Shortening of patellar ligament and patella baja with improvement of quadriceps muscle strength after high tibial osteotomy.

One hundred and eight osteoarthritic knees that had high tibial osteotomy were examined, in the length of the patellar ligament, patellar height, and the strength of the quadriceps muscle. Patellar ligament shortening occurred until one year after surgery. Subsequently, shortening was not observed to be significant over a 10 year followup period. Using Insall-Salvati ratio, a majority of knees seemed to have lower patellae, because of the shortening of the patellar ligament. However, using patellotibial distance, 68 percent of patellae maintained the same height as preoperatively and 26 percent became patella baja. The strength of the quadriceps muscle increased postoperatively, reached the maximum at 2 years, and preserved the same strength over 10 years. Patellar ligament shortening and patella baja were probably thought to be caused by the biological adaptation of the extensor mechanism and the shrinking of the scar tissue in and around the postoperative patellar ligament.