Background Intra-articular corticosteroid injection can be used to treat arthritis. It is unknown whether and which signs of joint inflammation on magnetic resonance imaging (MRI) change after such treatment.

Objectives To evaluate changes in signs of synovial inflammation by MRI.

Methods In the RIA study (Remicade Intra Articularly), a prospective, randomized, double-blind trial to compare the efficacy of intra-articular (ia) injection with infliximab (IFX) or methylprednisolone (MP), 23 patients with active inflammatory recurrent gonarthritis despite ≥1 previous ia corticosteroid injection underwent T1 contrast enhanced MRI of the affected knee before and 4 weeks after the study medication. MRIs were scored using the MRI Osteoarthritis Knee Score (MOAKS), scoring Hoffa synovitis 0-3, and the Knee Osteoarthritis Scoring System (KOSS), scoring joint effusion 0-3. Outcomes of two consecutive MRIs were compared between the randomization groups.

Results Two consecutive MRIs were available for 20 knees of 18 patients, which were treated with ia IFX (14 interventions) or with MP (12 interventions). There were no differences in age, number of disease modifying antirheumatic drugs (DMARDs) and number of previous ia corticosteroid injections between the IFX and MP treated patients. Median (IQR) Hoffa synovitis scores and effusion scores were similar prior to IFX injections or MP injections. Four weeks after an injection the Hoffa synovitis scores and effusion scores had decreased significantly in IFX injected knees (from 2.5 (1.8-3.0) to 2.0 (1.0-2.3), p=0.021 and from 2.5 (2.0-3.0) to 1.0 (1.0-3.0), p=0.007, respectively) but not significantly in MP injected knees (from 2.0 (2.0-2.0) to 1.5 (1.0-2.0), p=0.157 and from 3.0 (2.0-3.0) to 2.0 (1.0-3.0), p=0.102, respectively). Clinical evaluation 6 months after the injections showed recurrence of clinical arthritis in all IFX injected knees, and in 50% of MP injected knees. Median (IQR) Hoffa synovitis scores and effusion scores before injection were similar in MP injected patients who did or did not had recurrence of clinical arthritis 2.0 (2.0-3.0) and 2.0 (1.0-2.0) p=0.080 in patients with recurrence, respectively, and 3.0 (3.0-3.0) and 2.5 (1.8-3.0) p=0.617 in patients with no recurrence, respectively. MP injected patients who did or did not have a recurrence of clinical arthritis also showed no difference in improvement in Hoffa synovitis scores and effusion scores after injection (delta Hoffa synovitis score 0.0 (-1.5-0.5) p=0.414 and 0 (-1-0) p=0.157, respectively, delta effusion score 0.0 (-1.0-0.0), p=0.157 and 0.0 (-0.5-0.0) p=0.317, respectively.

Conclusions In patients with chronic or recurrent gonarthritis treated with ia IFX or MP, there is a statistically significant improvement in MRI Hoffa synovitis and effusion scores after ia IFX injections but not after ia MP injections. This may represent short term efficacy which could be greater for IFX than for MP. However, improvement in MRI scores was not associated with long term clinical efficacy: after 6 months all IFX injected knees and 50% of MP injected knees showed clinical recurrence of arthritis.

Disclosure of Interest G. Akdemir: None declared, A. van der Bijl: None declared, B. de Lange-Brokaar: None declared, T. Huizinga: None declared, C. Allaart Grant/research support from: The study was sponsored by Schering-Plough BV and Centocor, Inc., M. Kloppenburg: None declared