Comparison of Knee Valgus Angle and Postural Sway in Two Conditions with and without Carrying a Military Backpack between Military with and without Patellofemoral Pain Syndrome

Patellofemoral pain syndrome (PFPS) is a common musculoskeletal disorder with a high prevalence among military personnel. Changing the movement pattern and applying loads can lead to an increase in postural sway and contribute to the development of patellofemoral pain syndrome in military personnel. Therefore, the aim of the present study is to comparison of knee valgus angle and the effect of carrying a military backpack on postural sway in the military with and without patellofemoral pain syndrome.

In this case-control study, 21 military personnel with patellofemoral pain syndrome participated voluntarily with Convenience Judgmental Sampling method and 21 healthy military personnel with the case group matching method. The indices of postural sway, including the path length, the standard deviation of medial-lateral sway (M-L), and the standard deviation of anterior-posterior sway (A-P) were measured using the Zebris pressure distribution device in two situations with and without carrying a military backpack. Also, the knee valgus angle was assessed during the single-leg squat test. To analyze the data, an independent t-test and paired sample t-test with a significance level of 0.05 were used in SPSS software version 23.

The results of the independent t-test showed that knee valgus angle, path length, SD(M-L), SD (A-P), in both positions with and without carrying a military backpack showed a significant increase in patellofemoral pain syndrome group in comparison with the healthy military (P<0.05). Comparing the changes in the center of pressure variables during the static balance test, and static balance with carrying a military backpack, there were also significant changes between the two positions (P<0.05).

According to the results, military with patellofemoral pain syndrome who had an increase in knee valgus angle had more postural sway and changes in postural sway indices compared to the healthy military, which could be caused by changing posture control strategies and changing the movement pattern of the military with patellofemoral pain syndrome. It is necessary to pay attention to these changes in providing an appropriate treatment plan for preventing re-injury and secondary changes in military suffering from patellofemoral pain syndrome.