Joint pain: characteristics, and its 5 most common causes

A joint is an anatomical structure that allows the union between two bones or between a bone and a cartilage. When we think of joints, those of the shoulders or knees, diarthrosis, come to mind (synovials) that bring two bony structures into contact and allow a wide range of movements in all spatial axes.

However, not all joint elements fall into this category. Of the 360 ​​joints, about 86 are located in the skull, joining flat bones with practically zero mobility. In total, the body counts 76 joints in the spine and pelvis, 66 in the chest, 6 in the throat, 32 in each arm, and 31 in each leg. All of them are necessary for the maintenance of the form and posture of the human being or, failing that, for the development of movements.

Unfortunately, joints can sometimes fail for various reasons, causing a greater or lesser disability in the affected person. Without going any further, the World Health Organization estimates that 1.710 million people suffer from at least one musculoskeletal disorder across the globe, making these conditions the leading cause of universal disability (at least in countries with high entry). If you want to know everything about

joint pain and its possible causes, keep reading.

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What is joint pain?

Of the more than 150 musculoskeletal disorders that can affect humans, low back pain is the most common of all. It affects more than 568 million people worldwide, making it the leading cause of occupational disability in 160 different countries. However, there are many more disorders that can affect gait and locomotion, and many of them manifest in the form of joint pain.

For its part, joint pain or arthralgia is considered a symptom in the clinical setting, rather than a common disease. Frequently, this discomfort comes from the dysfunction of external structures, such as muscles, tendons or ligaments. In other cases, mineral stools (such as calcium pyrophosphate) can form in the joint synovium and cause damage to the joint itself.

According to the Global Year Against Musculoskeletal Pain, the pain usually occurs during the development of physical activities and decreases with rest or postural maintenance. A greater sensitivity to pain in the joint area can be explained by the following mechanisms:

• Peripheral sensitization: it is characterized by an amplified response in nociceptors, receptors that pick up and send harmful stimuli to the brain. This change is induced by inflammatory intermediates, such as cytokines and prostaglandins.
• Central sensitization: a pathological process that affects the central nervous system (CNS) and consists of a reduction in the pain threshold. It is accompanied by the exaggerated perception of annoying stimuli (hyperalgesia) and the appearance of pain in the presence of apparently innocuous stimuli (allodynia).

Also, joint pain it can be acute (transitory) or chronic (of continuous onset, for months or years). This discomfort is usually localized in the affected joint (s), but sometimes it is also possible to notice discomfort referring to the leg or arms. Pain, on the other hand, leads to motor limitation, lameness, physical impediments and loss of strength, either in the short or long term.

• You may be interested in: "Diarthrosis: what are they, types and anatomical characteristics"

Possible causes of joint pain

As we have said, joint pain is a symptom, and therefore a consequence of an underlying process, more or less serious. Here are some clinical entities that can manifest with arthralgia at different levels. Do not miss it.

1. Ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic form of arthritis. The cause of the disease is unknown, but genetics seem to play an essential role in its development: most of the sick people (90%) are positive for the leukocyte antigen HLA-B27, associated with various pathologies of nature autoimmune.

This condition affects almost 2% of the population in some high-income countries, and thought to be due to a wrong immune response by the immune system, especially CD8 T lymphocytes. In any case, it has not yet been shown that it is due to a self-antigen recognition mechanism (an event whereby lymphocytes see normal tissues of the human body as pathogens).

• You may be interested in: "Immune system: what is it, parts, functions and characteristics"

2. Osteoarthritis

Osteoarthritis (OA) is the most common joint disorder in the world. Over the years, the articular cartilage wears down, causing the bones to rub against each other and diminish their functionality. over time. It is estimated that 70 to 90% of patients older than 75 years of age have some radiological sign osteoarthritis, so it is a pathology completely related to aging and age.

Osteoarthritis is what we usually refer to when we think of rheumatism: an elderly person with swollen, hooked hands who has trouble performing daily tasks. In any case, it should be noted that the term “rheumatism” actually encompasses more than 200 clinical entities of a rheumatic nature, all with joint and / or tendon wear in common.

3. Rheumatoid arthritis

Rheumatoid arthritis can be confused with osteoarthritis, but the etiology is not the same. This time, cells of the autoimmune system seem to start attacking joint tissue without any specific biological sense, probably due to the action and primary activation of exogenous triggers (such as viruses or bacteria).

This causes chronic inflammatory responses (usually in the joints of the hands and fingers), that gradually damage ligaments, joints and tendons in the active focus of cells immune. Presents with long-lasting morning stiffness, a very important differential trait to distinguish rheumatoid arthritis from osteoarthritis.

• You may be interested in: "Rheumatism: what is it, causes, treatment and associated symptoms"

4. Fibromyalgia

A chronic condition that goes beyond the joints, because in this case too ligaments, muscles, and tendons are affected. Interestingly, this clinical picture can manifest itself in a very similar way to joint pain, but the problem focus is really in the muscles, and not in the joints.

It is a much more common condition than it seems, since it affects 2 to 6% of the world's population, especially if we talk about women. Fibromyalgia is established chronically and the symptoms are very general: fatigue (90%), sleep disorders (80%), pain in one or more muscle, joint or ligament points (100%) and even chronic depression or anxiety (25%). On this occasion, special emphasis is placed on muscle discomfort.

5. Other conditions that cause joint pain

Many conditions can cause joint pain beyond those already described. For example, sometimes bacteria from a primary focus of infection can travel to and progress into the synovial fluid of the joint, an event known as infectious arthritis. The patient shows local swelling, inability to move the affected area, and even fever and chills.

On the other hand, a cancerous tumor can also endanger the structures of the joints, as is the case with synovial sarcoma. Interestingly, this type of malignancy is more common in children and young adults, although it can also occur in the elderly population. There is also a chance that a bone tumor (osteosarcoma) will spread to a joint area, which also causes joint pain.

Resume

In summary, joint pain is multifactorial. As it is a symptom and not a disease, there can be many causes that generate it, from cancers to autoimmune pathologies, through infections, mechanical injuries, metabolic disorders and many other things more. In any case, we emphasize again that osteoarthritis is the most common type of joint pain, something relatively normal associated with the passage of time and age.

Still, just because something is normal does not mean that a patient should live with it. In the clinical field there is a maxim: living with pain and adapting to it is never a possibility. With physical therapy, occupational therapy, drugs (analgesics, anti-inflammatories, and immunosuppressants), and psychological therapy, chronic pain can be addressed.