Articular Cartilage Injury

Articular Cartilage Injury - Melbourne Knee Surgery

What is articular cartilage injury?

Cartilage lines the ends of the bones in the knee joint. It allows smooth movement within the knee joint and to absorb and distribute your body weight when walking. 

Cartilage damage can occur in younger patients and can be the result of a twisting or pivoting injury in a bent knee, a direct blow to the knee, or a dislocation of the kneecap. Small fragments of cartilage can break off and become loose. These loose fragments can intermittently jam in the knee joint and cause the knee to lock up.

Cartilage damage can vary in severity, from minor fissures and fraying of the cartilage to complete loss of cartilage with exposed bone.

What are the symptoms of articular cartilage injury?

Cartilage injury can cause the knee joint to become swollen. The knee may give way intermittently when the loose fragments of cartilage get stuck. Some people describe an intermittent inability to fully straighten the knee, which is referred to as ‘locking’. It can be associated with pain with weight bearing or when walking up and down stairs.

How do you treat articular cartilage injury?

There are many factors involved in the treatment of a cartilage injury:

  • Alignment of the lower limb

  • Stability of the knee joint

  • Treatment of any co-existing meniscal problems

  • Treatment of the cartilage problem

Sometimes, other problems that affect the knee joint need to be addressed before treating the cartilage issue. For example, a person with an ACL-deficient knee may need ACL surgery before treating the cartilage defect surgically. If the ACL is absent, ongoing episodes of instability may exacerbate the existing cartilage defect or cause the cartilage restoration procedure to fail.

Not all cartilage injuries require surgery. Some non-operative measures can be of great benefit.

Activity modification

Patients with cartilage damage should consider avoiding high-impact activities that involve prolonged running or jumping.

Bracing

If the knee alignment is such that there is more pressure going through the side with the cartilage injury, an off-loader brace may help. The brace is designed to change the alignment of the knee so that less force passes through the damaged side.

Injections into the knee joint

Loose cartilage fragments can cause the lining of the knee joint to become inflamed (synovitis), leading to swelling and pain. This can be treated with either an injection of steroids, platelet-rich plasma (PRP), or hyaluronic acid into the knee.

Physiotherapy

Swelling in the knee can inhibit the surrounding stabilising muscles and lead to muscle wasting. Over time, weakened muscles can reduce shock absorbency in the knee and overload the damaged cartilage.

Once the swelling is under control, a rehabilitation program that focuses on strengthening the quadriceps, hamstrings, and gluteal muscles is important so that they can act as effective shock absorbers and offload the cartilage in the knee joint.

Weight loss

The more force that passes through the knee joint, the more likely the cartilage damage is going to be exacerbated.  Loss of weight can slow down damage to the cartilage and may reduce the pain associated with it.

What does surgery for articular cartilage injury involve?

Numerous surgical procedures can be performed for cartilage injuries. The appropriate procedure depends on the size and location of the lesion, as well as the goals and expectations of the patient.

Debridement

Trimming any loose cartilage flaps around the area of cartilage injury so that there is a stable cartilage rim.

Microfracture

Trimming the edges of the cartilage injury so that there is a stable rim, then making multiple, evenly spaced holes in the bone beneath the cartilage. This allows the release of bone marrow and blood, which will eventually turn into cartilage. The type of cartilage produced is called fibrocartilage and differs from the type normally found within the knee joint (hyaline). This will protect the exposed bone in the area of cartilage injury.

Artificial matrix induced chondrogenesis

A microfracture procedure performed at the area of cartilage injury. A synthetic scaffold made up of collagen is cut to size and placed over the area of cartilage injury. This is held with fibrin glue. The scaffold allows the growth of a hyaline-like cartilage.

Autologous chondrocyte implantation

There are two types of ACI procedures available: AutoCart and MACI.

The AutoCart procedure is a single-stage autologous chondrocyte implantation procedure. The damaged cartilage area is assessed and cleared down to fresh bone. The cartilage is caught by a special shaver unit and minced into small but active pieces. A blood sample is taken from your arm whilst you are under the anaesthetic. Around 45mls of blood is spun down in a machine, separating the layers by cell type. The 'platelet-rich plasma' is removed. This is mixed with the minced cartilage to make a paste. This paste is re-inserted into the cartilage defect. This is done by an open or keyhole procedure. The paste will grow into the defect to create a new cartilage layer to fill the arthritic area. A gel layer made from your blood cells is then applied to the top of the paste to protect the newly added cartilage layer

Two procedures are involved with matrix-induced autologous chondrocyte implantation (MACI). In the first procedure, a sample of normal cartilage is taken from the knee and sent to a lab. The lab cultures the cartilage cells and grows them in number. Approximately 6-8 weeks later, the cartilage cells are reimplanted in the area of cartilage injury with a collagen scaffold. This results in the formation of hyaline-like cartilage. In Australia, the MACI procedure is not rebatable under Medicare.

Osteochondral autograft transfer

This involves harvesting a cylindrical block of bone with overlying cartilage from a part of the knee where there is not much weight bearing. The area of cartilage injury is then prepared to accept the harvest, which is press-fit into place. This is all performed in a single operation.

Osteochondral allograft

A cadaveric part of a knee is used as a donor. A cylindrical block of bone with accompanying cartilage is taken from the donor in accordance with the size of the cartilage injury. The cartilage injury site in the patient is then prepared to accept the cadaveric osteochondral block, which is press-fit into place. Over time, the patient’s bone will grow into the cadaveric graft and will incorporate.