Rib Stress Fractures & Intercostal Injuries

Rib stress fractures and intercostal muscle injuries are causes of chest wall pain in athletes: the first a bone stress injury from repetitive loading, the second an acute muscle injury.

Rib stress fractures are classically seen in rowers, and also in throwing sports such as baseball, golf, swimming and weightlifting. They are often misdiagnosed as intercostal strain or costochondritis. Always consider cardiac and pulmonary causes alongside the musculoskeletal ones.

Ribs 1 to 7 join the sternum directly (true ribs), ribs 8 to 10 attach to the cartilage above (false ribs) and ribs 11 and 12 float. The intercostal neurovascular bundle runs in the costal groove on the underside of each rib (vein, artery, nerve from top to bottom).

A rib stress fracture develops when repeated bending loads outpace bone remodelling. In rowers, about 86% of fractures with a known site are in ribs 4 to 8, mostly along the lateral and anterolateral cage. The mechanism is debated: proposed explanations include opposing pull from serratus anterior and the external oblique during the drive, and forces from the scapular retractors and abdominal muscles.

First rib stress fractures typically occur at the subclavian groove, the thinnest point, from scalene and upper limb traction in throwing and overhead sport. Healing callus can narrow the thoracic outlet and cause thoracic outlet syndrome.

Risk factors are poorly established: a systematic review found insufficient or conflicting evidence for training changes, technique, female sex and low bone density. Case reports link rib stress fractures to rising training volume with amenorrhoea or low bone density, and to low energy availability (relative energy deficiency in sport, REDs), low vitamin D and eating disorders.