Knee Cartilage Injury

The knee is the most complex joint in your body and uses a delicately balanced system of bones, ligaments, and other structures to allow you to run, jump, perform cutting movements, and other advanced activities. The knee is made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). The two joints of the knee are the tibiofemoral joint (between the femur and tibia bones, this is the main knee joint) and the patellofemoral joint (between the kneecap and the trochlea, a groove on the front of the femur). The fibula bone is a thin bone on the outside of your lower leg that does not contribute to the knee joint, but is important to ankle stability.  

Cartilage is present in all joints, where it’s called articular cartilage, and covers both ends of the bones in the joint. Cartilage allows the bones to glide easily as the joint is moved. Injury to cartilage can be due to an acute process or a chronic, long-standing process. Acute cartilage injury is associated with other injuries to the knee (meniscus, ACL, etc.), while chronic injury is due to arthritis, wear and tear of the knee, or history of infection of the knee. The extent of the cartilage injury is the main factor in determining treatment options.

Symptoms & Diagnosis

Patients with cartilage damage in the knee will often have pain in the knee with high-impact activities (running or other sports) or even with walking or using the stairs. Knee swelling is a common symptom and occurs due to the irritation and inflammation of the knee leading to an increase in joint fluid. Patients may also feel popping of the knee and may feel a catching feeling or hear a crunching sound when they move the knee.

Knee cartilage injuries are diagnosed using physical examination and imaging studies to confirm the diagnosis. The physical examination is used to identify areas of pain, swelling, and change in range of motion. X-rays are used to look at the bones of the knee and evaluate for arthritic changes. MRI (magnetic resonance imaging) is an important part of the diagnosis and will allow evaluation of all the knee ligaments, meniscus, cartilage, and any other structures that may have been injured.

Treatment

Cartilage injuries are treated based on the size and type of injury. Cartilage injuries can vary from injury to the superficial layers of cartilage to injuries extending down to the bone. Acute injuries are also treated differently than chronic injuries. Treatment of a cartilage injury requires a discussion with the patient about their symptoms and activity goals to arrive at an individualized plan.

Patients with long-standing knee pain and cartilage injury can benefit from non-surgical treatment to reduce knee inflammation and strengthen the muscles around the knee and core. Some non-surgical treatment measures are:

• Rest: Modifying your activities, particularly sports, is an important part of the treatment of knee pain.

• Non-steroidal anti-inflammatory medications (NSAIDs) can help decrease inflammation

• Brace: Some patients have cartilage injury due to the alignment of their knees (bowlegged vs knock-kneed) and may benefit from a brace that offloads the affected side of the knee.

• Injections: Steroid injections can help decrease inflammation in the knee and can be given every 3-4 months if patients have chronic knee pain. Viscosupplementation, or gel, injections can also provide relief by increasing the lubrication and glide of the knee. Recent data also shows good results from the use of PRP injections for patients with knee arthritis, or chronic knee cartilage injury.

• Physical therapy: This is an important tool to help you strengthen and retrain the muscles of the knee to work better together

Surgical treatment of cartilage lesions may be required for specific patients based on age, desired level of activity, and features of the cartilage injury. Surgery can be performed arthroscopically in some cases, but some procedures require an open approach. Many procedures exist to treat cartilage injury and include:

• Chondroplasty: This procedure is performed arthroscopically and is used to clean up loose cartilage fragments and smooth the cartilage surface.

• Microfracture: This procedure is performed arthroscopically and is used in cartilage lesions that reach the bone. A specialized instrument is used to perforate the bony surface with a series of small holes to encourage the area to heal with fibrocartilage. This type of cartilage is similar to articular cartilage and functions similarly, but does not exactly reproduce articular cartilage. Cartilage repair research continues to search for ways to heal cartilage, there is no treatment available that makes your body heal articular (joint) cartilage

• Cell-based therapies (MACI): This procedure is performed in two steps. The first step is performed arthroscopically and takes a sample of your cartilage. Your cartilage cells are then taken to a laboratory and grown over a period of several weeks to create a patch. The second surgery is performed with an open incision and implants the cartilage patch over your cartilage defect.

• Osteochondral graft transfer (autograft or allograft): This procedure is performed through an open incision. It can be performed with a graft taken from the patient’s own knee or from a graft taken from a deceased donor. The procedures are used based on the size of the cartilage defect and other factors that are discussed before the surgery. The cartilage defect is sized and a cylinder of cartilage and bone is taken from the donor area and implanted into the cartilage defect.