The study identified risk factors associated with radiographic severity of knee osteoarthritis (KOA) and their association with Kellgren-Lawrence (K–L) grade. Among KOA patients, there were significant gender differences in height, weight, and K–L grade distribution (all P < 0.05), whereas age, BMI, CRP levels, and VAS pain scores were not significantly different (all P > 0.05). CRP had the strongest correlation with K–L grade in both sexes (r = 0.51 in men, r = 0.60 in women). Multivariable logistic regression after adjusting for age, BMI, and VAS showed the strongest association of CRP with K–L grade. ROC analysis demonstrated a good discriminatory ability of the model to distinguish between mild (K–L 1–2) and moderate to severe (K–L 3–4) KOA with AUC = 0.865 (95% CI: 0.793–0.938) in men and AUC = 0.880 (95% CI: 0.827–0.933) in women. CRP showed a strong association with KOA severity after adjusting for factors, with a numerically stronger association in women.