Articular cartilage, or joint cartilage, lines the ends of our bones. It is a smooth and sturdy surface enabling motion and painless weight bearing. Typically the end of the bone lined by cartilage sees very little stress due to the unique load sharing characteristics of cartilage. Chondromalacia, or bad cartilage, refers to the wearing of the articular, or joint, cartilage. Similar to roadways, wear can range from cracks in the pavement (relatively minor, but potentially serious with time) to potholes (serious). The complete erosion of the cartilage leads to exposed bone. This is arthritis. As our cartilage thins, the supporting bone sees an increased amount of stress. Our bone often will have a haphazard response to this stress creating an inflammatory response causing pain and swelling. Figure One depicts a normal knee with smooth white, articular or joint cartilage lining the femur and tibia. Figure Two depicts a knee with an increasing amount of cartilage wear. Often the development of chondromalacia is silent. However, issues related to chondromalacia often cause disability and prompt medical evaluation. Symptoms may range from discomfort with changes of weather, stiffness when arising from a seated position, pain with ascending/descending stairs, pain with sports or activities, a sensation of catching or locking, or the presence of swelling called an effusion.

Figure One: A normal appearing knee with pristine cartilage

Figure Two: A knee with substantial cartilage wear, but no exposed bone can be identified. This knee is at higher risk of continuing to be sore following surgery

Nonoperative treatments for chondromalacia include:

1) anti-inflammatory medications (ibuprofen (e.g. advil); naproxen (e.g. aleve); celecoxib (e.g. Celebrex)
2) physical therapy
3) glucosamine and chondroitin sulfate
4) lubrication injections of hyaluronic acid (synvisc; hyalgan; supartz; orthovisc)
5) steroid injections
6) activity modification (transition from high impact exercise (running on pavement/basketball) to low impact exercise (swim/bike/elliptical))
7) weight loss

Arthroscopy can play a role in certain situations. Instruments may be used to polish the surface of the roughened cartilage to eliminate loose flaps causing pain and swelling. This also prevents the propagation of the flaps. It should be noted that this does not regenerate the cartilage.

Figure Three: A chondral flap able to be peeled back. This is amenable to
surgical polishing.

Arthritis is a condition where there is full-thickness cartilage loss. This may either result from a particular injury, or more commonly from wear and tear over time. The following image shows the complete loss of cartilage with exposed bone consistent with arthritis.

Typically, the treatment for arthritis is nonsurgical (see the above items). Persistent pain and swelling leading to major activity avoidance is best treated by a knee replacement.

CARTILAGE RESTORATION

Certain situations exist were an area of absent cartilage with exposed bone is surrounded by normal cartilage. This scenario is known as a chondral defect. In these situations, arthroscopy can be used to assist in the restoration of the cartilage.

1) Holes in the underlying bone are made to stimulate the growth of scar cartilage. This technique is known as microfracture.
2) A tube of normal bone and cartilage is transplanted from a normal portion of the knee that isn't involved in activities to the diseased portion. This technique is known as the OATS procedure.

For massive areas of involvement surrounded by normal cartilage, arthroscopy plays a much smaller role.

1) An arthroscopic biopsy of normal cartilage is harvested. This is taken to a laboratory and cartilage cells are grown. An operation through a formal incision transplants these into the involved area. (Cartilage transplant)
2) Normal cartilage and bone from a cadaver is placed into the diseased area through a small incision. (Allograft OATS procedure)

The image below shows an example of a chondral defect. Note the normal cartilage surrounding the defect.

MICROFRACTURE

Microfracture refers to an operation where small holes are punctured into the bone bed where cartilage is absent inside the knee. Following this, a blood clot equal to the level of the surrounding normal cartilage forms. Over time, the blood clot transforms itself into fibrocartilage, or scar cartilage. The advantage of performing a microfracture is it is minimally invasive and the least costly. Both large and small areas can successfully be microfractured.

OATS PROCEDURE

OATS, or osteochondral autograft transfer system, is a procedure where the focal area of absent cartilage and its underlying bone are cored out in a cylinder shape. An exact matching plug of normal cartilage and bone is taken from another area of the knee where it is less needed. One or two small incisions often are necessary to either harvest the plug or to gain access to the focal cartilage defect. Only smaller areas of involvement may be addressed this way.

The area of worn cartilage is identified visually and subsequently probed. Note how the flap peels back and underlying bone is exposed. Unfortunately there is no way to reattach the delaminated cartilage back to the bone.

The chondral defect then is sized. A tamp (here is purple) is used until the entire chondral flap has been engulfed. A cylinder of bone and cartilage with the chondral defect in the center is removed.

The harvested cartilage and bone plug then is pressfit into the cored out region. The knee is moved to ensure a smooth surface.

OATS ALLOGRAFT PROCEDURE

Similar to the OATS procedure, the OATS allograft involves coring out the chondral defect and the underlying bone. Allograft, or donor bone and cartilage, is matched exactly to the patient's size and contour based on MRI. Much larger areas of damage may be corrected than with the traditional OATS. An incision is needed to gain access to the defect and to place the allograft.

CARTICEL (CARTILAGE TRANSPLANT)

For large areas of involvement, or prior failed procedures, a carticel procedure may be performed. An arthroscopy is performed, and a small biopsy of cartilage is taken. After growing additional cartilage cells from this in the laboratory, the cells are implanted into the knee through a sizeable incision. This operation is very costly, and may not be covered by many insurance carrier.