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Nature has “constructed” our knees in such a way that – theoretically – they should serve us for up to 120 years. However, overweight, lack of exercise and injuries mean that osteoarthritis of the knee can develop in people in their thirties.
A sedentary man performs approx. 1,5 thousand jobs every day. leg movements, active – about 10, and athletes – even more. Our knees are used and stressed very differently, which means they age at an individual pace.
Degenerative changes are a natural phenomenon resulting from the wear and tear of the body. They affect all organs and systems, but among the joints of the lower extremities, it is the knees that are primarily exposed to the too early degenerative process. This is due not only to their complex biomechanics, but also to some evolutionary error. Our ancestors adopted a vertical posture at a stage when their knee joints were not completely prepared for it. Besides, humans are the only mammals that fully straighten their knees when walking or running.
Osteoarthritis of the knee joint – gonarthrosis – is currently one of the most common degenerative diseases of the musculoskeletal system. In this infamous ranking, it ranks second – right after osteoarthritis of the spine. Until recently, gonarthrosis was the domain of people over 50, especially women (about 60% of all cases). Doctors indicate, however, that nowadays it is diagnosed in younger and younger people, even in adolescents.
Watchmaking mechanism
The knee joint, approx. 11-12 cm wide, is the largest joint in the entire human body. Its function is equally important. It is he who decides about the correct movements of the lower limbs and the entire musculoskeletal system. The knee is one of the most complex joints – both in structure and biomechanical function. Thanks to it, it is possible not only to bend and straighten the leg, but also – in flexion – rotational movements of the lower leg in relation to the thigh.
In the knee joint, the bones of the femur, tibia and patella are joined. The articular surfaces of the femur are convex and the tibia are flat. Between them there are two so-called meniscus – medial on the inside and lateral on the outside of the joint. They are made of hard, but at the same time flexible and resistant to injuries cartilage. Their task is to limit rotational movements in the knee and to transfer loads between the femur and tibia.
In front, between the articular surfaces of the femur, is the patella (flattened, triangular bone with rounded edges). Together with these surfaces, it forms the so-called patellofemoral joint. It is the kneecap that helps straighten the knee through the quadriceps. The kneecap is also the front element of the so-called capsular ligament apparatus of the knee. Each of our joints is surrounded by a special membrane, called a joint capsule, which is reinforced with several ligaments.
The part specific only to the knee joint are additional ligaments, the so-called cross – front and rear. They connect the femur with the tibia, right in the center of the joint, and are designed to limit excessive forward and backward movement of the femur relative to the tibia.
The most important anatomical element stabilizing the knee joint, however, are not the ligaments, but the muscles of the thigh and lower leg. According to specialists, even if the ligaments are already stretched, weak, good, strong muscles are enough for the knee to function sufficiently for a normal life.
The beginning of trouble
The bones that make up each joint – including the knee joints – are covered with a layer of shiny, smooth articular cartilage, the so-called glassy. It is durable, resistant to friction and elastic, thanks to which it easily and properly deforms under the influence of loads transferred during joint movements. However, with age, the cartilage changes its color to yellowish, loses valuable pliability and may become thinner and thinner.
Since cartilage is neither innervated nor has blood vessels, it is very difficult to regenerate or rebuild. It is nourished only by the so-called synovial fluid produced by the synovium that lines the joint cavity. The goo acts as a kind of lubricant to facilitate smooth and painless movements of the joint.
Osteoarthritis of the knee joint begins with the slow wear of the cartilage. The mechanism of gonarthrosis formation can be twofold. In the first case, it may begin with overload changes in the back surface of the patella, which is exposed to heavy pressure while bending and straightening the knee. The diseased surface of the patella no longer fits the placenta in which it is located and it moves incorrectly when bending the joint. This causes pain, mainly when climbing stairs, as well as when getting up (e.g. from a chair, low sofas, armchairs), as well as – although rarely – the characteristic sound of clattering, jumping. We are then talking about the so-called patellofemoral conflict.
The second case is the so-called tibial-femoral conflict, when the primary lesion is damage to one of the ligaments or one of the menisci (most often the medial one), which causes incorrect and uneven loading of the articular surfaces. With this type of damage, pain occurs when standing, descending stairs, and especially when walking for a long time. In advanced osteoarthritis of the knee joint, it is very common for both of these conflicts to exist simultaneously, and they are caused by unrecognized damage to the meniscus or ligament.
Our fault
The main cause of premature wear of articular cartilage is overload and micro-injuries caused by an inactive lifestyle as well as overweight and obesity. On the one hand, lack of exercise leads to excessive weight gain. On the other hand, it is more difficult for overweight people to motivate themselves to exercise. Our joints are prepared to carry specific loads – adequate to the average body weight. The cartilage wears down faster when heavier loads are applied.
Another important cause of early osteoarthritis is the prolonged immobilization of the joint during treatment after the injury. When a joint is not moving, it is not nourished by the synovial fluid, which loses its valuable nutritional properties during “forced downtime”.
This is one of the basic problems faced by trauma surgery. For example, to heal a broken bone, it is often necessary to immobilize the joints adjacent to the fracture site, and changes in the articular cartilage may occur after only a few weeks of such treatment. It is therefore important that we prepare the body – especially the joints and muscles – for increased effort during the holidays. Osteoarthritis can begin with, for example, a slight twist in the knee and a rupture of the meniscus during a mountain hike.
But premature osteoarthritis can also be the result of overuse of the knee joint. Gonarthrosis is an occupational disease of footballers and dancers who during each training exercise from several hundred to several thousand movements that overload the knee joints. It’s all about the turns on the bent knee. In normal operation, this movement is rare.
Gonarthrosis can also be the result – although it happens extremely rarely – of various types of congenital malformations of the knee joint and past inflammatory (bacterial) diseases that may be located in the knee.
Knee SOS
Short-term pain in the knee area, especially with heavy treads when walking down and up stairs or carrying loads, is the first sign that our muscles are too weak to stabilize the knee. The problem is that we usually ignore this signal. It is enough to sit or lie down for a while, and the pain will pass by itself. We approach an orthopedist only when the knee, despite resting, does not stop hurting, it is swollen, and the skin in this place becomes visibly warmer. And these symptoms prove that the degenerative process has already started and that it is high time for a specialist to see the knee.
What’s happening in the pond? The synovial fluid turns into a fluid that does not nourish the cartilage. Over time, it ceases to be resilient, flexible, and gradually becomes thinner. If we do not stop this process in time, after a few years the bones – tibia and femur – will start to defend themselves against instability, creating various types of bone growths. Their task will be to “hold” the joint so that it does not tilt in all directions.
Another external symptom of a progressive degenerative disease is a change in the axis of the knee. A healthy leg for a man is straight, and a woman’s leg is formed into a delicate “x”. Ladies have a wider pelvis, therefore the knee joints point inward. With osteoarthritis, both women and men, the knee joints bend outwards. This effect is called varus.
An orthopedic surgeon who suspects an osteoarthritis will undoubtedly perform a clinical examination first. It consists in visual and tactile assessment, among others the axis of the limb, the mobility of the knee joints and their stability, checking that the menisci are not damaged. The first additional test in diagnosing a degenerative disease is an X-ray. The gap between the bones visible on it is nothing more than articular cartilage, which does not give any shadow in the radiographic image. The narrower the joint space, the thinner the cartilage. If, in addition, bone spurs are visible in the photo, it is a sign that the degenerative disease has been going on for at least several years.
X-ray examination is also performed in order to exclude congenital pathologies of the joint. Unfortunately, it will not show early degenerative changes when it comes to the so-called chondromalacia, a state where the cartilage has not yet started to wear off, but has already started to lose its strength. In order to assess its condition, as well as other structures of the knee joint, which cannot be seen on the X-ray image, an ultrasound examination (USG) is performed. Magnetic resonance imaging (RMI) gives an even more accurate assessment of the joint.
Knee under the scalpel
The surest, most detailed image of the joint, however, is provided by arthroscopy. Optical instruments are inserted through small incisions in the skin, enabling the inside of the joint to be viewed. The procedure is performed using an apparatus called an arthroscope, under full anesthesia.
Arthroscopy, the so-called exploratory and diagnostic are currently performed very rarely. Thanks to special surgical micro tools attached to the arthroscope, it became a repair procedure. During arthroscopy, for example, part of the synovium can be removed, a damaged meniscus can be stitched or a so-called shaving, i.e. remove a layer of used cartilage, and even reconstruct the cruciate ligament.
Progressive gonarthrosis may lead to the need to perform the so-called arthroplasty (or arthroplasty) – replacing the natural knee joint with an artificial one. However, while hip arthroplasty is a routine procedure today, knee replacement is much more complicated. If the knee is stable, then during the operation the articular surfaces are replaced with artificial elements – metal, plastic, ceramic. But once the ligaments are damaged, a sophisticated prosthesis is used to keep the knee stable.
Many types of endoprostheses are used in orthopedics, yet it is still impossible to recover all functions of the knee.
Protective treatment
Osteoarthritis of the knee joint cannot be completely cured, but its development can only be inhibited. In overweight and obese people, the main recommendation is to relieve the affected joint by reducing body weight. Many patients are also advised to use a cane or ball (s) to support themselves while walking for a designated period of time and to avoid climbing or descending stairs.
For over 20 years, one of the most effective methods of treating degenerative disease has been the direct injection of hyaluronic acid into the joint, which – by improving the condition of the synovial fluid – also indirectly improves the condition of the cartilage.
The biggest mistake in treating osteoarthritis is immobilization of the joint. That is why patients are usually referred to kinesitherapy, i.e. treatment with movement, but in a way that does not burden the joint – e.g. exercises on special suspensions. It is also beneficial to practice recreational sports – also those that do not burden the joints, e.g. swimming (better crawl than frog), Nordic walking, cycling (hiking and sitting), and exercises that strengthen the muscles of the legs. In some cases of the early stage of osteoarthritis, cryotherapy (cold treatment) also affects the joint well, but the use of these treatments should always be consulted with a specialist.
Doctors, however, emphasize the great importance of prophylaxis. In order to prevent the knee degeneration from occurring too early, you need to be relatively thin and move a lot. One hour of walking a day is enough to keep the joints and the whole body in good condition.
A way to deal with pain
Freeze your knee!
Pain in the knee joint is best relieved with a cold compress. We lie down or sit down comfortably, put a pillow under the slightly bent knees, and apply a cold compress to the exposed skin – e.g. from a wet cloth closed for half an hour in the freezer.
Remember, however, that the compress will relieve suffering, but will not heal the joint. In order to undertake proper treatment, we should report to an orthopedic specialist at the first sign of discomfort from the knee joints.
EXERCISES FOR HEALTHY KNEES
Seated:
1. Sit on a chair (knees bent 90 °).
2. Straighten your left leg and tense your thigh.
3. Keep the leg in the air at a height of 10 cm.
4. Hold your thigh tense for 15 seconds.
5. Return to the starting position and change the leg.
6. Do 5 sets on each leg.
Lying down:
1. Lie on your back, arms along your body.
2. Raise your left leg and bend it at the knee joint.
3. Slowly straighten and bend the leg without touching the ground.
4. Return to the starting position and change the leg.
5. Do 5 series of 30 extensions and flexes for each leg.
When exercising, remember about proper breathing!
Text: Magdalena Gajda
Consultation: lek. Jerzy Małożewski, orthopedic surgeon
Source: Let’s live longer
Also read: Stand on your own feet