Knee osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage breakdown, joint pain, stiffness, and reduced mobility. It is a leading cause of disability worldwide, particularly among older adults. This study aimed to determine the prevalence of knee osteoarthritis among patients attending Rivers State University Teaching Hospital (RSUTH), Port Harcourt, Nigeria, between January 2020 and December 2022, and to assess its association with selected socio-demographic factors. A retrospective cross-sectional hospital-based study design was adopted. Data were obtained from patients’ medical records in the orthopedic and medical records departments of RSUTH. A total of 606 cases diagnosed with knee osteoarthritis within the study period were included in the study. Relevant information such as age, sex, occupation, marital status, religion, body mass index (BMI), and year of diagnosis were extracted using a structured data collection form. Data were analyzed using Statistical Package for Social Sciences (SPSS) version 25. Descriptive statistics and chi-square tests were used, with a p-value of less than 0.05 considered statistically significant. The overall prevalence of knee osteoarthritis was 8.51%. The condition was more prevalent among females (64.3%) compared to males (35.6%). Prevalence increased with age, peaking in the 60–69 years age group (32.5%). Higher prevalence was observed among homemakers (44.5%), married individuals (67.1%), and those with higher BMI levels, indicating a strong association with obesity. Statistical analysis revealed significant relationships between knee osteoarthritis and socio-demographic variables such as age, sex, occupation, BMI, religion, and marital status (p < 0.05). In conclusion, knee osteoarthritis is prevalent among adults attending RSUTH, with higher occurrence in females, older individuals, and those with increased body weight. The findings highlight the need for early diagnosis, publi