Joints

What are synarthroses? Amphiarthroses? Diarthroses?

Synarthroses, amphiarthroses and diarthroses essentially refer to how moveable a joint is. This is a different classification to that used on my earlier post about the articular system.

Synarthroses are immovable joints. These include the suture joints referenced on that earlier post. Amphiarthroses are slightly moveable joints, and include synchondroses (cartilaginous) and syndesmoses (fibrous). Diarthroses are freely moveable joints, and include synovial joints.

Describe the components of a synovial joint.

See this post for more details.

What is the difference between a tendon and a ligament? A sprain and a strain?

Tendons are connective tissue that join muscle and bone, whereas ligaments join bone and bone. Tears in tendons are known as strains, whereas tears in ligaments are known as sprains. Both tendons and ligaments have poor blood supply, which results in poor healing if they do get damaged.

What is a subluxation? An avulsion?

A subluxation is a partial dislocation of a joint. An avulsion is a complete dislocation that may involve separation of a ligament or tendon from the bone.

What is Repetitive Strain Injury?

Repetitive strain injury occurs as a result of, well, repetitive strain (doing the same thing over and over). An example of this is carpal tunnel syndrome, enemy of typists and clarinettists worldwide. The transverse carpal ligament, which goes across the wrist, can press down on the nerves and blood vessels beneath, causing pain. If this is really severe, surgery may be required (my high school clarinet teacher can attest to that).

Describe the characteristics of the following spinal abnormalities and their possible causes: kyphosis, lordosis, scoliosis

Kyphosis and lordosis can refer to the normal curvature of the spine, but they can also refer to an exaggerated curvature. Kyphosis is when the spine is curved backwards, resulting in a "hunchback." This can result due to weakening of the bones due to osteoporosis or tuberculosis, or bones growing faster than muscles during adolescence. Lordosis is when the spine is curved forwards, resulting in a "swayback." This can occur due to obesity or pregnancy.

In scoliosis, the spine is not curved forwards or backwards, but rather to the sides. This can be due to uneven muscle weaknesses as in muscular dystrophy or cerebral palsy, some kind of trauma, a congenital problem, or maybe simply idiopathic (i.e. we simply don't know why it occurs in some cases).

What are the characteristics of Rheumatoid Arthritis?

I've already spoken about rheumatoid arthritis in one of my earlier posts on Immunology, but now we're going to learn a few more details. Rheumatoid arthritis usually affects smaller joints first, causing pain and swelling, resulting in contracture (shortening) of muscles around the joint. This contracture can result in other deformities, such as swan neck and Boutonniere deformities (deformed positions of fingers and toes). The pain and contracture can lead to disuse of the joint, which in turn can result in atrophy of the muscles.

Aside from pain and swelling, rheumatoid arthritis can also cause some more systemic symptoms, such as fatigue, malaise, anorexia (loss of appetite) and formation of nodules. These nodules, located close to joints, are granulomas (that is, tissue surrounding an area of necrosis).

Unfortunately, we're not 100% sure what causes rheumatoid arthritis, but some people may have genetic susceptibilities to this disease.

What is pannus? Ankylosis?

Since inflammation occurs within joints (synovitis) in rheumatoid arthritis, granulation tissue may also form. When granulation tissue forms inside the joint, this is called pannus. Fibrous tissue may also form, resulting in ankylosis, or joint fixation.

How does Juvenile Rheumatoid Arthritis differ from the adult form?

In contrast to adult rheumatoid arthritis, juvenile rheumatoid arthritis is acute with a remission rate of over 50% (rather than chronic, like in the adult form), and tends to affect large joints first, rather than small ones. Additionally, rheumatoid factor, which is present in 80% of adult patients, is not present in children. Instead, ANA (anti-nuclear antibodies) may be found. Systemic effects of juvenile rheumatoid arthritis include Still disease, which has symptoms such as rash, fever, enlarged spleen and uveitis (iris inflammation).

What is gout? What treatments are currently used for this disease? What are tophi?

Gout is a build-up of uric acid crystals in the synovial cavities, especially in the big toe. This results in the formation of tophi, which consist of tissue forming around a uric acid crystal. Uric acid may build up due to excess purine (adenine and guanine) breakdown or due to poor excretion of purines. Risk factors for gout include gender (males are more likely to have it), age (>40yr), obesity and alcohol use.

Treatments for gout include a low-protein diet (so as to avoid build-up of uric acid), allopurinol (to stop the breakdown of purines into uric acid), Colchicine (prevents gout attacks and relieves pain), uricosurics (drugs that increase the excretion of uric acid, such as probenecid), increasing fluid and increasing urine pH (increases the solubility of uric acid to aid in excretion).