Patterns of knee arthrosis and patellar subluxation.

This study was based on the unexpected observation of lateral patellofemoral subluxation in the varus osteoarthritic knee. Standardized radiographs of 109 knees (65 patients with osteoarthritis) were selected randomly from the authors' database and retrospectively reviewed. Hip-knee-ankle alignment data were correlated with patellofemoral subluxation and tilt, as well as with radiographic patellofemoral grades for arthrosis. The amount and site of patellofemoral arthrosis were correlated with patellar position and limb alignment. Patellae that were located centrally in the trochlear groove had the lowest radiographic score for arthrosis. Subluxation of the patella, either medially or laterally, was correlated with increased radiographic scores. Limb alignment was not correlated with the radiographic score. A significant percentage of varus knees (28%) had unexpected lateral subluxation of the patella. This observation has not been reported previously. It may have an impact on surgical decision-making for total knee arthroplasty and osteotomy.