A Simple Way to Understand the Types of Bone Stress Injuries in Athletes

Stress injuries to bones of athletes are often caused by relative overload, and in describing the spectrum of possible bone stress or overload injuries to patients, I often use the analogy of bending my pen while bored in class one day.

• If I just start trying to bend my pen, the pen doesn't bend much. This represents normal bone.
• As I continue to play with my pen, it does start to bend more. This represents a stress reaction where the bone is softer and less able to resist continued load. A stress reaction will create swelling (bone edema) on a Magnetic Resonance Imaging (MRI) study, but no true fracture line will be visible either on the MRI or plain x-ray study.
• If I'm really bored in class, or it's a longer class period, my continued attempts to bend the now even more weakened pen eventually may cause it to completely break on one side. This represents a stress fracture which is a progression of a stress reaction where a fracture line is seen on one cortex (outer lining of the bone) on either MRI or plain x-ray.
• Even more attempts to bend my pen may result in breaking it in half. This represents a complete fracture which is a progression of a stress fracture where the fracture line is now visible on both cortices (outer linings of the bone) on either MRI or plain x-ray.

Stress Fracture of Left Femoral Neck: This MRI picture shows a fracture line involving only one cortex (outer lining) of the femur (thigh bone) with bone swelling (edema) also present.

Look forward to an upcoming post on important things to consider after the diagnosis of a bone stress injury has been made.