The major types of arthritis that affect the knee are: osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis.
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 develops slowly and the pain it causes worsens over time.
Rheumatoid arthritis is a chronic disease that attacks multiple joints throughout the body, including the knee joint. It is symmetrical, meaning that it usually affects the same joint on both sides of the body.
In rheumatoid arthritis the synovial membrane that covers the knee joint begins to swell, This results in knee pain and stiffness.
Rheumatoid arthritis is an autoimmune disease. This means that the immune system attacks its own tissues. The immune system damages normal tissue (such as cartilage and ligaments) and softens the bone.
Posttraumatic arthritis is form of arthritis that develops after an injury to the knee. For example, a broken bone may damage the joint surface and lead to arthritis years after the injury. Tears and injuries can cause instability and additional wear on the knee joint, which over time can result in arthritis.
A knee joint affected by arthritis may be painful and inflamed. Generally, the pain develops gradually over times, but not always. 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. (OrthoInfo, 2019)
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 usually 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 (an indication of rheumatoid arthritis) (OrthoInfo, 2019)