Our musculoskeletal model is suitable for investigating lower extremity muscles during the sit-to-stand maneuver in the knee osteoarthritis (KOA) and total knee arthroplasty (TKA) populations. It is largely based on the previously published model by Bosch et al. (2022) and contains updates to muscle attachment points for the hip abductor muscles as done in Uhlrich et al. (2022). However, to better model the knee joint laxity often demonstrated by the KOA and TKA populations, we modified the knee joint to include two additional degrees of freedom: knee adduction/abduction and knee internal/external rotation. Finally, we also modified the passive muscle force properties of each muscle by calibrating each muscle’s passive force-length curve, such that the passive joint moments generated by the model’s muscles more closely matched experimental data, as done in Uhlrich et al. (2022). Our final, generic musculoskeletal model contains 25 degrees of freedom, 80 musculotendon actuators on the lower extremities, and 3 ideal torque actuators on the torso.