The posterior knee capsule resists hyperextension and provides the containment for the posterior joint space. The oblique popliteal ligament (from semimembranosus) reinforces the posteromedial capsule while the arcuate ligament reinforces the posterolateral aspect. The posterior capsule is distended in knee joint effusion — the posterior capsule fullness is palpable as the posterior knee bulging in acute effusions.
| Origin | Posterior femoral condyles and posterior intercondylar notch margins |
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| Insertion | Posterior tibial condyles and posterior meniscal horn attachments |
| Actions | Resists knee hyperextension; the oblique popliteal ligament (semimembranosus expansion) reinforces the posteromedial posterior capsule |
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Posterior capsule contracture is the primary cause of knee flexion contracture after prolonged immobilisation, total knee arthroplasty, or spasticity — it requires posterior capsular release in flexion contracture correction. During posterior-stabilised TKA, the posterior capsule and posterior cruciate ligament are both removed.
Posterior knee capsular fibrosis producing fixed flexion contracture managed with posterior capsular release in TKA or physiotherapy-based stretching.
