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Osteoarthritis of the knee happens when the cartilage that cushions the bones in the knee starts to erode. The bones begin to rub against each other, resulting in damage, swelling, and pain.

Cartilage is a smooth but tough tissue that stops the bones from rubbing together and prevents damage. It allows the bones to move pass smoothly over each other. As people get older, the weight they carry can cause the cartilage to wear away.

As the cartilage breaks down and the bones rub together, osteoarthritis (OA) can result.

OA is the most common type of arthritis. The symptoms include swelling, pain, and stiffness. When it affects the knee, it can be difficult for a person to exercise, to climb stairs, or even to walk.

OA usually affects people who are over 50 years of age, but it can happen earlier, too.

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Pain in the knee may be a sign of arthritis.

Symptoms that can appear at the early stages of knee OA are:

  • pain, especially on bending and straightening the knee and with weight bearing
  • swelling, caused by a buildup of fluid in the joint, or by bony growths called osteophytes that form as the cartilage breaks down
  • warmth in the skin over the knee, especially at the end of the day
  • tenderness when pressing down on the knee
  • stiffness when moving the joint, especially first thing in the morning or after a period of inactivity or walking
  • creaking or cracking on bending, known as crepitus

Activity can make symptoms worse, leading to pain at the end of the day, especially after a long time of standing or walking.

If the knee is red, the person has a fever, or both symptoms occur, the problem is probably not OA.

Treatment of OA depends on how severe the symptoms are.

Home treatment

Some remedies and over-the-counter treatments for OA of the knee can be used at home and are readily available from the pharmacy.

These include:

Applying heat or cold: Heat relieves stiffness, and cold can ease pain and swelling. The heating pad or ice pack should be covered with a towel so as not to burn the skin.

Using an assistive device: A cane or walker can help take some of the weight off of the knees. Holding the cane in the opposite hand to the painful knee is most effective.

Pain relief medications: These are available over the counter, but people should use them with caution as they can cause side effects.

Examples of over-the-counter medications

Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, and aspirin can help reduce swelling and pain. High doses or long-term use can cause a stomach upset, heart problems, bleeding, and damage to the liver and kidneys.

Topical creams containing NSAIDs or ingredients that create a warming or cooling sensation are a relatively safe way to reduce symptoms.

A range of creams and ointments are available for purchase online.

Acetaminophen can help reduce pain but not swelling. Acetaminophen has fewer side effects than NSAIDs, but large doses can damage the liver.

Find out more about NSAIDs and the alternative options.

Medical treatment

If home or over-the-counter remedies do not help, the person should see a doctor.

They may prescribe one of the following:

  • steroid injections in the knee joint to reduce inflammation
  • hyaluronic acid injections to provide fluid that cushions and lubricates the joint
  • physical therapy, with exercises to improve flexibility and range of motion in the joint

If these solutions do not work and damage is severe, the physician may recommend surgery to replace the joint.

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A doctor will examine the knee and ask about pain and stiffness.

For some people, pain and other symptoms are severe enough to interfere with daily life, and over-the-counter medications do not help.

The next step is to consult a general physician, who may refer the person to a rheumatologist or orthopedic surgeon.

To find out whether a patient has OA, the doctor may ask:

  • When and how did the pain start?
  • Where does it hurt?
  • Is there any stiffness, creaking, warmth, or swelling?
  • What makes it better? What makes it worse?
  • How have you treated it? Did home treatments work?
  • How have the symptoms affected daily activities?

The doctor will examine the knees, moving them forward and back to note the range of motion and to find out which movements cause pain.

They will look for areas of tenderness, check the warmth and see if any swelling is present. The physician will also check the ligaments for stability.

A number of tests can help to diagnose OA:

Joint aspiration: The doctor uses a needle to draw a sample of fluid from the joint. They send the fluid to a laboratory for tests to check for signs of other joint problems, such as gout or infection.

Magnetic resonance imaging (MRI): This can provide detailed images of the knees, which may show fluid buildup in the thigh or knee bones.

X-rays: These can reveal damage to the knee joints in the later stages but may not detect changes in the early stages.

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Swimming is a good way to exercise the knee without putting weight on it.

Some lifestyle changes can relieve the pain and stiffness that occurs with knee arthritis:

Losing weight can relieve pain and prevent further joint damage.

Exercise, and especially low-impact activities such as walking, riding a recumbent bicycle, or swimming, can relieve arthritis pain.

Swimming is ideal because the buoyancy of the water takes pressure off the joints, while the warmth soothes them.

Exercise increases motion and flexibility and strengthens the muscles that support the joints. It also helps people to maintain a healthy weight.

OA is a common but painful condition that affects many people as they age. Pain, stiffness, swelling, warmth, or cracking in the joints may be early signs that it is time to seek medical help.