Dynamic postural stability and muscle strength in patellofemoral pain: Is there a correlation?

Although females with patellofemoral pain (PFP) show a decrease in hip and knee muscle strength, there is a lack of studies that associates this with postural stability. The purpose of this study was to assess the dynamic postural stability and muscle strength in the hips and knees of females with and without PFP, and to verify the association between the postural stability and the muscle strength in the PFP group.

Two groups were tested: one with 25 PFP and one with 25 asymptomatic. Postural stability was evaluated during stepping up down tasks using a force platform to determine the center of pressure (COP) excursion and velocity. A handheld dynamometer was used to assess the muscles strength. The correlation analysis was conducted between the COP variables and the muscle strength.

The PFP group demonstrated greater total and medial-lateral COP displacement (8887.7±761.7 vs. 8129.4±691.9mm, P<0.001; 32.3±5.5 vs. 21.7±2.7mm, P<0.001) and a higher total of medial-lateral COP velocity (22.2±5.2 vs. 17.0±1.6 P=0.001). The PFP group showed weaknesses in all muscles (P<0.05), and there was a good positive correlation between the anterior-posterior displacement and the velocity of the extensor hip muscle (r=0.52, P<0.01; r=0.55, P<0.001).

Subjects with PFP have frontal dynamic postural stability deficit and show an association between hip extensor and sagittal plane stability.