## 4 Discussion
Therefore, it is possible that such differences occur only in women with hip abduction strength deficits. Similarly, although participants with PFP had slightly higher asymmetries in the standing, semi-squat and squat positions, this did not reach statistical significance. Additionally, we found a significant between-group difference in terms of ankle extension flexibility. These findings may be a result of an increased calcaneal version and foot pronation previously found in PFP patients [16; 17], although the small difference between groups limits definite conclusions. Although ankle extension flexibility seems to be lower than in the CG, further studies examining ankle flexibility in participants with PFP are warranted. The clinical relevance of these finding remains therefore unclear and requires further research. No other between-group difference was found in terms of flexibility. Surprisingly, the majority of participants with PFP defined their right leg as their dominant one. Our findings suggest that there is a strong relationship between side-dominance and hip extension strength in the PFP group. On the other hand, no significant correlation was observed between the outcome measures and dominant leg based on both groups. These findings suggest that leg dominance is associated with hip extension and adduction strength, but only in participants with unilateral PFP. Some limitations and considerations related to our study need to be addressed. First of all, because of a case-control study design, it was not possible to draw conclusions on the cause and effect relationships. Secondly, our sample of participants with PFP was small, preventing clear conclusions on the characteristics of PFP. A larger sample size is needed to better determine lower extremity strength and flexibility deficits in PFP patients. Another major limitation of our study is the inclusion of participants of all age groups. Considering the higher prevalence of PFP in adolescents, future studies should include only adolescents or young adults to better determine strength, flexibility and postural control deficits in this population. Additionally, most participants were female, which may limit our findings. Although PFP is more common in young females, future studies should aim to investigate muscle strength, flexibility and postural control in male participants with PFP. Lastly, it should be considered that we included both participants with uni- and bi-lateral symptoms. However, in participants with bilateral PFP, the side reported as worst was used in further analyses as the \"affected\" side and compared both to the \"non-affected\" and to participants without PFP [6; 8; 27; 45]. To the authors' knowledge, this was the first study measuring all trunk, hip, knee and ankle muscles' strength and flexibility outcomes in participants with PFP in respect to the affected side. Additionally, the study compared all the above-mentioned outcomes to participants without PFP and explored correlations with PFP levels and duration. As such, this study may provide valuable clinical guidelines in the prevention and rehabilitation of PFP. Preventative or rehabilitative exercise programs addressing weaknesses of the impaired muscle groups may lead to a more effective and long-lasting recovery with respect to the individuals' goals. Based on the results of our study, clinicians should consider implementing trunk strengthening exercises into PFP programs, when estimated as necessary. Therefore, routine testing should include testing of the trunk muscles along with knee muscles for providing a reliable base for a custom-designed rehabilitation program of PFP patients.