The procedure for single leg squat involved subjects being asked to stand on the test limb, facing the video camera. Participants were asked to squat down as far as possible, to at least 45° knee flexion but not greater than 60°, over a period of 5 s. Knee flexion angle was checked during practice trials (maximum of three) using a standard goniometer (Gaiam-Pro, Physiomed, Manchester, UK) observed by the same examiner throughout the trials. There was also a counter for each participant over this 5 second period in which the first count initiates the movement, the third indicates the lowest point of the squat and the fifth indicates the end of the movement with them returning to the start position. Trials were only accepted if the subject squats to the minimum degree of knee flexion (45°) and maintained their balance throughout while keeping their hands on their iliac crests [14]. The control group carried out this task on their dominant (right) leg, while the PFP group carried out the task on both legs. While carrying out the task perceived pain was recorded (scored after completion) by the participant marking perceived pain level on a 10 cm visual pain scale (0 equals no pain, 10 worse perceivable pain).