OpenCap is an open-source platform that computes full-body kinematics and musculoskeletal dynamics from two smartphone cameras, without a motion capture laboratory. This paper validates its accuracy against marker-based motion capture and force plates across walking, squatting, sit-to-stand, and drop jump tasks. It then tests whether the platform meets accuracy thresholds for four clinical applications: OA risk screening, gait intervention efficacy, between-group kinetic comparisons, and rehabilitation monitoring.
Quantitative movement analysis — knee adduction moment for OA risk, limb-symmetry index for post-ACL return-to-sport, joint moment distribution for fall risk. Has been out of reach for most clinicians because it requires a $150,000 lab, days of expert processing, and typically only 12–21 subjects per study.
OpenCap's error for the knee adduction moment (0.30% BW×height) sits below the published OA progression detection threshold (0.5–2.2% BW×height). Limb-symmetry classification for squatting reached AUC=0.90–0.93 in a 100-subject community study conducted by a non-expert in five minutes per subject.
When you want to screen a patient's medial knee loading after a gait modification program, or track quadriceps symmetry recovery after ACL reconstruction, OpenCap offers a validated low-cost option that does not require a biomechanics lab.
The authors are explicit that validation has so far been performed in healthy subjects simulating pathological patterns. Prospective studies in actual post-surgical and OA populations are the necessary next step before routine clinical adoption.
OpenCap is an open-source platform that computes full-body kinematics and musculoskeletal dynamics from two smartphone cameras, without a motion capture laboratory. This paper validates its accuracy against marker-based motion capture and force plates across walking, squatting, sit-to-stand, and drop jump tasks. It then tests whether the platform meets accuracy thresholds for four clinical applications: OA risk screening, gait intervention efficacy, between-group kinetic comparisons, and rehabilitation monitoring.
Quantitative movement analysis — knee adduction moment for OA risk, limb-symmetry index for post-ACL return-to-sport, joint moment distribution for fall risk. Has been out of reach for most clinicians because it requires a $150,000 lab, days of expert processing, and typically only 12–21 subjects per study.
OpenCap's error for the knee adduction moment (0.30% BW×height) sits below the published OA progression detection threshold (0.5–2.2% BW×height). Limb-symmetry classification for squatting reached AUC=0.90–0.93 in a 100-subject community study conducted by a non-expert in five minutes per subject.
When you want to screen a patient's medial knee loading after a gait modification program, or track quadriceps symmetry recovery after ACL reconstruction, OpenCap offers a validated low-cost option that does not require a biomechanics lab.
The authors are explicit that validation has so far been performed in healthy subjects simulating pathological patterns. Prospective studies in actual post-surgical and OA populations are the necessary next step before routine clinical adoption.