200 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. worsening muscle weakness and loss of muscle tissue. Depending on the specific type, the onset of MD may occur during either childhood or adulthood, and the symptoms vary. Some forms of MD affect only certain muscle groups, whereas other forms affect all of the muscles. The more severe types of MD begin in childhood symptoms may include intellectual disability, delayed development of motor skills, frequent falling, drooling, Muscle Disorders In addition to injuries, the muscular system is subject to a variety of disorders and conditions. Two of the more common disorders are discussed in this section. Muscular Dystrophy Muscular dystrophy (MD) is a group of similar, inherited disorders characterized by progressively Tennis Elbow Focus On Extensor muscles Humerus Lateral epicondyle Injured common extensor tendon Tennis elbow Right arm, lateral (outside) side Alila Medical Media/Shutterstock.com Beto Chagas/Shutterstock.com Cause Tennis elbow is the common name for lateral epicondylitis, or inflammation of the tendons on the lateral side of the elbow. A common cause of this condition is repeated twisting motions of the arm, as when hitting a backhand with poor technique in racquet sports. Other repetitive motions in activities such as painting, carpentry, plumbing, and yard work can also lead to lateral epicondylitis. A direct blow to the lateral elbow or a fall on an outstretched arm can also cause the condition. Melodia plus photos/Shutterstock.com Treatment The key to successful treatment is cessation of the activity that caused the irritation. Rest! Depending on the severity of the microtears in the tendons, weeks or months of rest may be needed. Applying ice packs for 10–15 minutes at a time several times a day can help relieve pain. Over-the-counter pain medications can also be used judiciously. Severe cases may require surgery. Elbow splints and sleeves have not been shown to help. Symptoms The onset of symptoms is usually gradual, with soreness or a dull ache around the lateral elbow that disappears within 24 hours following activity. With repeated occurrences, the pain may persist longer as the tendons are further damaged. In serious cases, any use of the arm during daily activities can cause pain. The pain may also spread to the hand, wrist, and other parts of the arm, shoulder, or neck. Sometimes the pain increases later in the day, making sleep difficult.