Background Patellofemoral Pain Syndrome (PFPS) is characterized by anterior knee pain most commonly on the patella lateral facet. Although the increased Frontal Plane Projection Angle (FPPA), core deficit and hip strength have been reported, there are no studies on the relationship of the anterior knee pain severity and functional capacity with the FPPA, core and hip strength1. Knowledge of the contribution of the FPPA, hip lateral rotator, extensor and abductor muscles strength to the pain level and functional capacity would provide an insight into factors associated with symptom severity in patients with PFPS, and help to provide a better treatment approach in subjects with this knee disorder.
Objectives The objective of the present study was to determine the relationships between isometric torque (hip lateral rotator, extensor and abductor muscles strength) and FPPA, symptom severity and functional capacity in females with PFPS.
Methods This cross-sectional study enrolled 22 women with age ranging from 18 to 45 years. Anterior knee pain was assessed using an 11-point visual analog scale (VAS) for pain. Functional capacity was using the Anterior Knee Pain Scale (AKPS). The FPPA was recorded using three adhesive markers were placed on the midpoint of the ankle malleoli, midpoint of the femoral condyles, and on the proximal thigh along a line from the ASIS to approximately 30 cm above the knee marker2. The height of the step was customized as being 10% of subject's height. The digital camera was positioned 2 m ahead of the subject2. A Nicholas handheld dynamometer was used to measure strength. To mitigate the influence of the examiner, a strap was used for all tests. Participants were instructed to push the dynamometer for 5 seconds, as hard as they could sustain. Three tests were performed, with 30-seconds between measures.
Results The FPPA showed moderate positive correlation with the intensity of pain (r=0.55; p=0.008), functional capacity moderate positive correlation with peak torque of hip abductor (r=0.46; P=0.03), hip extensor (r=0.49; p=0.02) and trunk side flexion (r=0.63; p=0.002). In the multiple regression model, the only predictor for the severity of knee pain was FPPA (r2=0.31; p=0.008). Regarding predictors of functional capacity, the peak torque of trunk side flexion, hip extensor and hip abductor explain 41.4% of the functional capacity of the knee in women with PFPS (r2=0.41; p=0.02).
Conclusions The increased FPPA was associated with greater anterior knee pain severity and lower peak torque of trunk side flexion, hip extensor and hip abductor was associated with lesser functional capacity in women with PFPS.
Powers CM. The influence of abnormal hip mechanics on knee injury: a biomechanical perspective. J Orthop Sports Phys Ther 40: 42-51, 2010.
Willson JD and Davis IS. Utility of the frontal plane projection angle in females with patellofemoral pain. J Orthop Sports Phys Ther 38: 606-615, 2008.
Acknowledgements À Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Disclosure of Interest None declared