Unicondylar knee replacement and the cruciate ligaments

Abstract

This chapter mainly addresses the way in which the actions of the cruciate ligaments affect the kinematics of the tibiofemoral joint after unicompartmental knee replacement (UKR). Although it is normal practise to excise one or both of the cruciate ligaments during total knee arthroplasty (TKA), this reflects the fact that, historically, TKA patients were severely disabled by their arthritis and so they did not demand high levels of function: pain relief was paramount. The degree of degenerative change in these osteoarthritic knees was such that the anterior cruciate ligament was usually absent, following a combination of soft-tissue degenerative changes associated with chronic inflammation and mechanical destruction mechanisms, such as sawing by the edges of the osteophytes that had formed around the antero-distal outlet of the femoral intercondylar notch. This has never been the case with UKR, as in these patients, who are often younger, only one compartment of the knee has arthritic damage severe enough to require arthroplasty. Therefore, the implants are required to work in harmony with the other structures of the knee and ideally with a high level of function.