## 2 Materials and Methods
### Procedures  
A general demographic questionnaire was completed first during the physical examination at our rehabilitation clinic to obtain the participant's contact details, e-mail address, age, sex, involved limb, dominant limb, previous injuries and PFP symptoms. Thereafter, the anterior knee pain scale (AKPS), also known as the Kujula patellofemoral scoring system, was completed verbally to capture knee-related pathologies where the total score out of 100 was captured electronically. The AKPS was the chosen questionnaire, as it was developed specifically for the evaluation of pain and disability in individuals with PFP [17], showed high test-retest reliability (intradas correlation coefficient [ICC] = 0.95), and exhibited moderate responsiveness to clinical change, which implies that the score will likely reflect meaningful changes in a patient's condition over time [21]. Body mass and stature were then measured to standardise the effect of jump-landing forces across individuals [22]. Body mass was measured to the nearest 0.1 kg with an electronic scale (Seca 874, Seca, Hamburg, Germany) and stature with a portable stadiometer (Holtain Ltd., Crymych, UK). A cycle ergometer (Wattbike Pro, Wattbike Ltd., Nottingham, UK) was used for a ten-minute warm-up at a light effort (RPE = 2; modified Borg scale) prior to the testing for optimal muscle performance and a reduced risk of injury [23]. After the warm-up, the isometric strength of the knee extensor muscle group was assessed on an isokinetic dynamometer (Cybex HUMAC Norm II, model CSMi 6000, Stoughton, MA, USA) which recorded torque data at 100 Hz. Participants were set up on the isokinetic dynamometer according to manufacturer's instructions, where the dominant side in the control group and the uninjured side in the PFP group were measured first. Briefly, the participant was seated with the rotation scale, fore-aft positions, and monorail of the rig adjusted such that the axis of rotation of the dynamometer was aligned with the centre of the knee joint axis. Gravity correction was performed to account for any potential additional torque induced on the attachment. The knee was positioned at an angle of 60\({}^{\circ}\) relative to anatomical zero, and the participants were then required to exert maximal knee extension force against the movable arm of the dynamometer for five seconds per trial. A total of three familiarisation trials with a 30 s rest period between trials preceded the actual trials, whereafter a one-minute rest period was granted. A total of 5 maximum effort isometric test trials lasting 5 s were recorded for each limb, and pain levels were monitored by asking the participant to rate pain on a scale of 1-10 throughout the procedure (where 1 = pain free, 2 = very mild, 3 = discomforting, 4 = tolerable, 5 = very distressing, 6 = intense, 7 = very intense, 8 = utterly horrible, 9 = excruciating/unbearable, 10 = unimaginable/unspeakable) [24]. Participants were permitted to stop the test if pain levels were above bearable levels (\(\geq\)4), although no such instances were recorded. To ensure that maximal efforts were consistently applied across trials, the coefficient of variation was evaluated on the dynamometer and had to be \(\leq\)5%, which was achieved by all participants. The raw torque-time data were exported to Matlab (version R2023b, The Mathworks, Natick, MA, USA) for processing, where all trials were ensemble-averaged and the peak torque values retained for analysis. The evaluation of the unilateral drop jump (DJ) was then completed on a tri-axial force plate (AMTI, Watertown, MA, USA), which was used to measure ground reaction force at a sampling frequency of 2000 Hz. Participants completed three familiarisation trials on each leg prior to the test and were granted two minutes of rest to ensure complete recovery before starting with the data collection. Participants followed the protocol outlined by [PERSON] et al. (2015), with only the DJ height being modified according to the recommendations by [PERSON] and [PERSON] (2016).