We compared the effectiveness of antibiotics alone and in combination with arthroscopy, arthroscopy with debridement, arthrotomy, or needle aspiration for the treatment of septic arthritis. Each modality has its proponents, but, to our knowledge, no comparative studies have been conducted in animals. We used biochemical and histological analysis to compare these methods of treatment in an experimental model. The right hind knee of thirty goats was injected with 1 x 10(5) Staphylococcus aureus bacilli. The left hind knee was not inoculated and served as the normal control. Seventy-two hours after inoculation, a two-week course of treatment with intramuscular administration of cefuroxime sodium, either alone or in combination with another mode of treatment, was initiated in each of five groups. The cartilage was evaluated histologically with biochemical, enzymatic, and interleukin-1 analyses. Despite the early therapeutic intervention, on the average, there was a 25 per cent loss of uronic acid (t test, p < 0.001) and a 43 per cent increase in neutral protease activity (signed-rank test, p = 0.003) in the treatment groups. There were no significant intergroup differences with regard to the histochemical-histological rating or the levels of uronic acid, neutral protease, or interleukin-1.