AN OVERVIEW OF TREATMENTS FOR THE KNEE
On the ends of your bones there is a smooth white surface only a few millimeters thick that helps the opposing bones that form the joint work together with less friction. This covering, called articular (joint) cartilage, has no blood supply to aid in the healing process; therefore if it becomes damaged, it is unable to heal on its own. Articular knee injury can be separated into either chondral lesions, which involves only the articular cartilage, or osteochondral lesions that includes a fragment of bone with the articular cartilage. Factors such as genetics and hormones have been associated with articular lesions but they are most often caused by a traumatic injury. These injuries can be as simple as bruising the cartilage and bone or more serious when either the cartilage or both bone and cartilage are damaged. The lasting effects of an injury are related to the size and location of the lesion, and other factors, such as your age, weight, and limb alignment.
Diagnosis of chondral injury has historically been difficult. Some patients describe the pain as a slight discomfort while others experience sharp, unbearable pain. You may have swelling, locking, or catching, but some patients never have any symptoms at all. Since the symptoms can masquerade as different conditions that occur within the knee, a thorough history, examination of the knee, and imaging is used to make a diagnosis.
X-rays are generally obtained as part of the initial evaluation of a knee injury. X-rays may not identify chondral or even osteochondral lesions of the knee when no or very little bone is involved, but they do help rule out other possible conditions. CT scans can be used to identify and determine the extent of injury when a bone fragment is involved. It can also be used to assess for bone healing, but a CT scan will not identify cartilage lesions that do not involve bone. A magnetic resonance imaging (MRI) scan is the best way to detect chondral and osteochondral lesions. Using a MRI scan, your physician can accurately locate the injury, show the extent of damage and assess the lesion.
There are a variety of treatments available for cartilage injury; however, no particular treatment has been identified the single best approach. Although, articular cartilage is not capable of repairing itself, injury to subchondral bone does stimulate a healing response but it does not restore the articular surface to its natural state and properties. The scope of treatment ranges from nonsurgical to a variety of surgical techniques that can reduce the pain and restore function. The treatment approach should take into account the injury as well as your lifestyle and goals.
The goal of nonsurgical treatment is to limit your symptoms, but it does not fix the problem. Treatment options include bracing, oral and topical anti-inflammatory medications, corticosteroid and hyaluronic acid injections, physical therapy, and modifying or avoiding specific activity.
For patients with more severe symptoms, surgery is often performed to relieve pain, restore function, and prevent further damage. The surgical continuum ranges from simple removal of loose bodies and debridement of a lesion to replacement of the joint. The course taken is based on many factors to include: injury size, depth, and location, and the patient’s symptoms, age, activity level, physical characteristics, and prior treatments.
Arthroscopic washout and debridement
Surgeons perform arthroscopic surgery using a tiny camera and instruments inserted into the joint through small incisions. Arthroscopic washout and debridement entails flushing the knee with a sterile solution to remove inflammatory agents and loose bodies and then using tools to remove and shape unstable cartilage edges. This technique alone was shown to improve symptoms in 68% of patients.1 After surgery, recovery is quick since there is no healing of bone or cartilage that needs to be protected with activity restrictions.
Marrow stimulating techniques
There are several marrow stimulating techniques used when a full thickness cartilage injury is present with exposed subchondral bone. Better results are seen with lesions <2cm2. The techniques release bone marrow cells into the damaged area to form a clot of cells. Bone marrow provides stem cells with the ability to form cartilage. The cartilage produced is not identical to the articular cartilage, but it does fill the defect and can relieve symptoms. Recently published outcomes of microfracture (a marrow stimulating technique) show that at 7 years, 80% of patients rated themselves as improved.
Osteochondral grafting involves using a graft from the patient or from a donor that has both cartilage and bone. This procedure works well for full thickness cartilage defects of moderate size, 2-4cm2 with well-defined borders. The process entails an open procedure to expose the damaged area, then removing a cylinder of bone from the damaged area and replacing it with a matched cylinder of bone with articular cartilage. The graft can be harvested from either the nonweightbearing portion of the patient’s knee or from a cadaver knee. For larger lesions cadaver graft is often used due to limitations on donor site from the patient. For patients with damage on either the femur (thighbone) or tibia (shinbone) side alone, osteochondral grafting has shown to provide good relief. In patients with damage to the femur and tibia, diffuse arthritic changes, or bone necrosis the outcomes are not as good.
Autologous chondrocyte implantation
Autologous chondrocyte implantation using your own chondral tissue is an option for knee lesions in the 2-4cm2 range with intact bone surface (Fig). The procedure is performed in 2 separate surgeries. First is a knee arthroscopy for evaluation and harvesting of cartilage. Between surgeries the cartilage gathered is cultivated for 6 weeks. The second surgery involves an open procedure to expose the damaged area and implant the cartilage cells that have been cultivated.
The cells are contained within the defect by either a periosteal flap or a collagen membrane. The periosteal flap is sutured in place while the collagen membrane is held in place with fibrin glue. Outcomes with autologous chondrocyte implantation are good; however, have not been proven to be superior to other treatments. Brittberg et al presented the results of 23 patients with a mean follow-up of 39 months. Good or excellent clinical results were reported in 70% of cases.
In younger active patients with arthritis limited to a single compartment of the knee, osteotomy (cutting of bone) can provide pain relief and delay further deterioration of the joint. The surgery involves cutting either the femur or tibia and realigning the bone to unload the affected compartment. Although early results demonstrated successful outcomes in 90% of patients, this rate had declined to only 65% by 10 years.4
Some chondral or osteochondral injuries are not amenable to any nonsurgical or surgical treatment. In those patients, a partial or total knee replacement may be the best option. Knee arthroplasty is an open procedure that involves removing the bone and cartilage from a single or all compartments of the knee and replacing it with metal and plastic. A knee replacement can reliably alleviate the pain associated with chondral or osteochondral defects.
No single method
Treatment of chondral or osteochondral lesions is difficult and must be evaluated and individualized for each patient. No single method of cartilage repair has been proven superior. Each technique brings with it advantages and disadvantages and these must be considered with the characteristics of the injury, and the patient’s expectations when treating these injuries.
Author: Dan Morris, DO
Reprinted with permission from the Hughston Health Alert, Volume 29, Number 4, Fall 2017.