TREATMENTS

Surgery for chondral damage

The articular cartilage covers the bony surfaces within the knee joint and its integrity is essential for optimal knee function. The articular cartilage in the knee is thicker than in most other parts of the body having to withstand significant loads during daily activities and particularly during high impact activities such as running and jumping sports. Unfortunately, like many other body tissues, the articular cartilage has very poor regenerative capacity. This means that any significant articular cartilage damage leaves the knee open to potential development of osteoarthritic change. The articular cartilage conditions range from superficial lesions to full thickness articular cartilage loss as seen in osteoarthritis. On presentation a number of symptoms that may lead one to suspect chondral injuries. There may be a history of trauma with subsequent pain injuries also but noted in association with ligamentous injuries. On occasions presentation may be with locking as a result of a loose body. At the more severe end of the spectrum full thickness osteoarthritis may present with stiffness, swelling and pain.

Assessment for chondral injuries

Assessment of articular cartilage is made with radiological studies initially. Plain X-rays will confirm the presence of a loose body or full thickness arthritic change but articular cartilage is radiolucent and further imaging in the form of MRI scan may well be indicated. MRI scan will also confirm any ligamentous damage or associated meniscal pathology. Ultimately if the condition of the knee remains unclear, arthroscopic assessment is a very accurate means of visualising the state of the articular cartilage.

knee straight knee flexed

Indications for surgery

The primary indication for surgery in articular cartilage damage is of ongoing pain. There may be other instances where surgery is considered such as locking resulting from a loose body or related to recurrent effusions (knee swelling). The other consideration regarding surgery is an attempt to prevent later osteoarthritic progression in the knee. Not all chondral lesions are appropriate for this type of surgery and extensive articular cartilage damage in the form of osteoarthritis is unlikely to be benefited by articular cartilage surgery. It may be more appropriate for either realignment procedures (osteotomy) or replacement procedures surgery. It is most likely to be beneficial on the lower end of the femur. It may also be appropriate for patellofemoral joint.

Surgical options

Arthroscopy and debridement

drilling knee

At the time of arthroscopy the articular cartilage throughout the knee is assessed as part of this assessment and treatment. Any articular cartilage lesions will be identified and some may be appropriate for treatment as part of the basic arthroscopy. These treatments include removal of loose chondral flaps which can cause catching and pain as well as on some occasions smoothing of the articular cartilage (chondroplasty). This may alleviate some symptoms of pain and catching within the knee but does not treat the underlying cartilage defect. Operative techniques aimed specifically at treatment of the defect including microfracture, ACL, chondral grafting and allograft.

Microfracture

Microfracture is an arthroscopic technique to encourage healing of the chondral defect by making multiple small holes within the bone. This acts as a stimulus to production of new cells to fill the defect. These cells although originating from bone have the capacity to resurface the area in the form of fibrocartilage. Initially this healing process provides a soft layer of healing tissue and therefore post surgery the patients are often kept from full weight bearing for a period of up to 8 weeks. This will vary depending on the part of the joint involved and extent of the defect. This technique is particularly effective for acute chondral defects such as sustained in sports injuries and they also offer help in more degenerative conditions.

Autologous chondrocyte implantation

A recently increased interest has been generated as it has become possibly to grow cartilage cells in the laboratory. This has enabled us to harvest cells from the knee to grow enough cells to re-implant into the knee to encourage healing of defects with normal chondrocytes. This does require 2 procedures, the first to harvest the cells with an arthroscopic procedure and subsequently approximately 6 – 8 weeks later the cells can be re-implanted either on a matrix which is inserted into the defect or under a periosteal cover which is sutured into place or glued. This procedure is experimental and is currently being performed as part of clinical trials but early evidence is supportive of good healing of the defect.

In situations with more advanced degenerative damage within the joint with significant areas of articular cartilage loss treatment may well require either osteotomy which is realignment of the knee as discussed elsewhere, or replacement which may be either partial or total joint.

The osteochondral grafting

Two commonly recognised techniques of osteochondral grafting – these are known as Oats (osteochondral autologous transplantation) and mosaicplasty. They involve a similar technique which involves transport of normal bone and articular cartilage from a low demand area and insertion of this into the defect and higher demand area of the knee. Unlike microfracture, this procedure realigns the damaged area with hyaline cartilage and is particularly effective in deeper articular cartilage defects. Particular conditions such as chronic osteochondral defects can be treated with this technique and this procedure can either be done arthroscopically or with a small open procedure (arthrotomy). The graft is taken either from the upper edge of the femur or from the notch of the femur and removed as bone cartilage plugs to fit into predrilled holes within the defect. The procedure can be performed as a day case but more commonly with a short in patient stay with early post operative mobilisation of the knee but with protected weight bearing. There are concerns with these techniques of taking articular cartilage from elsewhere in the joint and the possibility of long term damage, particularly in the patellofemoral joint in the case of mosaicplasty.