Background: Patellofemoral pain syndrome is a common cause of anterior knee pain. This condition may arise from abnormal biomechanical factors that alter tracking of the patella within the femoral trochlear notch. This in turn may contribute to increased patellofemoral contact pressure causing pain and dysfunction. Some impairment such as limited flexibility of key lower extremity muscles may be important impairments to consider in the conservative management of patellofemoral pain syndrome. The purpose of this study was to compare lower extremity muscle length between persons with and without patellofemoral pain syndrome.Methods: Fifteen patients with patellofemoral pain syndrome and 15 age and sex matched controls participated in the study. Lower extremity muscle lengths (quadriceps, gastrocenmius and soleus muscles) were measured by a standard goniometer in both groups.Results: Patients with patellofemoral pain syndrome demonstrated significantly less flexibility of the gastrocnemius and soleus muscles compared to healthy persons (respectively, p < /em>=.01 , p=.02), but flexibility of the quadriceps muscle was similar in the two groups (p < /em>≥.05).Conclusion: This study suggests less flexibility of the gastrocnemius and soleus muscles in patellofemoral pain syndrome patients. This may be an important consideration in management of this syndrome.