Clinical outcome after total knee replacement: forgotten knee. a single-centre prospective pragmatic study

Abstract

Purpose: Total knee replacement is the radical surgical treatment of knee osteoarthritis and usually produces good or very good results in terms of pain and function. However the patient may report that the knee, although free of pain, does not feel normal. As a result, the patient's assessment may be less favourable than the surgeon's assessment of the outcome. A “forgotten” knee is a joint that feels completely normal to the patient and is therefore the best possible outcome from the patient's viewpoint. To evaluate the prevalence of “forgotten knee” in a single-centre pragmatic prospective study of a uniform patient population, from January 2001 to December 2008. Methods: The study patients were selected for TKR by a specialized surgeon based on tibiofemoral and/or patellofemoral knee osteoarthritis stage IV in the Alback radiological classification, with a >70-mm visual-analogue-scale (VAS) pain score and non response to appropriate medical management. All procedures were done by the same surgeon (MB). A mobile-bearing posterior cruciate ligament-substituting prosthesis was used. The following were recorded at baseline and during regular post-surgery visits: VAS pain score, Knee Society knee and function scores, and four functional scores (KOOS, Oxford, WOMAC, and Lequesne). Forgotten knee was assessed at last follow-up based on the patient's answer to the following question: “Do you feel your knee is completely normal all the time?” Knee radiograph findings before and after TKR were recorded. The chi-square test was used for qualitative parameters and the t test and analysis of variance for quantitative parameters. Results: We included 498 knees in 406 patients (63% of women). Mean age was 70±8.6 years, mean body mass index was 29 Kg/m2, and mean follow-up was 6.4 (3-10) years. Varus deformity was noted in 63% and valgus deformity in 36% of patients. At last follow-up, 375 patients were still active. All functional scores improved significantly (p<0.001) from baseline to last follow-up: KOSS, 40±14 to 95±9; Oxford, 38±9 to 14±4; global WOMAC, 51±18 to 12±7; and Lequesne, 14±9 to 1±3. Among the patients, 80% felt satisfied with the procedure and 87% felt the results were consistent with their expectations, but only 44% met our criterion for “forgotten” knee. There were 17 complications (3.4%) including 5 cases of sepsis with favourable outcomes after reoperation. Conclusions: Only 44% of patients had a forgotten knee after TKR, although 80% were satisfied and free of pain. A forgotten knee may be a criterion for complete recovery that might be of use in future studies of TKR outcomes.