Anatomy of the pes anserine tendons and bursa
There are three pes anserine tendons located on the inside of the knee. A tendon attaches a muscle to the bone. The pes anserine tendons attach three muscles from the inside of the thigh onto a common insertion point on the inside of the tibia bone (just below the knee joint).
The image below helps to illustrate the anatomy. Sartorius (A), gracilis (B) and semitendinosus (C) are three large muscles located within the upper thigh. They are responsible for bringing your legs together (adduction) and bending your knee. These three muscles converge into one common tendon. This common tendon is called the pes anserine tendon (Latin for ‘goose foot’).
Surrounding the tendons on the attachment to the bone is a thin sac, known as the bursa. This bursa can also be involved in pain at this attachment point.