All About the Knee

What is the knee joint and how does it work?

The knee is the largest and most complicated joint in the body—and the most prone to injury and osteoarthritis. Its main movement is bending and straightening. Your knee joints are made up of a combination of tendons, ligaments, muscles, cartilage and bone.

What kinds of injuries and coditions can affect the knee?

Common knee injuries and coditions are:

• Torn ligaments
• Torn cartilage
• Torn meniscus
• Fractures
• Dislocations
• Sprains—injuries to a ligament
• Strains—injuries to a tendon
• Arthritis
• Bursitis

Which knee injuries are typical in athletes?

Common knee injuries among athletes are contusions (bruises), sprains and strains. A lot of athletes also suffer a torn cartilage or meniscus—these injuries are within the joint itself, and often require surgical repair.

How many ligaments does the knee have?

Four main ligaments stabilize the knee joint:

• Anterior cruciate ligament, or ACL
• Posterior cruciate ligament
• Medial collateral ligament
• Lateral collateral ligament

What is the most commonly injured knee ligament?

The ACL is the most-often injured knee ligament and is frequently damaged by athletes. ACL tears are common in sports that involve a lot of twisting and turning, such as football, skiing and soccer.

How can I tell if I've torn an ACL?

Some patients hear or feel a “pop” when they tear an ACL. There may not be a lot of pain at the moment an ACL tears, but as the knee starts to swell, it can become quite painful. The pain and swelling can be minimized by icing the knee. If you think you might have torn your ACL, you need prompt medical attention to diagnose the injury and treat it appropriately.

How serious is a torn ACL?

The ACL is the most severe of the knee ligament injuries. When it tears, it often requires surgery. Arthroscopic ACL reconstruction is the typical surgery done in this case.

How is ACL reconstruction surgery done?

Because it's inside the knee joint, the ACL does not have its own blood supply—so if you tear your ACL, it can't heal itself. During an ACL reconstruction, a ligament is taken from somewhere else in your body and reconstructed across the knee joint to re-create your ACL.

Operating through the arthroscope, the surgeon uses a piece of the patellar (kneecap) tendon, a hamstring tendon or a donated allograft tendon to reconstruct a torn ACL.

What is the meniscus and what does it do?

The meniscus is a disc that sits between the thighbone and the shinbone or tibia. It acts as a cushion between the two bones. The meniscus helps reduce friction and helps prevent impact between the two bones. There's a meniscus on the inside and one on the outside of each knee joint.

The meniscus is made of cartilage, so when you hear about a person who tore a cartilage, or tore the meniscus, it's the same thing. Meniscus is just a specific term for the cartilage in the knee joint.

What types of surgery are done on the meniscus?

There are surgical procedures to reconstruct the meniscus and to repair it. In a type of arthroscopic surgery called a meniscectomy, the surgeon removes just the torn part of the meniscus.

How can arthritis affect the knee?

Two kinds of arthritis can cause knee pain, stiffness and swelling:

• Osteoarthritis, also known as wear-and-tear arthritis or degenerative joint disease, is the most common type of arthritis affecting the knees. This is a progressive inflammation of the knee where the protective cartilage wears off the joint, eventually resulting in painful bone-on-bone arthritis.
• Rheumatoid arthritis or RA, the most disabling form of arthritis, is a systemic disease that may attack many parts of the body. It is believed to be an autoimmune disease caused by a virus or a genetic component.