Chondromalacia induced by patellar subluxation in the rabbit

A unilateral patellar malalignment was induced in 20 young and 20 mature rabbits by lateral displacement of the tibial tuberosity, the other knee serving as osteotomized in situ control. At 6 weeks, all the knees appeared macroscopically normal, but histologically definite cartilage degeneration was found on the experimental side. At 3 months, macroscopic changes occurred in 5 of 10 mature rabbits, and histologic cartilage degeneration was found in all the experimental knees, most pronounced in mature animals, and particularly in joint facets submitted to high pressure. This experimental model produces changes resembling chondromalacia patellae and early arthrotic changes suggesting the importance of malalignment in the development of patellofemoral cartilage degeneration.