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Osteoarthritis |
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CONTENTS
Overview
Warning Signs
Predisposing Factors
Osteoarthritic Process
Resources
Review/Quiz
Links of Interest
References
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AGE DISORDER |
Before |
45 yrs |
incidence higher in men |
After |
45 yrs |
incidence higher in women |
After |
65 yrs |
> 50% of population * |
After |
75 yrs |
estimated 80% of population |
* in one or more joints | |
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Osteoarthritis (OA)
is the most frequent cause of disability in adults. In the United States alone, OA affects an estimated 20 million people. As the body ages, increased wear on the joints causes progressive joint tissue degeneration. Joints in the hands are most frequently affected; however, osteoarthritis in load-bearing joints such as the knee and hip, is the most frequent cause of disability. The predominant tissue changes occur in cartilage, the cushioning material overlying bone ends. |
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While some persons experience no pain, particularly in the early stages, others may have joint swelling, stiffness, limited joint movement, and pain. |
WARNING SIGNS |
Stiffness |
after getting out of bed |
Joint Swelling
Tenderness |
one or more joints |
Crunching Sound |
bone rubbing on bone |
Pain |
steady or intermittent
may have no pain |
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More than half the population over the age of 65 has x-ray evidence in at least one joint. |
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Normal Knee Joint
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In the healthy joint, bone ends are covered with cartilage, a firm, glistening, spongy tissue which allows bones to glide over one another effortlessly. Cartilage acts as a protective cushion and absorbs much of the physical impact of movement. Cartilage has no blood supply of its own but is nourished by synovial fluid within the joint capsule (press to enlarge image at left). |
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PREDISPOSING FACTORS |
Age |
incidence increases with age |
Obesity |
associated with OA of knees;
increased weight and stress on joints |
Trauma |
injury causes instability;
can lead to degeneration |
Repetitive Joint Stress |
occupational use:
jackhammer operators, ballet dancers |
Genetic Factors |
familial mutation in DNA |
Bone Density |
changes from bone loss | |
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The Osteoarthritic Process
While not everyone with osteoarthritis experiences severe joint damage, there are a number of processes which can occur in the degenerative process.
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Initially, the cartilage swells from increased water content. The body tries to repair the cartilage by producing more proteoglycans, the elastic-giving molecules within the fibrous collagen network. The production of proteoglycans requires more water. This stage of arthritis can last for years before any cartilage degeneration begins. |
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As OA progresses, the cartilage thins, losing its sponginess and elasticity. The surface becomes worn and dull. Cracks and fissures begin to appear. The joint space narrows. |
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The ability of the damaged cartilage to absorb the nutrient-giving synovial fluid is decreased. Synovial fluid leaks into the cracks, promoting further degeneration. Detached cartilage fragments float freely in the joint fluid and can cause irritation to the synovial membrane. |
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As the protective, hard, slippery cartilage wears away, friction opens pits and fissures in the bone. As the cracks deepen into the bone, underlying blood vessels promote growth of fibro-cartilage plugs. The newly-formed cartilage plugs are inferior in their ability to withstand mechanical stress. Cysts also can form in the underlying bone to further weaken joint support. |
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The repair effort is further evidenced in small outgrowths of cartilage and bone, particularly at joint margins. These are often seen on x-rays and are known as spurs. Spurs can alter the shape of a joint and restrict movement. |
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Review/Quiz |
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Links of interest:
Slippers and Hip Fractures
21st Century: Living Laboratory
Further Progress in Cartilage Development
REFERENCES
The material presented by PatientFriendly LLC is for information only. It is not a substitute for medical advice or treatment. If you have any health problems consult your physician or health provider. | |
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