The relationship between quadriceps angle and anterior knee pain syndrome

Anterior knee pain syndrome (AKPS) represents a significant challenge for patients and for clinicians. The purposes of this study were: 1) to determine the reliability of the Q-angle measurement, 2) to quantify Q-angle changes that occur with knee flexion, and 3) to determine if subjects with AKPS (N = 52) have a significantly different Q-angle than subjects without AKPS (N = 50). With the knee in an extended position, intratester Q-angle intraclass correlation coefficients (ICC) ranged from .84 to .90, and standard error of measurement (SEM) values ranged from 2.01 to 2.23 degrees. Intertester Q-angle ICC was .83, and the SEM was 2.49 degrees. With the knee flexed, the intratester ICC was .83 for both testers, and SEM values ranged from 0.68 to 2.45 degrees. Intertester ICC and SEM were .65 and 3.50 degrees, respectively. No significant difference was found in intratester Q-angle values between the extended and flexed knee positions (p > 0.05). No significant difference in Q-angle was found between asymptomatic subjects (11.1 +/- 5.5 degrees) and symptomatic subjects (12.4 +/- 5.1 degrees) (p = 0.07). Increased Q-angles were not responsible for AKPS in this group of patients. Other factors were hypothesized to be responsible for their symptoms.