Background: Platelets and lymphocytes levels are important in assessing systemic disorders, reflecting inflammatory and immune responses. This study investigated the relationship between blood parameters (platelet count (PLT), mean platelet volume (MPV), lymphocyte count (LINF), and platelet-to-lymphocyte ratio (PLR)) and osteoarthritis (OA) severity, considering age, sex, and body mass index (BMI). Methods: Patients aged ≥40 years were included in this cross-sectional study and divided into groups based on knee OA severity using the Kellgren–Lawrence (KL) grading system. A logistic regression model, adjusted for confounders, evaluated the ability of PLT, MPV, LINF, and PLR to categorize OA severity. Model performance in terms of accuracy, sensitivity, and specificity was assessed using ROC curves. Results: The study involved 245 OA patients (51.4% female, 48.6% male) aged 40–90 years, 35.9% with early OA (KL 2 in 33.9%. The model showed that a 25-unit increase in PLR elevates the odds of higher OA levels by 1.30 times (1-unit OR = 1.011, 95% CI [1.004, 1.017], p p < 0.0005). The model’s accuracy was 73.1%, with 84% sensitivity, 52% specificity, and an AUC of 0.74 (95% CI [0.675, 0.805]). Conclusions: Higher PLR increases the likelihood of moderate/severe OA, suggesting that monitoring these biomarkers could aid in early detection and management of OA severity. Further research is warranted to cross-validate these results in larger populations.
