_applied sciences_  
_Article_  
**K Kinect Azure-Based Accurate Measurement of Dynamic Valgus Position of the Knee--A Corrigible Predisposing Factor**  
**of Osteoarthritis**  
**[PERSON] 1,*-\(\copyright\), [PERSON] 1, [PERSON] 1, [PERSON] 1, [PERSON] 2,3, [PERSON] 2, [PERSON] 4, and [PERSON] 1,*-**  
1 Research Center for Sports Physiology, University of Physical Education, 1123 Budapest, Hungary; [EMAIL_ADDRESS] (M.A.); [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (E.F.)  
2 Faculty of Information Technology and Biomics, Pazimany Peter Catholic University, 1083 Budapest, Hungary; [EMAIL_ADDRESS] (L.G.); [EMAIL_ADDRESS] (G.S.)  
3 Neurology and Neurosurgery, The Johns Hopkins Hospital, 855 N Wolfe St., Baltimore, MD 21205, USA  
4 Department of Mechatronics, Optics and Mechanical Engineering Informatics, Budapest University of Technology and Economics, 1111 Budapest, Hungary; [EMAIL_ADDRESS]  
* Correspondence: [EMAIL_ADDRESS] (A.U.); [EMAIL_ADDRESS] (Z.L.); Tel: 436-70-678-38-98 (A.U.)  
**Featured Application: Lateral disposition of the knee under load in the single-leg squat (SLS) test is widely used for screening functional instabilities of the knee under load, which is associated with elevated risk of lower limb injuries and early onset of osteoarthritis. We identified that approximation of the Quadriceps angle at the lowest point of squat is error-prone and not suitable for comparing patients or monitoring progress, as it is highly dependent on squat depth and muscle strength. The current study shows that the Kinect Azure-based Dynaknee software is able to simultaneously measure squat depth and the dynamic valgus position of the knee. We suggest that valgus shift, measured at 15% squat depth and expressed in percentage of lower limb length, may be a more reliable parameter for evaluating dynamic valgus in an orthopedic or physical therapy office.**  
**Abstract: (1) Dynamic knee valgus is a predisposing factor for anterior cruciate ligament rupture and osteoarthritis. The single-leg squat (SLS) test is a widely used movement pattern test in clinical practice that helps to assess the risk of lower-limb injury. We aimed to quantify the SLS test using a marker-less optical system. (2) Kinect validity and accuracy during SLS were established by marker-based OptiTrack and MVN Xsens motion capture systems. Then, 22 individuals with moderate knee symptoms during sports activities ([PERSON] > 4, Lyshohm > 60) performed SLS, and this was recorded and analyzed with a Kinect Azure camera and the Dynaknee software. (3) An optical sensor coupled to an artificial-intelligence-based joint recognition algorithm gave a comparable result to traditional marker-based motion capture devices. The dynamic valgus sign quantified by the Q-angle at the lowest point of the squat is highly dependent on squat depth, which severely limits its comparability among subjects. In contrast, the medio-lateral shift of the knee midpoint at a fixed squat depth, expressed in the percentage of lower limb length, is more suitable to quantify dynamic valgus and compare values among individual patients. (4) The current study identified a new and reliable way of evaluating dynamic valgus of the knee joint by measuring the medial shift of the knee-over-foot at a standardized squat depth. Using a marker-less optical system widens the possibilities of evaluating lower limb functional instabilities for medical professionals.**  
**Keywords:** osteoarthritis; ACL rupture; dynamic knee valgus; single-leg squat; motion capture; Kinect Azure