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.
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:
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