Knee Arthralgia and Cartilage Thinning in Psoriasis: Clues to Early Psoriatic Arthritis?

Background To compare femoral cartilage thickness between patients with psoriasis (PsO) and psoriatic arthritis (PsA), and to investigate whether knee joint pain in PsO patients could be an early risk factor for PsA. Methods Fifty‐nine patients (28 PsO and 31 PsA) were included in this cross‐sectional study. Demographic data were collected, and clinical assessments were performed using the Psoriasis Area and Severity Index (PASI) and the Disease Activity Score 28 (DAS28). PsO patients were evaluated for knee arthralgia symptoms within the past month. Femoral cartilage thickness was measured bilaterally at the medial femoral condyle, lateral femoral condyle, and intercondylar area using ultrasonography. Results Femoral cartilage thickness was significantly lower in PsA patients compared to those with PsO ( p < 0.05). Among patients with PsO, those reporting arthralgia ( n = 14) had significantly reduced lateral femoral condyle cartilage thickness in both knees compared to those without arthralgia ( p < 0.05). Spearman correlation analysis revealed a negative correlation between age and lateral cartilage thickness (e.g., right LFC: ρ = −0.338, p = 0.009, 95% CI –0.55 to −0.09). PASI scores showed a consistent positive correlation with femoral cartilage thickness across regions; for example, the correlation with the left LFC was significant ( ρ = 0.504, p < 0.01, 95% CI 0.29–0.67). These associations indicate that both demographic and disease‐related factors may influence cartilage status in PsO and PsA, although the confidence intervals indicate some degree of uncertainty and call for validation in larger cohorts. Conclusions Femoral cartilage thinning is evident in PsA patients and may begin even in the subclinical phase. In PsO patients, the presence of arthralgia, especially in the lateral femoral condyle, may reflect early structural changes and could serve as a predictor for PsA development. Ultrasonographic assessment offers a noninvasive, accessible method for early detection and follow‐up.