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Stress Fracture

Stress Fracture Overview

Stress fractures can be considered an overuse injury of a bone. The bones in the body are constantly changing, responding to the work load that is placed upon them, and there is a constant turnover of cells as bone acts to repair itself. The more load placed on the bone, the more likely that calcium will be placed at that site. The less use a bone receives, the less calcium can be found within it. If the stress of repetitive loads overwhelm the ability of the bone to repair itself, small cracks can begin to occur within the bone structure.

This is especially evident in the bones of the foot, leg, and pelvis. These bones need to absorb the forces created from walking, running, and jumping. Up to 12 times the weight of the body may be generated with each step; and the bones, joints, muscles, and ligaments need to cushion the body against that force.

Bone is normally in homeostasis (homeo= same + stasis=standing still), meaning that the natural turnover of bone cells is in balance between osteoclast activity (bone breakdown) and osteoblast activity (bone creation). When bone is under stress, it undergoes microscopic damage. Osteoclast cells are stimulated to absorb bone, and the injured site is weakened. If a long period of time elapses prior to the next injury, osteoblast cells produce more bone cells to protect the damaged area. If there is not enough time for the osteoblasts to produce more bone cells in the injured area; the micro fractures can join together to form a large enough area to cause a stress fracture.

Symptoms of a stress fracture may include pain and swelling, particularly with weight bearing on the injured bone. Often plainX-rays may appear normal.

If stress on the area of the compromised bone continues, and the microscopic damage increases in the area; the bone's integrity can be completely disrupted and cause a fracture that can be recognized on X-rays.

Stress fractures generally often occur in the following locations:

  • metatarsal bones of the foot,
  • navicular bone in the foot,
  • calcaneus (heel bone),
  • tibia (shin bone),
  • fibula,
  • femur (thigh bone),
  • femoral neck in the hip,
  • pubic rami of the pelvis,
  • sacrum, and
  • pars articularis of the lumbar spine.
Picture of the bones of the foot
Picture of the bones of the foot
Picture of the bones of the leg
Picture of the bones of the leg
Picture of the bones of the hip
Picture of the bones of the hip
Medically Reviewed by a Doctor on 7/30/2015

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Stress fractures can be simple and heal quickly, while others may require surgery.

Stress Fractures: Some Take Longer to Heal Than Others

Medical Author: Benjamin C. Wedro, MD, FAAEM
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

It takes a lot of effort to support 7 feet 6 inches and the two tons of force generated when NBA basketball star Yao Ming walks or jumps. The cushioning that absorbs the shock of his weight rests on two feet and their joints, ligaments, and muscles. The force of that weight during runningcan multiply a person's weight by more than12 times. Unfortunately for the Houston Rocket basketball player, his bones couldn't withstand the constant pounding and he developed a stress fractureof the navicular bone of his foot.

The navicular bone helps support the arch of the foot and is a bridge between the bones of the ankle and those of the toes. The bony arch is also supported by the plantar fascia, the thick band of tissue that connects the heel to the front of the foot. The solid bones and the pliable ligaments flex the foot to disperse the forces generated with walking, running, and jumping. But if the force placed on the bone is greater than its ability to withstand it, small micro fractures can occur in the bones that can develop into a stress fracture.

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