Orthopaedic surgery is currently a field that is reactive, rather than proactive. A movement screening tool could help identify individuals at risk for anterior cruciate ligament (ACL) injury before injury occurs and decrease the long term risk of osteoarthritis (OA). At present, accurate movement monitoring systems are prohibitive in cost and size to be practical and accessible to the general population. Current commercially available low-cost and more accessible systems lack the accuracy needed for clinical relevance.

To address these limitations, we have developed more accurate Low-Cost Movement Assessment Systems (LCMAS). We enhanced the retroreflective marker detection capabilities for the Microsoft Kinect depth camera (LCMAS-Single) and applied kinematic and kinetic calculations to the skeleton generated from the Microsoft Kinect2 depth camera (LCMAS-2).

Next, we laid out a detailed test-retest reliability study utilizing intraclass correlation coefficients (ICC), smallest detectable differences (SDD), Bland-Altman plots, minimal clinically important difference (MCID), and root mean squared (RMS) difference to assess the performance of our low-cost systems relative to the gold standard Vicon system for detecting kinematic and kinetic metrics associated with knee injury risk. Our study encompassed the evaluation of the drop vertical jump (DVJ), double leg squat (DLS), and single leg squat (SLS). This methodology can be applied to evaluating any new system of measurement to the corresponding industry gold standard system.

Our LCMAS-Single and LCMAS-2 have repeatable measures and SDD smaller than the MCID values from the scientific literature between at-risk and normal populations for six and eight metrics, respectively. These metrics include hip angle, knee angle, knee moment, and center of mass position. This outcome enables the use of both systems as screening tools for ACL injury risk and rehabilitation.

Finally, we evaluate our envisioned clinical utility by implementing a literature based algorithm to assess combined motion and again compare the low-cost systems to the industry gold standard with a test-retest reliability study.

We have demonstrated the potential for a clinically-relevant, accurate, low-cost movement assessment tool that can revolutionize orthopaedic medicine by shifting the focus from reactionary to preventative.