Cartilage

CARTILAGE DAMAGE: ASSESSMENT AND TREATMENT

What is articular cartilage?

The articular cartilage covers those parts of the joint which are in contact with one another, and its role is to provide frictionless movement of two bones against each other. Lubrication is achieved by the synovial fluid, which is produced by the synovial membrane inside the joint. As long as there is intact cartilage and good lubrication, the movement of the joint is smooth and painless.

Above, left: intact articular cartilage of the knee joint. Above, right: under Magnetic Resonance Imaging (MRI), the articular cartilage appears light grey, just next to the bone, which is darker (arrow).

Degenerative diseases affecting articular cartilage

There are diseases, mainly osteoarthritis and post-trraumatic arthritis, which cause cartilage degeneration, a process by which the cartilage softens, then crackles, and finally disappears, leaving exposed bone. Lubrication is lost, and as the surfaces become rougher over time, smooth gliding is no longer possible. There is inflammation, stiffness and pain.

Above: under MRI, the cartilage layer on the femur is lost, and bone is directly in contact with the joint fluid (arrow).

As arthritis progresses, pain worsens and restricts every life to a point when sometimes, a joint replacement is needed.

This chapter adresses early cartilage damage and its treatment. Treating cartilage early may prevent the future developement of osteoarthritis.

Trauma: cartilage damage can also arise in younger individuals during sports. Generally, there is less or no degeneration, but a focal defect of articular cartilage.

Medical (non surgical) treatments:

Primary treatment may consist of pain killers and anti-inflammatory drugs such as acetaminophen (tylenol) or ibuprofen (advil), if pain and impairement arise irregularly.

It is advised not to discontinue physical exercise. However, choose a sport that is "smooth", without repeated impacts, such as indoor or outdoor bicycle, swimming, fitness, yoga, piltes, etc. A regular practice maintains a good muscle strength, which allievate joint pain by taking up part of the loads of everyday or sports activities.

In more severe cases, injections of "artificial" articular fluid into the joint (viscosupplementation), may diminish pain and facilitate joint motion. In acute pain and swelling, cortisone injections may be required.

Surgical treatments

Arthroscopic Lavage and microfracture

In some cases, it is advisable to arthroscopically debride (clean) the joint by removing inflammatory tissue, loose pieces of cartilage, bone spurs, and, in those spots where cartilage has disappeared, to clean, then perforate the exposed bone. This will lead stem cells et growth factors from the bone marrow to enter the joint cavity and regenerate some of the lost cartilage.

Osteochondral graft

when cartilage damage in localised and well circumscribed, the "gold standard" operation may be performed: to insert a graft of healty cartilage with the underlying bone attached. The technique resembles core drilling in rock or ice.

localized defect of the articular cartilage of the knee

with a hollow drill, the damage area is removed

a piece of healty cartilage with bone is harvested from the groove where the kneecap articulates with the rest of the joint. On its medial facet, there is practically no loading of the kneecap during knee motion. This harvest site is filled with bone from the first drilling, and fibrin cement, which will soon transform into collagen fibers, and provide a smooth, if not totally adequate layer.

Rehabilitation is quite long: during 6-8 weeks, the patient is allowed only touch-weightbearing under protection of a velcro splint, with two crutches; mobilisation without weight bearing is initiated after one week with the help of a physical therapist.

A "kinetec" splint may also be used to passively train knee motion.

Autologous Matrix-Induced Cartilage (AMIC) repair

If the cartilage defect is too large, it is impossible to treat it with the osteochondral allograft technique described above. However, it is possible to provoke cartilage regeneration using drilling of the exposed bone, and covering by a synthetic collagen membrane. After perforation into the bone marrow, instead of letting alll the stem cells and growth factors move freely inside the entire joint, why not trap then in the particular spot where we need them?

localized cartilage defect of the knee

the lesion is "cleaned" of loose tissue, as is the underlying bone, then the usual perforations are made, allowing stem cells and growth factors to enter the defect from the bone marrow.

Stem cells and growth factors are depicted leaving the bone marrow through perforations, and being "trapped" under the collagen membrane, allowing for a more localized and efficient seeding.

a collagen membrane is cut to fit the shape of the defect, and sewn in place.

Rehab is similar to that of the osteochondral graft.