Cartilage Defects:

In the human knee there are two forms of cartilage.  Meniscal or fibrocartilage, or the cartilage that is on the ends of our bones.  That cartilage is known as articular cartilage and damage to the articular cartilage is the focus of this section.  If you have been diagnosed with a "cartilage tear" your physician was probably referring to meniscal cartilage, and I cover that in a separate section.  If your physician says you have a hole or defect in the cartilage, they are likely referring to the articular cartilage layer.  Articular cartilage is typically 1/8-1/4" thick in an adult knee.  It is a firm, exceptionally smooth surface and enables your joints to glide and move without friction, grinding, catching or discomfort.  This is a typical picture of normal appearing cartilage on the end of the femur when viewed during an arthroscopic procedure.   Articular Cartilage of the Knee

Injuries to articular cartilage can occur through numerous mechanisms. Many injuries occur in teenagers from track fields injuries.  In those cases, a piece of cartilage literally ripped off the end of the bone.  These are relatively uncommon and usually produce pain, swelling, locking, a feeling that something is loose within the knee and perhaps even a feeling of instability if the piece is caught within the knee. 

By far the most common injury is the results of blunt trauma---a fall from a height, a car accident where your knee hits the dashboard or falls directly onto the front of the knee. 

After practicing for a few years I have now seen a number of patients with identical cartilage defects in both the right and left knees.  This implies, but does not absolutely mean some form of genetic predisposition. 

In certain situation, osteoarthritis will cause defects or holes in the cartilage too.  But in cases of arthritis, typically all the cartilage in the knee is thinning (or disappearing) and the cartilage surrounding the defect is not normal.

 Here is another arthroscopic picture... in this picture you can see the cartilage literally peeling off of the bone beneath it. The small metal object on the lower right of the image is a small needle being used to determine the type of repair necessary.

Articular Cartilage Defect on the end of the Femur

Cartilage injuries can be severe, because the natural history of cartilage loss is a strong association with developing osteoarthritis as the cartilage around the defect takes on more stress, degenerates, thins and eventually disappears.  These lesions, if large enough, are best treated as soon as they are recognized. 

To aid in making the diagnosis an MRI might be necessary.  It depends on the index of suspicion of your surgeon. Not all knee problems require an MRI--- if you present with the symptoms I mentioned previously an MRI will be very useful for demonstrating the location, size and potential reparability. 

Once the diagnosis is made, a discussion will ensue to provide you with the techniques available to "repair" the lesion or defect in the cartilage. Bear in mind... in situations where multiple surgical options exist and there is no "clear winner", that means that the *perfect* repair has not been identified yet.  This is one of those situations.  We have many good procedures to help restore the cartilage, but none of them is perfect and some are more invasive then others.  The procedures available are:

Micro-fracture or "Marrow Stimulating Technique" This technique is arthroscopic and involves makes many small holes in the defect--deep into the bone beneath it. Bone marrow cells, stem cell and blood will come out of the holes and coat the defect.  This results in a layer of fibrocartilage covering the defect.  Fibrocartilage is not the same as the original hyaline articular cartilage.  It has different properties and might not stand the test of time. 

Genzyme developed a procedure known as Carticel.  This involves two procedures.  The first is an arthroscopic assesment of your defect and if we beleive you are a good candidate for a Carticel procedure, we will take a small biopsy of normal cartilage.  Genzyme will amplify, or grow the cartilage cells and send them back to us.  During a second stage procedure those cells are implanted and will hopefully grow into a layer of hyaline-like cartilage that covers the defect. 

What I find to be one of the more satisfying and successful procedures is known as a mosaicplasty, or OATS procedure.  This involves taking cartilage from low-weight bearing areas of the knee and transfering it into the defect in the end of the femur that bears all your weight.  The advantage is that you have a layer of true hyaline cartilage which should stand the test of time.   The area where we take the cartilage from is filled with a plug that will encourage hyaline-like cartilage growth.  Below are images of 1. a cartilage defect viewed arthroscopically, 2. the defect after it has been drilled out to create a hole to place the cartilage plug, and then 3. the cartilage plug in proper position. 

 Stage 1: Drilling Defect