The purpose of this study was to investigate whether there is a relationship between baseline LBP and the occurrence of knee OA symptoms 1 year later.
This was a retrospective longitudinal study embedded within the Osteoarthritis Initiative, which included 4796 individuals. This study enrolled 3284 participants in the incidence sub-cohort without symptomatic knee OA. We excluded 1033 participants who reported knee pain on most days of the month in either knee in the 12 months, 152 participants who used medication for knee symptoms, and another 401 participants for whom data were missing preceding baseline; thus, 1698 participants (mean age, 62.3±9.0 years; 991 females) were ultimately included. The dependent variable was the occurrence of knee pain on most days of the month in either knee during the 12 months after baseline (no=0, yes=1). The independent variable was LBP severity (none=0, most severe=9) at baseline. Adjusted variables taken at baseline included age, sex (male=0, female=1), body mass index (BMI), Kellgren-Lawrence (KL) grade on affected side, past history of knee injury and surgery (no=0, yes=1), family history of total knee arthroplasty (no=0, yes=1), presence of Heberden’s nodes (no=0, yes=1), risk of repetitive knee bending activities in daily life (ACTRISK) (no=0, yes=1), severity of depression measured by Center for Epidemiologic Studies Depression scale (CES-D), number of comorbidities measured by Charlson Comorbidity Index, isometric knee extension strength on affected side (IKES) (N), and amount of physical activity at baseline measured by Physical Activity Scale for the Elderly. The right side was included in patients with or without bilateral symptoms. All independent and adjusted variables were obtained from the baseline data. A logistic regression analysis using the direct method was performed to investigate the relationship between baseline LBP severity and the occurrence of knee OA symptoms in either knee 1 year later. Significance level was set at 5%.
A total of 607 participants had LBP at baseline and 358 had knee OA symptoms 1 year later. The following factors were significantly associated with the occurrence of knee OA symptoms in either knee at 1 year after baseline: LBP severity (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.05–1.23), sex (OR, 0.68; 95%CI, 0.49–0.94), age (OR, 0.98; 95%CI, 0.97–1.00), BMI (OR, 1.05; 95% CI, 1.02–1.08), KL grade (OR, 1.24; 95%CI, 1.11–1.39), ACTRISK (OR, 1.74; 95%CI, 1.29–2.35), CES-D (OR, 1.05; 95% CI, 1.03–1.07) and IKES (OR, 0.998; 95%CI, 0.996–0.999 ).
Baseline LBP severity was positively associated with knee OA symptoms 1 year later independent of other variables. The influence of LBP on knee OA may be due to changes in gait and/or lower back mechanics that increase mechanical stress on the knee joint. Moreover, an inflammatory state may affect LBP and knee OA.
These results indicate that LBP treatment is important in preventing the onset of symptomatic knee OA.
Low back pain
Pain
