Posterior Capsule (Knee)

capsula posterior articularis genus

The posterior knee capsule resists hyperextension and encloses the posterior joint space. It is taut in full extension and slack in flexion. The oblique popliteal ligament (from semimembranosus) reinforces the posteromedial capsule while the arcuate ligament reinforces the posterolateral aspect, and the popliteus tendon passes through it laterally. It is distended in knee joint effusion.

Anatomical Data

Boundaries & Contents

Location	Back of the knee joint, between the posterior femoral condyles and the posterior tibial condyles, forming part of the floor of the popliteal fossa
Boundaries	Attached above to the posterior margins of the femoral condyles and the intercondylar fossa Attached below to the posterior margins of the tibial condyles Reinforced posteromedially by the oblique popliteal ligament (expansion of semimembranosus) Reinforced posterolaterally by the arcuate popliteal ligament Pierced posterolaterally by the popliteus tendon
Contents	Posterior part of the knee joint cavity and its synovial lining Posterior horns of the menisci, anchored to it by meniscotibial fibres

Biomechanics

Function & Actions

Encloses the back of the knee joint and, with the PCL and posterior meniscal attachments, resists hyperextension. It provides attachment for the oblique popliteal ligament, semimembranosus expansions and posterior meniscal horns.

Clinical Relevance

Clinical Notes

Posterior capsule contracture is the primary cause of knee flexion contracture after prolonged immobilisation, total knee arthroplasty, or spasticity, and may require posterior capsular release. At TKA, posterior osteophytes are removed and the capsule is released from the femur to restore full extension, with care to protect the popliteal neurovascular bundle behind it. The posterior capsule is torn along with other capsular structures in combined PCL and posterolateral corner injuries.

Pathology

Common Injuries & Conditions

Posterior Capsule Contracture

Posterior knee capsular fibrosis producing fixed flexion contracture managed with posterior capsular release in TKA or physiotherapy-based stretching.

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