Osteomyelitis is a term used to describe bone infection. As a complication, it can occur after open bone fracture and is associated with the implantation of foreign material. Acute disease after surgery starts after about 7 days to 4 weeks, and is characterized by a suppurative infection. Chronic infection sometimes manifests even years after surgery with a purulent sinus tract. Diagnosis is based on clinical signs, microbiological culture, histological evidence of the presence of granulocytes, and on radiological signs of osteomyelitis. However, it is sometimes difficult to distinguish between merely soft tissue involvement and osteomyelitis, especially in the presence of implanted material. Management includes a thoroughly surgical débridement and antibiotic treatment. Though frequently used, bacterial cultures of swabs of superficial wounds or fistulas are often misleading, whereas needle biopsy or surgical sampling with at least three tissue samples provides more reliable information. Because of the prolonged antibiotic treatment, it is mandatory for a successful outcome to culture the microorganism in order to determine antibiotic susceptibility. In addition to conventional radiological approaches, magnetic resonance imaging has become useful for the diagnosis of osteomyelitis. Despite significant progress in antibiotic therapy and orthopedic surgery, osteomyelitis remains difficult to treat and often relapses, even after years.