The outcome of bacterial arthritis is generally poor: the mortality is 10 - 15% and there is loss of joint function in 25 - 50% of the survivors. The incidence of bacterial arthritis is low: 2 - 6 cases per 100,000 people per year. Risk factors are age, joint disease (especially rheumatoid arthritis [RA]), diabetes mellitus and the presence of a prosthetic joint. The predominant situations that can lead to bacterial arthritis are skin infections of the feet and rarely invasive medical or dental procedures. Due to the severity of the disease, antibiotic prophylaxis of haematogenous bacterial arthritis in patients with prosthetic joints is advocated. However, due to the rarity of the disease it is unclear whether the advantages of prophylaxis outweigh the disadvantages of the large-scale use of antibiotics, such as side effects, costs and bacterial resistance. In a decision-analysis of a large group of patients with joint diseases, antibiotic treatment of skin infections appeared to be cost-effective in the prevention of haematogenous bacterial arthritis, mainly in high-risk patients. On the other hand, prophylaxis around medical or dental procedures was not cost-effective, except possibly in a small group of patients with increased risk.