Osteoarthritis (OA) is the most common type of arthritis. It occurs most often in the hands, knees, hips, and spine.

OA affects cartilage-the slippery tissue that covers the ends of bones in a joint. Cartilage allows bones to glide over each other and absorbs the shock of movement. In OA, the top layer of cartilage breaks down and wears away, allowing the bones under it to rub against each other. This can cause pain, swelling, and difficulty in moving the joint.

Read more at: https://www.nccih.nih.gov/health/osteoarthritis-in-depth