Good day everyone, Today we are going to discuss fully on disorders of the joints ;
Learning outcomes
After studying this section, you should be able to:
- relate the features of the diseases in this section to abnormal anatomy and physiology
- compare and contrast the features of rheumatoid arthritis and osteoarthritis.
The tissues involved in diseases of the synovial joints are synovial membrane, hyaline cartilage and bone.
Disorders of the joints
Inflammatory joint disease (arthritis)
Rheumatoid arthritis (RA, rheumatoid disease)
This is a chronic progressive inflammatory autoimmune disease mainly affecting peripheral synovial joints. It is a systemic disorder in which inflammatory changes affect not only joints but also many other sites including the heart, blood vessels and skin.
It is more common in females than males and can affect all ages, including children (Still’s disease), although it usually develops between the ages of 35 and 55 years. The cause is not clearly understood but autoimmunity may be initiated by microbial infection, possibly by viruses, in genetically susceptible people. Risk factors include:
- age – risk increases with age
- gender – premenopausal women are affected three times as commonly as men
- genetic risk – there is a strong familial link in some cases, and some markers on the surface membranes of white blood cells have also been associated with higher risk of the disease.
Up to 90% of affected individuals have rheumatoid factor (RF-autoantibodies) in their body fluids. High levels of RF, especially early in the disease, are strongly associated with accelerated and more severe disease. Symptoms include joint pain and stiffness, particularly in the morning and after rest. Joints can be visibly swollen, hot and tender.
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Acute exacerbations of rheumatoid arthritis are usually accompanied by fever, and are interspersed with periods of remission. The joints most commonly affected are those of the hands and feet, but in severe cases most synovial joints may be involved. With each exacerbation there is additional and cumulative damage to the joints, leading to increasing deformity, pain and loss of function. The early changes, which may be reversible, include hypertrophy and hyperplasia of synovial cells and fibrinous inflammatory effusion into the joint. Progression of the disease usually leads to permanent tissue damage. Growth of inflammatory granulation tissue, called pannus, distorts the joint and destroys articular cartilage, expos ing the bone below and causing further damage. Fibrosis of the pannus reduces joint mobility. Pain, stiffness and deformity severely restrict the use of affected joints, and as a result the associated muscles start to waste. About a third of patients, usually those with the most aggressive form of the disease, develop nodules of connective tissue (rheumatoid nodules), usually in the forearm or elbow. Extra-articular symptoms can include anaemia, peripheral neuropathy, cardiac abnormalities, pleurisy and vasculitis.
In the later stages of the disease, the inflammation and fever are less marked. The extent of disability varies from slight to severe.
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Other types of polyarthritis
Polyarthritis means inflammation of more than one joint. This group of autoimmune inflammatory arthritic diseases has many characteristics similar to RA but the rheu- matoid factor is absent. The causes are not known but genetic features may be involved.
Ankylosing spondylitis. This tends to occur in young adults, and affects the joints of the vertebral column. Calcification of the intervertebral joints and laying down of new bone leads to reduced spinal flexibility and permanent deformity.
Psoriatic arthritis. This occurs in a proportion of people who suffer from psoriasis, especially if the nails are involved. The joints most commonly affected are those of the fingers and toes.
Reiter’s syndrome (polyarthritis with urethritis and conjunctivitis). This syndrome may be precipitated by Chlamydia trachomatis infection; the affected joints are usually those of the lower limb.
Rheumatic fever. Rheumatic fever is a diffuse inflammatory condition that affects many connective tissues. Polyarthritis is a common presenting feature, often involving the wrists, elbows, knees and ankles. Unlike cardiac effects, arthritis usually resolves spontaneously without complications.
Infective arthritis
Joint infection (septic arthritis) usually results from a blood-borne systemic infection (septicaemia, mainly staphylococcal), although it may also be caused by a penetrating joint injury. Often the joint has been damaged by pre-existing disease, making it more susceptible to infection. Normally, only one joint is involved, which becomes acutely inflamed, and the patient is likely to be ill from the associated septicaemia. Complete resolution is possible if treatment is prompt, but permanent joint damage occurs early in the disease.
Osteoarthritis (osteoarthrosis, OA)
This is a degenerative non-inflammatory disease that results in pain and restricted movement of affected joints. Osteoarthrosis is the more appropriate name but is less commonly used. In its early stages, OA is often asymptomatic. It is very common, with the majority of over-65s showing some degree of osteoarthritic changes. Articular cartilage gradually becomes thinner because its renewal does not keep pace with its breakdown. Eventually the bony articular surfaces come in contact and the bones begin to degenerate. Bone repair is abnormal and the articular surfaces become misshapen, reducing mobility of the joint. Chronic inflammation develops with effusion (collection of fluid) into the joint, possibly due to irritation caused by tissue debris not removed by phagocytes. Some- times there is abnormal outgrowth of cartilage at the edges of bones that becomes ossified, forming osteophytes.
In most cases, the cause of OA is unknown (primary OA), but risk factors include excessive repetitive use of the affected joints, female gender, increasing age, obesity and heredity. Secondary OA occurs when the joint is already affected by disease or abnormality, e.g. trauma or gout. Osteoarthritis usually develops in late middle age and affects large weight-bearing joints, i.e. the hips, knees and joints of the cervical and lower lumbar spine. In many cases only one joint is involved.
