Case of the week Details

• STIR and T2 images showing hyper intensity with partial discontinuity in the deep fibers of the medial head of gastrocnemius muscle at the musculotendinous junction
• Minimal fluid collection is seen insinuated between the distal medial head of the gastrocnemius muscle and the soleus muscle with edema.

Diagnosis : Tennis Leg

DISCUSSION:

• Tennis leg represents a myo-fascial or tendinous injury of the lower limb .
• Seen most frequently in tennis players.

Pathology :

It involves injury to the muscles of the calf (superficial posterior compartment of the leg) via two identified mechanisms:

• Tear of the myotendinous junction of the medial head of the gastrocnemius
• Rupture of the plantaris tendon

Both findings have been found in isolation or together.

Imaging:

Radiographic features

Ultrasound

• Ultrasound demonstrates fluid deep to medial gastrocnemius and superficial to the soleus muscle.
• Most prominent at the level of the myotendinous junction.
• A tear in the deep surface of gastrocnemius may be seen as a disruption in contour and echogenicity of muscle fibers.
• A torn plantaris tendon may also be identified.

MRI

MRI demonstrates the same features seen on ultrasonography. Findings include:

• High T2 signal fluid deep to medial gastrocnemius and superficial to the soleus
• A focal area of disruption of muscle continuity noted along the deep aspect of the medial head of the gastrocnemius, with associated muscle edema
• The plantaris tendon may either be torn or intact

DIFFERENTIAL DIAGNOSIS

• The differential diagnosis of calf pain includes the more serious clinical entities of deep venous thrombosis (DVT) and compartment syndrome, as well as Achilles tendon rupture.
• In the proper clinical situation, calf pain with an otherwise negative MRI raises suspicion for DVT. An Achilles tendon rupture is easily differentiated from plantaris tendon rupture on MRI.
• Compartment syndrome can also be distinguished from plantaris or gastrocnemius muscle injury, since it demonstrates a more diffuse muscle edema pattern.
• Compartment syndrome, however, may be seen in conjunction with calf muscle injuries, as a result of hematoma and swelling

References :

• Tennis leg. Br Med J. 1969;3 (5670): 543-4. Free text at pubmed- Pubmed citation
• Delgado GJ, Chung CB, Lektrakul N et-al. Tennis leg: clinical US study of 141 patients and anatomic investigation of four cadavers with MR imaging and US. Radiology. 2002;224 (1): 112 9. doi:10.1148/radiol.2241011067 – Pubmed citation
• Jamadar DA, Jacobson JA, Theisen SE et-al. Sonography of the painful calf: differential considerations. AJR Am J Roentgenol. 2002;179 (3): 709-16. AJR Am J Roentgenol (full text) – Pubmed citation
• Bianchi S, Martinoli C, Abdelwahab IF et-al. Sonographic evaluation of tears of the gastrocnemius medial head (“tennis leg”) J Ultrasound Med. 1998;17 (3): 157-62. J Ultrasound Med (abstract) – Pubmed citation
• Shah JR, Shah BR, Shah AB. Pictorial essay: Ultrasonography in ‘tennis leg’. Indian J Radiol Imaging. 2010;20 (4): 269-73. doi:10.4103/0971-3026.73542 – Free text at pubmed- Pubmed citation

Dr. PRAVEEN WALI
Senior Consultant Radiologist
Manipal Hospital, Yeshwanthpur, Bengaluru.

Dr. Srinivas P
Fellow in Radiology
Manipal Hospital Radiology Group (MHRG)
Manipal Hospital, Bengaluru