SKELETAL MUSCLE INJURIES

Skeletal muscles have an extremely high percentage of sports injuries.

Anatomical Characteristics

Muscles are composed of contractile cells, or fibers, that produce movement.

Muscle fibers have the ability to contract, plus the properties of irritability, conductivity, and elasticity.

Three types of muscles are within the body

1. smooth
2. cardiac
3. striated

Of major concern in sports medicine are conditions that affect striated, or skeletal muscles. 

Tendons and aponeuroses are extremely resilient to injuries.

• They will pull away from a bone, a bone will break, or a muscle will tear before tendons and aponeuroses are injured. 

Skeletal muscles are generally well supplied with blood vessels that permeate throughout their structure.

Muscle Injury Classification

Acute Muscle Injuries

The two categories of acute muscle injuries are contusions and strains.

Contusions

• A bruise or contusion is received because of a sudden traumatic blow to the body. The intensity of a contusion can range from superficial to deep tissue compression and hemorrhage.
• Interrupting the continuity of the circulatory system results in a flow of blood and lymph into the surrounding tissues. A hematoma is formed by the localization of the extravasated blood into a clot, which becomes encapsulated by a connective tissue membrane.

A contusion can penetrate to the skeletal structures, causing a bone bruise. The extent to which an athlete may be hampered by this condition depends on the location of the bruise and the force of the blow. Typical in cases of severe contusion are the following:

1. The athlete reports being struck a hard blow.
2. The blow causes pain and a transitory paralysis caused by pressure on and shock to the motor and sensory nerves.
3. Palpation often reveals a hard area, indurated because of internal hemorrhage.  Ecchymosis, or tissue discoloration, may take place.

Muscle contusions are usually rated by the extent the muscle is able to produce range of motion in a part.

Strains

A strain is a stretch, tear, or rip in the muscle or adjacent tissue such as the fascia or muscle tendons.  The cause of muscle strain is often obscure. Most often a strain is produced by an abnormal muscular contraction. The cause of this abnormality has been attributed to many factors.  Among the possible explanations advanced are:

1. that it may be related to a mineral imbalance caused by profuse sweating
2. fatigue metabolites collected in the muscle itself
3. a strength imbalance between agonist and antagonist muscles.

A strain may range from a minute separation of connective tissue and muscle fibers to a complete tendinous avulsion or muscle rupture (grade 1, 2, or 3). 

Grade 1 strain

• is accompanied by local pain, which is increased by tension of the muscle, and a minor loss of strength. There is mild swelling, ecchymosis and local tenderness.

Grade 2 strain

• is similar to the mild strain but has moderate signs and symptoms and impaired muscle function.

 Grade 3 strain

• has signs and symptoms that are severe, with a loss of muscle function and commonly a palpable defect in the muscle.

Tendon Injuries

A tendon attaches a muscle to a bone and concentrates a pulling force in a limited area. 

Because a tendon is usually double the strength of the muscle it serves, tears commonly occur at the muscle belly, musculotendinous junction, or bony attachment.

Muscle Cramps and Spasms

Muscle cramps and spasms lead to muscle and tendon injuries.

• A cramp is usually a painful involuntary contraction of a skeletal muscle or muscle group.

• Cramps have been attributed to a lack of water or other electrolytes in relation to muscle fatigue.

• A reflex reaction caused by trauma of the musculoskeletal system is commonly called a spasm.

The two types of cramps or spasms are:

1. the clonic type, with alternating involuntary muscular contraction and relaxation in quick succession

2. the tonic type, with rigid muscle contraction that lasts over a period of time.

Overexertion Muscle Problems

One constant problem in physical conditioning and training is overexertion.

Acute-onset muscle soreness

• Occurs immediately after exercise
• Acute-onset muscle soreness is related to an impedance of circulation, causing muscular ischemia. Lactic acid and potassium collect in the muscle and stimulate pain receptors.
• Acute soreness is resolved when exercise has ceased.

Delayed-onset muscle soreness

• Related mainly to early-season or unaccustomed work.
• Severe muscular discomfort occurs 24 to 48 hours after exercise.
• Delayed-onset muscle soreness (DOMS) increases in intensity for 2 to 3 days and then decreases in intensity until it has completely disappeared within 7 days.
     

There are many ways to reduce the possibility of delayed-onset muscle soreness.

• One is a gradual and complete warm-up before engaging in vigorous activity, followed by a careful cool-down.
•  In the early part of training, careful attention should be paid to static stretching before and after activity.
• If there is extreme soreness, the application of ice packs or ice massage to the point of numbness (approximately 5 to 8 minutes) followed by a static stretch often provides relief.

Muscle stiffness

• Muscle stiffness does not produce pain.
• It occurs when a group of muscles have been worked hard for a long period of time.
• The fluids that collect in the muscles during and after exercise are absorbed into the bloodstream at a slow rate. As a result the muscle becomes swollen, shorter, and thicker and therefore resists stretching.
• Light exercise, massage, and passive mobilization assist in reducing stiffness.

Muscle cramps

Like muscle soreness and stiffness, muscle cramps can be a problem related to hard conditioning. The most common cramp is tonic, in which there is continuous muscle contraction. It is caused by the body's depletion of essential electrolytes or an interruption of synergism between opposing muscles. Clonic, or intermittent, contraction stemming from nerve irritation may rarely occur.

Chronic Muscle Injuries

• Chronic muscle injuries are representative of a low-grade inflammatory process.
• These injuries are often attributed to overuse microtraumas.
•  The acute injury that is improperly managed or that allows an athlete to return to activity before healing has completely occurred can cause chronic injury.

Myositis / fascitis

• In general, the term myositis means inflammation of muscle tissue. More specifically, it can be considered as a fibrositis or connective tissue inflammation.
• Fascia that supports and separates muscle can also become chronically inflamed after injury. A typical example of this condition is plantar fascitis.

Tendinitis

• Tendinitis has a gradual onset, diffuse tenderness because of repeated microtraumas, and degenerative changes.

•  Obvious signs of tendinitis are swelling and pain that move with the tendon.

Tenosynovitis

• Tenosynovitis is inflammation of the synovial sheath surrounding a tendon.

• In its acute state there is rapid onset, articular crepitus, and diffuse swelling.

• In chronic tenosynovitis the tendons become locally thickened, with pain and articular crepitus present during movement (Figure 6-8).

Bursitis

• The bursa is the fluid-filled sac found in places where friction might occur within body tissues.

• Bursae are predominantly located between bony prominences and muscles or tendons.

• Sudden irritation can cause acute bursitis, and overuse of muscles or tendons, as well as constant external compression or trauma, can result in chronic bursitis.

• The signs and symptoms of bursitis include swelling, pain, and some loss of function.

Ectopic calcification

• An ectopic calcification known as myositis ossificans can occur in a muscle that directly overlies a bone.
• Two common sites for this condition are the quadriceps region of the thigh and the brachial muscle of the arm.

•  In myositis ossificans, material that resembles bone rapidly accumulates.

Atrophy and contracture

Two complications of muscle and tendon conditions are atrophy and contracture.

Muscle atrophy is the wasting away of muscle tissue.

• Its main cause in athletes is immobilization of a body part, inactivity, or loss of nerve stimulation.

Muscle contracture  is an abnormal shortening of muscle tissue in which there is a great deal of resistance to passive stretch.

• Commonly associated with muscle injury, a contracture is associated with a joint that has developed unyielding and resisting scar tissue