranon, and radial head. Pronate and supinate the forearm while palpating to confirm the radial head.
Anterior-Posterior Radial Head Glide
Purpose: Restores flexion (anterior glide) or extension (posterior glide) at the humeroradial joint. Particularly useful when humeroulnar mobilization alone does not fully restore elbow ROM.
Patient position:
- Supine or seated
- Elbow at 70° flexion (resting position)
- Forearm in neutral (midprone)
Hand placement:
- Stabilizing hand: Cups the medial elbow, stabilizing the distal humerus
- Mobilizing hand: Thumb on the posterior radial head (for anterior glide) or anterior radial head (for posterior glide). The index finger supports from the opposite side.
Technique execution:
- Anterior glide (for flexion): Thumb pushes the radial head anteriorly. Small oscillations into the anterior end-range resistance.
- Posterior glide (for extension): Thumb pushes the radial head posteriorly. Small oscillations into the posterior resistance.
- Grade I–II: Pain modulation — small oscillations within pain-free range
- Grade III: Oscillations into end-range capsular resistance
- Duration: 20–30 seconds per set, 2–3 sets
Indications:
- Decreased anterior or posterior radial head glide on joint play testing
- Elbow flexion or extension limitation not fully responsive to humeroulnar mobilization
- Post-immobilization stiffness with radial head involvement
Technique notes:
- Common error: Applying rotational force instead of translatory — keep the force direction strictly anterior or posterior.
- Reassessment: Re-test elbow flexion and extension PROM after mobilization.
Muscles Crossing This Joint
Muscles Acting on the Humeroradial Joint
Common Extensor Origin (Lateral Epicondyle)
Conditions Affecting This Joint
- Radial head fracture — the most common elbow fracture in adults; caused by falling on an outstretched hand (axial compression through the radius); classified by Mason classification (Types I–IV)
- conditions/lateral-epicondylitis — common extensor origin tendinopathy; the lateral epicondyle is the attachment site for muscles crossing this joint
- Posterolateral rotatory instability (PLRI) — LUCL insufficiency allows the radial head to sublux posterolaterally; the most common pattern of chronic elbow instability
- Nursemaid's elbow — radial head subluxation in children; annular ligament interposition
Clinical Notes
- Radial head fractures are often missed. A patient who falls on an outstretched hand and has lateral elbow pain with limited supination/pronation should be assessed for radial head fracture. The "fat pad sign" on lateral radiograph (displaced fat pads indicating joint effusion) is the most reliable initial indicator. If radial head tenderness and a positive fat pad sign are present, treat as a fracture until proven otherwise.
- The humeroradial joint contributes significantly to elbow stability. Radial head excision (historically used to treat comminuted fractures) increases valgus laxity and proximal radial migration. Modern treatment favors radial head replacement to preserve load transmission and stability.
- Lateral epicondylitis involves the humeroradial joint. While lateral epicondylitis is primarily a tendinopathy, the proximity of the common extensor origin to the humeroradial joint means that joint stiffness and tendinopathy often coexist. Assess humeroradial joint play in all lateral elbow pain presentations.
Key Takeaways
- The humeroradial joint bears ~60% of compressive load across the elbow — radial head fractures from axial loading are the most common adult elbow fracture.
- Concave radial head on convex capitulum means glide is in the same direction as the restricted movement.
- Always assess humeroradial joint play in lateral elbow pain — joint stiffness and lateral epicondylitis frequently coexist.
- Nursemaid's elbow (pulled elbow) in children results from radial head subluxation under the annular ligament — reduced by supination with flexion.
