Knee Pain Information

The Femur, Tibia and Patella

A joint is formed by two major bones that are connected by thick bands of tissue called ligaments. The knee is the largest joint in the body and is made up of three main parts:

The lower end of the thigh bone, or femur.

The upper end of the shin bone, or tibia.

The kneecap, or patella.

Treating Knee Pain

The thigh bone (femur) turns on the upper end of the shin bone (tibia), and the kneecap (patella) slides in a groove on the end of the thigh bone. Ligaments, which are bands of tissue, connect the thigh bone and the shin bone to help keep the knee joint steady. The quadriceps, the long muscles on the front of the thigh, help strengthen the knee.

A smooth substance called articular cartilage covers the surface of the bones where they touch each other within the joint. This articular cartilage acts as a cushion between the bones. The rest of the surfaces of the knee joint are covered by a thin, smooth tissue liner called synovial membrane, which makes a small amount of fluid that acts as a lubricant so that the joint bones will not rub against each other.

Knee Pain: Normal Knee  Knee Pain: Arthritic Knee

What Causes Knee Pain?

Knee Anatomy
and Arthritis Video

Click below to view our Anatomy and Arthritis Video.

Knee Anatomy & Arthritis Video

One of the most common causes of knee pain and loss of mobility is the wearing away of the joint's cartilage lining. When this happens, the bones rub against each other, causing significant pain and swelling. The most common cause is a condition known as osteoarthritis. Trauma or direct injury to the knee can also cause osteoarthritis. Without cartilage there is no shock absorption between the bones in the joint, which allows stress to build up in the bones and contributes to pain.

Arthritis is one of the most common causes of joint disorders. More than 42 million people in the United States are diagnosed with arthritis.1 The most common types of arthritis are:

1. Arthritis Foundation website,, accessed Oct. 2008.