How does osteoarthritis affect the knees?

Dr. Kevin J. Soden, MD
Family Practitioner

Because the cartilage at the ends of the bones are what wears down in osteoarthritis, the knee becomes painful and stiff and any movement can be uncomfortable.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)
The knee is the joint most commonly affected by osteoarthritis (OA). Well over 400,000 people get total knee replacement surgery every year, almost entirely because of knee OA. Osteoarthritis in the knee can make your joint so stiff and swollen that you can no longer easily bend or straighten it. You might have trouble going up and down stairs, walking, kneeling or stooping. You might also find that after sitting in one position for a while, your knee locks up and you can't straighten it without significant effort. But that doesn't have to happen to you. Knee OA responds well to exercises that strengthen the muscles that hold the knee in place, and to weight loss, which takes a lot of strain off the joint.
Osteoarthritis causes deterioration of the cushion between the bones of the knee. This causes the bones to rub together resulting in pain and swelling.
Osteoarthritis affects the knees in several ways. The most obvious is pain. That can lead to compensatory movement -- you change the way you move because of the pain -- which can then result in increased joint destruction or injury to other joints or muscles. The inflammation associated with knee osteoarthritis can cause the joint to become stiff when it's inactive for even a short period of time. Also, when the bones just below the cartilage become less protected by the cartilage -- or affected by the inflammation in the joint -- those bones can be further damaged, and the process and pain accelerate. These changes can cause a loss of joint space on X-ray.
Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner
In knees, osteoarthritis occurs when cartilage, or the protective slippery cushion of tissue that lines the end of the femur and top of the tibia, becomes damaged and unable to do its job. Over time, the joint cartilage breaks down to the point of bone-on-bone contact. This can be very painful and can cause inflammation. Over time, it can lead to disability. It can be treated, but a person may eventually need a total knee replacement.
Dr. Jeanne Morrison, PhD
Family Practitioner

Osteoarthritis (OA) affects the knees when the cartilage that supports and cushions the knee joint wears away.
The knee contains a small amount of fluid that lubricates the cartilage. It also helps cushion the joint. With osteoarthritis, this fluid does not work as well, so it can be hard to move your joints.

OA may cause the knee joint to become deformed, causing pain and stiffness. Medication and physical therapy may help ease the pain. In severe cases, joint replacement surgery may be necessary.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.