Healthy Knee

Understanding how your knee works

The knee is the joint in your body, where the lower end of the thighbone (femur), the upper end of the shinbone (tibia) and the kneecap (patella) meet. In a healthy joint, these bones are cushioned with cartilage and a thin lining called the synovial membrane to reduce friction and absorb shock. Your knee also contains large ligaments, which help control motion by connecting bones and by bracing the joint against abnormal types of motion.

Osteoarthritic Knee


Osteoarthritis (OA) can affect any joint in your body, but most commonly affects the knee and hip joints. It’s the most common reason for total joint replacement.When OA affects the knee joint, the cartilage cushioning the bones softens and wears away, causing the bones to grind against one another. That grinding hurts. You can feel it climbing stairs, working in the garden or just bending your knees. It may even keep you up at night.

Although osteoarthritis is more common among people over 50 years old, people of any age can have OA due to previous injury, overuse of the joints or obesity. Osteoarthritis is the most common type of arthritis and affects an estimated 27 million Americans.1

Symptoms2 of osteoarthritis include:

  • Joint aching and soreness
  • Pain, especially following activity
  • Stiffness after periods of rest
  • Swelling of the affected joint
  1. Osteoarthritis Fact Sheet. US Department of Health and Human Services.
  2. Osteoarthritis. National Institute of Arthritis and Musculoskeletal and Skin Diseases.
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Talk to your surgeon about whether joint replacement or another treatment is right for you and the risks of the procedure, including the risk of implant wear, loosening or failure, and pain, swelling and infection. Zimmer Biomet does not practice medicine; only a surgeon can answer your questions regarding your individual symptoms, diagnosis and treatment.