Knee Osteoarthritis in Type 2 Diabetes Mellitus: Does Insulin Therapy Retard Osteophyte Formation?

OBJECTIVE: The aim of this study was to investigate whether or not radiographic changes observed in knee osteoarthritis (OA) in type 2 diabetes mellitus (T2DM) patients on insulin therapy differed from those not on insulin. MATERIAL AND METHODS: A cross-sectional study was performed in 311 subjects: 211 T2DM patients and 100 without diabetes (controls) in Mubarak Hospital, Kuwait. Patients were categorized into 3 groups: T2DM patients not on insulin (G1, n = 99), T2DM patients on insulin (G2, n = 112) and a nondiabetic control group (G3, n = 100). Plain X-ray of both knees was used to assess the changes of knee OA and graded using the Kellegren-Lawrence scale (0-4) and the Osteoarthritis Research Society International Atlas grading scale (0-3). A total of 622 knee X-rays were evaluated. SPSS version 21.0 was used for data analysis. RESULTS: A highly significant association (p < 0.0001) was observed for joint space narrowing (JSN) as well as for osteophyte formation between the three groups. Comparing G2 and G3, a highly significant association (p < 0.0001) was retained for JSN [201 (89.7%) vs. 199 (99.5%)] and for osteophyte formation [26 (11.7%) vs. 72 (36.0%)]. Comparing G1 and G2, significantly less osteophyte formation was noted in G2 patients compared to G1 patients [26 (11.7%) vs. 39 (19.7%), p = 0.02]. Multivariate logistic regression analysis showed that the G2 group had less chance of osteophyte formation than either the G1 group or G3 control group (OR = 0.294, p = 0.008 and OR = 0.098, p < 0.001, respectively). CONCLUSION: Our findings show that T2DM patients with OA knees on insulin therapy have less radiographic osteophytes compared to T2DM patients not on insulin.