Twenty-eight samples of synovial fluid were analyzed for the presence of different antibiotics following their administration as specified. Unfortunately, no determination of the drug levels in the blood was done at the same time as the synovial-fluid examination, and it is possible that in some instances adequate concentration of the drug was not present in the blood to permit its diffusion into the joint fluid. In the dosage given, which is claimed by its manufacturer to be adequate, only the aqueous solution of potassium penicillin G was found consistently in the fluid tested, while the other drugs were present in small amounts in some cases or not at all. Since the synovial membrane is semipermeable, allowing the passage of true solutions of small molecules, both chloramphenicol and potassium penicillin G, which have the smallest molecular weights, should have been present in the fluid of all cases tested. However, it has been demonstrated that chloramphenicol did not pass freely; this may be due either to changes in its molecular structure as it passes through the gastro-intestinal tract, or to the fact that molecular weights have no effect on the diffusion of substances through the synovial membrane. The results of this study showed no difference in the permeability of the membrane in the different age groups. Neither a history of recent acute trauma nor chronic inflammation had any definite effect on the permeability of the synovial membrane.

The antibiotic of choice in the management of pyogenic arthritis is potassium penicillin G, provided the organisms are penicillin-sensitive; the other antibiotics are of value only in preventing the spread of the infection into the blood stream.