eMedicine Specialties > Sports Medicine > Lower Limb

Medial Gastrocnemius Strain: Differential Diagnoses & Workup

Author: Anthony J Saglimbeni, MD, Staff Physician, Family Practice Residency, President, South Bay Sports and Preventive Medicine Associates; Private Practice; Team Internist, San Francisco Giants; Team Internist, West Valley College; Team Physician, Bellarmine College Prep; Team Physician, Presentation High School
Contributor Information and Disclosures

Updated: Aug 6, 2009

Differential Diagnoses

Achilles Tendon Rupture
Compartment Syndromes

Other Problems to Be Considered

Baker cyst rupture
Deep venous thrombosis
Plantaris tendon rupture
Acute compartment syndrome after rupture of the medial head of the gastrocnemius
Chronic exertional compartment syndrome (posterior)
Posterior tibial tendon rupture or tendinitis
Popliteal artery entrapment syndrome
Anomalous gastrocnemius muscle rupture

A Baker cyst is a reactive outpouching of the knee joint capsule. The presence of a Baker cyst implies chronic internal knee pathology, often arthritic in nature, but it may also include traumatic meniscal pathology. The cyst is usually painless but often cosmetically unacceptable to the patient. If the Baker cyst ruptures, the leg swells, and the pain is diffuse. This condition can be confused with a ruptured gastrocnemius muscle.

(See also the eMedicine articles Baker Cyst [in the Radiology section], Knee Injury, Soft Tissue [in the Emergency Medicine section], and Cystic Lesions About the Knee and Limping Child [in the Orthopedic Surgery section].)

A femoral or popliteal deep venous thrombosis (DVT) can cause leg swelling, which can result in leg pain. If this condition occurs in the same time frame as an acute leg injury, the 2 conditions can be confused.

(See also the eMedicine articles Deep Venous Thrombosis and Thrombophlebitis [in the Emergency Medicine section] and Deep Venous Thrombosis, Lower Extremity [in the Radiology section].)

The plantaris tendon originates in the popliteal area, and this tendon is also a plantar flexor of the ankle. If the plantaris tendon ruptures, the leg swells, and the resulting tenderness can be in the same area as where a gastrocnemius strain would occur.

Achilles tendon injury can occur with the identical mechanism of a medial gastrocnemius rupture. Because the ensuing fluid and edema may migrate proximally, the 2 conditions may mimic each other. An Achilles tendon rupture results in an inability to plantar flex the foot, and a more distal defect of the tendon is usually palpable. A Thompson test can be used to differentiate the 2 injuries. The test is performed with the patient prone and the knee held in flexion. Then, the gastrocnemius muscle is squeezed. A negative sign results in normal plantar flexion of the foot and ankle. If the flexion is not appreciated, the test is positive and due to a disrupted Achilles tendon. (See also the eMedicine article Achilles Tendon Rupture.)

Acute compartment syndrome of the lower extremity occurs after trauma, with accumulation of blood or fluid in a closed compartment of the leg. The resultant pressure produces pain and swelling, and if the posterior compartment is affected, this could clinically present similarly to a medial gastrocnemius tear.

(See also the eMedicine articles Compartment Syndrome, Lower Extremity [in the Orthopedic Surgery section], Compartment Syndrome [in the Physical Medicine and Rehabilitation section], and Compartment Syndrome, Extremity [in the Emergency Medicine section].)

Chronic compartment syndrome results in affected individuals after a degree of exertion and from vascular compromise with edema in the compartment of the leg. The pain that ensues can mimic that of gastrocnemius muscle strains, but this condition becomes symptom-free after the exertion is completed. (See also the eMedicine article Compartment Syndromes [in the Sports Medicine section].)

The popliteal tendon courses posteriorly on the medial side of the leg. Injuries to this structure can distribute pain in the same regions as a tennis leg injury. (See also the eMedicine articles Pes Planus [in the Orthopedic Surgery section] and Athletic Foot Injuries [in the Sports Medicine section].)

The popliteal artery may be entrapped during its course in the leg. The most common cause is an anomalous gastrocnemius muscle. Typically, popliteal artery entrapment manifests during exertion, and the symptoms of this condition are more consistent with the symptoms of chronic exertional compartment syndrome.

(See also the eMedicine articles Peripheral Arterial Occlusive Disease [in the Vascular Surgery section], Compartment Syndrome, Lower Extremity [in the Orthopedic Surgery section], and Compartment Syndromes [in the Sports Medicine section].)

Workup

Laboratory Studies

• The ruptured medial gastrocnemius can usually be diagnosed clinically. Although laboratory and imaging studies can also be used to evaluate some of the other diagnostic possibilities (see Differentials and Other Problems to Be Considered), they are not necessary.
• Laboratory studies are usually not necessary in the workup of gastrocnemius strains. They may, however, aid in the evaluation of a potential DVT, if clinical suspicion is present.
  • Complete blood cell (CBC) count: If a DVT is present, the platelet count may be abnormal, but in gastrocnemius strains, the CBC count is normal.
  • Coagulopathy panel: Before initiating treatment for DVT, prothrombin time (PTT), activated partial thromboplastin time (aPTT), protein C, protein S, and D-dimer levels should be measured. Of course, these results all are within the normal reference range in a medial gastrocnemius strain.

Imaging Studies

• Radiographs
  • In the face of a classic history and presentation for a medial gastrocnemius strain, radiographs are usually normal and do not offer additional information for treatment.
  • X-ray films may be ordered to rule out an avulsion fracture, especially when the patient describes an audible pop or any history of impact or trauma to the calf region. (See also the eMedicine article Tibial Tubercle Avulsion.)
  • Plain films of the leg and tibia/fibula are usually normal, except for the finding of soft-tissue swelling.
• Studies have shown that magnetic resonance imaging (MRI) and ultrasound studies can be useful in the diagnosis and/or follow-up of injuries to the lower leg.
  • MRI is the most sensitive and specific imaging method, and this technique is able to show the area of disrupted soft tissue better than other imaging modalities (eg, computed tomography [CT] scanning, ultrasonography).
    • Koulouris et al retrospectively reviewed 59 MRIs from patients who had sustained calf muscle injuries.⁷ The authors reported that of the 39 isolated strains, gastrocnemius injuries were the most common (48.7%), in which the majority of these (94.7%) involved the medial head, followed by soleus muscle injuries (46.2%), including 2 cases of distal avulsions of the plantaris. In cases in which there were dual injuries, the most common finding (60%) was a combined gastrocnemius and soleus muscle injury. Koulouris et al concluded that dual injuries to the calf region may be more common than has been reported and such injuries may have a prognostic significance. The authors also noted that in the literature, soleus muscle injury is a rarely reported finding with ultrasonography.
  • In areas where ultrasound experience is good, this modality may also demonstrate the medial gastrocnemius injury and usually costs less than MRI. However, limited MRI protocols, in which a few images of the suspected region of pathology are performed, can have competitive pricing and demonstrate superior images than ultrasonography. However, in emergency department settings, rapid diagnostic ultrasonography can be used to evaluate the structure of the medial gastrocnemius and to rule out some of the diagnostic possibilities, such as DVT (see Differentials and Other Problems to Be Considered).⁸
    • In a Korean study, 22 patients with clinically suspected ruptures of the medial head of the gastrocnemius under went ultrasound examination of both the affected and unaffected limbs.⁹ The authors reported that 7 of the 22 patients were diagnosed with a partial rupture, and the remaining 15 patients were diagnosed with complete ruptures of the head of the gastrocnemius. In addition, the authors noted fluid collection between the head of the gastrocnemius and the soleus muscle in 20 patients, and they reported the thickness of the fluid collection was significantly greater in those patients with complete gastrocnemius medial head ruptures (mean: 9.7 mm) compared with those of the individuals with partial tears (6.8 mm). The authors concluded that ultrasound is a useful imaging modality for the diagnosis and follow-up of patients with ruptures of the medial head of the gastrocnemius.

Other Tests

• Other tests are not necessary for the diagnosis of an uncomplicated medial gastrocnemius strain. If the suspicion of DVT persists, then further evaluation with Doppler ultrasonography is indicated.

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