by Contributing Writer, MedPage Today
Low knee extensor (KE) muscle strength is associated with an increased risk of systematic and functional deterioration in knee osteoarthritis (KOA), a team of international investigators has found.
Adam G. Culvenor, PhD, Institute of Anatomy, Paracelsus Medical University in Salzburg, Austria and colleagues, conducted a systematic review and meta-analysis of 15 studies evaluating low KE strength, and published their findings online in Arthritis Care & Research.
While the meta-analysis determined that lower KE strength was associated with an increased risk of symptomatic and functional decline, there was no association with an increased risk of tibiofemoral joint space narrowing.
Knee osteoarthritis is a leading cause of disability among older adults. In fact, according to the American Physical Therapy Association, about 16% of adults 45 years and older have knee osteoarthritis,
The researchers pointed out that despite the prevalence in this condition among American adults, regulatory approved therapies designed to delay or moderate the onset of the condition “have remained elusive” and that many adults suffering from KOA will end up undergoing surgical knee replacement.
Accordingly, Culvenor and his colleagues argued, “identification of modifiable risk factors for KOA structural, symptomatic and functional decline is therefore a priority.” One of the modifiable risk factors is believed to be knee extensor strength.
In their systematic review and meta-analysis, the researchers identified 15 studies covering more than 8,000 patients with, or at risk of, KOA, for review and analysis.
The 15 studies had a follow-up time ranging from 1.5 to 8 years, and ranged in size from 82 to 3,975 participants. The studies consisted of older adults (mean age greater than or equal to 60) who were generally overweight.
The meta-analysis determined that lower KE strength was associated with an increased risk of symptomatic decline in the participants (WOMAC-Pain: OR 1.35, 95% CI 1.10, 1.67). When stratified by sex the meta-analysis showed and increased risk of symptomatic decline and total knee replacement (TKR) for women, but not for men.
It also showed that lower KE strength was associated with an increased risk of functional decline (WOMAC-Function: OR 1.38, 95% CI 1.00, 1.89; chair-stand task: OR 1.03, 95% CI 1.03, 1.04).
However, the meta-analysis also determined that lower KE strength was not associated with an increased risk of radiographic tibiofemoral joint space narrowing (OR 1.15, 95% CI 0.84, 1.56). The evidence was inconclusive for lower KE strength’s association with an increased risk of patellofemoral deterioration.
“Our pooled results, demonstrating that lower KE strength is associated with an increased risk of symptomatic and functional decline, particularly in women, underpin the importance of optimizing KE strength,” Culvenor and his colleagues wrote.
The fact that women with knee strength deficits are at greater risk for total knee replacement could be explained by a number of other factors that patients take into account when count when considering TKR , the authors observed, such as a greater willingness to undergo surgery.
They added that since lower KE strength is associated with that increased risk of symptomatic and functional decline it suggests that interventions designed to increase KE strength could mitigate that risk. They pointed out that one study found an average gain of 17% in KE strength as a result of up to 6 months of resistance training in patients with KOA, resulting in reports of improved self-reported pain and function in a majority of those patients.
The authors wrote that one limitation of their review was the “large variety of outcome measures used to assess deterioration in KOA.” This limited their ability to pool all data and meant that only two studies were pooled for most outcomes — a problem that reflects that fact that there is lack of universally acceptable outcomes measures in KOA.
“The pooled data from this low number of studies needs to be interpreted with some caution given the considerable influence that one study can have on the pooled results,” Culvenor and his colleagues wrote.
The study was funded by the European Union Seventh Framework Program.
The authors reported financial relationships with Chondrometrics, Merck Serono, Bioclinica/Synarc, Samumed, Meddtronic, AbbVie, Kolon, Ampio, BICL, and Orthotrophix.
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