Myofascial Continuum

When talking about a skeletal muscle, one should think not of a single district, but of a myofascial continuum. The gastrocnemius muscle tension is transmitted not only to the foot but to the knee, hip, and lumbar area, thanks to its fascial connections: the latter is the anatomical links with other tendons (insertion and origin) and the fascia covering muscles. A shortened gastrocnemius muscle could cause dysfunctions to the physiological movements of the hip, decreasing its anteversion.[10] The fascial system plays a fundamental role in the transmission of the force produced by the contraction of the contractile component of the muscle.[11]

When the muscle contracts, the first tissue that receives the tension produced is the connective tissue of the muscle stroma. The tension travels along the axis of the fibers through the epimysium, up to the tendon (if the muscle has a fusiform morphology), with a longitudinal pattern. If the muscle is pennate, like the gastrocnemius, the force produced follows the interfilament inside the Z line of the sarcomeres, up to the sarcolemma, the extracellular matrix and the epimysium (and hence the tendon); the vector has a transverse trajectory, and only later, follows the longitudinal structures of the epimysium.[12]

In the first case, with the fusiform muscles, the speed of arrival of the expressed force is rapid, but less effective, while in the second case, with the pennate muscles, the arrival of force to the tendons is slower but with values of tension expressed more wide. For example, the biceps brachii is faster but weaker than the deltoid muscle, just as the gastrocnemius muscle is stronger than the soleus muscle, which is faster but less powerful.

The calcaneal tendon is the widest and longest tendon of the human body.[1] The tendon connects with the plantar fascia of the foot (from the calcaneus to the metatarsal heads), which is considered fundamental for the stability of the different tarsal joints. Dysfunction of the gastrocnemius muscle negatively affects the tension of the plantar fascia, altering the physiological support of the foot.[13]

Muscular Phenotypes

Another important difference between the gastrocnemius muscle and the soleus muscle is that the first muscle has a majority of anaerobic or white fibers, while the latter is rich in aerobic or red fibers.[14] In a movement that requires the expression of great power quickly, it is the gastrocnemius that will be called to intervene. If walking is the main component of physical effort, it will be the soleus muscle that plays the main role.

Nature and anatomy always reserve extraordinary adaptations and differences. The gastrocnemius does not escape the rule. One can find the gastrocnemius tertius, an accessory muscle district that is an integral part of the muscle, as well as an extra soleus muscle. Rarely, these accessory muscles can be found simultaneously and bilaterally, without effects on joint function and innervation by the tibial nerve. The gastrocnemius tertius could cause problems in the popliteal fossa if it should come into contact with the popliteal artery and create an arterial entrapment.[15]

There are anatomical variants in literature. Specifically, it is possible to find a quadriceps gastrocnemius muscle. Practitioners do not know if this variant causes dysfunctions and pathologies; the tibial nerve innervated this variant.[16]

The gastrocnemius may present the absence of a head (in particular the lateral one), or be absent or present anomalies not in the number of heads but with respect to the area of origin.[16] A case of compression of the popliteal artery and popliteal vein is reported in the literature due to an anomaly of the origin of the lateral head of the gastrocnemius. This alteration led to the formation of a venous and arterial thrombus, resulting in secondary pulmonary hypertension.[17]

One of the dangers during gastrocnemius muscle surgery is the accidental injury of the sural nerve. Furthermore, the patient may be unsatisfied by a poor cosmetic result. It is possible to divide the anatomical area for a surgical procedure into 5 levels, with the fifth level starting proximally and the last level ending distally.[1] The fifth level includes the origin of the 2 muscle heads of the popliteal area; the fourth level involves the muscular portion of the 2 heads (before arriving at the aponeurosis); the third level begins where the contractile fibers of the muscle merge with the aponeurosis, until the fusion of the fascial area of the gastrocnemius and the soleus. The second level includes the aponeurosis of the gastrocnemius and the soleus, up to the distal part of the calcaneal tendon, before its insertion; the fifth and last level comprises the portion of the calcaneal tendon that involves the heel and its final insertion.[1]

Reconstruction

The medial head of the gastrocnemius can be used to detect an innervated flap; the latter is used for the recovery of several pathological pictures, such as the foot drop, muscular defects of the upper limbs, Volkmann contractures and for the recovery of the movement of the tongue. In cases of post-surgical infection (replacement with knee joint prosthesis), a gastrocnemius muscle flap can be used to improve the clinical results of cicatrization. Using a medial head flap is used to improve the cicatrization of transtibial amputation intervention.[18] Using a part of the gastrocnemius muscle has few negative collaterals and fast use.[19]

Baker's Cyst

The name of this popliteal cyst comes from the doctor who first described it in 1877, surgeon William Morrant Baker. These cysts are formed in the presence of an already compromised knee joint (osteoarthritis, meniscal rupture), which creates effusions from the articulation toward the posterior area of the knee, toward the bursa of the medial head of the gastrocnemius. Often, there is a joint material in the cyst coming from inside the capsule; this transit of fluids is always unidirectional. Generally, they are asymptomatic and discovered with the magnetic resonance in a knee with known functional problems. Surgical excision is used only in limited cases, with a posterior approach.[20]

Injury of Muscle Fibers or Tearing

Muscle tearing or muscle distraction can be common for those who play sports. Depending on the severity of the injury, one can distinguish 3 types of calf muscle tears. The most serious is the third degree, which involves at least three-quarters of muscle mass. In first-degree injuries, when the lesions are modest and do not exceed 5% of muscle mass, there is no significant reduction in muscle function. The subject usually experiences a sensation of continuous cramp. In the second-degree lesion, the manifestations are those of pain; pain is felt during movement. Generally, the indications for the first 2 levels are conservative. In the third degree muscular tear, hematomas, edema, and swelling may appear, the pain becomes very strong, and the subject is in a disabling condition because he can not move the leg. This lesion is felt on palpation as a depression, a real step that testifies to the extent of the breakup.[1]

Achilles Tendon Disorders

Achilles tendon (or "calcaneal" tendon) disorders are relatively common injuries.  Disorders can occur in adolescents, adults, and etiologies include traumatic and nontraumatic mechanisms.  The spectrum of pathology ranges from insertional tendinitis, intra-substance tears and/or tendinopathy, and partial versus complete ruptures. [21]

Acute ruptures of the achilles tendon may be misdiagnosed in up to 25% of cases.  The most common misdiagnosis is that of an ankle sprain.  Missed or delays in diagnosis can be problematic for patients, and a chronically dysfunctional tendon is harder to repair surgically.[22] Acute and sudden pain in the calcaneal tendon, the functional impotence and the palpatory sensation of the interruption of the tendon are the basis of the diagnostic suspicion confirmed by the ultrasound investigation. This injury is the consequence of chronic tendinitis often unrecognized or undervalued. Other causes may be related to systemic diseases (diabetes, lupus erythematosus) or chronic administration of steroid drugs.[23] Collagen fibers change their phenotype, with increased collagen type III they are less elastic and less able to handle mechanical stresses.

The injury mainly involves jumpers, runners, soccer players, and tennis players, realizing as a consequence of a sharp muscle contraction. Treatment is surgical. Many types of tendon suture can be performed. The calcaneal tenorrhaphy is now performed with a technique that uses tiny incisions to avoid the scarring disorders related to very long incisions, and the benefit of reduced recovery times. Sometimes, a reinforcing plastic is made using the tendon of the gracilis muscle plantar or the use of the peroneus longus muscle tendon.[22]

Gastrocnemius Shortening

Several diseases cause a shortening of the gastrocnemius muscle: lesions of the nervous system, central or peripheral, hereditary diseases such as myopathy and dystrophies, or acquired disease like diabetes. All age groups can be involved, from the children to the elderly. The most evident functional disturbance of this shortening is the equine foot, where the tip of the foot points toward the bottom and the gait is characterized by toe of the foot to the ground. First of all, it is essential to distinguish the cause of equinism, to evaluate its characteristics in the context of walking, and to establish an appropriate treatment. The treatment uses conservative methods (physiotherapy, stretching, tutors, botulinum toxin) and surgical methods, such as stretching the calcaneal tendon.

With the Silfverskiold test, it is possible to discriminate whether the equinism is caused by a retraction of the soleus muscle (extended knee) or the gastrocnemius muscle (flexed knee). If the ankle can be dorsiflexed with the knee bent at 90 degrees but can not be dorsiflexed with the extended knee, it is probable that the gastrocnemius muscle is shortened, but not the soleus; it can be done with a patient sitting or lying on the back.

The most recent surgical procedures use endoscopy to reduce collateral damage, in particular by creating a small cut at leg level 4; the release of the calcaneal tendon could produce an evaluation error, with an excessive elongation of muscle.[24][25]

THe clinician should first observe how the patient moves, how he compensates, and whether there are any differences in muscle shape between the 2 calves. The clinician will palpate the tone of the muscles, both on the fleshy level and on the fascia (aponeurosis and tendon); the movement is first activated by the patient, so as not to condition the person or the perception of pain. Passively evaluate the knee and ankle after active movements. Finally, the anamnesis will be fundamental.

Correct Evaluation of the Equine Foot

To perform the Silfverskiold test correctly, the force applied by the operator must be about 2 kilos, with the hand placed under the sole or under the head of the second metatarsal. If the patient has a non-rigid flat foot, the heel is in a position of valgism; in this case a pure dorsiflexion does not occur, with a movement that expresses itself on an oblique plane, thanks to the joints of the hindfoot. To obtain a clean movement and to improve the execution of the test, the hindfoot must be placed in a neutral or slightly variant position. Before performing this test, it is possible to carry out the Taloche test or the Taloche sign. If the gastrocnemius muscle is contracted, the patient will not be able to maintain the orthostatism if it is resting on an inclined plane (a tablet).[26]

Tibial Nerve Trapping

A tibial nerve tract can be palpated both in the popliteal cavity and slightly below; in these areas, it is superficial and very simple to hear manually. The nerve becomes posterior tibial nerve when it reaches the ankle area, travels in the tarsal tunnel, deeper than the flexor retinaculum and the posterior tibial artery and vein.[9] Another point of contact with the tibial nerve is behind the medial malleolus, just below and medially the calcaneal tendon; with the thumb, look for the malleolus and slowly bring a finger toward the tendon with a horizontal pattern. It is often a painful area of which the patient is unaware.  

The tibial nerve rarely undergoes an entrapment to the popliteal cavity, while it more frequently has an entrapment to the tarsal tunnel, as previously mentioned. At this level there are different causes such as a tumor, a previous intervention and trauma, or systemic diseases such as diabetes or neurological diseases, and deformity of the same foot. It is possible to carry out a stress test with the Tinel test to evoke the painful symptom or paresthesia symptoms.[9]

Calcaneal Tendon Rupture Evaluation

The Thompson squeeze test or sign of Simmonds-Thompson is a semiotics maneuver of the objective examination of the lower limb which, if positive, indicates a complete rupture of the calcaneal tendon. The examiner compresses the patient's calf between the fingers, lying in a prone position with the feet over the edge of the bed. Under normal conditions, the squeezing of the muscular masses causes the plantar flexion of the foot, while when there is a full-thickness tear of the posterior calcaneal tendon structures, it evokes intense pain with no movement of the foot.[27]

Physiotherapy for Tears: First and Second Degree

With an anatomical lesion, the treatment in the first 24 to 48 hours consists of the RICE protocol (Rest, Ice, Compression, Elevation), a treatment that avoids the aggravation of the lesion and inflammation. This protocol includes rest, ice 3 to 4 times a day for 20 minutes, bandaging, and elevation of the limb.

Generally, muscle relaxants and analgesics are taken, the latter being preferable to anti-inflammatories (NSAIDs) because post-injury inflammation is a physiological mechanism of repair of the human body. The athlete must stay away from the field for a variable time depending on the size of the injury, ranging from 1 week to 2 months.[28]

After an injury the muscle closes the lesion forming a fibrous cicatricial result, that is a less elastic connective tissue of the muscle. If the muscle is immobilized, the scar is formed with fibers that can go in any direction, if instead the muscle is kept moving, the fibers of the connective tissue that is formed have an arrangement according to the lines of force and are more elastic. Instrumental physiotherapy with CO2 laser, ultrasound and Tecar therapy is indicated; when the lesion is closed, an activity is needed to make the muscle more elastic and to prevent recurrences. Stretching and eccentric reinforcement is important. In general, the elective exam is muscle-tendon ultrasound, but if the lesion is deep, in a very developed muscle, magnetic resonance may be necessary.[28]

Rupture of the Calcaneal Tendon

The rehabilitation treatment of calcaneal tendon rupture has a duration of about 12 weeks, at 3 sessions per week, alternating between the gym and swimming pool, including massage on the scar and on the calf muscles, physical therapies for pain and swelling, exercises for the articulation, for restoring strength and correct walking and running.[22]

After about 3 months, it is possible to perform an isokinetic test to measure the muscular strength of the leg. Based on the result, the therapeutic protocol must adapt to the athlete's sport, to speed up the return, refining the recovery of the coordination of the specific technical gesture of the sport practiced.[29]

Kinesio Taping

The application of elastic bands on the muscle tissue could be helpful for some conditions of the gastrocnemius muscle. In the presence of trigger points, the application of taping has proved useful in reducing the symptomatology.[30]

It would seem that the use of taping on the calcaneal tendon has a rationale to prevent sports injuries.[31]

Osteopathy

The osteopathic approach with gentle techniques in the presence of scars may be of help in preventing further pain and improving function.[32]

Osteopathy in patients with tendinitis has proven to be helpful in reducing symptomatology and improving active movement of plantar flexion.[33]

Popliteal fossa: an important area for the function of the gastrocnemius muscle

In the popliteal fossa, a fundamental site for the gastrocnemius muscle, it is possible to find tensor fasciae suralis (also known as ischioaponeuroticus), a muscle that could disturb the function of the calf area and is clinically relevant. One of the variants of the tensor fasciae suralis muscle is to lean over the lateral head of the gastrocnemius muscle, innervated by the common peroneal nerve. The abnormal presence of this muscle could alter the function of the gastrocnemius, with dysfunctional problems in the knee and ankle, with repeated traumas in these articular areas. This is because the lines of tension are altered and do not allow the joints to withstand the workloads correctly, from running to jumping. 

Another muscle variable that could alter the function of the gastrocnemius muscle is a strip of muscle (it does not have a name) that goes from the medial head transversely to the tendon tissue of the biceps femoris; this anomaly is innervated by the tibial nerve. This muscular structure covers the neurovascular components of the popliteal fossa. Its hypertrophy could cause paresthesia, entrapment of the popliteal artery and create abnormal tensions for a correct function of the calf area.

A Baker's Cyst in the popliteal fossa could mimic a problem of deep vein thrombosis. An examination with ultrasound may not be sufficient to understand the reasons for the pain (for example in the area of insertion of the gastrocnemius muscle, when bending the knee). A further consideration is the MRI. If the pharmacological therapy for thrombosis does not remove the pain from the popliteal fossa, one of the causes reported in the literature is the presence of this cyst.