Effect of quadriceps contraction on tangential patellar radiography.

This study examined whether the addition of quadriceps contraction to standard Merchant views provides additional useful information in the evaluation of patients with extensor mechanism malalignment. Fifteen patients (23 knees) with anterior knee pain due to lateral patellar compression syndrome and 22 control patients (44 knees) underwent standard Merchant views with the quadriceps relaxed and with an isometric isotonic contraction. Congruence and lateral patellar angles were measured for all groups. Although the congruence angle differed significantly between the control and symptomatic groups with the quadriceps contracted (P< or = .001), this difference also was seen without quadriceps contraction. There was also no significant difference within each group on addition of quadriceps contraction. No significant difference existed between the two groups for lateral patellar angle with quadriceps contraction. The addition of a controlled isometric quadriceps contraction did not add to the diagnostic yield of the standard Merchant view in terms of a predictable change in measured radiographic parameters.