Knee Osteoarthritis

Knee osteoarthritis is the everyday wear-and-tear form of arthritis. The smooth cartilage that caps the ends of the thighbone and shinbone and the back of the kneecap gradually thins and breaks down. As it wears, the space between the bones narrows, the surfaces begin to rub instead of glide, and small bony growths called bone spurs form at the edges of the joint. The result is pain, stiffness, and swelling that make walking and stairs harder over time.

Osteoarthritis is one of the leading causes of lost mobility in adults, and it occurs most often in people age 50 and older, though it can appear earlier. It cannot be cured, and worn cartilage does not grow back. It can, however, be managed well for years. The goal of treatment is to relieve pain and keep the joint working, not to reverse the wear, and most people stay active with the right plan. It is one of several knee conditions treated at the practice.

Three kinds of arthritis affect the knee, and telling them apart guides treatment:

• Osteoarthritis is the most common. It is the degenerative, wear-and-tear type that develops slowly as cartilage breaks down, usually in middle age and beyond.
• Rheumatoid arthritis is a body-wide inflammatory disease in which the immune system attacks the joint lining. It tends to affect the same joint on both sides of the body and is managed by a rheumatologist alongside orthopedic care.
• Post-traumatic arthritis develops years after a knee injury such as a fracture, a ligament tear, or a meniscus tear, when the earlier damage changes how the joint wears.

Symptoms usually build slowly over months to years, though they can flare after activity. Common ones include:

• Pain that comes with activity at first and, as arthritis advances, with lighter activity or at rest
• Stiffness after sitting or in the morning that eases as the joint warms up
• Swelling that often worsens after being on your feet
• A grinding, clicking, or grating sensation with movement, called crepitus
• A feeling that the knee may catch, lock, or give way
• Pain that some people notice more with changes in the weather

Osteoarthritis develops as cartilage loses its resilience and wears down. Several factors raise the risk or speed it up:

• Age. The risk rises with age as cartilage has carried load for longer.
• Extra body weight. Every pound of body weight multiplies the force across the knee with each step, so added weight accelerates wear.
• Prior injury. A previous fracture, ligament tear, or meniscus tear changes how the joint loads and can lead to arthritis later.
• Repetitive heavy loading. Work or activity that puts high, repeated stress on the knee over many years.
• Family history and joint alignment. Genetics and a bowed or knock-kneed alignment that concentrates load on one side of the joint.

Diagnosis starts with your history and a physical examination that checks the knee for swelling and tenderness, measures how far it bends and straightens, tests its stability, and watches how you walk. Because arthritis in several joints at once can point to rheumatoid arthritis, other joints are checked as well.

X-rays taken while you stand and put weight on the knee show how far the joint space has narrowed under load, along with bone spurs and changes in the bone. How the knee feels and functions matters more than how far the arthritis has progressed on an image. An MRI is not needed to diagnose osteoarthritis and is reserved for specific questions about the cartilage or soft tissues. Blood tests are used when an inflammatory arthritis such as rheumatoid arthritis is suspected.

Most knee arthritis is managed without surgery, and non-surgical care is the starting point. Typical first-line measures include:

• Activity changes. Trading high-impact activity for lower-impact options such as swimming or cycling keeps you moving with less load on the joint.
• Exercise and physical therapy. Strengthening the muscles around the knee and improving flexibility reduces pain and improves function, and exercise is recommended for osteoarthritis.
• Weight loss. Losing weight takes real force off the knee with every step and is one of the most effective things a person carrying extra weight can do.
• Medication. Anti-inflammatory medicines (NSAIDs) taken by mouth or applied to the skin can improve pain and function; acetaminophen is an alternative when NSAIDs are not tolerated.
• Bracing and support. A cane, a knee sleeve, or an unloader brace that shifts weight away from the worn side of the knee when arthritis is limited to one compartment.
• Steroid injection. A steroid injection can settle a painful flare. It is spaced out over time, generally no more than three or four per joint in a year.

Supplements such as glucosamine and chondroitin are widely used, but there is no evidence that they slow or reverse arthritis. Biologic injections such as platelet-rich plasma and stem cell preparations are offered in some settings, but clinical studies have not yet confirmed their value for osteoarthritis.

Surgery is considered when arthritis is advanced, pain limits daily life, and non-surgical care no longer controls it. The options depend on age, activity, and where the arthritis sits within the knee:

• Osteotomy reshapes the shinbone or thighbone to shift load off the worn side. It is used mainly in younger people with early arthritis limited to one side of the knee.
• Partial knee replacement resurfaces only the damaged compartment when the rest of the joint is healthy.
• Total knee replacement resurfaces the whole joint and is the reliable option for advanced arthritis across more than one compartment.

• Total knee replacementKnee

For a fuller explanation, including anatomy, diagnosis, and the full range of treatment:

• Arthritis of the Knee — AAOS OrthoInfo