Introduction The aim of this study was to compare running kinematics between recreational runners with and without running-related knee injury using two-dimensional video analysis.

Materials and methods Forty-two recreational runners (18 injured, 24 non-injured) participated in the study. The injured group consisted of runners with anterior or lateral knee pain, resulting in altered running activity for at least one week. All participants ran on a treadmill at preferred speed. Digital videos were recorded in the frontal and sagittal plane with two iPads. Outcome measures included foot and tibia inclination at initial contact, and lateral trunk position, contralateral pelvic drop, femoral adduction, hip adduction, knee flexion and ankle dorsiflexion during midstance. All angles were manually drawn using Kinovea and an average of seven consecutive steps was calculated for each angle. Participant characteristics (gender, age, body weight, body length, body mass index, running volume before injury, running speed) and two-dimensional measured angles were compared between groups with independent t-tests (normally distributed) and the Mann Whitney U test (non-normally distributed).

Results There were no significant differences in participant characteristics between groups (p>0.05). The injured group exhibited significantly more femoral adduction (p=0.031) and hip adduction (p=0.004) during midstance, and significantly less foot inclination at initial contact (p=0.026).

Conclusion Two-dimensional video analysis discriminated kinematics between runners with and without running-related knee injury. More femoral adduction and hip adduction during midstance, and less foot inclination at initial contact may provide gait retraining targets when treating runners with running-related knee injury.