Patellofemoral pain syndrome: validity of clinical and radiological features

Data regarding validity of clinical and radiographic findings in diagnosing patellofemoral pain syndrome are inconclusive. We prospectively assessed how sensitive and specific key patellofemoral physical examination tests are, and evaluated the prevalence of physical examination and radiographic findings. Sixty-one infantry soldiers with patellofemoral pain syndrome and 25 control subjects were evaluated. The sensitivity of the patellar tilt, active instability, patella alta, and apprehension tests was low (less than 50%); specificity ranged between 72% and 100%. Although the prevalence of positive patellar tilt and active instability tests was significantly greater in subjects with patellofemoral pain syndrome, there were no significant differences between the groups in the results of the other two tests. Soldiers with patellofemoral pain syndrome presented with increased quadriceps angle, lateral and medial retinacular tenderness, patellofemoral crepitation, squinting patella, and reduced mobility of the patella. There were no differences between the groups in the prevalence of lower limb and foot posture alignment and knee effusion. Plain radiography showed increased patellar subluxation in soldiers with patellofemoral pain syndrome. Other radiographic measures (sulcus angle, Laurin angle, Merchant angle, and Insall-Salvati index) were similar in both groups. We provide evidence regarding the validity of clinical and radiographic features commonly used for diagnosing patellofemoral pain syndrome. Physical examinations were more useful than plain radiography.