The humeroulnar (ulnohumeral) joint is the principal hinge of the elbow, with the deep trochlear notch of the ulna wrapping around the humeral trochlea to provide inherent bony stability. The coronoid and olecranon stabilise against posterior and anterior displacement of the ulna respectively, and even small fractures of the anteromedial coronoid can destabilise the joint. The anterior bundle of the UCL stabilises this medial compartment against the valgus forces of throwing.
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In throwers, valgus extension overload produces tension on the medial UCL and compression between the posteromedial olecranon and the trochlea. UCL insufficiency is assessed with valgus stress testing, the milking manoeuvre and the moving valgus stress test, and complete tears in overhead athletes are treated by UCL reconstruction (Tommy John procedure) with a palmaris longus or gracilis graft. Ulnohumeral arthritis produces pain, stiffness, and osteophytes at the olecranon and coronoid tips that block terminal extension and flexion; arthroscopic debridement or the Outerbridge-Kashiwagi fenestration of the olecranon fossa restores motion. In the terrible triad injury, coronoid and radial head fractures with lateral ligament rupture leave the joint unstable. Anteromedial coronoid facet fractures cause varus posteromedial rotatory instability.
Elbow osteoarthritis producing pain, stiffness, and mechanical block from osteophytes at terminal motion, managed with arthroscopic debridement or fenestration.
Repetitive valgus stress tears the anterior bundle of the UCL, causing medial elbow pain in late cocking and acceleration; partial tears are managed conservatively and complete tears by UCL reconstruction.
Posteromedial olecranon impingement on the trochlea during throwing, producing osteophytes, cartilage damage and pain at terminal extension, treated by arthroscopic osteophyte removal.
Posterior elbow dislocation with radial head and coronoid fractures, leaving the joint unstable; treated by fixing or replacing the radial head, fixing the coronoid and repairing the lateral ligament.
