Increased Physical Activity Improves Mobility After Joint Replacement in Older Women

knee replacement
knee replacement
Women with osteoarthritis who reported lower physical activity levels before total joint replacement were more likely to experience mobility limitations in late life.

Older women with osteoarthritis (OA) reporting mild or no physical activity prior to total knee replacement (TKR) or total hip replacement (THR) demonstrated greater mobility limitations at age 85 compared with their more active counterparts, according to findings published in The Journal of Rheumatology.

Researchers sought to examine the relationship between previous physical activity and survival to age 85 with mobility restrictions at age 85. Data from the Women’s Health Initiative — a prospective longitudinal study of US women who were recruited between 1993 and 1998 and followed through 2012 — along with fee-for-service Medicare claims were used to enroll women ≥65 years at baseline (mean age, 69.5 years) who subsequently underwent TKR (n=1986) or THR (n=1034) in this retrospective analysis. 

Baseline physical activity was self-reported on average 6.7 years before surgery and recorded as metabolic equivalent of task (MET)-h per week. Lower physical activity levels corresponded with less baseline mobility. Late-life mobility was evaluated at age 85 using the physical function portion of the 36-Item Short Form Health Survey. Age-related outcomes at 85 years were defined as survival without mobility limitations, survival with limitations, or death before reaching 85 years. Risks were reported as odds ratios (OR).

At age 85, 35.3% of patients in the THR group had intact mobility, 47.7% had mobility limitations, and 17.0% had died before age 85. Compared with women with the highest physical activity levels (>17.42 MET-h/wk), women considered physically inactive before hip surgery demonstrated the greatest mobility limitation risk (OR, 2.36; 95% CI, 1.30-4.26; P <.001). Women with no reported moderate to vigorous physical activity (MVPA) had the highest chance of mobility limitations vs women reporting ≥15 MET-h/wk, indicating high MVPA levels (OR, 2.00; 95% CI, 1.24-3.22; P <.001). Patients who did not walk at all before THR carried the greatest risk for limitation in mobility at follow-up vs women who walked regularly (OR, 1.81; 95% CI, 1.20-2.72; P =.003).

In patients who underwent TKR, follow-up at age 85 revealed that 31.7% had intact mobility, 48.7% had limitations, and 19.6% had died before age 85. Patients who were inactive before surgery carried the greatest odds of limitation of mobility (OR, 1.68; 95% CI, 1.15-2.45; P =.007), as well as the highest chances of expiration before age 85 (OR, 1.79; 95% CI, 1.09-2.95; P =.02) vs individuals reporting the highest physical activity levels. Patients claiming no MVPA had the greatest risk for mobility limitation (OR, 1.60; 95% CI, 1.16-2.19; P =.002), as well as the highest odds of death before age 85 (OR, 2.24; 95% CI, 1.47-3.42; P =.01) compared with women with high MVPA levels.

Dose-response relationships between lower physical activity levels and higher risks of mobility limitation or death before age 85 were statistically significant. However, following adjustment for baseline mobility, the correlations between baseline physical activity levels and late-life mobility or death did not remain significant.

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Study strengths included the use of a population-based sample with extended post-surgical follow-up and the use of combined Women’s Health Initiative and Medicare data.

Study limitations included use of physical activity self-reporting, which lacked objective strength, resistance, and flexibility information; lack of information on activity types; potential measurement error secondary to self-reported total energy expenditure; possible lack of generalizability to managed care populations; inability to assess ethnic differences; and lack of investigation into the effect of physical activity levels on mortality risk.

“Our data underscore that a large proportion of women with hip or knee OA may reach old age with poor mobility despite [total joint replacement],” the authors emphasized. They recommended that future trials attempt to differentiate between the influence of physical activity on patients undergoing TKR vs THR and investigate similar effects on patients with severe disease.

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Shadyab AH, Eaton CB, Li W, Lacroix AZ. Association of physical activity with late-life mobility limitation among women with total joint replacement for knee or hip osteoarthritis [published online June 1, 2018]. J Rheumatol. doi:10.3899/jrheum.171136