Knee Buckling a Prelude to a Fall

BOSTON, Oct. 16 -- Knee buckling, the sudden loss of postural support across the knee during weight-bearing activity such as climbing stairs, affects more than one in 10 adults, and may lead to falls investigators here determined.

In a study of more than 2,300 adults in the general population, about 12% reported at least one episode of knee buckling within the previous three months, and, of those, nearly 13% said they'd fallen when the knee buckled, according to David T. Felson, M.D., M.P.H., of Boston University School of Medicine, and colleagues, in the Framingham Osteoarthritis Study.

"We suggest that asking patients with knee problems whether they have buckling might identify and prevent consequential events that follow from buckling and falling," they wrote in the October 16 issue of the Annals of Internal Medicine.

The authors conducted a cross-sectional, population-based study consisting of members of the Framingham Offspring Study cohort -- the children of the original Framingham Heart Study participants and their spouses -- plus a new community-based cohort. The merged groups were dubbed the Framingham Osteoarthritis study cohort.

A total of 2,351 men and women ages 36 to 94 (median, 63.5) were enrolled. The participants were asked if during the previous three months they had experienced knee buckling or "giving way," and if so, whether that had led to falling.

The participants were also asked about knee pain in the preceding week and limitations in function according to the Short Form-12 and Western Ontario and McMaster Universities Osteoarthritis Index.

The volunteers also underwent isometric tests of quadriceps strength and weight-bearing radiography. Community-based participants also had an MRI of the right knee, with the scan read for evidence of anterior cruciate ligament tears and other damage.

The authors conducted logistic regression analysis controlling for age, gender, body mass index, and the severity of knee pain.

They found that 278 of the participants (11.8%) reported having had at least one episode of knee buckling within the prior three months, and more than three-fourths of this group (78.1%) had more than one episode. In addition, of those who experienced knee buckling, 12.6% fell during an episode.

"Buckling was far more common in knees with pain at any time in the past 30 days (14.1%) than in knees with no pain at all (2.1%)," the authors wrote.

And the likelihood of buckling increased as pain increased. "The prevalence of buckling was 26.7% among knees with pain rated as severe compared with 9.9% among knees with pain rated as mild."

The authors noticed independent associations between buckling and the presence of knee pain and quadriceps weakness.

In analyses adjusted for pain severity and knee weakness, participants who reported knee buckling had worse physical function than those without buckling. Work limitations were reported by 46.9% of participants with buckling, compared with 21.7% of those without buckling (adjusted odds ratio, 2.0, 95% confidence interval. 1.5 to 2.7).

The authors noted that the study was limited by a lack of comprehensive anatomical and dynamic biomechanical information and a cross-sectional design that did not allow for establishment of causality.