What is cartilage?
There are many forms of cartilage in the body. The cartilage that lines the knee joint, and many other joints in the body, is called ‘Articular cartilage’. This articular cartilage provides a protective covering over the ends of the bones that make up the knee joint. It allows for a very low level of friction during normal function, and protects our joints from pain during walking.
What causes knee cartilage damage?
Articular cartilage can be damaged in several ways. A local area of cartilage damage can occur during a direct injury to the knee. This can result in a small-moderate sized area of cartilage ‘coming away’ from the end of the bone that it is protecting. Generalised ‘wear and tear’ of the articular cartilage is termed ‘Arthritis’ and is very common with increasing age. Dislocations of the knee cap (patella) can also result in damage to the cartilage, as the knee cap ‘knocks’ off a piece of articular cartilage during its displacement.
Knee cartilage damage – Symptoms
Localised cartilage loss often results in pain over the ‘lesion’, catching and clicking, stiffness, and swelling of the knee. The catching and clicking is often the result of either a loose body inside the knee joint, or an unstable ‘flap’ of articular cartilage.
Knee cartilage damage – Making the diagnosis
Local cartilage damage is best appreciated on an MRI scan or an arthroscopy. Xrays are often normal, as the adjacent cartilage is intact, the bone ends usually maintain there relationship.
An MRI scan shows excellent detail of the overall state of cartilage, in comparison to xrays and a CT scan. However, it is not 100% accurate, and arthroscopy is considered the gold standard for this assessment.
An arthroscopy gives the most detailed evaluation of the lesion. This determines the size of the lesion, the exact location in respect to weight bearing forces, and any additional damage to the meniscus or cruciate ligaments.
Why doesn’t articular cartilage heal?
Articular cartilage lacks a blood supply. Unfortunately, this means that once the articular cartilage is damaged, the body is unable to regenerate this same cartilage. It is possible for the body to form ‘scar (fibro-) cartilage’, to replace this damaged articular cartilage. Surgical techniques have been developed to improve the formation of this fibrocartilage.
What are the indications for cartilage surgery?
Cartilage lesions come in all shapes and sizes. It is important to undergo a thorough evaluation including a detailed history and examination, followed by an MRI scan.
Typically, younger patients with a single cartilage lesion are the best surgical candidates, however there are exceptions.
Knee cartilage damage – Surgical Options
The majority of the treatment options are performed arthroscopically, depending on the complexity of the case.
Arthroscopic debridement of loose/unstable cartilage flaps back to smooth surface.
After creating a stable base, small holes are created in the bone to stimulate blood flow and fibrocartilage formation.
Matrix Induced Autologous Chondrocyte Implantation (MACI)
MACI is a 2 step procedure aimed at restoring normal articular cartilage to the knee joint.
Osteochondral Autograft Transplantation (OAT)
An OATs procedure uses a less important donor site to harvest a bone/cartilage plug, and to insert it into the more important region that is affected.