Introduction
More than 10 million sports injuries are treated each year in the United States. Common sports injuries include stress fractures of the foot, shin splints, tendinitis, runner's knee, hamstring injuries, tennis elbow, head injuries (see Section 6, Chapter 87), foot injuries (see Section 5, Chapter 72), and myriad other sprains and pulled muscles. In addition, certain sports, including weight lifting, can cause low back pain (see Section 6, Chapter 94). The techniques used to treat sports injuries can be used to treat many other types of musculoskeletal injuries, which often resemble sports injuries but have different causes. For example, tennis elbow can be caused by carrying a suitcase, turning a screw, or opening a stuck door. Runner's knee can be caused by rolling the feet onto the outside (pronation) excessively while walking.
Causes
The most common cause of sports injuries is overuse, which is generally due to faulty training methods: The exerciser does not allow for adequate recovery after a workout or does not stop exercising when pain develops. Every time muscles are stressed by an intensive workout, some muscle fibers are injured and others use up their available energy, which has been stored as the carbohydrate glycogen. More than 2 days are required for fibers to heal and glycogen to be replaced. Because only uninjured and adequately nourished fibers function properly, closely spaced, intensive workouts eventually require comparable work from fewer healthy fibers, increasing the likelihood of injury. Stopping exercise at the first sign of pain, which precedes most wear-and-tear injuries, limits the injury to these fibers, resulting in a quicker recovery. However, continuing to exercise with pain tears more fibers, extending the damage and delaying recovery.
Structural abnormalities can make a person susceptible to a sports injury by stressing parts of the body unevenly. For example, when the legs are unequal in length, unequal forces are placed on the hip and knee. Habitually running along the sides of banked roads has the same effect; repeatedly hitting the slightly higher surface increases the risk of pain or injury on that side and increases the forces acting on the other leg, exposing it to injury as well. A person who has an exaggerated curve in the lower spine (lordosis) may have back pain when swinging a baseball bat or golf club.
Excessive pronation--a rolling onto the outside of the feet after they strike the ground--is the cause of most foot, leg, and hip injuries. Some degree of pronation is normal and prevents injuries by helping distribute the foot's striking force throughout the foot. However, excessive pronation can cause foot, knee, and leg pain. In people with excessive pronation, the ankles are so flexible that the arches of the feet touch the ground during walking or running, giving the appearance of flatfeet. A runner with excessive pronation may have knee pain when running long distances.
The opposite problem--too little pronation--can occur in people who have rigid ankles. In these people, the foot appears to have a very high arch and does not absorb shock well, increasing the risk of developing small cracks in the bones (stress fractures) of the feet and legs.
The way in which the legs are aligned on the hip bone (pelvis) can produce pain in the legs, particularly in women with wide hips. Such women develop knocked knees, with a tendency for the knee caps to be pushed outward from the midline. This force on the knee caps causes pain. Wide hips also can result in increased tension on a structure called the iliotibial band, causing pain over the outer part of the pelvis and down the outer side of each thigh.
Muscles, tendons, and ligaments tear when subjected to forces greater than their inherent strength. For example, they may be injured if they are too weak or tight for the exercise being attempted. Joints are more prone to injury when the muscles and ligaments that support them are weak, as they are after a sprain. Bones weakened by osteoporosis may fracture easily.
Many injuries are caused by chronic wear and tear, which results from repetitive motion that stresses susceptible tissues. Such is particularly the case in people with structural abnormalities that stress certain parts of the body more than others. In addition, sports injuries are more likely when people do not warm up properly (exercising muscles at a relaxed pace) before an intense workout. Improper technique while exercising is a major contributor to sports injuries. Performing exercises in ways that place joints at unstable angles, increase the impact on tender structures, or overstress ligaments are common causes of sports injuries. Exercises performed too quickly or with an excessive load on the muscles can also lead to injury while the person is training.
Diagnosis
To diagnose a sports or other musculoskeletal injury, a doctor asks when and how the injury happened, what recreational and occupational activities the person has recently or routinely been engaged in, and whether there has been a change in the intensity of the activity. The doctor also examines the injured area. The person may be referred to a specialist for further testing. Diagnostic tests may include x-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, bone scanning, dual-energy x-ray absorptiometry (DEXA) (see Section 5, Chapter 59), arthroscopy (see Section 5, Chapter 59), electromyography (see Section 6, Chapter 77), and computer-aided testing of muscle and joint function.
Prevention
Allowing at least 2 days between intensive workouts or alternating workouts that stress different parts of the body can help prevent chronic injury. Some training programs alternate a hard workout one day with rest or an easy workout the next. The person can also change the type of exercise to stress different body parts. If an athlete trains twice a day, each hard workout should be followed by at least three easy ones (for instance, a hard morning workout should be followed by an easy workout in the afternoon and two easy workouts the next day). Only swimmers can perform both a hard and an easy workout every day without injury. The buoyancy of the water helps protect their muscles and joints.
Warming up before beginning strenuous exercise helps to prevent injuries. Exercising at a relaxed pace for 3 to 10 minutes warms the muscles enough to make them more pliable and resistant to injury. This active method of warming up prepares muscles for strenuous exercise more effectively than passive methods such as warm water, heating pads, ultrasound, or an infrared lamp. Passive methods do not increase blood circulation significantly.
Stretching exercises do not generally seem to prevent injuries, but they do lengthen muscles so they can contract more effectively and perform better. To avoid damaging muscles when stretching, a person should stretch after warming up or exercising, and each stretch should be comfortable enough to hold for a count of 10.
Cooling down--gradually slowing down before stopping exercise--prevents dizziness by keeping blood flowing. When strenuous exercise is stopped abruptly, blood may collect (pool) in the leg veins, temporarily reducing the flow of blood to the head. The result may be dizziness and even fainting. Cooling down also helps remove waste products, such as lactic acid, from the muscles, but it does not seem to prevent next-day muscle soreness, which is caused by damaged muscle fibers.
Strengthening exercises help prevent injuries. Regular endurance (aerobic) exercise neither enlarges nor strengthens muscles significantly. The only way to strengthen muscles is to exercise against progressively greater resistance, as in performing a sport more intensely, lifting progressively heavier weights, or using special strength training machines. Rehabilitation exercises to strengthen healed muscles and tendons are usually done by lifting or pressing against resistance, in sets of 8 to 12 repetitions, no more often than every other day.
Shoe inserts (orthotics) can often correct foot problems such as excessive pronation. The inserts, which may be flexible, semirigid, or rigid and may vary in length, should be fitted into appropriate running shoes. Orthotics are used in place of the inserts found in the shoes at the time they are purchased. Good running shoes have a rigid heel counter (the back part of the shoe that surrounds the heel) to control movement of the back of the foot, a support across the instep (saddle) to prevent excessive pronation, and a padded opening (collar) to support the ankle. The shoe must have adequate space for the insert. Orthotics usually reduce the shoe's width by one letter size; for example, a D width shoe with an orthotic becomes a C width shoe.
Treatment
Immediate treatment for almost all sports injuries consists of rest, ice, compression, and elevation (RICE). The injured part is rested immediately to minimize internal bleeding and swelling and to prevent the injury from worsening. Ice helps to limit inflammation and reduce pain. Wrapping the injured part with tape or an elastic bandage (compression) and raising the injured part above the heart (elevation) help limit swelling. A commercial ice pack or a bag of crushed or chipped ice--which conforms to body contours better than ice cubes--can be placed on a towel over the injured part for 10 minutes. An elastic bandage can be wrapped loosely around the ice bag and the injured part. The injured part is kept elevated, but the ice is removed for 10 minutes, then reapplied for 10 minutes over a period of 1 to 1½ hours. This process can be repeated several times during the first 24 hours.
Ice reduces pain and swelling in several ways. The injured part swells because fluid leaks from blood vessels. By causing the blood vessels to constrict, cold reduces their tendency to leak, thus restricting the amount of fluid and swelling in the injured part. Lowering the temperature of the skin over the injury can reduce pain and muscle spasms. It also limits tissue destruction.
Applying ice for too long, however, can damage tissue. The skin reacts reflexively when it reaches a low temperature (around 59° F [15° C]) by widening blood vessels in the cold area. The skin turns red, feels hot and itchy, and may hurt.
Injections of corticosteroids into an injured joint or the surrounding tissue are sometimes used in addition to rest to relieve pain and reduce swelling. However, corticosteroid injections can delay healing, increase the risk of tendon and cartilage damage, and enable a person to use an injured joint before it is fully healed, perhaps worsening the injury.
Dietary supplementation with glucosamine and chondroitin sulfate may be useful to help repair damage to an injured joint. However, such supplementation must be taken for 6 months or longer.
Physical therapists may incorporate heat, cold, electricity, sound waves, traction, or water exercise into a treatment plan in addition to therapeutic exercises (see Section 1, Chapter 7). How long physical therapy is needed depends on the severity and complexity of the injury.
The activity or sport that caused the injury should be avoided or modified until the injury has healed. Substituting activities that do not stress the injured part is preferable to abstaining from all physical activity because complete inactivity causes muscles to lose mass, strength, and endurance. For example, a week of rest requires at least 2 weeks of exercise to return to the level of fitness before the injury. Substitute activities include bicycling, swimming, skiing, and rowing when the lower leg or foot is injured; jogging in place or on a trampoline, swimming, and rowing when the upper leg is injured; bicycling and swimming when the lower back is injured; and jogging and skating when the shoulder or arm is injured.
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