PARIS – Impaired vibratory sense and muscle strength may be important risk factors for knee instability in persons with or at risk for symptomatic knee osteoarthritis, according to an analysis of a large, longitudinal cohort.
"Buckling is commonly been thought of as a mechanical phenomenon, but no one really knows the risk factors," Dr. Najia Shakoor said in an interview at the World Congress on Osteoarthritis. "For many, sensory input may be important. If you have greater sensory input, in this case, greater vibratory sense, perhaps you can protect yourself from buckling."
Knee instability is common in persons with knee osteoarthritis (OA) and has been found in studies to be associated with muscle weakness. None have examined whether weakness predicts onset or worsening of knee instability, she said.
Patrice Wendling/Frontline Medical News
Dr. Najia Shakoor
It is also unknown whether decreased vibratory sense, often seen in older adults with knee OA, may distort one’s sense of knee position and increase the risk of instability.
For the current analysis, unilateral knee extensor strength and bilateral vibratory perception thresholds (VPT) were evaluated in 2,212 participants with or at risk for knee OA in the Multicenter Osteoarthritis Study (MOST). VPT was measured using a biothesiometer, with the tip placed on the tibial tuberosity and the voltage increased by 1 volt/sec from 0 until the participant acknowledged sensation.
The mean age of study participants was 68 years, mean body mass index (BMI) was 31 kg/m2, and 60% were women.
At the 60-month visit, 17% of participants reported knee buckling in the past 3 months, 29% reported slipping or "shifting, slipping, or going to give way, but didn’t actually do so," and 37% reported instability (buckling and/or slipping), said Dr. Shakoor, a rheumatologist with Rush University Medical Center, Chicago.
During follow-up, 32% of patients developed incident instability, 20% incident buckling, 11% worsening instability, and 21% worsening buckling.
In Poisson regression person-based analyses, the risk of incident knee instability was significantly less in those with greater quadriceps strength (relative risk, 0.60; P = .003) as well as in those with better vibratory sense (P value for linear trend of .024), after adjustment for age, sex, BMI, race, clinic site, Kellgren-Lawrence OA grade, Western Ontario and McMaster Osteoarthritis Index knee pain, and both predictors.
Better vibratory sense also protected against worsening of both knee instability (RR, 0.42; P = .021) and buckling (RR, 0.67; P = .020), Dr. Shakoor reported in the poster presentation at the meeting, sponsored by the Osteoarthritis Research Society International.
Although it’s not known whether vibratory sense can be improved, muscle strength can be. "So these are potentially modifiable risk factors for a common problem," she said.
Prior work by the group has found that vibratory sense is impaired in hip as well as knee OA, compared with healthy controls.
The study was supported by the National Institutes of Health. Dr. Shakoor reported no conflicting interests.