In the clinical practice of paediatric orthopaedic surgery, there are a few cases of acute osteomyelitis which are not characterized by general and local infectious syndrome, making the diagnosis difficult and leading to severe complications. The specific locations, seldom affected, are the spine, pubis, ilium, ischium, sacrum and coccyx. Comparing with other regions, spinal osteomyelitis is less frequent (1:80). It affects not only children, sometimes aged under one year, but also adults of 40-50 years old. The infection may be located in the vertebral body or vertebral arch. Osteomyelitis of the pubis is diagnosed too late if based only on clinical data. The bone abscess is frequently located in the horizontal branch. During the first three days of evolution, the patient has an acute infectious syndrome and tenderness in pelvic area. Osteomyelitis of the ilium is the most frequent osteomyelitis of the hip bones. The abscess may diffuse anteriorly in the Scarpa triangle or may infiltrate the lesser pelvis. The lack of local signs may lead to serious errors, which may determine severe complications, including death. The infection of the ischium is extremely rare. The local infectious syndrome becomes apparent late and consists of gluteal and perineal swelling. Most frequently, the osteomyelitis of the sacrum is also diagnosed late and clinically appears like septicemia, meningitis or peritonitis. Being situated close to the skin, the osteomyelitis of the coccyx is easily diagnosed, but it appears only exceptionally.