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Cartilage Injuries

There are two basic types of cartilage in the knee:

  • Meniscal Cartilage (medial & lateral) – the ‘sports cartilages’ which act as shock absorbers
  • Articular Cartilage – the ‘surface’ cartilage which lines the bottom end of the femur, top of the tibia and back of the patella, providing smooth movement
Bucket handle tear of medial meniscus (Click to Enlarge)

Bucket handle tear of medial meniscus (Click to Enlarge)

Both types of cartilage can become torn. Knee arthroscopy is the best treatment for all cartilage injuries.

Meniscal Cartilage Injury

Tears of either meniscus can occur as a result of a sporting injury but may also occur as a result of a simple twisting injury, for example when getting out of a chair or standing from a squatting position. Our cartilages become more brittle as we age and therefore become more susceptible to tearing. Meniscal tears do not heal unless they are very small and near the capsule of the joint.

MRI scan showing medial meniscal tear (Click to Enlarge)

MRI scan showing medial meniscal tear (Click to Enlarge)

The symptoms of a torn meniscus include:

  • Pain over the torn area i.e. inner or outer side of the knee
  • Knee swelling
  • Loss of motion
  • Locking if the cartilage gets caught between the femur and the tibia
  • A subjective feeling of the knee giving way – ‘instability’
Arthroscopic view of repaired medial meniscus (Click to Enlarge)

Arthroscopic view of repaired medial meniscus (Click to Enlarge)

Treatment

The loose, ragged pieces of the torn cartilage are removed by arthroscopic surgery. Once the torn section is removed the knee should recover and become symptom free.

Under certain circumstances, repair of a torn meniscus can be performed. The usual criteria are a young patient with a relatively recent injury and with a tear that is anatomically amenable to repair.

Tears that occur in association with rupture of the anterior cruciate ligament (ACL) tend to heal well if treated early by repair; however a second operation to reconstruct the ACL is necessary (usually 6 weeks later) if the meniscus is to be protected in the longer term. The ACL reconstruction serves to restore stability to the knee.

Once the meniscus has been torn the knee is more likely to develop osteoarthritis (wear and tear) in later years. It must be emphasised that it is the damage done to the meniscus, not the surgery that predisposes to later arthritis.

Articular Cartilage Injury

Damage to the articular (‘surface’) cartilage is a significant injury as the major shock-absorbing function of the knee is compromised. Large pieces of articular cartilage can float in the knee, sometimes with bone attached.

Cartilage damage on medial femoral condyle (Click to Enlarge)

Cartilage damage on medial femoral condyle (Click to Enlarge)

As with meniscal cartilage injuries, symptoms of damaged articular cartilage include:

  • Pain
  • Locking
  • Instability
  • Swelling

Further damage to the joint can also be caused by the loose body floating around the knee. Most surface cartilage wear will ultimately lead to osteoarthritis.

Treatment

Symptoms can be helped with arthroscopic surgery – the edges of the surface cartilage are smoothed and loose bodies removed.

Larger areas of articular cartilage damage are usually treated by micro fracture, performed at the same time as arthroscopy. A small, sharp pick is used to perforate the underlying bone and encourage healing of the cartilage defect. A good outcome can result, but does not replace the damaged area with normal cartilage.

For very large areas of damage, cartilage replacement techniques may be required to delay the onset of osteoarthritis:

MICRO FRACTURE is where small cylinders of bone and cartilage are harvested from a less important area of the knee and packed into the defect, creating a cobblestone-like repair which has a true cartilage surface.

AUTOLOGOUS CHONDROCYTE GRAFTING involves harvesting cartilage cells from the affected knee, sending these cells to a laboratory where they are cultured to multiply. The large amounts of cells produced are then placed back into the damaged area of the knee. Although a fairly new technique, results are encouraging.

After most cartilage injuries have been treated the knee can return to normal function. There is however an increased risk of developing osteoarthritis in the long term and depending on the degree of injury, activity modification may be required.

Summary

  • 2 types of cartilage in the knee; meniscal and articular
  • Symptoms of damage include pain, locking, swelling and instability
  • Arthroscopy provides safe and effective means of treatment
  • Long term risk of osteoarthritis if damage is severe
  • Microfracture, mosaicplasty and autologous chondrocyte grafting may reduce risk of long term osteoarthritis