The plantaris muscle and the soleus muscle in the calf are prone to injuries related to running. In some cases, an injured plantaris muscle is often associated with calf pain and injury to the soleus muscle. It is important that you speak to your doctor if you suspect you have a lower leg injury from running. She can help determine treatment to help you recover and get you back to running.
Plantaris Muscle
The plantaris muscle is a thin band of muscle tissue that contributes to helping bend your ankle and knee. The narrow muscle originates behind the knee joint and extends down to the back of the heel, near the Achilles tendon. Commonly mistaken for a nerve, the small plantaris muscle's motor function is insignificant, which makes it a candidate for surgical tendon grafts and reconstruction of other musculature in the body.
Soleus Muscle
The soleus muscle is a powerful calf muscle that enables you to flex your ankle. The muscle originates just beneath the back of the knee joint. Its heads bulge out along the back of the upper portion of your lower leg and taper off down toward the heel, where it eventually combines with the gastrocnemius aponeurosis to form the Achilles tendon.
Injuries
Though the muscle function of the plantaris is insignificant, it can cause pain from injuries, such as a torn Achilles tendon. Overuse injuries to the muscle can also occur, which are spurred by running or jumping. Such an overuse injury in the plantaris muscle is known as "tennis leg". The injury does not always originate in the plantaris.
Tears in the soleus muscle or the head of the gastrocnemius can also cause pain in the plantaris and lead to "tennis leg." The repetitive motion from running places an eccentric load on the ankle when the knee is in an extended position, which is when injuries to the plantaris and soleus muscles occur most frequently. Such injuries are the result of a mechanism -- namely running -- that may feel as if the muscles have been struck with force.
Symptoms & Treatment
Swelling and pain are typical signs of "tennis leg," which eventually causes your muscles to become sore. The pain from the injury can often become more intense after you stop running and rest for a few hours. The swelling can reach from the muscle heads all the way down to the ankle and foot, and is usually extremely painful if you try to flex your ankle. Your doctor may recommend treatment, such as cryotherapy -- medical therapy that uses low temperatures to cool body parts -- passive stretching and ultrasound therapy. Post-therapy treatment often includes strength training. In less severe cases of pain in the soleus muscle, you can ice your calf for 10 to 15 minutes after running, followed by performing some basic calf muscle stretches and heel lifts.