What You Should Know About Plantaris Muscle Tears

The plantaris muscle is a small muscle in the back of the leg. Running along with the other muscles of the calf, the plantaris muscle and tendon are in a similar location to the muscles of the calf and Achilles tendon. 

Injury to the plantaris muscle can mimic some of the symptoms of a calf strain or Achilles tendon tear, but the recovery from a plantaris muscle injury is typically much simpler.

The major muscles in the back of the leg are the gastrocnemius and the soleus muscles. The gastrocnemius has two major portions, the medial and lateral heads of the gastrocnemius, and is more superficial (closer to the skin). The soleus is located deeper in the leg. 

Together, the gastrocnemius and soleus muscles form the Achilles tendon, which blends into a tight tendon in the back of the heel.  The Achilles tendon attaches to the heel bone (the calcaneus). When the calf muscles contract, the point the foot downward. This motion is important in propelling the body forward when walking, running, and especially when sprinting. 

The plantaris muscle is a smaller component of the calf muscles. The plantaris muscle and tendon sit roughly in the center of the calf, between the two heads of the gastrocnemius. Not everyone has a plantaris muscle, and in cadaver examinations, roughly 10-20% of the population is found to not have a plantaris muscle.

Injuries to the plantaris muscle can either occur as a muscle strain or more commonly, a plantaris muscle rupture. Plantaris muscle ruptures have also been called "tennis leg" as many people who sustain this injury are athletes who are lunging forward, such as a tennis player might do.

Typical symptoms of a plantaris muscle rupture include:

• Sudden pain in the back of the calf
• A swelling or bunching of the calf muscle
• Swelling and bruising in the back of the leg
• Cramping and spasm sensations of the calf muscle

The most important step is to confirm the diagnosis, in large part to ensure the injury is not a more serious Achilles tendon tear. Patients with Achilles tendon tears typically cannot point their foot downward because of the severed tendon, whereas plantaris muscle injuries do not cause this limitation. Plantaris ruptures can also be confused with a blood clot in the large veins of the calf, called a DVT.

If the diagnosis is unclear, there are tests that can be performed to confirm or exclude the diagnosis of a plantaris rupture. The two tests most often used are either an MRI or an ultrasound. Both of these tests can be useful in confirming an injury to the plantaris muscle or to look for other possible causes of calf pain.

Treatment of a plantaris muscle injury is almost always non-surgical. While the injuries can cause pain and disability, the symptoms almost always resolve with simple treatment steps. The initial treatment of a plantaris injury is with the usual R.I.C.E. (Rest, Ice, Compression, Elevation) treatments. If the pain is significant, patients may require a brief time of immobilization or crutch use to allow the pain to subside.

Gradual increases in mobility and strength can be obtained with the assistance of an athletic trainer or physical therapist. Most often symptoms gradually resolve, although it is not uncommon for a full recovery to take 6 to 8 weeks, depending on the severity of the injury.