The patellofemoral kinematics in patients with untreated developmental dislocation of the hip suffering from patellofemoral pain

Abstract Purpose This study reviews the dynamic patellofemoral CT results of 39 patients with untreated developmental dislocation of the hip who are suffering from knee pain. Method The mean age of the patients with unilateral developmental dislocation of the hip was 33.3 (±7.9), for bilateral patients 36.2 (±11.3), and for the control group, it was 31.5 (±8.5). While 14 of them were bilateral, 25 were unilateral. The CT results of 24 asymptomatic adult knees served as the control group. The patellofemoral parameters of patients with unilateral and bilateral developmental dislocation of the hip, the control group’s parameters and the effect of femoral anteversion, limb length discrepancy, severity of dislocation, the mechanical axis deviation on patellofemoral parameters were analyzed. Results In patients with unilateral untreated developmental dislocation of the hip, although the patella was located more laterally at initial flexion degrees, it was located more medially at 30° and 60° flexion with respect to the control group. For the involved extremity, the PTA angles at 15°, 30°, and 60° flexion were significantly higher than in the control group corresponding to medial patellar tilt. In patients with bilateral developmental dislocation of the hip, the course of the patella during tracking in terms of patellar shift was similar to that of the unilateral patients. The amount of leg length discrepancy and the severity of dislocation, as well as the mechanical axis deviation, did not affect the patellofemoral parameters. Conclusion The patients with untreated developmental dislocation of the hip and suffering from knee pain should be analyzed not only for tibiofemoral abnormalities but also for patellofemoral malalignment. Level of evidence Case–control study, Level III.