Although knee stability is well known as an important element for the success of total knee arthroplasty (TKA), the direct relationship between clinical outcomes and knee stability is still unknown. The purpose of this study was to determine if postoperative knee stability and soft-tissue balance affect the functional outcomes and patient satisfaction after cruciate-retaining (CR) TKA.
Fifty-five patients with varus osteoarthritis of the knee who underwent CR TKA were included in this study, and their postoperative knee stability was assessed by stress radiography at extension and flexion 1 month postoperatively. Timed Up and Go test, patient-derived clinical scores using the 2011 Knee Society Score, and Forgotten Joint Score-12 were also assessed at 1 year postoperatively. The effects of stability parameters on clinical outcomes were analyzed using Spearman's rank correlation.
Medial stability at both knee extension and flexion had significant correlations with the shorter Timed Up and Go test and the higher patient satisfaction. Moreover, lateral laxity at extension was significantly correlated with the better patient satisfaction and Forgotten Joint Score-12. However, these correlation coefficients in this study were low in the range of 0.32-0.51.
Medial stability and lateral laxity play an important role in influencing 1-year postoperative clinical outcomes after CR TKA. However, we should keep in mind that these correlations are weak with coefficients at 0.50 or less and the clinical results are also affected by various other factors.