Must Know
- Synovial hinge joint between humerus, radius and ulna, continuous with the proximal radioulnar joint.
- Capitulum faces forwards and down and is not visible from behind.
- Trochlea wraps round to the back and meets the trochlear notch.
- Medial trochlear lip projects lower than the capitulum, creating part of the carrying angle.
- Ulnar shaft obliquity to the trochlear notch ridge gives most of the carrying angle.
- Carrying angle is about 170 degrees between arm and forearm, greater in women.
- Flexion range is about 140 degrees.
- Nerve supply from musculocutaneous, median, ulnar and radial nerves.
Capsule and Ligaments
- Capsule attaches above the coronoid and radial fossae in front and above the olecranon fossa behind.
- Distally it attaches to the trochlear notch margins and the annular ligament, not the radius.
- Synovium lines the humeral fossae.
- Quadrate ligament joins the radial notch lower edge to the radial neck.
| Ligament | Attachments | Notes |
|---|---|---|
| UCL anterior band | Medial epicondyle to sublime tubercle of coronoid | Strongest band |
| UCL posterior band | Sublime tubercle region to medial olecranon | Weaker than anterior band |
| UCL middle band | Joins anterior and posterior bands | Ulnar nerve lies on it |
| Radial collateral | Lateral epicondyle to annular ligament | No direct radial attachment |
| Annular | Front and back of radial notch | Radius free to rotate |
Clinical Anatomy
- Olecranon tip lies in line with the epicondyles in extension.
- In full flexion the three points form an equilateral triangle, disturbed by dislocation.
- Posterior dislocation often comes with a coronoid fracture.
- Brachial artery, median and ulnar nerves can be hurt in dislocation.
- In children, supracondylar fracture endangers the brachial artery and median nerve from the forward proximal fragment.
- Increased valgus after lateral condyle injury can stretch the ulnar nerve over years.
- Cubital tunnel is the arch between humeral and ulnar heads of FCU.
- Ulnar nerve compresses more readily against the coronoid than behind the medial epicondyle.
More on the cubital fossa
- Floor is brachialis above and supinator below.
- Bicipital aponeurosis separates the median cubital vein from the brachial artery and median nerve.
- PIN supplies ECRB and supinator in the fossa, then passes between the two supinator layers.
- Supinator arises from the lateral epicondyle, lateral and annular ligaments and the ulnar supinator crest.
Numbers to Remember
- Carrying angle. About 170 degrees.
- Flexion. About 140 degrees.
Memory Aids
- Annular and lateral ligaments ignore the radius. The radial head must spin freely.
Exam Traps
- The capsule has no attachment to the radius.
- The equilateral triangle is a flexion sign, not an extension sign.
- Most of the carrying angle comes from the ulna.
Source
Sinnatamby CS. Last’s Anatomy. Regional and Applied. 12th ed. Edinburgh, Churchill Livingstone Elsevier, 2011. Chapter 2, Upper limb.
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 17 October 2026.