The Slippery Slope - Cartilage Injuries

The slippery slope. A surface that’s never straightforward to navigate. Once you lose your bearings on such a surface, its difficult to, although not impossible to recover from. So where am I going with this? Which part of the human body could I possibly be referring to?

It’s the articular cartilage. Found in the joints of our body, they primarily act as a surface on which two articulating bones meet and form a joint. Simply put, they function to reduce friction and distribute loads in the joints. Without these slippery surfaces, we could never have joints, and humans would probably have to move around like a huge tree from a cartoon. 

Looked at under a microscope, the cartilage is made out of layers of cells called chondrocytes, stacked on top one another. They make up the one the substance found in cartilage. Others include water (up to 60-80% of the total cartilage mass) as well as collagen. When looked at from the naked eye, cartilage is a white, shiny and smooth material. When this surface is bathed in synovial fluid (gel like substance found naturally in joints), in becomes lubricated and thus slippery. This makes up an important part of a well-functioning joint.

Being the surface on which two bones literally move on each other can have its downsides. Like an old shirt, no matter how good the quality, its going to eventually have its wear and tear effects. This is usually my go to analogy when trying to explain to patients why the cartilage in their joints, the knee especially, aren’t like what they use to be. With age, the cells within the cartilage increases in size but reduces in number. Amount of water found within the cartilage also decreases, leading to it becoming more stiff and less elastic.

Although degeneration is the most common cause of cartilage defects, there are many other reasons why this can happen. Chief among them, is from an acute trauma, be it from a sporting injury or from an accident. During these events, the joints experience an abnormally high amount of pressure onto its surfaces resulting in focal damage. This is not to say that exercise is bad for the cartilage, quite the opposite in fact. Under normal loads/stress, cartilage thickness can increase, however, when there is excessive force the opposite effect may take place. A force of over 24 MPa will disrupt normal cartilage.

In the elderly, cartilage disease tend to present in the form of osteoarthritis which may be primary, after a previous trauma or even as a form of inflammatory disease. This form of articular damage is more diffuse within a joint. Treatment, as described in my previous column title “Getting stuck in, literally”, ranges from conservative to surgery. Surgery will involve either a realignment surgery or a partial or total joint replacement.

For younger patients, articular cartilage damage tend to be smaller and more focal. As mentioned above, these injuries occur in the younger age group due to a particular trauma. However, in a some younger patients, it can occur as a result of a vascular problem or maybe hereditary. This particular presentation of cartilage disease is called osteochondritis dissecans. As with everything else, in its milder forms, it can be treated conservatively with physiotherapy and bracing. Surgery is indicated in patients who have failed non operative measures.

Surgical options depend on the size and depth of the cartilage defect. Treatment may range from something less invasive like bone marrow stimulation to stimulate the growth of cartilage or arthroscopy and stabalisation of a defect. In more severe cases, something more extensive like bone grafting (taking bone and cartilage from elsewhere and pasting it at the site of defect) may become necessary. More recently, the use of biopoly implant to “patch up” these defects is gaining popularity.

So again, why the title slippery slope? Well, we now understand that the surface of the articular cartilage is a slippery one. But why a slippery slope? Well, cartilage damage never heals well, and even when it does, its never to its original self. This disease often times tend to progress. Its usually not a matter of if, but a matter of when. While we cant completely halt the progress, we can definitely try and slow down the progress. The slope maybe slippery, and you may fall, but your friendly neighbourhood doctor can help you get back up again and prevent you from tumbling down the hill.