Recalcitrant septic knee arthritis due to adjacent osteomyelitis in adults.

We asked whether adjacent osteomyelitis with acute septic knee arthritis explained a lack of response to initial management, and whether patient comorbidities predisposed to the nonresponsiveness. From 147 adult patients (151 knees) with septic arthritis, we identified 29 patients (33 knees) who had persistence or recurrence of symptoms after surgical drainage. Adjacent osteomyelitis was present in 31 (94%) of the 33 knees (27 of 29 patients) with poor response to treatment. Patients with adjacent osteomyelitis had more comorbid conditions (23 of 27 patients, 85%) than patients without osteomyelitis (64 of 120, 53%). The most common comorbid conditions in patients with adjacent osteomyelitis were diabetes mellitus (10 patients, 37%) and intravenous drug use (eight patients, 30%). We identified Staphylococcus aureus in 19 of 31 knees (61%) with osteomyelitis, eight (26% of total cases) of which were methicillin-resistant. Persistence of clinical signs of infection after surgical management of septic knee arthritis in adults should raise the suspicion of adjacent osteomyelitis, especially in patients with comorbid conditions. Additional imaging studies may be necessary to evaluate the distal femur and proximal tibia.