Pathology of the Musculoskeletal System
Fractures, Osteoporosis, Arthritis, Tendon/Ligament Tears, Muscular Dystrophy
The bones of the skeleton become thinner and weaker as a normal part of the aging process. The bone-building activity of the body begins to slow down between the ages of 30 and 40. Women lose roughly 8 percent of their skeletal mass every decade. Men lose about 3 percent per decade. Not all parts of the skeleton are equally affected. The vertebrae, jaws, and the area near the ends of bones (at the "growth plate") lose more bone tissue than other bones, resulting in a loss of height, loss of teeth, and limbs prone to fracture.
When bone mass is reduced to a point where normal function is inhibited, the condition is known as osteoporosis. The fragile bones that result are likely to break when exposed to the stresses that younger individuals could easily tolerate. For example, a hip fracture in a women in her late eighties can occur simply in an effort to stand. Loss of mobility further weakens the skeleton.
Risk factors for the development of osteoporosis include:
The older you are, the greater your risk. Bones become weaker and less dense as you age.
The risk of osteoporosis is greater if you are a woman. Women have less bone tissue and lose bone more rapidly than do men because of the changes involved in menopause.
Caucasian and Asian women are more likely to develop osteoporosis. However, African American and Hispanic women are at a significant risk for developing the disease.
Bone structure and body weight
Small-boned and thin women are at greater risk.
Normal or early menopause (brought about naturally or because of surgery) increases your risk of developing osteoporosis. During perimenopause/menopause, a decline in circulating estrogen contributes to bone loss. In addition, women who stop menstruating before menopause because of conditions such as anorexia or bulimia, or because of excessive physical exercise, also might lose bone tissue and develop osteoporosis.
Smoking, drinking too much alcohol, consuming an inadequate amount of calcium, or getting little or no weight-bearing exercise increases your chances of developing osteoporosis.
Medicines and disease
Osteoporosis is associated with certain medicines (such as cortisone-like drugs) and is a recognized complication of a number of medical conditions, including endocrine disorders (having an overactive thyroid gland), rheumatoid arthritis, certain cancers, and immobilization.
Susceptibility to fractures might be, in part, hereditary. Young women whose mothers have a history of vertebral fractures also seem to have reduced bone mass.
Despite its mineral strength, bone can crack or even break if subjected to extreme loads, sudden impacts, or stresses from unusual directions. The damage produced constitutes a fracture. Fractures are classified according to their external appearance, their location, and the nature of the crack or break in the bone. Closed, or simple fractures, are completely internal. The affected bones remain close together and they do not break the skin. Open, or compound fractures, break through the skin. These fractures can be more serious than closed fractures because of the possibility of uncontrolled bleeding or infection. There are numerous types of fractures, including the following.
These are the shattering of the affected areas into many bone fragments.
These are complete breaks across the long axis of the shaft of a bone.
These are produced by the force of a fall, such as to the vertebra in a fall that lands one on his/her seat.
These are produced by twisting stresses that spread along the length of the bone.
These usually occur in children, when only one side of the bone is cracked and the other side is bent.
Arthritis includes all the rheumatic diseases that affect synovial joints. (A synovial joint is a freely movable joint where the opposing bone surfaces are separated by a lubricating fluid called synovial fluid.) Arthritis always involves damage to the articular cartilages, but the specific causes can vary. For example, arthritis can result from bacterial or viral infection, injury to the joint, metabolic problems, or severe physical stresses.
When an articular cartilage has been damaged, the tissue begins to break down. The exposed cartilage changes from a slick, smooth gliding surface to a roughened surface. This rough surface drastically increases friction, which damages the cartilage further and causes pain. Eventually, the central area of the articular cartilage might completely disappear, exposing the underlying bone.
There are several forms of arthritis:
- Osteoarthritis, also known as degenerative arthritis or degenerative joint disease, results from cumulative wear and tear at the joint surface.
- Rheumatoid arthritis is an inflammatory condition. At least some cases occur as a result of the body attacking its own tissue (a so-called "autoimmune" disease). Allergies, bacteria, viruses, and genetic factors are thought to contribute or trigger the destructive inflammation.
- Gouty arthritis involves the accumulation of crystals within the synovial fluid of joints, which over time, interferes with normal movement. The crystals are derived from uric acid (a metabolic waste), and the joint most often affected is the first joint of the big toe.
Tendonitis and tendon tear
Tendonitis is an inflammation or irritation of the tendon, a thick cord that attaches bone to muscle. It is most often caused by repetitive, minor impact on the affected area or from a sudden, more serious injury. Many sport and work-related activities can cause tendonitis. Incorrect posture at work or home, or poor stretching or conditioning before exercise or playing sports, also increases a person's risk.
Other risk factors for tendonitis include:
- An abnormal or poorly placed bone or joint (such as length differences in your legs or arthritis in a joint) that stresses soft-tissue structures can lead to tendonitis.
- Stresses from other conditions, such as rheumatoid arthritis, gout, psoriatic arthritis, thyroid disorders, or unusual medicine reactions can contribute to tendonitis
- Occasionally, an infection can cause tendonitis. If left untreated, tendonitis can lead to a tear within the tendon or a complete rupture of the tendon.
Ligaments are chords of connective tissue that connect one bone to another. Ligaments are very strong. In a sprain, a ligament is stretched to the point that some of the fibers are torn, but the ligament as a whole survives and the joint is not damaged. With excessive force, it is more likely that one of the attached bones will break before the ligament tears. In general, a broken bone heals much more quickly and effectively than does a torn ligament.
Muscular dystrophies are inherited diseases that produce progressive muscle weakness and deterioration. One of the most common and best understood conditions is Duchenne’s muscular dystrophy, a type of muscular dystrophy that appears in childhood. The skeletal muscle fibers of individuals with dystrophies are structurally different from those of other individuals. Abnormal membrane permeability, cholesterol content, rates of protein synthesis, and enzyme composition have been reported. A protein that provides mechanical strength to the muscle fiber is also missing in these individuals.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 4/7/2005...#12262