[Synoviorthesis of the knee with osmic acid (OsO4). Results at mid-term]

Synoviorthesis of the knee joint with OsO4 is a simple procedure with few short or long term side effects. The substance used is inexpensive and easy to handle. All studies published so far have confirmed its suitability in the treatment of synovitis of the knee and various other joints. The initial good results deteriorate steadily, primarily in the first year following injection. However, intra-articular administration of OsO4 may be repeated without risk, and achieves as good results as the first synoviorthesis. The less advanced the lesions and the less active clinically and biologically the systemic manifestations, the better the results. Osmic acid does not appear to damage the joint either radiologically or functionally. The effect of OsO4, although probably shorter in duration, is comparable to that of yttrium-90, with the additional advantage that it can be used in young patients. 100 mg (5 ml of 2% solution) can be considered the optimal dose. Synoviorthesis with osmic acid can be performed before going on to surgical synovectomy. Synoviorthesis with osmic acid is ineffective in the treatment of gonarthrosis.