Knee buckling: Prevalence, risk factors, and associated limitations in function

Background: Knee buckling is common in persons with advanced knee osteoarthritis and after orthopedic procedures. Its prevalence in the community is unknown. Objective: To examine the prevalence of knee buckling in the community, its associated risk factors, and its relation to functional limitation. Design: Cross-sectional, population -based study. Setting: The Framingham Osteoarthritis Study. Participants: 2351 men and women age 36 to 94 years (median, 63.5 years). Measurements: Participants were asked whether they had experienced knee buckling or "giving way" and whether it led to falling. They were also asked about knee pain and limitations in function by using the Short Form-12 and Western Ontario and McMaster Universities Osteoarthritis Index, had isometric tests of quadriceps strength, and underwent weight-bearing radiography and magnetic resonance imaging of the knee. Radiographs were scored for osteoarthritis by using the Kellgren-Lawrence scale, and magnetic resonance images were read for anterior cruciate ligament tears. The relationship of buckling to functional limitation was examined by using logistic regression that adjusted for age, sex, body mass index, and knee pain severity. Results: Two hundred seventy-eight participants (11.8%) experienced at least 1 episode of knee buckling within the past 3 months; of these persons, 217 (78.1 %) experienced more than 1 episode and 35 (12.6%) fell during an episode. Buckling was independently associated with the presence of knee pain and with quadriceps weakness. Over half of those with buckling had no osteoarthritis on radiography. Persons with knee buckling had worse physical function than those without buckling, even after adjustment for severity of knee pain and weakness. For example, 46.9% of participants with buckling and 21.7% of those without buckling reported limitations in their work (adjusted odds ratio, 2.0 [95% Cl, 1.5 to 2.71). Limitation: Causal inferences are limited because of the study's cross-sectional design. Conclusion: In adults, knee buckling is common and is associated with functional loss.