Muscle Injuries


Skeletal muscle injuries represent great part of all traumas in sports medicine, with an incidence from 10% to 55% of all sustained injuries. They should be treated with necessary precaution since a failed treatment can postpone an athlete’s return to the field with weeks or even months and cause recidivism.

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Databases Consulted: Pedro - Pubmed

Key Words: Muscle Injuries - Muscle Strain - Muscle Contusion - Muscle Repair

Types of Skeletal Muscle Injuries

Literature study does not reveal great consensus when it comes to classifying muscle injuries, despite their clinical importance. However, the most differentiating factor is the trauma mechanism. Muscle injuries can therefore be broadly classified as either traumatic (acute) or overuse (chronic) injuries.

Acute injuries are usually the result of a single traumatic event and cause a macro-trauma to the muscle. There is an obvious link between the cause and noticeable symptoms. They mostly occur in contact sports such as rugby, soccer and basketball because of their dynamic and high collision nature [1] [2].

Overuse, chronic or exercise-induced injuries are subtler and usually occur over a longer period of time. They result from repetitive micro-trauma to the muscle. Diagnosing is more challenging since there is a less obvious link between the cause of the injury and the symptoms [1]

Muscle Strains

See Muscle Strain

A strain to the muscle or muscle tendon is the equivalent of a sprain to ligaments. It is a contraction-induced injury in which muscle fibers tear due to extensive mechanical stress. This mostly occurs as result of a powerful eccentric contraction or overstretching of the muscle. Therefore, it is typical for non contact sports with dynamic character such as sprinting, jumping [3].

Strains are categorized into 3 grades of severity [4] [5] [6]:

Grade I (Mild)

  • Strains affect only a limited number of fibers in the muscle. There is no decrease in strength and there is full active and passive range of motion. Pain and tenderness are often delayed to the next day.

Grade II (Moderate)

  • Strains have nearly half of muscle fibers torn. Acute and significant pain is accompanied by swelling and a minor decrease in muscle strength. Pain is reproduced on muscle contraction.

Grade III (Severe)

  • Strains represent complete rupture of the muscle. This means either the tendon is separated from the muscle belly or the muscle belly is actually torn in 2 parts. Severe swelling and pain and a complete loss of function are characteristic for this type of strain. Th is is seen most frequently at the musculotendinous junction.

A number of factors predispose an athlete to muscle strains:

  • Inadequate Warm-up
  • Insufficient Joint Range of Motion
  • Excessive Muscle Tightness
  • Fatigue / Overuse / Inadequate Recovery
  • Muscle Imbalance
  • Previous Injury
  • Faulty Technique / Biomechanics
  • Spinal Dysfunction

Common Strain Injuries:

Muscle Contusion

A bruise, or contusion, is a type of hematoma of tissue in which capillaries and sometimes venules are damaged by trauma, allowing blood to seep, hemorrhage, or extravasate into the surrounding interstitial tissues. Bruises, which do not blanch under pressure, can involve capillaries at the level of skin, subcutaneous tissue, muscle, or bone. As a type of hematoma, a bruise is caused by internal bleeding into the interstitial tissues which does not break through the skin, usually initiated by blunt trauma, which causes damage through physical compression and deceleration forces. Trauma sufficient to cause bruising can occur across a wide range of sports. Bruises often induce pain, but small bruises are not normally dangerous alone. Sometimes bruises can be serious, leading to other more life-threatening forms of hematoma, such as when associated with serious injuries, including fractures and more severe internal bleeding. The likelihood and severity of bruising depends on many factors, including type and healthiness of affected tissues.

Common Injury:

Quadriceps Muscle Contusion

Muscle Cramp

Sudden, involuntary muscle contraction or over-shortening; while generally temporary and non-damaging, they can cause mild-to-excruciating pain, and a paralysis-like immobility of the affected muscle(s). Onset is usually sudden, and it resolves on its own over a period of several seconds, minutes, or hours. Cramps may occur in a skeletal muscle or smooth muscle. Skeletal muscle cramps may be caused by muscle fatigue or a lack of electrolytes (e.g., low sodium, low potassium, or low magnesium).

Muscle cramps during exercise are very common, even in elite athletes. Muscles that cramp the most often are the calves, thighs, and arches of the foot. Such cramping is associated with strenuous physical activity and can be intensely painful; however, they can even occur while inactive/relaxed. Around 40% of people who experience skeletal cramps are likely to endure extreme muscle pain, and may be unable to use the entire limb that contains the "locked-up" muscle group. It may take up to seven days for the muscle to return to a pain-free state.

According to Brukner & Kahn [7] disturbances at various levels of the central and peripheral nervous system and skeletal muscle are involved in the mechanism of cramp and may explain the diverse range of conditions in which cramp occurs. Other popular theories as to the cause of cramps include dehydration, low potassium or low sodium levels, inadequate carbohydrate intake or excessively tight muscles but these hypotheses appear to be falling out of favor as the weight of evidence supports the ‘neural excitability’ hypothesis.

Muscle Soreness

Repair Process

Regardless the underlying cause, the processes occurring in injured muscles tend to follow the same pattern. Functional recovery however varies from one type of injury to another. Two phases can be distinguished in the repair process [4] [8] [9].

Destruction Phase 

Starts with the actual trauma that causes muscle fibers to tear. Immediate necrosis of myofibers takes place due to detoriation of the sarcoplasm, a process that is halted within hours after the trauma by lysosomal vesicles forming a temporary membrane [6]. An inflammatory process takes place as a reaction on the torn blood vessels. Specialized cells start removing necrotized parts of the fibers [10].

Repair and Remodeling Phase

The actual repair of the injured muscle takes place. Myofibers start regenerating out of satellite cells (= undifferentiated reserve cells) and a connective tissue scar is being formed in the gap between the torn muscle fibers. In the first 10 days after the trauma, this scar tissue is the weakest point of the affected muscle.  After 10 days however, eventual re-rupture will rather affect adjacent muscle tissue than the scar tissue itself, although full recovery (up to the point of preinjury strength) can take a relatively long time. Vascularisation of the injured area is a prerequisite for recovering from a muscle injury. New capillaries originate from the remainings of injured blood vessels and find their way to the center of the injured area. Early mobilization plays a very important role since it stimulates the vascularisation process. Similar wise, intramuscular nerves will regenerate to re-establish the nerve-muscle contact [11] [12].

Diagnostic Procedure

Both for acute and chronic injuries, thorough anamnesis is primary in identifying muscle injuries. Particular attention for the history of occurrence of the trauma is needed. A clinical examination and testing of the muscle function together with the anamnesis are mostly sufficient for making the right diagnosis. In some cases, additional tests (MRI, X-ray, Ultrasound, CT Scan) may be required to determine the extent of the injury or to identify possible additional injuries.


Acute Skeletal Muscle Injuries

The RICE-principle (Rest, Ice, Compression and Elevation) is generally considered as being the best method to minimize swelling and relief pain within the first 24 to 48 hours. Although the different components of the RICE-principle have each shown their effectiveness in experimental studies, the use of the all-round concept is yet to be proved in randomized clinical trials [4].

After first aid, therapy must be tailor made according to the severity and extent of the injury. A short period of immobilization after the trauma prevents excessive formation of scar tissue (which will have a deleterious effect on mobility and strength of the healed muscle) and prevents rerupture by allowing the scar tissue to gain sufficient strength to bear contraction forces. Immobilization should not be continued after the acute phase (first few days) to avoid the negative effects such as muscle atrophy, retarded strength recovery and excessive formation of connective tissue within the muscle [11].

Early mobilization already starts after a few days, if the acute phase has passed without further complications and recovery seems to be progressing. In comparison to immobilization, mobilization induces significant histological changes such as increased vascularisation of the injured area, better regeneration of muscle fibers and more parallel orientation. It has the additional advantage that the muscle will sooner gain its original strength [4] [13] [5].

The active treatment needs to be built up gradually from isometric exercises to isotonic exercises. Only if those exercises can be performed without pain, isokinetic training should be started.

As muscle injuries generally recover well with conservative treating, surgical intervention is only to be considered in cases with very specific indications [4]:

  • Large intramuscular hematoma
  • Complete muscle tear (strain of third degree)
  • Partial strain (2nd degree) if more than half of the muscle belly is affected
  • Scar adhesions that cause persistent pain and limited extension (>4-6 months)

Chronic Skeletal Muscle Injuries

Clinical Bottom Line

Treatment of muscle injuries usually has good outcome. However, the importance of a well-balanced therapy is not to be underestimated. Therefore, physiotherapists should have an elaborate knowledge of muscle function, healing processes in a muscle and training principles.

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