Wearable Estimation of Knee Joint Contact Forces: SiMPLeSENSE, a Simulated-IMU Pipeline Validated Against In Vivo Loads

SiMPLeSENSE estimates knee joint compressive forces from simulated IMU orientations that closely match in vivo implant loads during level walking and stair descent, with median RMSE about 0.3–0.5 BW and correlations near 0.95.

• Why it matters: Knee joint contact forces are key for studying loading and degeneration, but direct measurement is limited to instrumented implants, leaving IMU-based estimates insufficiently verified against in vivo data.
• What they did: The pipeline derives virtual IMU orientations from optical motion capture using subject-specific SMPL meshes, reconstructs kinematics with OpenSense, and estimates KCF in OpenSim using a Rapid Muscle Redundancy solver on CAMS-Knee, including robustness tests with added thigh/shank orientation noise.
• The result: Agreement with the optical mocap-driven estimates is higher for stair descent; realistic orientation error increases RMSE only modestly, but doubling it markedly overestimates peak force, supporting portable monitoring with inertial motion capture plus limited EMG and instrumented force shoes.

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