from numerous articles ive read, and the couple of times ive helped assist professors performing similar tests in that area ive personally only ever heard/seen 3d motion capture system, goni/accelerometer used, with  Analysis for test–retest reliability included Bland–Altman graphs, intraclass correlation coefficients (ICC 2,1) and standard errors of measurements (SEM). again this is from my experiences only

Yes it is possible, if you access the kinetic energy produced by the knee joint of the leg using inertial parameters obtained from the literature to estimate its mass and velocity by integrating the acceleration data. But it would be ideal to use a magnetometer and gyroscope embedded along the accelerometer, so you can get absolute parameters of limb position.

The musculoskeletal model from the software of  SIMM.

Thanks! I will check these solutions.