Decrease in Number of Risk Factors for Knee Pain With Osteoarthritis Progression

Few risk factors for knee pain associated with osteoarthritis (OA) remain significant as the condition progresses, according to the results of a study published in Arthritis Care & Research.

Data for this study were sourced from the Osteoarthritis Initiative (OAI), which is a multicenter, prospective, longitudinal study sponsored by the National Institutes of Health and conducted at 4 sites in the United States. Risk for pain associated with OA of the knee was evaluated among 4446 patients. No pain experienced in the previous 30 days was defined as a numeric rating scale (NRS) score of 0, mild pain was defined as scores ranging from 0 to ≤3, and moderate to severe pain was defined as a score greater than three.

Study population consisted of 41.9% men, the mean age of study participants was 61.07 (standard deviation [SD], 9.17) years, mean BMI was 28.57 (SD, 4.81) kg/m², 31.6% reported a history of injury, 12.4% squatted frequently, 11.2% kneeled frequently, and 43.5% had a Kellgren-Lawrence (K-L) system for classification of osteoarthritis grade 0 or 1, respectively.

No knee pain was reported by 35.4% of patients, mild pain was reported by 25.6% of patients, and moderate to severe pain was reported by 39.0% of patients. Patients with more pain were found to also have increased BMI, fewer were men, more had a history of injury, and had more had K-L grade 4 (all P <.01).

Increased risk for knee OA was associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs; adjusted odds ratio [aOR], 1.547; 95% CI, 1.351-1.771; P <.001), previous injury (aOR, 1.510; 95% CI, 1.331-1.714; P <.001), diabetes (aOR, 1.27; 95% CI, 1.012-1.597; P =.039), and depression according to the Center for Epidemiologic Studies Depression Scale (aOR, 1.034; 95% CI, 1.034-1.043; P <.001).

Compared with patients who had normal alignment, patients with valgus alignment were at increased risk for knee pain (aOR, 1.172; 95% CI, 1.022-1.344; P =.023).

Knee pain was negatively related with quadriceps size (aOR, 0.824; 95% CI, 0.776-0.878; P <.001) and age (aOR, 0.972; 95% CI, 0.965-0.979; P <.001).

Compared with patients who had K-L grade 4, patients with grades 0 or 1 (aOR, 0.192; 95% CI, 0.146-0.253; P <.001), 2 (aOR, 0.284; 95% CI, 0.216-0.373; P <.001), and 3 (aOR, 0.507; 95% CI, 0.383-0.671; P <.001) were at lower risk for knee pain.

Stratified by premorbid (n=1934), initial stage (n=1343), middle stage (n=876), and advanced stage (n=293) osteoarthritis, the number of significant risk factors decreased from 7 to 5, 4, and 2, respectively. Among patients with the most advanced disease, only age and quadricep size were important predictors for knee pain.

This study was limited by its cross-sectional design, from which causal relationships could not be evaluated.

Study authors state that multiple risk factors are important for predicting knee pain associated with OA, but that as disease progresses fewer risk factors remain important. They further advise, “These findings provide important insights for the precise treatment of OA-related pain; thus, strategies to manage OA-related pain should differ based on radiographic grades.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.