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Cartilage Injury and Repair


You’re watching your daughter play in the high school championship soccer game. She runs down the field, plants her foot, and cuts sharply to her left. Suddenly, she grabs her knee. After the game, her knee is swollen and stiff, and she tells you it’s really sore.

When these symptoms don’t go away after a few days, you set up a doctor’s appointment. After doing a physical examination and running some diagnostic tests, the orthopaedist tells you that your daughter has suffered an injury to the articular cartilage, a type of connective tissue that covers the ends of the bone in joints like your knee and elbow.

Articular cartilage injuries are a common joint injury, especially among those who are physically active. This type of injury most frequently occurs in the knee, but it may also involve the hip, elbow, shoulder, and ankle. While articular cartilage injuries can be painful and may make it difficult to go about your daily activities, there are several treatments available to both relieve bothersome symptoms and repair and restore damaged articular cartilage.

The treatment of cartilage injuries remains one of the most difficult challenges in medicine. Articular cartilage injuries are difficult to treat successfully and require technical expertise,” says Christina Allen, MD, chief of Yale Medicine Orthopaedics & Rehabilitation Sports Medicine and head team physician for Yale Athletics.  

What is articular cartilage?

To understand articular cartilage, it’s best to start with the basics. Cartilage is a tough but flexible tissue that helps keep joints in good working order.

A joint is the area where the ends of two or more bones join one another. For instance, the knee is the joint where the shinbone (tibia), thighbone (femur), and kneecap (patella) all come together.

The most common type of joint is known as a synovial joint, which allows for a lot of movement. Synovial joints include the knee, elbow, hip, ankle, and wrist. The bones that meet at synovial joints are covered with a thin layer of cartilage known as articular cartilage. (Articular simply means “having to do with joints.”)

Articular cartilage forms a smooth, durable covering (almost the consistency of linoleum) at the end of each bone in the joint. Fluid from within the synovial joints lubricates this cartilage, allowing the opposing bones to slide over one another—for instance when the knee or elbow bends—smoothly and with little friction.

Articular cartilage is one of two types of cartilage found in the joints. The other is known as meniscus cartilage, which can also be found in the knees and which acts to distribute load between the articular cartilage surfaces.

How do articular cartilage injuries occur?

While articular cartilage is strong, as well as capable of bearing heavy loads and withstanding decades of use, it can become damaged by injury or overuse.

Articular cartilage injuries can result from a number of causes, including:

  • Forceful impacts to the joint as a result of sports injuries or a fall
  • Repetitive smaller impacts to the joint
  • Twisting the joint while it bears weight, for instance twisting the knee while the foot is planted
  • Progressive wear and tear, usually over several decades of use
  • Poor alignment of joints due to a congenital (meaning “at-birth”) abnormality or previous injury

Articular cartilage injuries most frequently occur in the knee, but they may also involve the hip, ankle, shoulder, and ankle.

In many cases, the damage is limited to the thin layer of articular cartilage at the end of a bone, which is referred to as a chondral injury or chondral defect. (Chondral simply means “relating to cartilage.”) Chondral injuries typically don’t heal well on their own, in part, because articular cartilage does not have a blood supply, which promotes healing.

What are the symptoms of articular cartilage injuries?

Articular injuries can cause a number of symptoms, including:

  • Pain and/or swelling in the joint
  • A “catching” feeling when bending or moving the joint
  • A crackling, grating, or popping sound and sensation that occurs when bending or moving the joint
  • Joint locking (an inability to fully extend or bend the joint)
  • Feeling that the joint may give way or is unstable
  • Stiffness
  • Reduced range of motion

Some articular injuries do not cause any symptoms.

How are articular cartilage injuries diagnosed?

Diagnosing cartilage injuries and damage usually entails obtaining a medical history, performing a physical exam, and ordering one or more diagnostic tests.

The doctor will start by asking about pain and other symptoms in and around the affected joint. He or she may also ask about previous surgeries, whether any specific injury precipitated the symptoms, and the types of physical activities typically performed.  

During the physical exam, the doctor will observe how the joint moves. He or she may bend and rotate the joint to evaluate pain, swelling, range of motion and ligament stability. He or she may also ask the patient to move in certain ways; for instance, if the knee is injured, the patient may be asked to perform a squat, walk, or “duck walk.”

Imaging studies, including a weight-bearing X-ray and/or a magnetic resonance imaging (MRI) study, may also be needed. These tests allow a doctor to detect and determine the severity of any damage to the articular cartilage, underlying bone, and surrounding tissues and ligaments. In patients with arthritis, in which cartilage loss is extensive, weight-bearing X-rays will show the bones touching one another.

Sometimes, a procedure called arthroscopy is done to help diagnose articular cartilage injury or damage. Arthroscopy is a minimally invasive surgical procedure in which a surgeon makes a one or two small incisions on the skin around the affected joint, then inserts an arthroscope—a thin, pencil-sized tube equipped with a camera—and surgical tools into the joint. The camera transmits a video of the inside of the joint to a monitor, which allows the surgeon to see the structures and tissues of the joint. 

How are articular cartilage injuries treated?

Several treatments and therapies are available, including nonsurgical and surgical options. The choice of treatment depends on several factors, including age and overall health, physical activity level, desired post-treatment activities, and the type and severity of the articular cartilage injury.

Nonsurgical Treatment. Nonsurgical treatments (listed below) are used to relieve symptoms and to prevent or slow further degeneration of cartilage. Nonsurgical treatments can improve quality of life by reducing pain and enhancing strength and mobility, but they cannot repair damaged articular cartilage. They are often used in the initial period following an injury, or when cartilage loss is extensive, as in the case of arthritis.

  • Resting
  • Applying ice to the affected joint for 15 minutes every one or two hours to reduce swelling
  • Elevating the joint to reduce swelling
  • Taking over-the-counter anti-inflammatory medications, such as acetaminophen, to reduce pain and swelling
  • Avoiding sports and activities that cause pain or involve heavy use of the affected joint
  • Using an unloader brace to “unload” (or lessen the weight on) the cartilage injury
  • Corticosteroid injections, to reduce inflammation and pain
  • Viscosupplementation, a treatment in which a physician injects the affected joint with hyaluronic acid. This lubricates the affected joint, reducing friction between bones in the joint and decreasing pain.

Often a doctor will refer the patient to a physical therapist, who will design an exercise and stretching program. The goal is to strengthen the muscles around the affected joint, improving joint stability and increasing range of motion.

Surgical Treatment. Surgery is often the best treatment option for damaged articular cartilage since it does not heal well on its own. Some surgeries aim to relieve symptoms, while other surgical procedures are intended to repair and restore damaged articular cartilage. In most cases, surgery for articular cartilage injury is done arthroscopically. It’s worth noting that procedures to repair articular cartilage are not designed to treat the kind of extensive cartilage loss associated with osteoarthritis. But there are procedures that are highly effective in treating cartilage damage in a particular location, especially if it is the result of an acute injury.

  • Microfracture. The surgeon drills small holes in the bone and bone marrow under the damaged articular cartilage. These holes stimulate the bone to repair itself, triggering cells from the bone marrow to repair the damaged cartilage. The newly formed cartilage tissue, however, is fibrocartilage. While this fibrocartilage can keep the bones in a joint from rubbing directly against one another, it is not as effective or durable as normal, healthy articular cartilage.
  • Osteochondral Autograft/Mosaicplasty. In this procedure, the surgeon removes a small plug of healthy articular cartilage and underlying bone from a non-weight-bearing part of the joint. Then, at the site of the injury, where a small hole has been drilled, the plug (sometimes several) is installed. This procedure restores the smooth surface of the articular cartilage so that the joint can move smoothly and without pain. There are limits to the area of cartilage loss in the knee that can be treated this way, because there are only a few non-weight-bearing sites in the knee from which plugs can be taken.
  • Osteochondral Allograft. This procedure is similar to the osteochondral autograft described above but uses tissue from a cadaver (a donor). It is especially appropriate for treating large articular cartilage injuries; however, the transplanted cartilage is not as durable as the patient’s own cartilage.
  • Autologous Chondrocyte Implantation (ACI). In this procedure, a surgeon removes healthy articular cartilage from a non-weight-bearing part of the joint. This tissue is sent to a laboratory where its cells—called chondrocytes—are harvested and grown over several weeks. In a second surgical procedure, the surgeon implants chondrocytes into the site of damaged articular cartilage and covers the area with a patch or glue. The chondrocytes then form new cartilage.
  • Matrix Autologous Cartilage Implantation (MACI). This procedure is similar to ACI with one difference. MACI uses the same approach, only the chondrocytes are grown on a collagen membrane (called a matrix or scaffold) that a surgeon later inserts into the area of damaged articular cartilage.

What is the outlook for people with articular cartilage injuries?

The outlook is good for patients with these injuries, although not everyone will be able to resume all activities. Pain and discomfort can be relieved with both nonsurgical and surgical treatments. When the articular cartilage is damaged, surgical procedures can effectively repair and restore the tissue. In general, healthy individuals younger than 40 with minor articular cartilage injuries have the best outcomes and often successfully return to pre-injury activities. But not every patient is a suitable candidate for cartilage restoration or repair. These procedures are ideal for active people under age 50.

If left untreated, articular cartilage injuries can lead to the development of osteoarthritis, a condition in which the articular cartilage wears away, exposing the underlying bone. Joint replacement surgery may be required to treat osteoarthritis.

What makes Yale Medicine's approach to articular cartilage injuries unique?

“Our experienced providers will assess your condition and help you make an informed decision,” says Dr. Allen. “Our Sports Medicine surgeons are fellowship-trained and have expertise in meniscus transplant, osteochondral autograft and allograft procedures, and 2nd and 3rd generation cartilage restoration procedures.”