Osteoarthritis (OA) is the most common degenerative joint disease, and its severity is commonly assessed using the Kellgren–Lawrence (KL) classification. Understanding patient characteristics across different severity levels is essential to support clinical evaluation and optimize patient management. This study aimed to analyze the sociodemographic, clinical, and laboratory characteristics of patients with OA according to KL severity. A retrospective analytical observational study was conducted using the medical records of 1,124 patients diagnosed with OA at Sultan Agung Islamic Hospital, Semarang, Indonesia, between January 2020 and January 2025. Sociodemographic, clinical, and laboratory data were collected from electronic medical records. Descriptive statistics were used to summarize patient characteristics, while differences across KL severity levels were analyzed using the Chi-square test with a significance level of p<0.05. Significant differences in OA severity were observed according to age and body mass index (p<0.05), whereas sex was not significantly associated with KL severity (p>0.05). Clinical characteristics, including OA type, comorbidity status, number and type of comorbidities, and pain intensity, differed significantly across KL grades (all p<0.05). Laboratory parameters, including blood pressure, blood glucose, renal function, and lipid profile, also demonstrated significant differences according to OA severity (all p<0.05). These findings indicate that OA severity is associated with distinct sociodemographic, clinical, and laboratory characteristics, providing valuable evidence to support risk stratification, clinical assessment, and individualized management of patients with OA.