Video-Based Two-Dimensional Kinematic Analysis for the Evaluation of Lower Limb Function in Patellar Tendinopathy

Patellar tendinopathy (PT) is a common manifestation in jumping sports characterized by pain and a reduced load bearing capacity. The exact cause of PT has not been determined, which makes it difficult to prevent and treat. A stiffer landing technique might be a risk-factor for PT. Retraining of the landing technique into a less stiffer technique could be an important treatment for PT. Therefore, the aim of this study was to determine whether athletes with PT exhibit altered lower limb kinematics in the landing technique of a drop vertical jump test (DVJT) compared to asymptomatic athletes. DVJTs were performed by athletes diagnosed with PT and asymptomatic athletes. The DVJTs were recorded on video in the sagittal plane with a single camera in the Erasmus MC University Medical Center (Rotterdam, the Netherlands). A convolutional neural network was trained to extract coordinates of lower limb landmarks from the videos. The knee and ankle joint angles were calculated on the coordinates using least-squares. Functional Principal Component Analyses (FPCA) were performed to determine differences in lower limb kinematics between athletes with PT and asymptomatic athletes. In addition, the following kinematic features were compared between athletes with PT and asymptomatic athletes: angle at landing, maximal angle during landing, range of motion and time to maximal angle. Video-based 2D kinematic analysis of the landing DVJT was performed in 69 athletes with PT (53 men, mean age 24.6 ± 3.8 years) and 32 asymptomatic athletes (16 men, median age 20.5 (4) years). FPCA of knee (FPC1: p=0.5, FPC2: p=0.3) and ankle (FPC1: 0.7, FPC2: 0.1, FPC3: 0.5) joint angles did not show significant differences in the landing technique between these two groups. No significant differences were observed in angle at landing, maximal angle during landing, range of motion and time to maximal angle (knee: p=0.3, p=0.8, p=0.7, p=0.4; ankle: p=0.5, p=0.6, p=0.4, p=0.1). Athletes with PT do not have altered lower limb kinematics during the landing phase of a DVJT compared to asymptomatic athletes. These findings implicate that landing technique is not an important factor to address during rehabilitation of patients with PT. Technical Medicine | Sensing and Stimulatio