Osteoarthritis of the knee
Description
When most people say they have arthritis in their knees, they are referring to a type of arthritis called osteoarthritis.
Osteoarthritis is caused by "wear and tear" inside your knee joints. It starts when the knee joint cartilage is damaged.
- Cartilage is the firm, rubbery tissue that cushions all of your bones and joints. It allows bones to glide smoothly over one another.
- If the cartilage breaks down and wears away, the bones rub together. This causes pain, swelling, and stiffness.
- Over time, bony growths called bone spurs form, the ligaments can become stiffer and muscles around your knee become weaker, and your whole knee gets stiffer. These are the symptoms of osteoarthritis.
What does knee arthritis feel like?
If you have osteoarthritis in your knees, your knees are likely becoming stiffer and harder to move. You may notice a rubbing, grating, or crackling sound when you move your knee joint.
The phrase "morning stiffness" is the pain and stiffness you may feel when you first wake up in the morning. This stiffness usually lasts for 30 minutes or less, and it gets better with mild activity that "warms up" the joint.
During the day, the pain may get worse at the end of the day when you are active and better when you are resting. After a while, you may have pain after you are resting. You can have stiffness and pain after you sit for a while and try to get up. It may even wake you up at night.
How and why does arthritis start?
Usually, the cause of osteoarthritis is unknown. The symptoms usually appear in middle age. Almost everyone has some symptoms of arthritis by age 70.
These symptoms may be minor for some and severe in others. Before age 55, osteoarthritis occurs equally in men and women. After age 55, it is more common in women. It also tends to run in families.
These are some factors that make it more likely you will develop osteoarthritis in your knees as you get older:
- Being overweight increases the risk because extra body weight causes more wear and tear on your knee joints.
- Fractures or trauma to the knee in the past.
- Other knee injuries, such as a torn knee cartilage (meniscus) or torn knee ligaments.
- Doing manual labor for many years. Jobs that require kneeling or squatting for more than an hour a day put you at the highest risk. Jobs that involve lifting, climbing stairs, or walking also put you at risk.
- Playing sports that involve direct joint impact (such as football) or twisting (such as basketball or soccer).
- Misalignment of your legs can cause wear and tear in your joints.
Reviewed By: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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