Joints are an essential part of the musculoskeletal system
The human musculoskeletal system is an organ system that provides human beings the ability to move using their muscular and skeletal systems. Indeed, this system supports form, support, stability, and movement to the body. The primary function of this system includes supporting the body, allowing motion, and protecting vital organs.
This system involves the bones, muscles, cartilage, joints, tendons, ligaments and other connective tissue, all of which supports and binds tissues and organs together. Bones are connected to other bones and muscular fibers through connective tissues, such as tendons and ligaments. While the bones provide stability to the body, the muscles keep bones in place and play a role in bone movement. Muscles are also connected to bones via tendons, with small sacs of fluid (bursae) which lower the friction between them. Nevertheless, connecting different bones, the joints are key elements to allow motion.
What is a joint then? A joint is where two bones meet. The movement of joints is controlled by muscles that attach to the bone through tendons. Almost all the bones in our bodies form part of a joint. The bones are held together by ligaments and cushioned by smooth cartilage, which is lubricated by synovial fluid. The cartilage prevents the bone ends from rubbing directly onto each other, and the muscles contract to move the bone attached at the joint.
Types and basic structure of Joints
Joints are responsible for movement (such as limb movement) and stability (such as that found in skull bones). There are two ways to classify joints: on the basis of their structure or on the basis of their function. The structural classification divides the joints into fibrous, cartilaginous and synovial joints, depending on the material composing the joint and the presence or absence of a cavity in the joint. In turn, the functional classification divides joints into immovable joints in which two bones are connected rigidly by fibrous tissue (synarthroses), slightly movable joints with surfaces of bones connected by ligaments or cartilage (amphiarthroses) and joints that can move freely in various planes (diarthroses).
The fibrous joints contain fibrous connective tissue. There is no cavity present between the bones, so most fibrous joints do not move at all. The cartilaginous joints contain cartilage and allow little movement.
By contrast, synovial joints are the only joints that have a space or gap (a synovial cavity filled with fluid) between the adjoining bones, which is filled with synovial fluid. Synovial fluid lubricates the joint, lowering friction between the bones allowing for movement. The ends of the bones are are cushioned and protected from direct contact with each other through cartilage. Cartilage, the smooth, rubbery connective tissue on the end of bones, cushions joints and helps them move smoothly and easily. Walking, exercising, and moving puts work on our cartilage. A membrane named the synovium produces a thick fluid that helps keep the cartilage healthy and makes joints run smoothly.
The entire synovial joint is surrounded by an articular capsule composed of connective tissue. This allows movement of the joint as well as opposes to dislocation. Articular capsules may also possess ligaments that hold the bones together.
Synovial joints are capable of the greatest movement of the three structural joint types; however, the more mobile a joint, the weaker the joint. Knees, elbows, and shoulders are examples of synovial joints. The degeneration of cartilage can cause chronic inflammation in the joint, transforming a “healthy joint” in “unhealthy joint”.
In light of this background, it is easy to understand that having healthy joints allows our bodies to move freely, without discomfort. Fortunately, there are ways to improve and maintain joint health, and quality of life as a result.
Joint ages as we do
As cartilage deteriorates, adjacent bones may no longer have enough lubrication from the synovial fluid and cushioning from the cartilage. As we age, joint movement becomes stiffer and less flexible because the lubricating fluid inside the joints decreases, the cartilage becoming thinner. Ligaments also tend to shorten and lose flexibility, making joints feel stiff. Once the bone surfaces come in direct contact, this results in pain and inflammation to the surrounding tissues. As bones continually scrape one another, they can become thicker and begin growing “bone spurs” (known as osteophytes).
With aging, the more common it is to experience mild soreness or aching when we stand, climb stairs, or exercise, and recovery is much slower as compared to younger years. The age-related cartilage deterioration implies that such smooth tissue that cushions joints and helps them move is vanishing. In addition, we lose muscle tone and bone strength the older we get. All this picture explains why conduct physically demanding tasks more difficult and costing for the body.
Many of the age-related changes to joints, however, are caused by lack of exercise. Movement of the joint, and the associated ‘stress’ of movement, helps keep the fluid moving. Being inactive causes the cartilage to shrink and stiffen, reducing joint mobility, so that performing physical activity can help to reduce disability and chronic disease, including joint problems.
Younger active people can also develop OA, but it’s often the result of a trauma, which increase the chance of suffering OA.
Osteoarthritis (OA) is a joint degenerative disease associated with pain, stiffness, joint deformity, and disability, which currently affects millions of people and still remains an unsolved problem. The joints most commonly affected by OA are in the hands, feet, spine, and weight-bearing joints, such as the hips and knees
The disease starts with cartilage damage but then progressively involves the subchondral bone, causing an imbalance between bone resorption and bone formation. Currently, in contrast with previous concepts of looking OA as exclusive cartilage disease, currently OA is accepted as a progressive disease of a joint as a whole.
OA involves multiple cellular and molecular pathways that converge on the progressive destruction of cartilage and resulting joint changes. Activation of cartilage regenerative potential and specific targeting pathogenic mediators have been the major focus of research efforts aimed at slowing the progression of cartilage degeneration and preserve joint function.
OA is characterized by irreversible destruction of articular cartilage and bone erosion, induced by pro-inflammatory molecules (such as cytokines and tumor necrosis factor α, namely TNF-α). These molecular mediators increase the synthesis of certain proteins, namely collagenase or matrix metaloproteinase (MMP), and the degradation of collagen type II (the biochemical hallmark of OA), while decrease the synthesis of collagenase inhibitors, collagen and proteoglycans.
Other joint problems can include rheumatoid arthritis or joint inflammation, bursitis which is inflammation of the bursae, tendonitis or inflammation of the tendon, joint infection, and injury such as sprain, strain or bone fracture.
Statistics highlights and risk factors
OA, one of the most common musculoskeletal disorders, affect about 15% of the population. In Australia, the results of the latest Australian Bureau of Statistics (ABS) National Health Survey show that 15% or 3.5 million Australians suffer from arthritis. Of those, about 2.1 million Australians (9% of the population) have OA.
Although can appear alone, OA tends to coexist with many other diseases, mainly in the old population. The main co-morbid conditions with OA are cardiovascular disease, mental health problems, asthma, diabetes, chronic obstructive pulmonary disease (COPD) and cancer.
In addition to age, other factors may raise a person’s chances for developing OA, such as sex, overweight, increased body mass index (BMI), genetics, ethnicity, diet, trauma, and certain physical or occupational activities that imply biomechanical stress across the joints. So, genetics (family members with OA) may make you more prone to suffer OA; gender differences reveal that before age 45, men are more likely to develop OA. After 50, women are more likely to develop OA than men. This gender difference wears off around age 80. Also, certain occupations (labor, agriculture, cleaning, among others, increase the risk for developing OA since they require that bodies are used more rigorously, and their joints are worked more and age faster than people on desk job.
Other risk factors, which can be controlled, include excess of weight, since being obese or overweight puts additional stress on joints, cartilage, and bones, mainly on the knees, which limits the ability to be physically active. Also, physical inactivity predispose to OA because many joint problems can occur through disuse. The ABS Survey shows that nearly 30% of people reported being insufficiently physically active (less than 150 minutes of exercise per week), and 15% reported doing no exercise at all.
In addition, metabolism is important for cartilage and synovial joint function. Under adverse microenvironment, mammalian cells undergo a switch in cell metabolism from a resting state to a highly metabolically activate state to maintain energy homeostasis. This phenomenon leads to increase metabolic intermediates for the synthesis of inflammatory and degradation proteins, which in turn activate key molecular factors and inflammatory pathways involved in catabolic processes. In the past few years, several studies have demonstrated that metabolism has a key role in inflammatory joint diseases. In particular, metabolism is drastically altered in OA. It is interesting to note that one such metabolic risk factor could be high cholesterol levels, although this association is still on debate.
Maintaining joint health and managing problems
OA prevention and management include lifestyle changes can also help in improving and maintaining joint function.
Body weight loss can help to reduce pressure on the joints, especially in large joints, such as the hips and knees. Also, it is important to participate in exercise where possible to improve joint health. Nevertheless, be careful which exercise you choose. Low-impact exercise can improve joint mobility and can help strengthen muscles and keep bones. Don’t be involved in heavy-impact exercises, such as tennis and baseball, and practice low-impact exercises, such as playing golf, swimming, yoga, and cycling. Nevertheless, giving painful, sore joints adequate rest can relieve pain and reduce swelling.
Use of warm compresses or cold packs to joints when they are sore can help relieve pain and lower inflammation. Use of externally devices (orthosis) (braces, splints, and canes) may help to achieve control biomechanical alignment, correct or attenuate deformity, protect and support an injury, or limit the repeated movement of a damaged joint. So, using them can help your body support weak joints.
Several medications have been used at different stages to manage people with OA, such as over-the-counter (OTC) pain relievers, including acetaminophen (Panadol), aspirin, and non-steroidal anti-inflammatory drugs (NSAIDs). Complementary medicines have a role for managing OA as well. However, if symptoms worse or don’t improve, stronger pain drugs may be needed. Corticosteroid and hyaluronic acid injections can help reduce pain in affected joints, but their use remains controversial because they can cause additional joint damage over time.
Surgery is typically reserved for people who have severe and debilitating OA, while osteotomy is a bone-removal procedure can reduce the size of bone spurs if they have started to interfere with joint movement, being a less-invasive option for people who want to avoid joint replacement surgery. If osteotomy is not suitable or it does not work, doctors may recommend bone fusion (arthrodesis) to treat severely affected joints. The last resort for hip and knee joints is a total joint replacement (arthroplasty).
To avoid these extreme solutions it is better to start with the healthy life style changes indicated above as soon as we age. The combination of these measures together with first stages interventions (compresses, orthosis, use of OTC drugs and complementary medicines) may delay, reduce and alleviate the impact of OA.
Having healthy joints is important to overall health. Taking steps to maintain your joint health can help keep you moving freely, especially as you get older. Any of the measures referred above should align with your doctor’s advice.
Joint problems lead to pain, stiffness, joint deformity, and disability, and increase progressively with age. Some factors can precipitate joint problems, while other can prevent the advance of such conditions. Follow steps to help maintain joint health.
Mobasheri A, Rayman MP, Gualillo O, Sellam J, van der Kraan P, Fearon U. The role of metabolism in the pathogenesis of osteoarthritis. Nat Rev Rheumatol 2017; 13:302-311.
Farnaghi S, Crawford R, Xiao Y, Prasadam I. Cholesterol metabolism in pathogenesis of osteoarthritis disease. Int J Rheum Dis. 2017; 0:131-140.