Influence of anteromedial and central anterior cruciate ligament reconstruction on patellofemoral joint biomechanics during walking and running: a musculoskeletal modelling study

<i>Purpose</i>: This study investigated the effect of anteromedial (AM) and central anterior cruciate ligament (ACL) reconstructions on the patellofemoral joint (PFJ) contact mechanics during walking and running. <i>Methods</i>: Six knee models were established under a musculoskeletal multibody dynamic framework. The ACL attachment points and muscle volume of the quadriceps femoris and hamstrings were modified to simulate ACL reconstructions and post-operative muscle atrophy. Walking and running simulations were performed to quantify ACL graft force and PFJ contact force. A single stance phase of the motion cycle was divided into eleven time points (periods 0.0-1.0). The computational results were statistically tested at each time point. <i>Results</i>: The results showed that central ACL reconstruction reduced graft force at contralateral toe-off and toe-off phases under walking conditions and the entire cycle under running conditions, with maximal reductions were 10.96 ± 7.42% and 29.00 ± 10.41%, respectively. Compared to AM reconstruction, central reconstruction increased the mean PFJ contact force by up to 2.12 ± 1.17% of body weight during periods 0.4-0.9 of the walking cycle and exhibited a complex pattern during the running cycle. <i>Conclusions</i>: Central ACL reconstruction provided a significantly higher PFJ load compared to AM reconstruction during walking after surgery. No consistent conclusions were reached between the two surgical protocols on PFJ contact force during running. These findings provide clinicians with a better understanding of the PFJ mechanics after ACL reconstruction.