The diagnosis of Patella-Femoral Pain (PFP) is one of the most common and frustrating orthopaedic conditions seen clinically. Significant research has been directed at identifying the root cause of PFP. Recent research suggests that proximal joint mechanics contributes to abnormal stress and strain to the patella femoral joint. This research suggests that excessive hip internal rotation, adduction and weakness of the hip musculature specifically hip abduction, external rotation and extension contribute to excessive joint stress to the patellar-femoral joint.
Sousa and Powers sought to assess whether females with PFP demonstrate altered hip motion, strength and muscle activation patterns when performing functional task compared to a control group without PFP. The authors recruited 21 females between the ages of 18 and 45 with PFP and 20 females age matched without PFP to serve as a control group. Inclusion criteria for the PFP group included pain greater than 3 out of 10 with common functional activities such as sitting, stair ascent and descent, squatting, kneeling, pain located directly around the patella femoral joint and pain duration greater than 3 months. The control group could have none of the above symptoms, an absence of swelling, no prior knee injury/trauma or any conditions that would affect their gait.
The two groups participated in 2 testing sessions. First, they underwent motion assessment performing 3 different tasks including running, a drop jump, and a step-down maneuver. To eliminate the influence of fatigue, subjects returned for hip strength testing on a separate day.
The results of the study demonstrate that the PFP group demonstrated increased internal rotation with the functional task especially with running. Subjects in the PFP group were also found to have significantly less, (15-16%) hip abduction and extension torque production as compared to the control group during strength testing. There also appeared to be an increase in gluteus maximus contraction while performing functional task of step downs and running in the PFP group as compared to the control group. These differences in females with PFP suggest that these subjects were attempting to recruit a weakened muscle, perhaps in an effort to stabilize the hip joint.
Results of this study contribute to the growing body of literature that supports the influence of the proximal lower extremity affects the PF joint. This data suggest that an assessment of hip strength, motion and muscle performance should be included when assessing a patient with P-F complaints. At SP.OR.T.S this is a common practice with our P-F patients to assess the entire lower extremity. This research further supports this practice and assessment approach.
For more information, contact Sports & Orthopaedic Therapy Services today!
Souza, RB, Powers, CM. Differences in Hip Kinematics, Muscle Strength, and Muscle Activation Between Subjects With and Without Patellofemoral Pain. Journal of Orthopaedic & Sports Physical Therapy 2009;39:12-19.