Elbow Posterior Compartment

compartimentum posterius articulationis cubiti

The elbow posterior compartment is the posterior extension of the elbow synovial cavity between the olecranon process and the olecranon fossa of the humerus. In full extension the olecranon fills this space; in flexion the olecranon withdraws and the posterior fat pad expands to fill the recess. The posterior compartment is accessed through posterocentral and posterolateral arthroscopic portals.

Anatomical Data

Boundaries & Contents

Location	Back of the elbow joint, in the olecranon fossa above the tip of the olecranon
Boundaries	Olecranon fossa of the humerus (front) Medial and lateral supracondylar columns (sides) Posterior capsule and triceps tendon (behind) Olecranon tip (below)
Contents	Synovial fluid Posterior fat pad Loose bodies when present

Biomechanics

Function & Actions

Accepts the olecranon tip in full extension and collects fluid in an effusion, which lifts the posterior fat pad into view on X-ray. Loose bodies and osteophytes here block extension.

Clinical Relevance

Clinical Notes

The elbow posterior compartment is the primary site of loose body accumulation in elbow osteoarthritis, osteochondromatosis, and after osteochondritis dissecans. Posterior elbow osteophytes from olecranon tip and olecranon fossa rim project into this compartment, causing an extension block managed by arthroscopic posterior compartment debridement. The posterior fat pad sign (visible on lateral radiograph) indicates effusion within this compartment. Posterior elbow impingement in throwing athletes from olecranon osteophyte formation in the posterior compartment is a common cause of elbow pain managed arthroscopically.

Pathology

Common Injuries & Conditions

Posterior Elbow Loose Bodies

Osteochondral loose bodies from OCD, arthrosis, or osteochondromatosis accumulate in the posterior elbow compartment behind the olecranon, causing intermittent locking, catching, and a fixed extension deficit, removed arthroscopically through posterior central and lateral portals.

Valgus Extension Overload Posterior Impingement

The posteromedial olecranon tip impinges against the posteromedial olecranon fossa during the follow-through phase of throwing, producing osteophytes in the posterior compartment and chondromalacia of the posterior trochlea in throwers, managed by arthroscopic posterior osteophyte excision.

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