Knee problems commonly occur in young people and adults. This article contains general information about several knee problems. It includes descriptions and a diagram of the different parts of the knee. Individual sections of the article describe the symptoms, diagnosis and treatment of specific types of knee injuries and conditions. Information on how to prevent these problems also is provided.

What Do the Knees Do? How Do They Work?

The knees provide stable support for the body and allow the legs to bend and straighten. Both flexibility and stability are needed for standing and for motions like walking, running, crouching, jumping and turning.

Several kinds of supporting and moving parts, including bones, cartilage, muscles, ligaments and tendons, help the knees do their job. Any of these parts can be involved in pain or dysfunction.

What Causes Knee Problems?

There are two general kinds of knee problems: mechanical and inflammatory.

Mechanical Knee Problems

Some knee problems result from injury, such as a direct blow or sudden movements that strain the knee beyond its normal range of movement. Other problems, such as osteoarthritis in the knee, result from wear and tear on its parts.

Inflammatory Knee Problems

Inflammation that occurs in certain rheumatic diseases, such as rheumatoid arthritis and systemic lupus erythematosus, can damage the knee.

Joint Basics

The point at which two or more bones are connected is called a joint. In all joints, the bones are kept from grinding against each other by padding called cartilage. Bones are joined to bones by strong, elastic bands of tissue called ligaments. Tendons are tough cords of tissue that connect muscle to bone. Muscles work in opposing pairs to bend and straighten joints. While muscles are not technically part of a joint, they’re important because strong muscles help support and protect joints.