What is Cartilage?
Articular cartilage. It’s the protective lining that covers the ends of bones where they come together. It’s a very strong, smooth slippery substance that helps your joints move freely; its major functions are to reduce friction, and absorb shock and disperse load as you place weight on your limb. If you’ve ever pulled a chicken drumstick apart, the articular cartilage is the smooth white lining you see at the top.
There are several ways in which you can injure the bone lining. In young, health, fit sports people, injuries usually occur as a result of a big injury, often several structures are damaged at the same time (e.g. ACL, meniscus). Usually this acute trauma results in a piece of lining being chipped, creating a little hole in what should be a smooth surface. This is called a defect. See the picture below taken by a camera inserted into the knee.
As we age, unfortunately, our tissues do to. Consider how much load has been placed through your knee over your lifetime; landing from a jump incurs loads of about 10 times body weight, going downstairs, perhaps 4 times body weight. It’s no wonder then that ‘wear and tear’ can happen in our later years! A general wearing away of cartilage here might be referred to as the early stages of osteoarthritis.
Is Repair Possible?
The articular cartilage doesn’t have a blood supply, therefore I’m afraid it doesn’t repair; usually the damage gets worse over time. Rehabilitation and conditioning exercises to build the muscles around the knee will help reduce the symptoms and improve the stability of the knee. I can’t emphasise enough how important this is! (See here 1, 2, 3, 4, 5, 6, for a few different posts on muscle conditioning).
As the cartilage doesn’t repair, surgery is usually required at some stage. Sometimes, smoothing over the edges of the defect to prevent painful catching in the joint – a bit like removing the loose bits of tarmac from a pothole in the road, can help.
If you’re lucky and your defect is the right size and shape, you might be invited on to a research trial investigating a pioneering technique called Autologous Chondrocyte Implantation (ACI). This involves taking a sample of your cartilage and growing hundreds of thousands of the same cells in the lab, which are then injected in to the hole/defect. The advantage of this technique is that you’re repairing the damage with the same strong cartilage – and it has been known to resurrect sporting careers. However, it is hugely expensive and only a few centres around the UK are permitted to perform this technique
A leading Orthopaedic Hospital in Shropshire (RJAH Orthopaedic NHS Trust) is one such centre in the UK. I’m very lucky to have completed my clinical training here (and looking forward to starting a new clinical trial into ACL rehabilitation early summer! Watch this space….).
They’re a driving force into cartilage repair and very recently published the following paper, which you may find interesting (abstract available here).
If you have any questions about cartilage injury, knees and, or rehabilitation and get in touch or register your suggestions for future news items.
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