Pain in the knee can occur for many reasons. It can be mild or severe, and involve one or both knees. Most cases of knee pain do not pose a serious threat to a person’s health, but a few are serious.
What are the causes and risks of the condition?
There are many possible causes of knee pain, including:
trauma or injury
overuse of the knee
infections in or around the knee, such as septic arthritis
disease or infection throughout the body, which may produce generalized joint pain. Examples include sexually transmitted diseases (STDs) and flu.
gout or pseudogout, which are disorders that can deposit crystals into the joint space
autoimmune disorders, conditions in which a person produces antibodies against his or her own body for unknown reasons. Autoimmune disorders such as rheumatoid arthritis or systemic lupus erythematosus can cause knee pain.
Baker’s cyst, a small abnormal sac that may develop behind the knee
Osgood-Schlatter disease, a condition that usually occurs in teenage boys
deep venous thrombosis, which is a blood clot in the leg
a tumor or cancer affecting the bone
Symptoms & Signs
What are the signs and symptoms of the condition?
When a person complains of knee pain, the healthcare provider will ask questions such as:
exactly where the pain is located
when the pain started
the type of pain, such as sharp, dull, or throbbing
whether the pain is constant or only occurs sometimes
whether there has been any injury to the painful area
whether anything makes the pain better or worse
whether there is any difficulty in bending the affected knee or knees
whether or not there has been any other symptoms, such as swelling, skin rash, or fever
what other medical conditions a person has, if any
what medications, drugs, or herbs a person takes, if any
Other questions may also be asked in some cases.
Diagnosis & Tests
How is the condition diagnosed?
Diagnosis of knee pain begins with the history and physical exam. This may be all that is needed to make the diagnosis.
Other cases may require further testing. For instance, joint x-rays of the knee are commonly taken. These can help diagnose a bone fracture, or break, and a bone tumor or cancer. Blood tests may also be ordered, such as a test called an antibody titer, if an autoimmune disorder is suspected. Other imaging tests, such as an MRI, may be done to look at the knee in more detail.
If arthritis is suspected, a procedure called arthrocentesis is often done. The procedure involves inserting a needle through the skin and into the knee joint to remove a sample of joint fluid for analysis.
Prevention & Expectations
What can be done to prevent the condition?
Eating a healthy diet and avoiding alcohol can prevent some cases of knee pain due to gout. Avoiding overuse of the knees can help prevent cases from this cause. Some knee injuries can be prevented by following sports safety guidelines for children, adolescents, and adults. Many cases cannot be prevented.
What are the long-term effects of the condition?
Long-term effects are related to the amount and the cause of the knee pain. An injury may cause no long-term effects at all if minor, or may cause permanent deformity of the knee. Arthritis may slowly destroy the knee joint over time. Autoimmune disorders can affect many different organs of the body. Tumors or cancer may cause death if treatment doesn’t work.
What are the risks to others?
Most cases of knee pain are not contagious and pose no risk to others. If the cause of knee pain is an infection, such as a sexually transmitted disease or the flu, the infection may be contagious.
Treatment & Monitoring
What are the treatments for the condition?
For common knee pain, such as that from injury or osteoarthritis, over-the-counter pain medications are often used. If an infection is present, antibiotics may be needed. If a serious injury occurs, surgery may be needed. Long-term arthritis may destroy a joint and require a total knee replacement.
Autoimmune disorders are often treated with medications to suppress the immune system and reduce inflammation. If a tumor or cancer is the cause of pain, surgery, chemotherapy, or radiation therapy may be needed.
What are the side effects of the treatments?
Side effects depend on the treatments used. For instance, aspirin and antibiotics can cause stomach upset and allergic reactions. Any surgery carries a risk of bleeding, infection, or allergic reactions to anesthesia.
What happens after treatment for the condition?
Pain medication can be increased, changed, or decreased as needed. Someone with an injury often heals with treatment and needs no further monitoring. A person with a tumor or cancer may need regular monitoring for years after treatment.
How is the condition monitored?
Those with autoimmune disorders may need repeat blood tests to help monitor their disease. Any new or worsening symptoms should be reported to the healthcare provider.