Muscle knots in the Soleus are located deep in the lower leg and can be felt about midway down the lower leg on either side of the Achilles tendon. These muscle knots often refer pain to the heel, Achilles tendon, and posterior ankle, and in rare cases, even to the sacroiliac joint or jaw. You may experience a deep ache or cramping sensation, especially when walking uphill, climbing stairs, or standing for long periods.