Influence of stability on range of motion after cruciate-retaining TKA

BACKGROUND: A loosely balanced total knee arthroplasty (TKA) is reported to produce a good postoperative range of motion (ROM), but too much laxity is thought to be the cause of persistent pain and worsened functionality. METHODS: The anteroposterior and mediolateral laxity values were measured to evaluate the influence of stability after cruciate-retaining (CR) TKA on ROM and the modified Knee Society score at 4-8 years after the operation. Twenty-one knees in 15 patients with an average age of 68 years who had undergone a CR TKA for osteoarthrosis were examined. The mean preoperative and postoperative ROM was 124 degrees and 112 degrees, respectively. The mean anteroposterior and mediolateral laxity values were 9.7 mm and 10.6 degrees, respectively. RESULTS: No correlation was found between the postoperative ROM and laxity or between the modified Knee Society score and laxity. A loosely balanced TKA did not produce a good postoperative ROM. No parameters suggested that lax knees showed a higher pain score and lower functional score than stable knees.