Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Muscle Ruptures

Muscle fibers respond and adapt quickly to change. Damaged muscle can heal quickly with fibers regenerated in about 3 weeks. When injury occurs, however, there is almost inevitably some degree of bleeding, and this can affect the healing process mechanically by reducing contact between the ruptured ends of the muscle fibers. If bleeding can be controlled, healing is more likely to be quick and complete. Sporting activities can cause a number of different types of muscle rupture.

1. Strains. These are caused by overstretching or eccentric overload, and are located in the muscle-tendon junction. These ruptures occur as a result of the intrinsic force generated in the athlete’s muscles, often in the change between eccentric and concentric traction.
2. Contusions. These occur as a result of direct impact (trauma). The muscle is pressed against the underlying bone, e.g. when a player’s knee hits another’s thigh during a soccer game. A muscle tear and heavy bleeding deep within the muscle may result. A distinction should be made between complete ruptures, in which all the muscle fibers are torn and function is lost, and partial ruptures, which involve only some fibers, with preserved continuity and some function. A number of factors contribute towards the occurrence of muscle ruptures:
– the muscle may have been poorly prepared because of inadequate training or lack of warm-up;
– the muscle may have been weakened by previous injury followed by inadequate rehabilitation;
– the muscle may previously have been extensively injured with resultant scar tissue formation (scar tissue is less elastic than muscle and therefore more susceptible to recurrent injury);
– a muscle that is overstrained or fatigued is injured more easily;
– tense muscles that do not allow a full range of joint movement may be injured in sports demanding flexibility;
– muscles subjected to prolonged exposure to cold are less contractile than normal.

Strains

Strains frequently occur in sports that require explosive muscular effort over a short period of time, for example in baseball, sprinting, jumping, American football, and soccer. When the demand made upon a muscle exceeds its innate strength, rupture may occur; for example, in overload during eccentric muscle traction. Other examples in sport include sudden stopping, deceleration (eccentric work), rapid acceleration (concentric work) or a dangerous combination of deceleration and acceleration when turning, cutting, jumping and so on. Strains often occur in muscles that move two joints, for example, the hamstring muscles which flex the knee and extend the hip joint. These muscles cannot perform the two functions at the same time during running, so they are strictly governed by a sensitive neuromuscular system. Failure of this system will potentiate injuries. Other examples of muscles susceptible to distraction ruptures are the quadriceps muscle in the front of the thigh, the gastrocnemius muscle in the calf, and the biceps muscle in the upper arm. Strains can be classified by the degree of rupture: first- and second-degree strains are partial ruptures, and third-degree strains are complete ruptures or disruptions.
– A first-degree or mild strain describes an overstretching of the muscle with a rupture of less than 5% of the muscle fibers. There is no great loss of strength or restriction of movement. Active movement or passive stretching will, however, cause pain around the area of damage and there will be some
discomfort. It should be remembered that a small rupture or mild strain can be just as distressing to the athlete as a more serious injury.

– A second-degree or moderate strain involves a more significant but less than complete tear of the muscle. The pain will be aggravated by any attempt to contract the muscle.
– A third-degree or severe strain involves complete disruption of the muscle.

Symptoms and diagnosis
The following features suggest that a strain has occurred.
– A sharp or stabbing pain is felt at the moment of injury and reproduced by contracting the muscle concerned. Usually there is little pain if the muscle is rested.
– In a partial rupture the resulting pain can inhibit muscle contraction. In complete ruptures, the muscles are unable to contract for mechanical reasons.                                                                                                                                            – In partial ruptures it is sometimes possible to feel a defect in part of the muscle on examination. In a completely ruptured muscle the defect can be felt across the entire muscle belly. The muscle may ‘bunch up’ and form a lump resembling a tumor.
– There is often localized tenderness and swelling over the damaged area.
– After about 24 hours, bruising and discoloration may be seen, often below the site of injury; these are signs of bleeding within the damaged muscle. Muscle spasm may occur. Clinical examination by local inspection and palpation is initially carried out to analyze the degree of trauma. The most effective diagnostic test is often a test of function, with or without resistance.
Healing
When a muscle is overstretched, the muscle fibers and blood vessels will tear. The torn ends will retract from the injured area, leaving it filled with blood. Initially there will be inflammation and thereafter resorption of the bleeding. The repair of a muscle injury involves two ‘competitive’ events: formation of
new muscle fibers (regeneration) and the simultaneous production of scar tissue (granulation tissue). Skeletal muscle has a great capacity to regenerate but the new muscle fibers will be shorter and
incorporate inelastic scar tissue. If the scar covers a large area, function will be impaired because contraction is restricted. Areas of different elasticity may be formed in the muscle which increase the risk of recurrence of rupture. It is therefore important to follow a muscle injury with a long-lasting  rehabilitation program.

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