Histologic comparison of posterior cruciate ligaments from arthritic and age-matched knee specimens

Twenty-four posterior cruciate ligaments (PCLs) harvested at the time of total knee arthroplasty (TKA) were histologically compared with an age-matched group of 36 PCLs harvested from above-knee amputations, cadavers, and bone bank donors. Ligaments were considered histologically abnormal and degenerative if either loose, mucoid, myxoid, or cystic changes were noted. The magnitude of degeneration was defined as normal, slight, mild, moderate, or marked, based on the amount of tissue demonstrating change. Examination of the PCLs from the TKA group demonstrated 17% normal ligaments, 20% with mild focal changes, and 63% with marked degenerative changes. The control group demonstrated 45% normal cruciate ligaments and 33% with slight, 11% with mild, and 11% with moderate focal changes. No PCL from the control group showed marked changes. The overall degenerative changes between these two groups were found to be statistically significant (P < .001). This study demonstrated that the PCL obtained at the time of TKA is characterized by distinct histologic degenerative changes that are different from age-related changes (P < .001) and that the PCL is not spared degenerative changes in involved osteoarthritic knees. This may help explain the finding that the PCL in osteoarthritic knees is biomechanically abnormal. Many studies have reported excellent results with TKA systems that retain the PCL, implying that a completely normal PCL is not required or that neural input is sufficient for proper kinematic knee function in knees that have undergone total joint arthroplasty.