Summary: A 40-year-old woman experiences sudden onset of calf pain while rounding the bases in a game of softball. She
presents after several days of continued pain, tenderness, and limited mobility. MR of the lower extremity was obtained.
Plantaris muscle rupture
MR demonstrates edema in the medial head of the
gastrocnemius as well as a thin collection of T1-hyperintense fluid deep to the
gastrocnemius in the expected path of the plantaris muscle.
The plantaris muscle originates on the lateral
supracondylar line of the femur just above the origin of the lateral head of
the gastrocnemius muscle. Its muscle belly courses obliquely deep to the
lateral head of the gastrocnemius muscle, continuing inferiorly between the
medial head of the gastrocnemius muscle and the soleus muscle. Distally, its
tendon travels medial to the Achilles tendon to combine with or insert
anteromedially to the Achilles tendon on the calcaneus.1 The
plantaris is diminutive compared to other muscles of the superficial posterior
compartment, so much so that it has earned the moniker the “freshman nerve” for
its propensity to be misidentified by junior medical students.
Although contribution of the plantaris muscle to motor
function in humans is likely minimal, injury to the muscle or tendon is an important
consideration in the workup of acute calf pain. Patients classically experience
acute onset of calf pain while running or jumping followed by focal tenderness
and swelling or the so-called “tennis leg” condition, a clinical syndrome also
seen with injury to the myotendinous junction of the medial head of the
MR findings depend on severity of injury and range
from increased T2/STIR signal in the plantaris muscle belly and/or medial head
of the gastrocnemius to frank muscle rupture with hemorrhagic fluid
accumulating in the expected course of the plantaris muscle.3,4
Concurrent injuries to the anterior cruciate ligament and arcuate complex are
Spina AA. The plantaris muscle: anatomy, injury, imaging, and treatment. J Can Chiropr Assoc. 2007;51:158-165.
- 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;224:112-119.
Bencaridino JT, Rosenberg ZS, Brown RR, et al. Traumatic musculotendinous
injuries of the knee: diagnosis with MR imaging. Radiographics. 2000;20:S103-120.
Helms CA, Fritz RC, Garvin GJ. Plantaris muscle injury: Evaluation with MR
imaging. Radiology. 1995;195:201-203.