Articular cartilage is the smooth layer that covers the ends of bones in joints to allow them to bend, rotate, and glide smoothly on one another. Cartilage has no blood supply or nerves, and has almost no ability to heal on its own after an injury. Cartilage changes over time as we get older and some injuries are due to degeneration of this tissue over time, however new cartilage injuries in young patients also occur, usually due to trauma. Preservation of the cartilage is key to joint health.
What is a cartilage (chondral) defect?
A cartilage defect is a focal area of damage to the articular cartilage that lines the joints, with the remaining cartilage generally remaining healthy and intact. This is different from the generalized, diffuse cartilage changes of osteoarthritis. Focal defects are graded by severity. Grade I is the mildest and grade IV (exposed bone) is the most severe.
A chondral lesion is a common injury affecting 5-10% of people over age 40, but it can also affect young patients that experience traumatic injuries. Damage to knee cartilage can lead to post-traumatic osteoarthritis of the knee over time. Normal wear and tear on the joint can cause the cartilage to break down, thereby leading to pain and disability as well as osteoarthritis.
What are the symptoms?
A focal injury to the cartilage may cause pain, intermittent swelling, and a grinding sensation. The injury may cause cartilage fragments to float in the joint causing locking, catching and swelling.
How is a chondral injury diagnosed?
Dr. Cooper will review your injury and what events occurred to lead to your pain as well as the symptoms of your current pain. His focus is on helping you get back to the activities and sports you enjoy.
Chondral defects can be difficult to diagnose as the symptoms may not appear immediately. Additionally, small defects are usually not visible on x-ray.
Dr. Cooper will conduct a comprehensive physical examination involving range of motion, stability, and gait. However, physical exam alone may not reveal the damage. X-rays will assess arthritis, bony defects, and misalignment. MRI imaging is helpful for evaluating the chondral surfaces. However, the most reliable diagnostic procedure is knee arthroscopy which allows him to see inside the joint to evaluate the damage.
How is a chondral defect treated?
The choice of treatment will depend on the size of the defect, its location, and the patient’s goals. Chondral defects are difficult to treat and can sometimes require surgical repair if all conservative measures have failed.
When the symptoms are mild, the first line treatment is nonoperative, including anti-inflammatory medications, icing, activity modification and physical therapy. Corticosteroid, hyaluronic acid, or platelet-rich plasma injections and bracing may be recommended. In addition, protective supplements of glucosamine and chondroitin may be recommended in specific cases. All of these treatments will provide symptomatic relief but will not heal a defect.
The choice of procedure depends upon the patient’s age and weight, and their activity goals; and on the size and location of the defect. Cartilage restoration is the goal. Surgery is aimed at restoring the articular surface. It is not used in cases of wear and tear chondral defects.
- Arthroscopic debridement is a procedure to remove cartilage fragments in the joint to relieve symptoms.
- Arthroscopic microfracture is a procedure to stimulate the creation of new cartilage-like tissue called fibrocartilage. This fibrocartilage can provide functional improvement, but it is not as long-lasting as the original articular cartilage.
- Osteochondral autograft of cartilage and bone is a procedure where healthy cartilage is harvested from one part of your knee and transplanted into the defect.
- Osteochondral allografts of donor cartilage can be implanted into the lesion. Survival rates have been reported to be excellent even at 10 years.
- Autologous chondrocyte implantation is a procedure where your own cartilage cells are harvested, grown in a lab and implanted into the defect. This is a two-stage cell-based procedure, because it requires an initial arthroscopic procedure to harvest the cells (small biopsy from your cartilage). The patient’s own cartilage cells (chondrocytes) are harvested from a non-weight bearing joint and grown (cultured) in a lab over several weeks. The lesion is also debrided to remove damaged cartilage at this initial procedure. When ready, the cultured cells are implanted into a membrane which will then cover the cartilage defect. Because the transplants are made of the patient’s own cells, there is no risk of rejection. MACI is best for younger patients that want to remain active and can commit to post-op rehabilitation. It is most commonly used for patellofemoral (knee cap) cartilage injuries.
- Osteotomies are a powerful treatment method for managing cartilage defects. An osteotomy involves changing the orientation of the bones of the knee. The first step is evaluating xrays to determine where your body places most of the weight on your knee. Everyone is different in this regard, but if you have cartilage defects on one side of your knee, and all of your weight is pushing through this defect, it is possible to alter the alignment and offload the injured part of your knee. Multiple surgical options exist for this including high tibial osteotomies, and distal femoral osteotomies. These are extra-articular procedures that generally heal very well and provide a robust fixation to alleviate pain in the knee.