Images of the Knee

The knee is one of the most commonly injured joints.  Here are some images to help you understand the knee joint and the common causes of knee pain.

The knee joint is the junction of the thigh and the leg (part of the lower extremity).  The thigh bone (femur) contacts the shin bone (tibia) at the knee joint.  The kneecap (patella) sits in front of the knee joint.  Four major ligaments connect the bones and stabilize the knee joint.  In this image, the physician is pointing to the anterior cruciate ligament, or ACL, one of these important ligaments.

Inside the knee joint is a smooth cover on the ends of the bone called articular cartilage.  Between the articular cartilage layer, is a shock absorbing cushion called meniscus cartilage.  When people talk about knee cartilage, they may be talking about either the meniscus cartilage or the articular cartilage.

The lower extremity spans includes the thigh bone (femur), shin bone (tibia), and foot and ankle bones.  We call the segment between the hip and knee the thigh, and we call the segment between the knee and ankle the leg.  Some people confuse the words leg and lower extremity, but in anatomic terms the leg spans only the distance from the knee to the ankle.

X-rays of the knee are a commonly performed test to evaluate the knee joint. This is a front view of the knee joint, called an AP view of the knee. AP stands for anterior to posterior, meaning the image is directed from the front to the back of the knee joint.

A lateral x-ray is performed to see the knee joint from the side.  While an AP x-ray looks from front to back of the knee joint, the lateral view looks from the side of the joint.  Lateral x-rays are particularly helpful at seeing the kneecap, or patella, and the cartilage space behind the kneecap.

Knee arthritis is one of the most common cause of knee pain.  When arthritis occurs, it can cause joint pain and swelling.  There are many types of arthritis, the most common of which is called osteoarthritis.  People often use the words "wear-and-tear" to describe osteoarthritis, as it causes wearing away of the smooth cartilage on the ends of the bones, and tears of the meniscus cartilage.

A knee replacement surgery is performed to replace a damaged or worn out joint with a new joint made of metal and plastic. Knee replacement is a common surgical treatment of severe arthritis of the joint. 

Arthroscopic knee surgery is performed as a minimally invasive surgical procedure to look inside the knee joint with a small camera, and then treat problems of the knee joint such as meniscus tears, loose cartilage, and ligament injuries, with specialized instruments.  The advantage of this less-invasive surgical technique is often recovery is faster, and side-effects of the surgery are less significant.