Arthroscopic determination of patellofemoral malalignment.

Patellofemoral alignment was determinant by arthroscopy according to the degree of knee flexion at which the lateral facet, the patellar ridge, and the medial facet of the patella gained contact with the femur. The intraarticular pressure was 75 mm Hg. In 17 patients with a normal patellofemoral joint, the lateral facet aligned at a mean knee flexion of 20 degrees, the patellar ridge at 35 degrees, and the medial facet at 50 degrees. Twelve patients with patellar subluxation showed no difference in the alignment of the lateral facet, but differed significantly with regard to alignment of both the ridge and the medial facet with contact at a mean flexion of 55 degrees and 85 degrees, respectively. The median measurements in 20 patients with idiopathic anterior knee pain did not deviate significantly from the normal material. However, the dispersion was increased significantly, with eight patients having increased measurements consistent with malalignment and three having decreased measurements below the lower limit of normal alignment. Patients with idiopathic anterior knee pain apparently can be reclassified according to the arthroscopically determined alignment, which may prove important in the treatment of these patients.