This is a case of ours. This young man had a left total knee reconstruction (Left ACL and posterolateral compartment reconstruction; allograft ligaments for both areas). This video is roughly 3 months post surgery. Q: What anatomical variants are seen in this individual? A: Note the genu and tibial varum present. This results in an increased amount of pronation necessary (right greater than left, because of an apparent Left sided short leg length; * NOTE: post-operatively at this point the client had still some loss of terminal left knee extension. thus the knee was in relative flexion and we know that a slightly flexed knee appears to be a shorter leg. Go ahead, stand and bend your left knee a few degrees, the body will present itself as a shorter leg on that left side with all the body compensations to follow such as right lateral hip shift and left upper torso shift to compensate to that pelvic compensation.) Normally, in this type of scenario (although we have corrected much of it at this point by giving him more anterior compartment strength and strategy as evidenced by his accentuated toe extension and ankle dorsiflexion strategies, these are conscious strategies at this point for the patient), the functionally shorter left leg has a body mass acceleration down onto it off of the longer right leg stance phase of gait. This sagittal (forward) acceleration is met by a longer stride on the right with an abrupt heel strike (in other words, the client is moving faster than normal across the left stance phase so there is abrupt and delayed heel strike on the right because of a step length increase. (again, this is just commentary, had we videoed this client weeks before this, you would have seen these gait pathologies. This video shows him ~70% through a gait corrective phase with us.) Again, this client has bilateral tibial varum. You can see this as evidence due to the increased calcaneal valgus (ie. rearfoot pronation; look at the achilles valgus presentation). He increases his arm swing on the Left to help bring the longer Right lower extremity (relative) through. if you look closely you can also see early right heel departure which is driven by the increased forward momentum of the body off of the short left limb. In other words, the body mass is moving forward faster than normal onto the right limb (because of the abbreviated time spend on the left "short" leg) and thus the forward propulsed body is pulling the right heel up early and the heel is spinning inwards creating a net external rotation on the right limb (look for the right foot to spin outwards/externally ever so slightly in the second half of the video). Early heel departure means early mid and forefoot weight bearing challenges and thus reduced time to cope ... https://www.youtube.com/watch?v=xMkWQGPdYm8