Posterior Knee Capsule Extension Fibres

fibrae extensionis capsulae posterioris genus

The posterior knee capsule extension fibres are longitudinal condensations within the posterior capsule running from the posterior femoral condyles to the posterior tibia, resisting knee hyperextension as the primary passive check.

Region: Knee

Biomechanics

Function & Actions

Resist knee hyperextension beyond the normal 5-10 degree range, protect the posterior neurovascular structures from excessive joint opening, and are the capsular fibres disrupted in posterior knee dislocation.

Clinical Relevance

Clinical Notes

Isolated posterior capsular laxity allows genu recurvatum (hyperextension deformity), seen in connective tissue disorders and post-ligament reconstruction. Posterior capsular plication or bone-block augmentation addresses symptomatic genu recurvatum.

Pathology

Common Injuries & Conditions

Genu Recurvatum from Posterior Capsule Laxity

Posterior capsule extension fibre insufficiency producing knee hyperextension deformity, managed by posterior capsulorrhaphy or tibial slope modification osteotomy.