Knee arthroscopy with repair of cartilage lesion or osteochondral lesion
Pre-Operation
This key-hole surgery is performed in an operating theatre with the patient under a general anaesthetic, and is usually a day surgery procedure.
Many patients will have had an MRI prior to seeing the surgeon, although not always necessary. These images combined with the clinical assessment may lead the surgeon to recommend a knee arthroscopy with repair of the lesion.
Above left shows a cartilage injury which would be appropriately treated with micro fracture. Small holes are made into the bare bone using either a pick or a fine drill, so that the holes bleed (above right) and cells from the underlying bone marrow will bleed into the knee and with time form "fibrocartilage" which fills the defect. The cartilage which forms is similar to the quality of cartilage achieved with cartilage grafting techniques.
Sometimes the cartilage injury is too large, or the surrounding cartilage in too poor condition, for micro-fracture to be appropriate. In order for micro-fracture to be successful the healing cartilage needs to be protected by firm edges (ie a punched out defect is ideal). If this the case, the next option is to move cartilage and bone from another area in the knee, where its role is less important (similar to moving carpet from a low traffic area in the house to a high traffic area). Cylinders of cartilage and bone are moved from a low demand areas to high demand (weight bearing) areas. Because the cartilage is moved with a bed of bone, the grafted bone and cartilage heal in a manner similar to that for bone injuries or fractures. This is referred to a “osteochondral autograft”. Therefore the healing process is reliable. On rare occasions the size one the defect is so large that that done cartilage-bone graft has to be used and this is referred to as “osteochondral allograft”.