SummarySixty-six patients admitted to our institution over an 8-year period with the diagnosis of osteomyelitis were analyzed to determine the incidence of adjacent joint involvement. Patients with osteomyelitis of the hand, foot, spine, and extraarticular pelvis were excluded from this study. The average age was 5.8 years (range, 1 month to 17 years). Forty-two percent of our patients who had osteomyelitis had evidence of adjacent joint involvement (either septic or nonseptic). One third of our patients had evidence of septic joint involvement. The most commonly involved joint was the knee. There was no difference in the incidence of adjacent joint involvement in those patients who were younger than 18 months compared with the incidence in older children. Our study suggests that the incidence of adjacent joint involvement in children who have osteomyelitis is higher than that suggested in the literature. We believe that careful evaluation of the adjacent joint should be an important part of the evaluation of any child who has osteomyelitis.