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Articular Cartilage Injury of the Knee

What is the articular cartilage of the knee?

This term is used to describe damage to a type of cartilage in the knee. The ends of the three bones in the knee joint are covered with what is know as articular cartilage, a tough, elastic material that helps absorb shock and allows the knee joint to move smoothly.

What are the signs of articular cartilage injury?

The most frequent symptom is a dull pain around or under the knee cap that worsens when walking down stairs or hills. A person may also feel pain when climbing stairs or when the knee bears weight as it straightens. The disorder is common in runners and is also seen in skiers, cyclists, and soccer players.

What causes an injury to the articular cartilage?

This disorder occurs most often in young adults and can be caused by injury, overuse, parts out of alignment, or muscle weakness. Instead of gliding smoothly across the lower end of the thigh bone, the knee cap rubs against it, thereby roughening the cartilage underneath the knee cap.

How does a doctor tell if a patient has articular cartilage injury?

A patient's description of symptoms and a follow-up X-ray usually help the doctor make a diagnosis.

How is articular cartilage injury treated?

A difficult challenge for orthopaedic surgeons is the treatment of injured joint surface cartilage in the young and active patient. Localized damage to one of the surfaces of the knee joint can lead to degradation and destruction of the opposing healthy joint surface. Total knee replacement is an excellent option in the older patient, but for young active patients who are not candidates for knee replacement we must find a way to get healing of these injured surfaces with healthy hyaline cartilage to avoid longterm problems with degenerative arthritis. Traditional treatments have focused on stimulating the bone at the base of a full thickness cartilage defect by drilling, burring, or microfracturing with a special pick. These treatments cause bleeding and healing with fibrocartilage or "scar cartilage" which is not as resilient as normal hyaline cartilage. These treatments remain the first line of treatment for isolated lesions of articular cartilage in the knee.

Autologous Chondrocyte Implantation (ACI)

A recent surgical technique developed in Sweden by Dr. Lars Pederson has shown some promising results in the treatment of articular cartilage defects in the knee. The procedure is called autologous chondrocyte implantation (or ACI) and it shows promise in restoring hyaline cartilage to the healing joint surface rather than fibrocartilage. ACI requires two surgeries. The first is an outpatient arthroscopic procedure to biopsy a small portion of a patient's normal articular cartilage. This biopsy is sent to a lab (Genzyme Tissue Repair) where the patient's own cartilage cells are grown. Approximately 4 weeks later the cells are reimplanted into the knee through a small incision. A bone lining flap (periosteum) is sewn as a roof over the cartilage defect and the cultured cartilage cells are injected into the defect under the periosteal flap.

Postoperatively, the patient remains on crutches for approximately 2 months and uses a continuous passive motion machine (CPM) immediately after surgery to maintain knee motion and help the cartilage cells mature. Return to impact loading sports is delayed until at least 1 year after the second surgery.

This procedure is currently offered in Keene and Lebanon. The procedure is not indicated for generalized knee arthritis but rather for isolated articular cartilage defects of the femur. The ideal patient is a younger patient (younger than 40 years of age) who has developed an isolated lesion of the femur following a traumatic injury or from a developmental problem such as osteochondritis dissecans. Results of ACI have been encouraging although not always successful but most studies show a significant majority of patients receiving partial or complete improvement with the implantation technique.

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