As mentioned previously, patients with posterolateral instability may have difficulty with normal gait. In these instances the patients normally have a varus thrust gait. In this circumstance, at foot strike the lateral aspect of the knee will gap open and the patient needs to shift their weight in order to reduce the knee back into normal positioning. It is a very visible gait abnormality which should be performed by having the patient ambulate in the hall. A varus thrust gait can also be caused by medial compartment arthritis where there is “pseudolaxity” of the medial compartment where it collapses at foot strike. A good physical exam and radiographs will help discern whether it is a posterolateral corner injury or medial compartment arthritis which is the ideology of a varus thrust gait.
Most patients with a varus thrust gait also have underlying varus alignment of their lower extremity. In these circumstances, it is important to assess for this also because patients with chronic posterolateral corner knee injuries and varus alignment would need a proximal tibial osteotomy prior to any soft tissue reconstruction or the soft tissue reconstruction would be at a very high risk of stretching out over time.
Assessment of a varus stress gait is performed by having a patient ambulate in the hall. One assesses for any varus thrusting which occurs at foot strike. Some patients can adapt to a varus stress gait by walking with a flexed knee. This should also be assessed when one is having a patient ambulate in the hall to determine if they have varus thrusting.