Tibiofemoral Instability

Knee instability encapsulates any injury whereby a patient reports episodes of the knee giving way under load or where the patient has lost confidence that the knee will hold their weight during functional activities. Clinical indication of knee instability is normally supported by ligamentous (with or without meniscal disruption) disruption, more frequently affecting the anterior cruciate ligament, observable with MRI. Anterior tibial, or rotational laxity is normally observable with clinical tests (Lachman, pivot-shift) and a history of trauma to the presenting joint. Knee instability may present as a primary episode or subsequent to a failed surgical intervention to restore stability (ACL reconstruction), requiring a revision procedure.

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Anterior cruciate ligament (ACL) injury is the most common complete ligament injury of the knee with an estimated incidence of 4 new cases per 10 000 people annually (Eggerding et al. 2015). An ACL injury frequently occurs in fit and active patients, especially among those who engage in sporting pursuits (Ajuied et al. 2014).

There is increased risk of ACL injury found in female athletes, with females found to have a 3-fold greater risk of ACL tear than males participating in the same sport (soccer or basketball) (Sutton & Bullock, 2013; Ajuied et al. 2014).

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Rupture of the ACL can cause significant disability in active individuals; however, approximately one-third of this population does not experience impairment or disability, and these people are labelled “copers” (Herrington & Fowler, 2006).