Purpose: Intra-articular corticosteroid injections is a well established treatment for knee osteoarthritis (OA). However, only 60% of patients have a good short-term response and about 20% of patients have a satisfactory long-term response. Genetic variants may play a role in predicting response to corticosteroids. A genetic variant of the macrophage inflammatory factor (MIF) (a physiologic counter-regulator of glucocorticoids), has been associated with poor clinical response in various inflammatory diseases. No studies to date have evaluated the effect of this variant on steroid injections for knee OA. We set out to determine the impact of the – 173(C) variant of the MIF gene on clinical response to intra-articular injections for knee OA.

Method: 80 patients with Kellgren-Lawrence Grade 2–3 OA of the knee were prospectively followed for three months following a standard dose of steroid injection. All patients were genotyped for the – 173 variant of the MIF gene. WOMAC questionnaires for knee OA were done at baseline, one, four and twelve weeks to assess response to treatment.

Results: 21 patients (25%) carried the C allele of – 173 variant of the MIF gene. At 12 weeks, patients with the C variant had a statistically significant decrease in the pain dimension of the WOMAC compared to the G variant. Similar responses were not obtained at weeks one and four.

Conclusion: A specific polymorphism in the MIF gene appears to be associated with a poor response to intra-articular knee injections. Further validation is required with larger sample sizes to assess the impact of prospectively genotyping for this variant prior to knee injections.