A stress fracture is a microscopic crack in a bone that occurs from overuse. Muscles normally absorb the shock of physical activities, but when they become too fatigued to do so, they transfer the stress to the bones which results in a hairline-sized fracture.

Stress fractures usually develop in the weightbearing bones of the feet and lower legs, often after a rapid increase in the duration or intensity of exercise or from wearing improper or worn out athletic shoes.

The most common form of arthritis, osteoarthritis, can affect any joint in the body, but most often afflicts the knees, hips, and fingers. Most people will develop osteoarthritis from the normal wear and tear on the joints through the years.

Joints contain cartilage, a rubbery material that cushions the ends of bones and facilitates movement. Over time, or if the joint has been injured, the cartilage wears away and the bones of the joint start rubbing together.

As bones rub together, bone spurs may form and the joint becomes stiff after long periods of activity or inactivity.

When muscles become inflamed, they can also spasm, or contract tightly, as a response to injury. While they are the body’s way of protecting itself from further injury, they often produce excruciating and often debilitating pain. Muscle spasms are common in the low back (lumbar) muscles.

Degenerative disc disease is a general term applied to back pain that has lasted for more than three months. It is caused by degenerative changes in the intervertebral discs in the spine and can occur anywhere in the spine: low back (lumbar), mid-back (thoracic), or neck (cervical).

Under the age of 30, these discs are normally soft, and they act as cushions for the vertebrae. With age, the material in these lumbar discs becomes less flexible and the discs begin to erode, losing some of their height.

As their thickness decreases, their ability to act as a cushion lessens. The less dense cushion now alters the position of the vertebrae and the ligaments that connect them.

In some cases, the loss of density can even cause the vertebra to shift their positions. As the vertebrae shift and affect the other bones, the nerves can get caught or pinched and muscle spasms can occur.

Degenerative disc disease is primarily a result of the normal aging process, but it may also occur as a result of trauma, infection, or direct injury to the disc. Heredity and physical fitness may also play a part in the process.