Degenerative Joint Disease (Osteoarthritis)
The knee is the largest and strongest joint in your body. It is made up of the lower end of the femur (thighbone), the upper end of the tibia (shinbone), and the patella (kneecap). The ends of the three bones where they touch are covered with articular cartilage, a smooth, slippery substance that protects and cushions the bones as you bend and straighten your knee.
Two wedge-shaped pieces of cartilage called meniscus act as “shock absorbers” between your thighbone and shinbone. They are tough and rubbery to help cushion the joint and keep it stable.
The knee joint is surrounded by a thin lining called the synovial membrane. This membrane releases a fluid that lubricates the cartilage and reduces friction.
Cause & Symptoms
Osteoarthritis is the most common form of arthritis in the knee. It is a degenerative,”wear-and-tear” type of arthritis that occurs most often in people 50 years of age and older, but may occur in younger people, too.
In osteoarthritis, the cartilage in the knee joint gradually wears away. As the cartilage wears away, it becomes frayed and rough, and the protective space between the bones decreases. This can result in bone rubbing on bone, and produce painful bone spurs.
Osteoarthritis usually develops slowly and the pain it causes worsens over time.
A knee joint affected by arthritis may be painful and inflamed. Generally, the pain develops gradually over time, although sudden onset is also possible.
There are other symptoms, as well:
The joint may become stiff and swollen, making it difficult to bend and straighten the knee.
Pain and swelling may be worse in the morning, or after sitting or resting.
Vigorous activity may cause pain to flare up.
Loose fragments of cartilage and other tissue can interfere with the smooth motion of joints. The knee may “lock” or “stick” during movement. It may creak, click, snap or make a grinding noise (crepitus).
Pain may cause a feeling of weakness or buckling in the knee.
Many people with arthritis note increased joint pain with rainy weather.
During your appointment, your doctor will talk with you about your symptoms and medical history, conduct a physical examination, and possibly order diagnostic tests, such as x-rays or blood tests.
During the physical examination, your doctor will look for:
Joint swelling, warmth, or redness
Tenderness about the knee
Range of passive (assisted) and active (self-directed) motion
Instability of the joint
Crepitus (a grating sensation inside the joint) with movement
Pain when weight is placed on the knee
Problems with your gait (the way you walk)
Any signs of injury to the muscles, tendons, and ligaments surrounding the knee
Involvement of other joints (a possible indication of rheumatoid arthritis)
These imaging tests create detailed pictures of dense structures, like bone. They can help distinguish among various forms of arthritis. X-rays of an arthritic knee may show a narrowing of the joint space, changes in the bone and the formation of bone spurs (osteophytes).
Occasionally, a magnetic resonance imaging (MRI) scan, a computed tomography (CT) scan, or a bone scan may be needed to determine the condition of the bone and soft tissues of your knee.
Your doctor may also recommend blood tests to determine which type of arthritis you have. With some types of arthritis, including rheumatoid arthritis, blood tests will help with a proper diagnosis.
Great Lakes Physical Therapy
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