Effect of isometric quadricep activation on "Q" angle in young females.

The Q angle represents an estimate of the resultant force of the quadriceps on the patella and is a predictor of the lateral movement of the patella under dynamic conditions. The aim of the present study was to observe whether isometric quadriceps activation (IQA) can decrease the Q angle and to identify people at high risk of patellar subluxation. Q angles were measured in 23 non impaired young women (22.9 +/- 2.3 years) in relaxed standing and during IQA. There was a significant decrease (4.65 +/- 2.74 degrees) in the Q angle values for subjects with IQA as compared to subjects with measurements in relaxed standing Significance levels were set at P < 0.05. The Q angle decreases with IQA which was highly significant (t = 8.01, P < 0.001). The result supports the view that an excessive Q angle may predispose women to greater lateral displacement of the patella during vigorous activities and sports in which the quadriceps muscle is stressed.