Chondral cartilage is the material that covers the end of the bones in the knee joint, to protect them from friction when moving. Damage to this cartilage (chondral knee defect) can cause symptoms such as knee pain and stiffness, and reduced mobility. Untreated full-thickness cartilage lesions may be associated with significant pain and, eventually, arthritis. This is a major cause of disability.
There are several approaches to managing chondral knee defects. Surgical options depend on the characteristics of the person and the defect. There are 2 main categories of procedure:
Procedures that mainly aim for symptom relief include:
debridement
osteotomy
knee replacement.
Procedures that aim for symptom relief and also to re-establish the cartilage surface include:
marrow stimulation techniques (such as Pridie drilling and microfracture)
mosaicplasty
osteochondral allograft transplantation
focal articular resurfacing implants
autologous chondrocyte implantation (in which chondrocytes harvested from the knee are cultured and implanted into the damaged cartilage).
Sometimes matrix-induced autologous chondrocyte implantation is done. This is a 2‑step procedure because cells have to be cultured outside the body. The cells are harvested for culturing in the first operation, then the cultured cells and scaffold are introduced in the second.
In this procedure, a scaffold is inserted into the area of damaged cartilage to encourage cells to grow into new cartilage. This is a single-step procedure because the cells are not cultured outside the body. A range of techniques can be used to introduce the cells that grow into new cartilage, supported by the scaffold. For example, tiny holes can be drilled into the bone (microfracture) to release the cells, or substances like bone marrow aspirate can be put into the area of damage. Whichever method is used, it is always done in the same operation as the scaffold insertion.
There are different types of scaffold and ways of doing the procedure. For example, some scaffolds are solid and some are injectable gels. Some of the solid scaffolds must be cut to size and applied over the defect. Other scaffolds are a standard size and shape, and are implanted into the subchondral bone in the damaged area.
The procedure aims to repair the damaged cartilage, reduce symptoms and keep the joint working.