Comparison Of Running Mechanics In Healthy Versus Injured Runners With Patellar Tendonitis

Recent studies focused on running biomechanics and correcting its flaws to treat common running injuries such as iliotibial band syndrome, anterior knee pain, and patellofemoral pain syndrome. However, there have been no studies identifying specific biomechanical measures that may predispose athletes to patellar tendonitis (PT). PURPOSE: To compare running biomechanics between healthy and injured runners with PT. STUDY DESIGN: Case-control study. METHODS: Running video images of healthy and injured runners were taken between January 1, 2010 and October 31, 2013, and a total of 40 treadmill running videos (14 males and 26 females) were extracted. A group of 20 runners with PT (7 males and 13 females) was compared with gender, age, and BMI matched healthy control runners. The video image sequences were randomized and analyzed by a single examiner using software ImageJ, and the examiner was blinded from the randomization process and statistical analysis. Extracted biomechanical data include foot strike pattern, overstride angle, trunk posture angle, hip drop angle at mid-stance, knee position (varus, valgus), knee angle at mid-stance, and mid-stance foot position (pronate, supinate, neutral). Those variables were compared between runners with PT and healthy control runners. An independent t-test was performed to compare a statistical significance between the two groups. Alpha level was set at 0.05 priori. RESULTS: Healthy control runners demonstrated a 2.3° greater hip drop angle (6.0° ± 2.6°) on ipsilateral hip during the mid-stance of treadmill running compared to runners with PT (3.7° ± 2.4°, p=0.01). Also, the runners with PT showed 2.3° increased knee valgus angle (-0.7° ± 4.0°) compared to healthy control runners (1.6° ± 4.1°, p=0.04). There were no significant differences in other mechanical variables between the two groups. Additionally, the runners with PT were collectively significantly taller (172.3 cm ± 9.8) than the healthy control runners (164.0 ± 8.5 cm, p=0.01). CONCLUSIONS: There is a significant difference between knee angle and hip drop angles at mid-stance during treadmill running as well as average height between healthy control runners and runners with PT.