DR HQ: Anatomy 101—Cartilage injuries of the knee

When we hear about knee injuries in both baseball players or in friends, the most common type of injury (or so it seems) is torn cartilage. We are going to focus on cartilage injuries of the knee in this edition of Anatomy 101.

Articular Cartilage
In the knee joint, there are three bones: the femur (thigh bone), tibia (shin bone) and fibula. On the surface of these bones in the proximity of the joint they are coated with a cartilage called articular cartilage. Articular cartilage provides protection along with synovial fluid to form some of the smoothest surfaces in the body. It is this type of cartilage that helps provide protection of the surfaces of the bones from the repetitive motions of the working knee.

courtesy: www.orthogate.org 

Damage to the articular cartilage is called a chondral defect. Damage to the underlying bone, causing bone loss is called osteochondral defects. The important points to remember regarding injuries to articular cartilage is that it is painful (bone-on-bone) and it does not heal on its own. That’s because the blood supply to that part of the body is limited.

Up until recently there weren’t any options regarding repair of this type of injury. A surgical technique called microfracture surgery; simply put, the surgeon drills very small holes in the surface of the bone where the articular cartilage is damaged or missing. This technique helps facilitate in most cases, a regrowth of some articular cartilage. The recovery from this type of surgery is long as the rehab usually is arduous to say the least.

Meniscus Cartilage

The other type of cartilage injury is to the meniscus. Each knee has two menisci; C-shaped pieces of cartilage that act like a cushion between your shinbone and your thighbone. Meniscus cartilage is composed of elastic, smooth and dense connective tissue. The meniscus on the inside of the knee is called the medial meniscus. The lateral meniscus protects the outside of the knee joint. The graphic below provides a terrific view of the meniscus cartilage and its location in the knee joint.courtesy:


When there is a tear to the menisci, the surgeon really has two options, and the extent of the damage and the age of the patient are two key factors. First if the tear is large enough and factoring all the other considerations, the damaged portion of the meniscus is removed. This should prevent further tearing of the cartilage and provide pain relief. The downside is the meniscus will not regenerate to replace the part that was surgically removed. A knee without a portion of the meniscus cartilage is likely to develop arthritis down the road due to the lack of protection. While meniscus transplants are available, they are not common or successful enough to be the standard treatment for torn meniscus injuries.

courtesy: www.towerorthopaedics.com 

The standard treatment is a rigorous rehab program that builds up the strength of the muscles in the upper and lower leg to help support the knee joint and helps protect the knee. In most cases a knee brace isn’t used once the rehab program is completed.

Another Treatment Option
Joint lubrication treatment of the knee may be an option with a player that has developed an early case of osteoarthritis or his knee needs some protection to help reduce the pain and discomfort. In that case, Synvisc a medication called hyaluronan is injected into the knee joint. This fluid provides protection of the knee joint and can save a players knee. Randy Johnson had some major issues with the health of his knees, particularly the right one. Synvic injections were given to him a couple times of the year and he was able to prolong his career for a few extra seasons because of this treatment.

Sports Medicine has made some impressive inroads in treating knee injuries in recent years. In time, cartilage injuries will have even less impact on player careers as newer and improved treatments are developed.

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  For more information about the terms used in this article, see our Glossary Primer.