Tuesday, 07 April 2020
OF around 250 species of primate, it is only we humans that go around exclusively on two legs. Trust us to be awkward.
Unfortunately, this means that, rather than spreading the weight of the body through four limbs, we channel it through just two, meaning our knees have their work cut out.
If we delve into the world of physics for a brief moment, we know that the knee is a hinge joint primarily so it flexes (bends) and extends (straightens).
To make matters more complex, there is some rotational movement in there too, though not to the degree of, say, the shoulder, which is a different type of joint altogether.
The joint connects the femur (thigh bone) to the two bones in the lower leg, the tibia and fibula. The knee cap is the fourth bone involved and is known as the patella.
The patella (from the Latin “small plate”) is an unusual bone in that it has connections only with tendons or muscle and is embedded within these with no other connections.
It is by far the largest example of this type of bone in the body. Known as sesamoid bones, all the others are much smaller — more like sesame seeds, hence the name.
The patella’s importance lies in its interaction with the rest of the knee joint as it acts as the fulcrum, enabling the mechanical leverage of the muscles used to bend the joint.
At times, certain movements of the knee, for example if we are going upstairs, can generate forces through it that are equivalent to up to five times the body’s weight.
To keep the bones and tendons all stable within this busy area of the body, there are 14 ligaments (fibrous tissue connecting two bones together) that provide stability.
If a force becomes too great or if one of these is weakened, they can be torn and cause a lot of pain, not to mention reducing the stability of the knee.
Michael Owen suffered a nasty cruciate ligament injury at the 2006 World Cup, which demonstrated with gruesome clarity what happens to the position of the knee if the ligaments go. I like to think of them as guy ropes holding down a marquee.
The joint space between the three large bones in the knee is a self-contained system bathed in synovial fluid. This is found in most joints of the body and serves mostly to reduce friction over the cartilage which lines the connecting surfaces of the bones.
Cartilage is a smooth, connective tissue that has many applications in the body. In fact, the entire skeleton of sharks is made up of cartilage rather than bone.
In the joint, it acts rather like a cushion protecting the surface of the bone underneath. This is the stuff that gets worn away and gives rise to arthritis.
Between the two layers of cartilage is another type of connective tissue called a meniscus, one on either side of the joint.
The meniscus is named after the Greek “meniskos”, meaning crescent, because of its shape that curves around the edges of the joint in order to distribute the load so that the forces on the knee don’t all go through the centre.
These, too, can get torn and can cause pain, particularly when twisting or squatting. Sometimes, if the tear is large, the joint can start to lock in place as well.
Often, meniscal tears will settle with anti-inflammatories and physiotherapy but more severe cases can sometimes require keyhole surgery to clear the joint out.
Undoubtedly the biggest issue, however, is arthritis, particularly as we get on a bit. A recent survey by Arthritis Research UK concluded that about one in five adults in England aged over 45 has osteoarthritis in the knee.
It’s not a new thing either, with scientists having found evidence of arthritic knees in Egyptian mummies.
These days, aside from the fact that we are living longer, obesity is a big cause of knee wear and tear. I would say it is also the first thing to address if one wishes to prevent or reduce symptoms of pain related to osteoarthritis.
(Osteoarthritis is different from rheumatoid arthritis, which results from the body’s own immune system causing inflammation in the joints and tends to affect more than one joint, usually in the hands, feet and wrists).
Beyond weight loss, physiotherapy is important to strengthen the surrounding muscles and correct any misalignment that puts pressure on some parts of the joint more than others due to muscular imbalance. This is also a preventative measure so keeping active is really important.
Pain relief in the form of paracetamol and other anti-inflammatory medication has a role, as do steroid injections which can stave off pain for many months at a time. These can often be done at your GP.
Surgery in the form of a knee replacement is a last resort due to the risk of infection and of the anaesthetic involved. In the past, certain supplements have been recommended for the maintenance of the joint.
In particular chondroitin and glucosamine, either separately or in combination, have been a popular product for those suffering from knee pain and I have certainly had one or two patients tell me how taking these supplements has helped them.
However, there is actually no reliable scientific evidence that they are effective in reducing perceived joint pain or in joint space narrowing.
There was quite an extensive meta-analysis carried out in 2010 that found no evidence of their effectiveness and, although it also showed they were harmless to take, this is something to bear in mind as they can be quite expensive.
In younger people, the more common causes of knee pain are trauma and sports injury.
It is also worth mentioning some other common causes. Gout can cause red and swollen knees and can be combated with anti-inflammatories and by reducing red meats and alcohol in your diet.
Any swelling over the front of your knee just below the knee cap can represent something known as pre-patellar bursitis, otherwise known as housemaid’s knee or clergyman’s knee as it happens in those who tend to kneel a lot in their line of work.
(Student’s elbow is an equivalent condition in the elbow — from leaning on the desk, not drinking lots of beer!) This is non-infective inflammation of the soft tissue pad in the front of the knee and can be resolved, unsurprisingly, by reducing kneeling time, taking anti-inflammatory medication and applying ice.
In teenagers, there is a similar condition known as Osgood-Schlatters, which results in pain and swelling over the top of the tibia, just below the knee.
This happens in sporty individuals and the best way to sort it is either by using paracetamol and ibuprofen and putting up with it (it should eventually go) or by giving it a good period of rest.
If you are ever unsure about what might be causing pain in your knee, you must head to see your GP in case it is something more serious.
Fever, knee pain and lack of movement in the knee in particular must be seen immediately in case of infection in the joint itself.
The knee is important and the value of having healthy ones cannot be underestimated.
They allow one to get around and, although we might take that for granted when there is nothing wrong, it becomes apparent how much we rely on them when they’re not quite co-operating.
Michael Flatley allegedly insured his knees and legs for $40 million. While that sort of extravagance is not necessary for most of us, it is still worth taking good care of them.
15 October 2018
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