The Chitranjan Ranawat Award: functional outcome after total knee replacement varies with patient attributes

Abstract

Total knee replacement effectively relieves arthritis pain but improvement in physical function varies. A clearer understanding of the patient attributes associated with differing levels of functional gain after TKR is critical to surgical decision making. We reviewed 8050 primary, unilateral TKR patients enrolled in a prospective registry between 2000 and 2005 who had complete data. We evaluated associations between 12-month function (SF12/PCS) and preoperative gender, age, BMI, emotional health (MCS), knee diagnosis, quadriceps strength, and physical function (PCS). More than 98% of patients reported pain relief (KS pain score). At 12 months, mean PCS gain was 13.6 points, but the distribution was bimodal. The mean gain in PCS in the 63% of patients with greater improvement was 21 (SD = 7), and 4.1 (SD = 7) in the remaining 37%. Increased likelihood of poor functional gain was associated with older age, body mass index (BMI) over 40, lower MCS, and poor quadriceps strength. While two-thirds of patients reported functional gain well above national average at 12 months post-TKR, 37% reported limited functional improvement. Further understanding of the patient attributes associated with limited improvement will guide the design of innovative strategies to improve functional outcomes.

Level of evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

Pain distributions before TKR and at 12-months post-TKR are similar in patients with high and low emotional health.

Fig. 2

Pre-TKR physical function (SF12/PCS) distribution is unimodal while the 12-month post-TKR physical function distribution is bimodal.

Fig. 3

Twelve-month post-TKR function distributions vary by age group and the oldest age group is associated with greatest functional variation.

Fig. 4

Pre-TKR and12-month post-TKR function distributions do not vary by gender.

Fig. 5

Twelve-month post-TKR function distributions vary by body mass index (BMI) and the highest BMI values are associated with greatest functional variation.

Fig. 6

Twelve-month post-TKR function distributions vary by emotional health (SF12 MCS) and lower emotional health is associated with greatest functional variation.

Fig. 7

Twelve-month post-TKR function distributions—poor quadriceps strength is associated with low functional outcome.

Fig. 8

Model predicts two patient groups, those with high and low 12-month functional outcome (SF12/PCS).