In extensive chronic serous effusion in the knee-joint, injection of iodine has been successfully practised by Velpeau and others. One part of iodine, 2 of iodide of potassium, and 8 of water, are injected in about the same quantity as is withdrawn by aspiration; air should be carefully excluded from the wound. Mr. C. Macnamara has injected 1 oz. of the pure tincture with quite satisfactory result ("Lectures on Diseases of Bones and Joints," 1881).

In less severe cases of effusion, in bursal effusions (housemaid's knee), and in rheumatic and gouty joints, the external application of iodoform, or iodine paint, promotes absorption, and should be tried before puncture. Dr. Fuller recommended a lotion containing 1/2 oz. of tinct. iod. co. in 6 oz. each of glycerin and water, and applied on lint covered with flannel; frictions and douches should be combined with this treatment (Lancet, i., 1863).