Morganella morganii is a gram-negative, facultative anaerobic bacillus whose natural habitat is the gastrointestinal system. While it rarely causes infection alone, it is generally encountered in people with suppressed immunity and in cases of hospital infection. It may also manifest itself as a superinfection. Morganella morganii often demonstrates a course characterized by slow-paced progression with occasional attacks and remissions. Osteoarticular pathologies are not commonly observed in Morganella morganii infections and it has a high mortality rate. We present a 56-year-old male patient with Morganella morganii osteomyelitis in the distal femur and proximal tibia, complicated by septic arthritis in the knee joint.