In order to assess the effect of 24 h observed bed rest following intra-articular steroid injection of the knee joint in patients with an inflammatory arthritis such as RA, AS or colitic arthropathy, 91 patients with inflammatory arthritis of one knee joint were randomized to receive 24 h bed rest in hospital following intra-articular steroid injection or were injected in outpatients. The clinical and laboratory assessments such as pain and stiffness on a 10-cm visual analogue scale, knee circumference (cm), 50 ft walking time (s), CRP and ESR were measured before receiving the steroid injection and at 3, 6, 12 and 24 weeks. Both groups of patients improved clinically and serologically at 3 weeks. By 12 weeks the degree of improvement in the pain score, stiffness score, knee circumference, 50 ft walking time and CRP was better in the rest group and these differences persisted to 24 weeks. For each outcome variable the summary measure of response was significantly better in the rest group compared to the no rest group. Intra-articular steroid injection of the knee joint followed by strict i inpatient bed rest for 24 h results in a greater degree of clinical and serological improvement, compared to routine outpatient injections for up to 6 months. It is therefore possible that 24-h post-injection rest will result in a prolonged duration of clinical response and reduce the need for frequent steroid injections and the risk of complications.