The prevalence and severity of low back pain (LBP) may be higher in patients with knee osteoarthritis and varus thrust, particularly bilateral varus thrust, according to study results published in Arthritis Care & Research.
LBP has been reported in previous studies to be more common in patients with knee osteoarthritis, possibly due to a contribution of the joint disease. Varus thrust during gait is a simple measure defined as dynamic worsening or abrupt onset of varus motion during weight acceptance. The goal of the study was to explore the association between varus thrust during gait and frequency and severity of LBP in patients with knee osteoarthritis.
In this cross-sectional study, 296 patients age ≥45 years with Kellgren and Lawrence grade ≥1 in at least one knee who were able to walk independently on a flat surface were enrolled. Of the initial 296 participants, 205 (mean age, 68.19 years; 72.2% women) were included in the final analysis. In this cohort, 45 patients (22%) had varus thrust, of whom 29 exhibited the phenomenon possibly during any step and 16 during all steps.
Patients with vs without varus thrust had greater prevalence of any LBP (68.89% vs 54.38, respectively; odds ratio [OR], 1.78; 95% CI, 0.81-3.90) and of moderate to severe LBP (40% vs 16.88%, respectively; OR, 3.63; 95% CI, 1.62-8.10). Patients with bilateral vs unilateral varus thrust had a greater prevalence of moderate to severe LBP (OR 5.39; 95% CI, 1.92-15.16).
Participants with LBP (n=118) with vs without varus thrust had a 2.25-fold increased odds of reporting more severe LBP (95% CI, 1.02 to 4.96). Unilateral and bilateral varus thrust were associated with a 1.57-fold (95% CI, 0.58-4.25) and 3.10-fold (95% CI, 1.09-8.84) greater odds of higher LBP intensity, respectively, compared with patients without varus thrust.
Study limitations include its cross-sectional design, which precludes causal interpretation, a lack of information on pain in other joints, and a lack of radiographic examinations.
“These findings support the biomechanical link between knee kinematics and LBP, the so-called knee-spine syndrome. Close attention to varus thrust may be a key in clarifying the pathomechanics of [osteoarthritis]-related LBP,” concluded the researchers.
Iijima H, Suzuki Y, Aoyama T, Takahashi M. Relationship between varus thrust during gait and low back pain in people with knee osteoarthritis. Arthritis Care Res (Hoboken) [published online June 29, 2019]. doi:10.1002/acr.24020