Background: As one of the most common forms of joint disease, osteoarthritis (OA) causes progressive impairment in adults because of the deterioration of articular cartilage in the joints. Multiple variables, including comorbidities (such as diabetes mellitus, hypertension, obesity, and dyslipidemia), lifestyle choices, food, age, and genetics, might influence the occurrence, development, and severity of OA symptoms. Objective: To assess knee pain severity & patterns in cases with OA & OA with diabetes mellitus. Patients and Methods: This is cross-sectional research that was done in Benha University Hospitals on 100 cases, which were separated into two groups: Group one included fifty OA patients and group two consisted of fifty OA patients with diabetes mellitus (DM). Group two was divided into two subgroups: good control and poor control patients according to diabetes control. Knee pain was measured according to three subscales: WOMAC (The Western Ontario and McMaster Universities OA Index), KOOS (Knee Injury and OA Outcome Score) and VAS (visual analogue scale). Results: There was a statistically significant variance amongst the examined groups concerning diabetes parameters (HbA1c, fasting glucose and two hours post prandial), Kellgren-Lawrence scale, correlation of diabetes duration with other parameters of pain in OA patients and correlation of HbA1c with other parameters of pain among OA patients with DM. Conclusion: Our study concluded that WOMAC pain subscale was significantly increased with worsening of DM and KOOS pain subscale was significantly decreased with worsening of DM. This suggests the crucial need for management of DM to achieve better outcomes of OA.