FormalPara Content Overview

  • Physical examination

  • Ultrasound appearance

  • Treatment

The gastrocnemius muscle is the most superficial muscle of the calf and consists of two heads, i.e., medial and lateral; the medial head is larger than the lateral one. The distal aponeurosis of the medial and lateral heads blends with the underlying aponeurosis of the soleus to create the Achilles tendon [1]. The function of the gastrocnemius is plantar flexion of the foot and flexion of the knee. The gastrocnemius muscle consists predominantly of type II muscle fibers, crosses two joints, contracts eccentrically, and is located superficially, so it is the most commonly injured muscle in the calf [2, 3]. Tears to the medial head of the gastrocnemius were first described as “tennis leg” in 1883 [4]. It is the third most commonly strained muscle in elite athletes, after the biceps femoris and rectus femoris [5]. Although especially frequent among tennis athletes, this injury also occurs in other sports such as skiing, running, and jumping [6,7,8,9].

The mechanism consists of a forceful dorsiflexion of the ankle and simultaneous extension of the knee, leading to a contraction and stretching of the medial head of the gastrocnemius (Fig. 12.1) [10]. Patients generally present with local pain in the middle third of the calf, calf swelling, and local ecchymosis. Physical examination typically reveals a painful swollen calf with tenderness along its medial side. The diagnosis is made clinically, but imaging is useful in excluding other causes of calf pain (Table 12.1) [11]. In the professional athlete, imaging is also useful in establishing the grade of the lesion; ultrasound and MRI are the imaging modalities of choice in the diagnosis of strains of the medial head of the gastrocnemius [12]. For ultrasound examination of the gastrocnemius , the patient is prone with the foot hanging over the distal edge of the examination bed and the foot perpendicular to the leg. Longitudinal planes should always be obtained over the distal aponeuroses of the medial head-soleus complex. The ultrasound appearance depends on the size and the time of examination [13, 14]. In partial tears, sonographic images (Fig. 12.2) show an ipo-anechoic area interposed between the distal aponeurosis and the distal belly of the medial head (hemorrhagic infiltration). In larger ruptures (partial tears involving more than half of the muscle or complete tears), a fluid anechoic collection is found distal to the medial head of the gastrocnemius, with the medial head torn (Fig. 12.3). The process of organization of the hematoma is stereotypical and can be followed with ultrasound (Table 12.2).

Fig. 12.1
figure 1

Tennis leg . Schematic diagram shows the location of the lesion between (red oval)

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Table 12.1 Causes of calf pain
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Fig. 12.2
figure 2

Tennis leg : small tears. Initial phase (a): hematoma with thin walls interposed between the gastrocnemius and the aponeurosis. Intermediate phase (b, longitudinal sonogram; c, axial sonogram): the walls of the lesion are thicker, and the amount of fluid is decreased

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Fig. 12.3
figure 3

Tennis leg : complete tear. Initial phase (a, longitudinal sonogram; b, axial sonogram): hematoma with thin walls interposed between the gastrocnemius and the aponeurosis, with the muscular belly retracted. Intermediate phase (c, longitudinal sonogram): the walls of the lesion are thicker and the amount of fluid is decreased. Chronic lesion (d, longitudinal sonogram; e, axial sonogram): thickened echoic fibrous band interposed between the medial head of the gastrocnemius and the soleus

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Table 12.2 Process of organization of the hematoma
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Treatment is generally conservative. Healing occurs slowly and takes at least 3 weeks, but it may take up to 16 weeks for complete healing [15,16,17,18,19]. Although the most common calf injury is a tear of the medial gastrocnemius, other structures including the lateral gastrocnemius, plantaris, and soleus may also be the cause of muscular pain. The soleus, unlike the gastrocnemius, consists predominantly of slow twitch type I muscle fibers and crosses only one joint but must be considered in the differential diagnosis of calf pain [17, 20,21,23].

FormalPara Implication for Patient Care

The soleus, unlike the gastrocnemius, consists predominantly of slow twitch type I muscle fibers and crosses only one joint, so it has very lower incidence of strains; however soleus strain can happen and must be considered in the differential diagnosis of calf pain.

FormalPara Key Points

  • The gastrocnemius muscle consists predominantly of type II muscle fibers, crosses two joints, contracts eccentrically, and is located superficially, so it is the most commonly injured muscle in the calf.