Psychological distress and functional disability in knee osteoarthritis: a cross-sectional analytical study

Knee osteoarthritis (KOA) is a prevalent chronic condition associated with pain, functional limitation, and reduced quality of life. Psychological distress is common among patients with KOA and may influence symptom perception and functional outcomes; however, its independent association with functional disability remains uncertain when major clinical determinants are considered.

To examine the associations between psychological distress, pain intensity, and functional disability in patients with knee osteoarthritis.

A cross-sectional analytical study was conducted in adult patients with symptomatic knee osteoarthritis. Psychological distress was assessed using the Hospital Anxiety and Depression Scale (HADS), the Patient Health Questionnaire-9 (PHQ-9), and the Mental Component Summary (MCS) of the SF-36. Pain and functional disability were evaluated using the WOMAC index. WOMAC function scores were reverse-coded such that higher values indicate better functional status. Correlation analyses and two complementary multivariable linear regression models were performed to identify factors associated with functional disability. Model 1 adjusted for age, body mass index, and radiographic severity, while Model 2 additionally included pain intensity as a covariate to examine the extent to which pain accounted for the association between depressive symptoms and functional status.

Depressive symptoms assessed by the HADS-D were highly prevalent, with all participants (100%) presenting scores ≥ 8, and were significantly associated with pain intensity and functional status in unadjusted analyses. In multivariable regression (Model 1), depressive symptoms were significantly associated with functional disability after adjustment for age, body mass index, and radiographic severity (β = -1.14; 95% CI [- 1.95; -0.33]; p = 0.006), indicating that higher depressive symptom severity was associated with poorer functional status. However, this association was attenuated and no longer statistically significant after additional adjustment for pain intensity (Model 2; β = -0.42; 95% CI [- 0.91; 0.07]; p = 0.092), whereas pain intensity emerged as the strongest independent determinant of functional status (β = 1.99; 95% CI [1.64; 2.35]; p < 0.001).

Knee osteoarthritis is associated with a substantial psychological burden. Depressive symptoms are closely linked to pain and functional status; however, their association with functional limitation was largely attenuated after adjustment for pain intensity, suggesting that pain may play a central role in this relationship. These findings support integrated management strategies focusing on both pain control and psychological assessment.