A rare, but increasingly frequent injury over the past few years, is stress fracture of the femoral neck. Stress fractures are caused by overuse and repetitive activity, and are common in athletes. The femoral neck is exposed to great forces, especially while running. These may contribute to an overload to the bone tissue, first on a micro level, before eventually the gradually weakened structure breaks down, and the stress fracture is may occur. Before a complete fracture line is formed, there are three degrees of less severe stress reactions. Sports, where running makes up a significant amount of the training, are particularly at risk of developing this injury in the femoral neck. Stress fractures are overall most common in long- and middle distance runners, but also among military recruits. A delay in the diagnosis results in an increased risk of developing complications. Stress fractures of the femoral neck are not always easy to uncover because of their unspecific and varying symptoms. Furthermore, there are many factors involved, resulting in this injury. Biomechanics, training program, nutrition and body weight are factors of big significance. The best method to confirm a clinical suspicion of stress fracture, is magnetic resonance imaging (MRI). Radiography does not show any signs until 2-3 weeks after the injury has occurred, and even then it may not show if it is only a stress reaction. On the MRI one can locate the injury; if it is on the compression or tension side of the femoral neck, and if it is a dislocated fracture. This is essential for the treatment and the prognosis. Stress fractures of the femoral neck are usually treated conservatively, but can be treated surgically if the injury is severe, if conservative treatment fails or if the patient is a high level athlete and eager to resume competition. The key is to regulate the training level to prevent reoccurrence of the fracture.