Trauma to the knee can tear the menisci (pads of connective tissue that act as shock absorbers and also enhance stability). Cartilage injuries and tears can often occur with sprains. Treatment may involve wearing a brace during an activity to protect the knee from further injury. Surgery may be needed to eliminate the tear.
Injury to the knee can cause damage to the articular lining cartilage in the knee joint, or sometimes to both the cartilage and the bone.
If the injury is restricted to the cartilage, it will not show up in a plain X-ray; it may be noted on an MRI. An arthroscopy (using a special instrument to look inside the joint) can thoroughly identify it.
Detached Cartilage of Bone in the Knee Joint
If a piece of cartilage or bone has become detached in the knee and the injury is not treated immediately, the loose part can ‘swim around’ in the joint. This means that it may occasionally get stuck, causing pain and a feeling that the knee is locked. The knee may also click and swell up. Such a condition is called a loose body in the knee.
As cartilage does not show up on an X-ray, the loose body will only be visible if it consists of some bone.
Cartilage damage is a relatively common type of injury. The majority of cases involve the knee joint.
Symptoms of cartilage damage include:
- Joint pain
- Decreased range of movement in the affected joint
- Instability or giving way
Cartilage is a tough, flexible tissue found throughout the body.
Cartilage serves two main functions:
Cartilage covers the surface of joints, enabling bones to slide over one another while reducing friction and preventing damage. It helps to support your weight when you move, bend, stretch and run.
The tough, flexible cartilage tissue is ideal for creating specially shaped and curved body parts that would otherwise have no support from the bones. For example, most of the nose and the outside of the ears are made up of cartilage tissue.
Unlike other types of tissue, cartilage does not have its own blood supply. Blood cells help repair damaged tissue, so damaged cartilage does not heal as quickly as damaged skin or muscles.
Types of Cartilage
There are several types of cartilage. These include:
Elastic Cartilage – this makes up the outside of the ears, some of the nose and the trachea (windpipe).
Fibro Cartilage – found between the discs (vertebrae) of the spine and between the bones of the hips and pelvis
Articular (hyaline) Cartilage – the smooth tissue covering the ends of bones
All types of cartilage can be damaged. For example, a blow to your ear can damage the elastic cartilage, making your ear look deformed. This condition is often seen in rugby players and wrestlers and is known as “cauliflower ear”.
The fibrocartilage between the discs in your back can also become damaged, resulting in a slipped disc.
Articular cartilage damage is one of the most common and potentially serious types of cartilage damage, and most commonly affects the knee joint. The damage can result in pain, swelling and some loss of mobility.
The main ways the articular cartilage can be damaged:
- a sudden accidental injury – for example, a fall or a sports injury
- osteoarthritis – this type of long-term cartilage damage to the joints is more likely if you’ve had your meniscus removed, are overweight, or have a problem with your joint structure
- osteochondritis dissecans – where a small section of cartilage and a piece of bone attached to it comes away from a joint
Conservative treatment (non-surgical) – some patients respond well to conservative treatment, which can include special exercises, NSAIDs (non-steroidal anti-inflammatory drugs), and sometimes steroid injections.
Exercises may include physical therapy and/or a program the patient can do at home. If the damage is not extensive, this may be all the patient needs.
Surgery – patients who do not respond to conservative treatment will need surgery. There are several surgical options, depending on a number of factors, which include the age and activity level of the patient, how big the lesion is, and how long ago the injury happened.
Surgical options include:
- Debridement – smoothing the damaged cartilage and removing loose edges to prevent it from rubbing and irritating other parts of the body. The procedure is done using small arthroscopic instruments, such as a mechanical shaver.
- Marrow stimulation – under the damaged cartilage, the surgeon drills tiny holes (micro-fractures), exposing the blood vessels that lie inside the bone. This causes a blood clot to form inside the cartilage that triggers the production of new cartilage. Unfortunately, the new cartilage that grows is less supple than the original cartilage type. This means it wears away more quickly, and the patient may need further surgery later on.
- Mosaicplasty – healthy, undamaged cartilage is taken from one area and moved to the damaged site. This procedure is not suitable when there is widespread damage, as in osteoarthritis. Mosaicplasty is only used for isolated areas of cartilage damage, generally limited to 10-20 millimeters in size; this technique is most commonly used in patients under the age of 50 who picked up damage from an accident.
- Autologous chondrocyte implantation – a small piece of cartilage is removed and taken to a laboratory. Here it is grown to produce more cartilage cells. About 1 to 3 months later, the new cartilage cells are implanted into the knee where they grow into healthy tissue.