Calf Strain

'Original Editors ' Kim De Maeght, Bettina Vansintjan, Maite Van Roozendael and Lenka Pé

Definition/Description

Calf strain is a common muscle injury. It is a tear of the muscle fibres of the muscles at the back of the lower leg. Strains are the result of excessive stretching or over stretching while the muscle is being activated. Strains may be referred to as a “pulled muscle”. 

Clinically Relevant Anatomy

The calf muscle, on the back of the lower leg, is composed of three muscles: the gastrocnemius, the soleus and the plantaris, which together constitute the triceps surae. These muscles come together as the achilles tendon and all three muscles insert into the calcaneus.

Gastrocnemius is part of the posterior compartment of the leg and comprises of two parts, the medial head and the lateral head. The medial head arises from the medial condyle of the femur and the lateral head originates from the lateral condyle of the femur.  The gastrocnemius provides primarily plantar flexion and flexion at knee joint.  Gastrocnemius is innervated by the tibial nerve, a branch of the sciatic nerve, passing through the popliteal fossa where the nerve gives off a branch to the gastrocnemius. 

Soleus is located beneath the gastrocnemius muscle in the superficial posterior compartment of the lower leg. The muscle originates from the upper 1/3 of the posterior aspect of the tibia, from the back of the head of the fibula and the upper part of the posterior surface of the fibular shaft and the fibrous arch that lies between the tibia and the fibula.  Its main function is plantar flexion of the ankle and stabilising the tibia on the calcaneus limiting forward sway.  The soleus is innervated by the tibial nerve, which passes behind the muscle through the fibrous arch of the soleus. 

Plantaris is located in the posterosuperficial compartment of the calf. The muscle originates from the lateral supracondylar line of the femur (superior and medial to the lateral head of gastrocnemius) and from the oblique popliteal ligament. It is a long, small muscle with a long thin tendon. The plantaris is also innervated by the tibial nerve. Functionally, plantaris is not a major contributor and acts with gastrocnemius, as both a flexor of the knee and a plantarflexor of the ankle. 

Epidemiology/Etiology

Muscle strains most commonly occur in bi-articular muscles such as the hamstrings, rectus femoris and gastrocnemius. During sporting activities such as sprinting, these long, bi-articular muscles have to cope with high internal forces and rapid changes in muscle length and mode of contraction. However, muscle strains have also been reported to occur during slow-lengthening muscle actions such as those performed by ballet dancers, but also during common daily activities.  Gastrocnemius is considered at high risk for strains because it crosses two joints (the knee and ankle) and has a high density of type two fast twitch muscle fibres.  A tear of the medial head of the gastrocnemius muscle is due to an eccentric force being applied to the muscle when the knee is extended and the ankle is dorsiflexed. The gastrocnemius muscle attempts to contract in the already lengthened state leading to tear of the muscle.  The soleus muscle on the other hand is injured while the knee is in flexion. Strains of the proximal medial musculotendinous junction are the most common type of soleus muscle injuries. Unlike gastrocnemius, soleus is considered low risk for injury. It crosses only the ankle and is largely comprised of type one slow twitch muscle fibres. Soleus strains also tend to be less dramatic in clinical presentation and more subacute when compared to injuries of gastrocnemius.  This condition frequently occurs in the middle-aged, poorly conditioned and/or physically active patient. 

Characteristics/Clinical Presentation

It is important to differentiate between muscle strains within the calf complex in order to formulate a correct prognosis, an appropriate treatment programme and prevention of recurrent injury. 

Gastrocnemius strains
Calf strains are most commonly found in the medial head of the gastrocnemius.  In an effort to contract, the forces of the eccentric movement on the already lengthened gastrocnemius muscle lead to injury at the myotendinous junction. The physical examination immediately after the injury reveals a palpable defect in the medial belly of the gastrocnemius just above the musculotendinous junction.  A sudden pain is felt in the calf, and the patient often reports an audible or palpable "pop" in the medial aspect of the posterior calf, or they have a feeling as though someone has kicked them in the back of the leg. Substantial pain and swelling usually develop during the following 24 hours.  Strains in the gastrocnemius are also referred to as a “tennis leg” as the classic presenttaion was a middle aged tennis player who suddenly extends the knee

Soleus strains
Soleus is considered low risk for injury in contrast to the gastrocnemius asit crosses only the ankle and is largely composed of type one slow twitch muscle fibres.  Soleus strains tend to be less dramatic in clinical presentation and more subacute when compared to injuries of the gastrocnemius. Injury of the soleus muscle may be under reported due to a misdiagnosis of thrombophlebitis or lumping of soleus strains with strains of the gastrocnemius.  A soleus strain causes pain when activating the calf muscle or when applying pressure on the achilles tendon approximately 4 cm above the insertion point on the heel bone or higher up in the calf muscle. Stretching the tendon and walking on tip-toe will also aggravate pain. 

Plantaris strains
Plantaris is considered largely vestigial and rarely involved in calf strains, although it crosses both the knee and the ankle joint as well.  Rupture of the plantaris muscle may occur at the myotendinous junction with or without an associated hematoma or partial tear of the medial head of the gastrocnemius muscle or soleus.  Injury to the plantaris muscle can present with similar clinical features as those of the gastrocnemius and soleus muscle. 

Differential Diagnosis

Strains are most common during sporting activity, but pain in the lower leg could indicate medial tibial stress syndrome, achilles tendinitis, plantar fasciitis, muscles strains and/or joint sprains which can be caused by lack of extensibility of the plantar-flexors and decrease in ankle dorsiflexion.  The different degrees of muscle strains are discussed above. Other lower leg injuries related to sports with the same symptoms and treatment as a calf strain are discussed below. 

Runners often complain about lower leg pain along the posteromedial border of the tibia.  This is medial tibial stress syndrome (MTSS) or commonly known as shin splints.  The pain is described as tenderness located a few centimetres proximal to the medial malleolus, spreading proximally about 4 to 10 centimetres. The cause of MTSS may be associated with repetitive stress or an overuse injury.  

Pain located anterior or anteromedial of the tibia could indicate a tibial stress fracture, a typical injury seen in runners and footballers   It can occur following abrupt changes in intensity, duration and frequency of training, but other personal and environmental factors can also contribute to this injury. Radiographs are initially negative, but with time fracture lines become visible. Operative treatment may occasionally be necessary, but it can be treated the same way as a calf strain: rest, restriction from aggravating activity, strengthening of the lower extremity musculature, NSAIDs and appropriate footwear.

Repetitive exercise without adequate rest for recovery can cause chronic exertional compartment syndrome (CECS).  CECS begins with mild pain during periods of training and can disappear after training. In the latter stages, pain presents earlier, becoming more painful and of a greater duration forcing a halt in activity. Common complaints are; cramps, paraesthesia, numbness and weakness in the lower leg. CECS is caused by the increased intramuscular blood flow during exercise so compartmental pressure arises, capillaries become compressed and ischemia develops. 

Leg pain around the same area as a gastrocnemius strain can be caused by Popliteal Artery Entrapment Syndrome (PAES), an abnormal course of the popliteal artery. Medial and cranial migration of the medial head of the gastrocnemius can catch the popliteal artery and swipe it medially. This is called anatomical PAES, an abnormal relationship between the popliteal artery and the surrounding myofascial structures. Functional PAES is caused by muscle contraction, often active plantarflexion of the ankle that compresses the artery between the muscle and underlying bone.  See http://www.physio-pedia.com/Posterior_Knee_Pain

See also:

Achilles tendinopathy
Plantar fasciitis

Diagnostic Procedures

A thorough clinical examination and history may be enough to conclude a diagnosis, but it is often difficult to reach an accurate diagnosis due to the clinical being shared with other pathological conditions. Diagnostic imaging is usually necessary and ultrasound (US) is considered to be the gold standard. It can also be used to evaluate the degree and extent of the muscular lesion and to exclude other pathologies such as ruptured Baker's cyst and deep vein thrombosis. 

Ruptures are usually associated with the presence of fluid collection between the soleus muscle and the medial head of the gastrocnemius. This can occur with or without hemorrhage. The measurement of fluid collection gives us information about the extent of the lesion. The degree of the lesion (partial or complete rupture) can be defined by the distance between the two muscles. Axial US scans are the most useful for differentiating between partial and complete rupture, as it is possible to depict the whole muscle belly in one single image. 

A calf muscle tear is a most common injury in sports such as running, volleyball, tennis, etc. These sports require quick acceleration of changes in direction and are more susceptible for a calf strain injury. Muscle strains are graded as mild, moderate and severe. The more severe the strain, the longer the recovery time. Typical symptoms are stiffness, discoloration and bruising around the strained muscle. 

Grade I:
A first degree or mild injury is the most common and the most minor. A sharp pain is felt at the time of injury or pain with activity. There is little to no loss of strength and range-of-motion with muscle fibre disruption of less than 10%. A return to sport would be expected within 1 to 3 weeks. 

Grade II:
A second degree or moderate injury is a partial muscle tear halting activity. There is a clear loss of strength and range of motion. with marked pain, swelling and often bruising. Muscle fibre disruption between 10 and 50%. 3 to 6 weeks is a usual recovery period for a return to full activity. 

Grade III:
A third degree or severe injury results in a complete rupture of the muscle and is often concomitant with a hematoma.  Pain, swelling, tenderness and bruising are usually present. Recovery is highly individualised and can take months before you are fully recovered for a full return to activity. 

Outcome Measures

1. LEFS: Lower Extremity Functional Scale
2. VAS: Visual Analogue Scale
3. NPRS: Numeric Pain Rating Scale
4. Muscle Strength testing: grade 0 is the lowest grade where the patient isn’t capable of doing any contraction of the muscle. Grade 5 is the highest grade where the patient is able to move his leg against a maximum resistance given by the therapist.

Examination

The physical exam isolates the site and severity of the injury. A combination of palpation, strength testing, and passive and active range of motion is necessary to help distinguish between strains of the soleus and gastrocnemius muscle.

Palpation of the calf should occur along the entire length of the muscles and the aponeuroses. This is required to identify swelling, thickening, tenderness, defects and masses if present. Strains of the gastrocnemius muscle usually present with tenderness in the medial belly or musculotendinous junction, while soleus strains often occur with lateral pain.

There are multiple techniques that exist to assess calf strains.
Considering that the origin of the gastrocnemius is situated above the knee (epicondylus lateralis and medialis femoris) and the origin of the soleus finds itself below the knee (caput fibulae), it allows the therapist to isolate the activation of the muscles by varying the degree of knee flexion. The soleus becomes the main source of force in plantar flexion, with the knee in maximal flexion. On the contrary, when the knee is in full extension, it is the gastrocnemius who provides most strength. This relationship allows for more accurate strength testing of the individual calf muscles and enables the examiner to describe which muscle has been injured.

Another similar method is used to test flexibility and pain during stretching and passive ankle movements. This technique determines the site of injury by isolating the gastrocnemius and soleus muscle. During the test, the knee is placed in maximal extension and thereafter in flexion while the ankle is passively dorsiflexed. This causes isolated stretch of the gastrocnemius and the soleus otherwise.

Additional testing that can be used includes the Thompson test for complete disruption of the achilles tendon. Simultaneous tears of the gastrocnemius and soleus are possible, which can complicate the clinical picture.

Medical Management

Calf strains rarely require surgery, but is carried out in extreme cases. such as in a complete rupture. Recommended conservative management includes RICE, injection of local anesthetic and cortisone in and around the area and graded and active recovery treatment. Where a hematoma is present, its removal as quickly as possible is essential, otherwise complications may occur such as myositis ossificans.

Prevention:

Regular stretching ensures that good joint mobility is maintained. Under extension, a greater force can also be delivered and the muscles are less tense, improving blood flow.   Stretching is easy to perform and has a low risk of side effects.  

Physical Therapy Management

Treatment aims to:

1. Reduce pain
2. Restore flexibility
3. Restore strength
   

The principal treatment of a calf strain consists of rest and allowing adequate healing time, but in severe cases, surgery is necessary. Conservative treatment includes passive stretching, isometric then concentric exercises.  In the latter stages, teatment can move onto massage and electrotherapy.  

Initial treatment aims to limit bleeding, pain and to prevent complications, such as rest, ice, compression and elevation. Cryotherapy can be used to decrease inflammation, pain and cell metabolism. Tape or a compressive wrap can be applied and the leg elevated. If major bleeding had occurred, the use of NSAIDs has to be carefully controlled as they have an antiplatelet effect which can increase bleeding, just as the premature application of heat and massage also can.

Gentle passive stretching exercises without pain promote range of motion of the plantar flexors, which is limited by shortnening and contractures.  Applying superficial heat simultaneously with a low load static stretch improves the flexibility of muscles.  

Isotonic exercises for the antagonists tibialis anterior, and the peronei are recommended as well as light exercises for the injured muscle. The process of stretching and exercises is carried out 2 to 3 times in the first 3 days after injury.  Lack of extensibility of the plantar flexors can cause decreases in ankle dorsiflexion and disturbances in gait. Shoes with a low heel are recommended to encourage improved heel-toe gait.  

After 48 hours, ice is no longer an effective analgesic. short wave diathermy can be used as an alternative. A strain with abnormal swelling and bruising can be treated with interferential therapy. The aim is to relieve pain and to stimulate the muscle fibres.  

When the calf muscles can be fully extended, the switch from passive stretching to a standing stretch can be made, either in a flexed knee position (soleus) or a straightened knee position (gastrocnemius).

After approximately 10 days isometric, isotonic and dynamic exercises to improve tensile strength can be performed.  Alternative treatments consist of vibration therapy (VT). Vibration therapy is applied specifically to the area of injury and treats muscle strains and other myo-tendinous injuries which involve trigger points.   Broadbent et al. suggested that VT stimulates the sensory receptors, but it also causes a decrease in inflammatory cells and receptors like IL6 and histamine.  The aim of this therapy is an increase in muscle strength, flexibility and extensibility. After a VT treatment, however, jumping and running are not permitted for at least 3 to 6 weeks and NSAIDS are discouraged, but other treatment routines can be continued. An advantage compared with other therapies like sound wave therapy and ESWT treatments, is that VT can be applied more frequently. 

Strains may cause long lasting pain, despite an adequate early treatment. The average time of treatment is nine days. Treatment outcome is successfully when: pain is resolved, the calf muscle can be fully extended, strength is back to normal, knee and ankle ROM are normal and when excessive tenderness has disappeared.  

Key Research

Millar, A. P., “Strains of the posterior calf musculature ("tennis leg")*.”The American Journal of Sports Medicine, vol. 7, no. 3, 1979, pp. 172-174.

Ellen, Mark I., Jeffrey L. Young, and James L. Sarni. "3. Knee and lower extremity injuries." Archives of physical medicine and rehabilitation 80.5 (1999): S59-S67.

Bryan Dixon J. Gastrocnemius vs. soleus strain: how to differentiate and deal with calf muscle injuries. Current Reviews in Musculoskeletal Medicine. 2009;2(2):74-77.

Clinical Bottom Line

Pain in the calf muscle is often due to a strain, however, there are other conditions which could cause similar symptoms, including deep vein thrombosis and contusions. Treatment of muscle injuries usually has good outcome. Healing time is hugely variable depending on the severity of the strain. Conservative management of stretching and exercises usually have the required outcome, but surgery may be required in the case of a rupture. Massage of the calf muscles, ultrasound and electrical stimulation are also effective treatments.