Excerpt from Injuries of the Medial Calf

Synonyms, Key Words, and Related Terms: tennis leg, medial calf strain, medial gastrocnemius muscle injury, gastrocnemius strain

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Background

A medial calf injury is a musculotendinous disruption of varying degree in the medial head of the gastrocnemius muscle that results from an acute, forceful push-off with the foot. This injury occurs commonly in sports activities (eg, hill running, jumping, tennis), but it can occur in any activity. A medial calf injury is often seen in the intermittently active athlete, often referred to as the weekend warrior.

This condition has been termed "tennis leg" because of its prevalence in this particular sport, but medial calf injury can happen in a variety of sports or other activities. One mechanism that occurs is on the back leg during a lunging shot, in which the knee is extended while the foot is dorsiflexed. This action puts maximal tension on the gastrocnemius muscle as the lengthened muscle is contracted at the "push off," resulting in medial calf injury.

Frequency

International

Medial calf injuries occur more commonly in men than in women and usually afflict athletes and others in the fourth to sixth decade of life. The injury is most commonly seen acutely, but up to 20% of affected patients report a prodrome of calf tightness several days before the injury, thus suggesting a potential chronic predisposition.

Functional Anatomy

The medial head of the gastrocnemius muscle originates from the posterior aspect of the medial femoral condyle, and as it courses distally, merges with the lateral head of the gastrocnemius. Further distally, the joined heads of the gastrocnemius merge with the soleus muscle-tendon complex to form the Achilles tendon. The main function of the gastrocnemius muscle is to plantar flex the ankle, but it also provides some knee flexion, as well as contributes to the posterior stability of the knee and partially to the motion of the menisci with flexion/extension of the knee. Throughout the belly of the muscle, the medial gastrocnemius has several origins of tendinous formation. Most strains occur at this musculotendinous junction.

Sport-specific Biomechanics

The medial calf injury usually occurs when an eccentric force is applied to the gastrocnemius muscle, which usually happens when the knee is extended, the ankle is dorsiflexed, and the gastrocnemius attempts to contract in the already lengthened state. This is the common position of the back leg in a tennis stroke, and it results in the greatest force to the muscle unit; but medial calf injuries can also occur during a typical contraction of ankle plantar flexion, especially if the athlete is pushing or lifting a large weight or force.