The Effect of Knee Replacement on Self-Reported Participation and Gait Speed:  The MOST Study and the Osteoarthritis Initiative

Background/Purpose:

Little research has explored participation outcomes, defined as involvement in life situations, among persons following total knee replacement (TKR).  Since confounding by indication is likely in a study of TKR outcomes, we examined whether participation restriction (PR) differed among persons following TKR compared to a propensity-score matched group with symptomatic knee osteoarthritis (SxOA). Research has found differences in results between self-reported and performance measures; and, as gait speed is strongly associated with disability, we also explored whether it differs by TKR status using the same methods.

Methods:

Subjects with SxOA were selected from The Multicenter Osteoarthritis (MOST) Study and the Osteoarthritis Initiative (OAI). We generated a propensity score for each subjects’ odds of having a TKR based on their values of 17 TKR-associated (p<0.2) variables (e.g. sex, medication use, comorbidities, living situation, pre-TKR participation).  Within each cohort using a greedy matching method, we matched 1 subject with SxOA, defined as radiographic evidence of knee OA and report of frequent knee pain over the last 30 days, with 1 subject with a TKR by their propensity scores. The clinic visit falling ≥ 1 year after the TKR date for each matched pair was used as the index visit. Participation was measured using the Late Life Disability Instrument (LLDI); and PR was defined using a previously established cut-point of < 69/100 on the Instrumental Limitation subscale of the LLDI.  Gait speed was calculated using the time required to ambulate 20 m on a straight walkway (m/s). Slow gait speed was defined as speed < 1.0 m/s. We compared the proportion of subjects with PR and slow gait speed among the TKR and non-TKR SxOA subjects using chi square analyses. We evaluated the association between TKR status (yes/no) and PR, and TKR status and gait speed, using logistic regression.

Results:                           

There were 258 and 247 matched pairs with post-index date PR and gait speed data, respectively. Table 1 presents the proportions of subjects with these data in each group, as well as estimates of association. The proportion with PR among the non-TKR subjects was 10% higher than that for the TKR subjects, and the proportions of subjects reporting PR was considerably higher than the subjects demonstrating slow gait speed. Having a TKR was associated with decreased odds of PR but not with slow gait speed.

Conclusion:

In this study, TKR subjects had two-thirds the risk of participation restrictions compared with demographically and clinically similar subjects not undergoing TKR, although there was no effect of TKR on gait speed.

Table. Proportions and odds ratios of participation restriction and slow gait speed by TKR status among propensity-score matched subjects.