Osteoarthritis of the Knee

Overview

Osteoarthritis of the knee is a common form of osteoarthritis in which the smooth cartilage that cushions the ends of the bones in the knee gradually wears away. As the cartilage thins, the bones rub together more, leading to pain, stiffness, swelling, and reduced movement. The knee is one of the joints most often affected because it bears much of the body's weight.

Knee osteoarthritis usually develops slowly over years and tends to worsen with time, though the rate varies. It is a leading cause of pain and disability in older adults. While the joint damage cannot be reversed, many treatments can ease symptoms, keep the knee moving, and help people stay active.

It helps to think of knee osteoarthritis as a whole-joint condition rather than simply worn cartilage, since the bone, joint lining, and surrounding muscles are all involved. This is why a combination of approaches, especially exercise and weight management, often works better than any single treatment and can make a real difference to comfort and mobility.

Symptoms

Symptoms of knee osteoarthritis usually come on gradually and worsen over time:

• Pain that worsens with activity such as walking, climbing stairs, or standing up, and eases with rest
• Stiffness, especially after waking or after sitting for a while, that usually eases within about 30 minutes of moving
• Swelling around the knee
• A grinding, clicking, or cracking sensation when moving the knee
• A feeling that the knee may give way or lock
• Reduced range of motion and difficulty fully bending or straightening the knee

Symptoms can flare and settle, and over time pain may occur even at rest or at night.

Causes

Knee osteoarthritis develops when the cartilage in the knee breaks down faster than the body can maintain it. This is often described as wear and tear, but it involves active changes in the whole joint, including the bone and lining. Contributing factors include:

• Aging, as cartilage becomes less resilient over time
• Excess body weight, which increases load on the knee
• Previous knee injuries, such as an ACL injury or fracture
• Repeated stress from certain jobs or high-impact activities
• Joint shape or alignment problems

Risk Factors

• Older age
• Being overweight or obese
• A previous knee injury or surgery
• Repetitive kneeling, squatting, or heavy lifting at work
• Family history of osteoarthritis
• Being female, particularly after menopause
• Misalignment such as bow-legs or knock-knees

Diagnosis

Knee osteoarthritis is usually diagnosed from the symptoms and a physical examination, supported by imaging:

• History and examination: Assessing pain pattern, stiffness, swelling, range of motion, and any grinding or instability.
• X-rays: Can show narrowing of the joint space, bony spurs, and other changes of osteoarthritis.
• MRI: Occasionally used to look at cartilage and soft tissues in more detail.
• Other tests: Blood tests or joint fluid analysis may be used to rule out other types of arthritis.

Treatment

Treatment focuses on relieving pain, improving function, and slowing the impact of the condition. A combination of approaches usually works best.

• Exercise and physical therapy: Strengthening the muscles around the knee and gentle aerobic activity reduce pain and improve function.
• Weight management: Losing excess weight significantly reduces stress on the knee.
• Pain relief: Acetaminophen, topical or oral NSAIDs, and other medicines as advised by a doctor.
• Supportive measures: Walking aids, braces, suitable footwear, and using heat or cold.
• Injections: Corticosteroid injections can relieve flares; other injections are used in some cases.
• Surgery: Joint replacement may be considered for severe, disabling osteoarthritis that does not respond to other treatments.

Most people do not need surgery and can manage well for many years with a combination of exercise, weight control, and medication.

Self-Care and Prevention

• Stay active with low-impact exercise such as walking, cycling, or swimming to keep the joint moving
• Maintain a healthy weight to reduce load on the knees
• Strengthen the thigh and hip muscles that support the knee
• Use good technique when lifting and protect the knee from injury
• Use heat, cold, and supportive devices to manage flares

When to See a Doctor

See a doctor if knee pain or stiffness is persistent, limits your activities, disturbs your sleep, or is not controlled by simple measures, so that a treatment plan can be put in place.

Seek prompt medical care if a knee becomes suddenly hot, very swollen, and painful with fever, or if you cannot bear weight after an injury, as these may indicate a joint infection, a different type of arthritis, or a fracture that needs urgent evaluation.

Related Topics

Frequently Asked Questions

References

1. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Osteoarthritis.
2. Mayo Clinic. Osteoarthritis.
3. Arthritis Foundation. Osteoarthritis.
4. MedlinePlus, U.S. National Library of Medicine. Osteoarthritis.