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Muscle Disorders

Muscle tissue has four key characteristics that result in the vital roles muscle tissue plays in the body. These four characteristics are; irritability, contractility, extensibility and elasticity. Irritability means that a muscle cell has the properties and components to recognized chemical/electrical signals that enable them to play out there specific role in the body. Contractility is the ability of muscle tissue to respond to a particular or appropriate signal, i.e. shorten or contract. In fact, muscle tissue is one of the most specialized contractile tissues found in the body.

When muscle tissue is instructed to shorten, that shortening results in; movement at joints in the body, generating heat for temperature regulation, maintaining posture and tone, closing off blood vessels or propelling food through the intestines to name a few.

Extensibility is the characteristic that allows muscle tissue to be stretched, like when you flex at the elbow, the extensors of the elbow must be able to stretch to allow flex to occur. Finally, elasticity is the ability of muscle tissue to return to its innate physiologic and functional shape (after being shorten or stretched).

Muscle Injuries

Strains/Sprains

A strain is most severe at the muscle tendon junction and result from stretching a muscle. Strains are graded from I to III depending on the severity. Grade I micro-tears are tender at the muscle tendon junction. Grade II partial tears in the muscle that can be physically felt.

A grade III strain is a complete dissociation of the muscle from its tendon. A sprain is an injury involving damage to the ligaments and are also graded I to III. Grade I is stretching of the ligament, grade II is a partially torn ligament and grade III is a completely torn ligament. The pain associated with a sprain is due to edema and bleeding.

Epicondylitis are strains of the muscles anchored to the lateral and medial epicondyles (the ridges just above the elbow) that translated into spur formation and inflammation of the bone ridges themselves. Medial epicondylitis is strain of the flexor carpi radialis tendon and is commonly know as golfer's elbow. Lateral epicondylitis is strain of the extensor carpi radialis longus and brevis and is commonly know as tennis elbow. Both are caused by too tight of a grip and repetitive motions and can become a chronic injury of not treated.

Autoimmune Myopathies

Myasthenia Gravis

The most common autoimmune neuromuscular disorder is characterized by degrees of weakness seen in eye and eyelid muscles, muscles of chewing, muscles of the limb and respiratory muscle (respiratory being the most potentially fatal form). Myasthenia is caused by an immune cell mediated attack on receptors and receptor proteins at the neuromuscular junction that is seen in both men and women, with the most common age of onset from the 20s to 30s (most common with women) and 60s to 80s (most common in men). Muscle weakness fluctuates, but appears to get worse as the day goes on or after exercise.

Eaton-Lambert Syndrome

This auto immune disease affects skeletal muscle, similar to Myasthenia, however the degree of weakness, distribution, the target receptor, and association is different. Fifty percent of Eaton Lambert syndrome is associated with small cell cancer of the lungs.

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