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.
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.
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.
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.
