Han, Seong-wonSawatsky, AndrewJinha, AzimHerzog, Walter2020-08-252020-08-252020-08Han, S., Sawatsky, A., Jinha, A., & Herzog, W. (2020). Effect of Vastus Medialis Loss on Rabbit Patellofemoral Joint Contact Pressure Distribution. "Journal of Applied Biomechanics". pp. 1-7. http://dx.doi.org/10.1123/jab.2020-0056http://hdl.handle.net/1880/112428https://doi.org/10.11575/PRISM/43931Vastus medialis (VM) weakness is thought to alter patellar tracking, thereby changing the loading of the patellofemoral joint (PFJ), resulting in patellofemoral pain. However, it is challenging to measure VM force and weakness in human studies, nor is it possible to measure the associated mechanical changes in the PFJ. To obtain fundamental insight into VM weakness and its effects on PFJ mechanics, the authors determined PFJ loading in the presence of experimentally simulated VM weakness. Skeletally mature New Zealand White rabbits were used (n = 6), and the vastus lateralis, VM, and rectus femoris were stimulated individually through 3 custom-built nerve cuff electrodes. Muscle torque and PFJ pressure distribution were measured while activating all muscles simultaneously, or when the vastus lateralis and rectus femoris were activated, while VM was not, to simulate a quadriceps muscle strength imbalance. For a given muscular joint torque, peak pressures were greater and joint contact areas were smaller when simulating VM weakness compared with the condition where all muscles were activated simultaneously. The results in the rabbit model support that VM weakness results in altered PFJ loading, which may cause patellofemoral pain, often associated with a strength imbalance of the knee extensor muscle group.engUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Vastus medialis weaknessOsteoartritisPatellofemoral joint mechanicsjournal articlehttp://dx.doi.org/10.1123/jab.2020-0056