What is a joint?
A joint is the point of connection between two (or more) bones. There are different types of joints, which have varying degrees of mobility. The knee, shoulder, hip and fingers are very movable joints, while the vertebrae are less movable, and the joints of the skull are immovable. The tolerated movements of the skeleton are delimited by the presence of ligaments, which connect the two bones and surround the joint capsule. The various movements are produced by the action of the muscle contracting and pulling on the tendon that attaches muscle to bone. Bursae facilitate the gliding motion between the various structures. They provide lubrication and absorb shock at pressure points of the bones, tendons and muscles near a joint.
The end of each bone is covered in a thin layer of articular cartilage, a pad of well-lubricated, smooth, elastic tissue. The space between the two cartilaginous ends contains synovial fluid, a clear, viscous fluid that serves to reduce friction by lubricating the joint and to absorb shock. Since cartilage is not vascularised, the synovial fluid also supplies oxygen and nutrients to the chondrocytes (cells) in the cartilage, eliminates metabolic waste, and contains phagocytes which destroy debris and microorganisms. The cartilage also receives nutrition via the subchondral bone, a layer binding bone to cartilage. It also supplies stem cells and structural molecules to the cartilage.
What are the possible causes of joint pain?
Joint pain can be acute (lasting a few weeks), for example, after a fall, an improper movement, a poor landing or repetitive, intense exercises. This is the case of strains or sprains, where the ligament (connecting the two bones in the joint) is badly stretched (or torn in severe cases) leading to inflammation, swelling and pain. With tendonitis, the tendon (attaching muscle to bone) becomes inflamed or irritated, causing a dull pain during movement. Bursitis is an inflammation of the bursae, which causes localised pain, redness and swelling and can affect different areas of the joint. Joints can also be dislocated. This is where the bones forming the joint are no longer in the correct position to allow proper contact.
Where pain lasts several months, or even years, it is considered to be chronic. The most common is osteoarthritis, which is caused by excessive degeneration of cartilage. It is a complex disease that also affects the subchondral bones (osteophytes, sclerosis), synovial fluid, ligaments and muscles. This abnormal wear may be due to several factors, in particular, impact and injury, physical inactivity, misalignment, being overweight, repetitive movements, certain intensive sports, muscle wasting, genetic or metabolic factors (especially for joints in the hands), inflammatory factors, or a vitamin deficiency. Back pain is very common across the population. Back pain can be triggered by a muscle contraction, but it can also be caused by degeneration of the intervertebral discs, often associated with osteoarthritis or, in rare cases, with a more serious underlying illness. Rheumatoid arthritis is another common joint disorder. It is an inflammatory autoimmune disease in which the immune system attacks the joints, causing them to become swollen, painful and stiff. This inflammation damages the cartilage, joint capsule, tendons, ligaments, muscles and bones. Rheumatoid arthritis often progresses erratically and is accompanied by extreme fatigue.
Other diseases can also have osteoarticular effects, for example, lupus, infections, tumours, gout or genetic disorders affecting the bones…
What can you do about joint pain?
In the event of persistent joint pain, the first step is to see a specialist doctor, especially if the cause of pain has not been identified. The specialist will be able to determine what condition you are suffering from and how advanced it is, and will therefore be able to tell you how best to proceed.
However, it is also well known that changing certain habits can be beneficial.
- Physiotherapy and specific exercises adapted to your condition can be particularly effective in overcoming inactivity, teaching you to use the affected joint correctly without overworking it, maintaining its mobility and strengthening the muscles and tendons around it. You can find some ideas here, or here, but the best is to get advice from a specialist.
- Eating certain foods can help to support joint health. Glucosamine1, chondroitin1, type II collagen2,3 and hyaluronic acid4 are essential molecules of joints. They can help to ease joint pain, inflammation and stiffness, restore healthy hydration, properties and metabolism of joint cells, improve motor function and strengthen joint stability. The anti-inflammatory and antioxidant properties of certain substances, such as MSM5, rosehip6, gentian7,8 and edelweiss9, can also protect the joints and reduce the need for painkillers that can cause undesirable effects. However, these foods are not usually part of our diet.
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- Reducing sugar intake (or eliminating it altogether) helps to lower inflammation. Studies have shown that regular consumption (1/day) of sweetened drinks can increase the risk of rheumatoid arthritis by 63%10 and increase the risk of osteoarthritis threefold11.
- Obesity and diabetes are major risk factors for the progression of diseases and weakness in the joints. Losing weight can also help to reduce pressure on the joints, particularly the knees.
- Eating fruit and vegetables is also vital for maintaining a healthy body.
- Quitting smoking can also promote healthy cartilage, because nicotine disrupts the supply of nutrients.
- Jerosch, J. Effects of glucosamine and chondroitin sulfate on cartilage metabolism in OA: Outlook on other nutrient partners especially omega-3 fatty acids. International Journal of Rheumatology 2011, (2011).
- Bello, A. E. & Oesser, S. Collagen hydrolysate for the treatment of osteoarthritis and other joint disorders: a review of the literature. Current medical research and opinion 22, 2221–32 (2006).
- Bagchi, D. et al. Effects of orally administered undenatured type II collagen against arthritic inflammatory diseases: a mechanistic exploration. International journal of clinical pharmacology research 22, 101–10 (2002).
- Gupta, R. C., Lall, R., Srivastava, A. & Sinha, A. Hyaluronic acid: Molecular mechanisms and therapeutic trajectory. Frontiers in Veterinary Science 6, (2019).
- Butawan, M., Benjamin, R. L. & Bloomer, R. J. Methylsulfonylmethane: Applications and safety of a novel dietary supplement. Nutrients 9, (2017).
- The Royal Australian College of General Practionners. Rosehip – an evidence based herbal medicine for inflammation and arthritis.
- Chen, L. et al. Down-regulation of NR2B receptors partially contributes to analgesic effects of Gentiopicroside in persistent inflammatory pain. Neuropharmacology 54, 1175–1181 (2008).
- Kesavan, R. et al. Gentiana lutea exerts anti-atherosclerotic effects by preventing endothelial inflammation and smooth muscle cell migration. Nutrition, Metabolism and Cardiovascular Diseases 26, 293–301 (2016).
- Speroni, E. et al. In vivo efficacy of different extracts of Edelweiss (Leontopodium alpinum Cass.) in animal models. Journal of Ethnopharmacology 105, 421–426 (2006).
- Hu, Y. et al. Sugar-sweetened soda consumption and risk of developing rheumatoid arthritis in women. American Journal of Clinical Nutrition 100, 959–967 (2014).
- de Christopher, L. R., Uribarri, J. & Tucker, K. L. Intake of high-fructose corn syrup sweetened soft drinks, fruit drinks and apple juice is associated with prevalent arthritis in US adults, aged 20-30 years. Nutrition and Diabetes 6, (2016).