Knee OA No Excuse to Skip Out on Physical Activity

WASHINGTON — Most people with knee osteoarthritis (OA) are able to walk the 6,000 daily steps they need to improve their condition and prevent disability, according to researchers here who divulged benchmarks for three key tests they say patients need to meet.

In a prospective observational study, knee OA patients (or high-risk knee OA patients) who walked more than 6,000 steps daily performed the sit-to-stand test (repeating five times) in a mean 10.5 seconds, walked 400 m in just over 5 minutes, and walked 20 m at a clip of 1.3 m/sec, reported Hiral Master, PT, MPH, CPH, of the University of Delaware in Newark, and colleagues.

Although not quite half the study participants actually walked 6,000 steps daily, most knee OA patients have the capacity to do so, said co-author and presenter Daniel K. White, PT, ScD; he suggested the three test means become benchmarks patients strive to meet, at the American College of Rheumatology annual meeting.

“Now that we have an idea of how much ability is necessary to be active, we can better develop intervention strategies that are personalized to patients’ individualized needs so we can get them to be more active,” said White, also at the Delaware institution.

Performing below the thresholds on the tests above may signal knee OA patients are not getting the appropriate amount of activity to prevent functional knee limitation, White added. In a previous paper, White and colleagues determined that activity to be 6,000 steps daily.

If patients not only fail to meet the benchmarks, but also exhibit sit-to-stand in >12 seconds, gait speed <1.2 m/sec, and 400 m walk >5.5 minutes, White recommended clinicians refer them to rehabilitation to meet the physical function thresholds. Researchers reported that taking longer than 12 seconds to perform the standing test is associated with fall risk for older adults, citing previous studies, while walking slower than 1.2 m/sec makes it difficult to walk in the community, and taking longer than 365 seconds to walk 400 meters is a risk factor for death in older adults.

The researchers analyzed data from patients at the 48-month follow-up visit enrolled in the Osteoarthritis Initiative (OAI). Included patients had to wear a monitor for at least 10 hours daily over at least 4 days. Participants had a mean age of 65 and 55% were female. The mean body mass index was 28.4 kg/m².

Just under one-half of the 1,925 participants walked 6,000 daily steps, with a mean 6,166 for the population total.

Thresholds of high specificity (80%-95%) of physical performance (6,000 steps) ranged from 11.4-14 seconds for the standing test, 315-350 seconds for the 400 m walk, and 1.13-1.26 m/sec on the 20 m walk.

The results need to be validated in other cohorts, but “we have the preliminary numbers to rely on,” White told MedPage Today. “We have confidence we’re on the right track.”

Study limitations included testing for only one cutoff for physical activity (6,000 steps) and using daily steps as a physical activity marker, without taking into consideration other physical activity with few or no steps, such as bike riding.

LAST UPDATED 11.21.2016