Knee pain is a very common condition.

Certain characteristics of knee pain, such as pain after sitting, can help to narrow the possible causes, but are not perfectly specific to any one disease. Multiple diagnostic approaches can help to establish the cause. Once the diagnosis is found, appropriate treatment can be initiated to slow or stop the disease process, or address the knee pain.

Causes

Knee pain after sitting can be caused by damage to the joint, as from arthritis. There are two basic types of arthritis according to "Current Medical Diagnosis and Treatment" by Drs. Stephen J. McPhee and Maxine Papadakis.

Osteoarthritis is from wear and tear to the joints and is common with age. The protective tissues in the joints break down, bones can rub against each other and cause inflammation and pain. Rheumatoid arthritis is from immune system dysfunction that causes damage to the joints.

Osteomyelitis is infection in the bone, and septic arthritis is infection of the joint space. Various injuries can also cause knee pain. These can include tears or rupture of cartilage, tendons, ligaments or bursa, which is a connective tissue layer.

Gout is a disorder in which crystals can build up in the knee and other joints. Tumors can also cause knee pain.

Risk Factors

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Risk factors for knee pain after sitting depend on the underlying cause. Some of the common risk factors include increasing age, family history and smoking, according to "Harrison's Principles of Internal Medicine" by Anthony S. Fauci MD.

Diagnosis

Diagnosis of knee pain after sitting involves a number of different steps. Future steps depend on the findings in preceding steps. The diagnosis will start with a detailed medical history. Other medical conditions, surgeries, medications, family history, and use of tobacco, alcohol and drugs are also clues to the diagnosis. After this, a physical exam of the knee is performed.

Depending on the findings, certain lab tests and imaging may be ordered. Blood can be tested for infections.

If there is excess fluid in the knee, the fluid can be drawn off and analyzed for inflammation, infection or crystals. Imaging, such as xrays or magnetic resonance imaging may also be utilized.

Treatment

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Treatment depends on the findings during diagnosis. Symptomatic treatment may involve the application of hot or cold presses and physical therapy. Mild pain medications such as tylenol or NSAIDs like ibuprofen may be used. Stronger pain medications such as Tylenol-codeine can be used in some people. Certain diseases can also be relieved by addressing underlying causes.

Drugs to suppress the immune system can be used in varying degrees to relieve or slow down the progression of rheumatoid arthritis. Various drugs are also used to treat gout; they act to either increase secretion or decrease the production of uric acid, which forms crystals in the joints.

Complications

The complications of joint pain in the knee are also different depending on the cause.

Infection can permanently damage the joint and spread to the blood stream. There, it can cause a severe immune system reaction and lead to septic shock, or spread to other organs, causing infections in the heart for example.