Updated December 19, 2014.

A hip stress fracture is a serious injury to the ball of the ball-and-socket hip joint. Stress fractures are injuries to the bone that result from overuse activity. Fractures occur for one of three reasons:

• High-Energy Injury
  In high-energy injuries, the bone is broken because the force acting on it was significant. These injuries would include falls, car accidents and sports injuries.
• Stress Injuries
  A stress fracture is due to repetitive micro-trauma to the bone. Over time, the body cannot keep up with the forces acting on the bone, and a fracture eventually occurs.

• Pathologic Injury
  In a pathologic fracture, the bone is abnormally weakened by some problem. Causes of pathologic fractures include osteoporosis, tumors and infections.

In the situation of a stress fracture, repetitive injury to the bone eventually leads to failure of the bone, or fracture. Normally, bone is constantly undergoing a cycle of turnover during which old bone is reabsorbed and new bone is created. If the process cannot keep up, eventually the bone can fracture.
Hip stress fractures most often occur just below the ball of the ball-and-socket hip joint. This location of the bone is called the femoral neck. Stress fractures can occur in other areas of the hip and pelvis, but the femoral neck is the most common, and most concerning location for a hip stress fracture.

Why Is a Hip Stress Fracture Considered a Serious Injury?
After a stress fracture, the bones often maintain their proper alignment. In fact, these fractures are sometimes not even visible -- especially in the early stages -- on a regular x-ray.

However, if the stress fracture is left untreated, and the bone continues to weaken, the fracture can displace, or cause the bones to go out of alignment.

Hip stress fractures are particularly concerning if they displace. Because of the delicate blood supply to the bone of the hip, a fracture can lead to injury of this blood supply and a condition called hip osteonecrosis.

Signs of a Hip Stress Fracture

People with a hip stress fracture are most often high-mileage runners, military recruits, or individuals doing significant impact sports activities. These athletes will typically complain of an aching groin pain that bothers them with activity, and is relieved by rest. Symptoms are usually noted after a recent increase in level of activity, such as increasing running mileage.
If a hip stress fracture is suspected, an x-ray will be performed. While some hip stress fractures will be seen on x-ray, some x-rays may appear normal. If the injury is still suspected, an MRI or bone scan can also be obtained to evaluate for a stress fracture.

Treatment of Hip Stress Fractures

Hip stress fractures require the immediate modification of activity levels so you don't have pain or discomfort. I do not recommend pain medications, as these medications can mask symptoms that are important for the patient and doctor to know about. If you only have pain when running, then the running must be stopped. If the pain occurs while walking, then crutches should be used. The important concept is to stay under the level of pain. If you avoid activities that aggravate your symptoms, then it is often possible that hip stress fractures will heal without surgery.
Surgery is needed if there is a concern that the fracture may displace. As mentioned, displacement of a hip stress fracture has very serious implications for long-term health. Therefore, if there are concerns about displacement occurring, then surgery should be performed to stabilize the bone. Hip stress fractures can occur in portions of the femoral neck that are more or less apt to undergo prompt healing. Your doctor may recommend surgical treatment in these specific situations.

<sub>Sources:

Shin AY, Gillingham BL. "Fatigue Fractures of the Femoral Neck in Athletes" J. Am. Acad. Ortho. Surg., Nov 1997; 5: 293 - 302.</sub>