Piriformis

The piriformis is a muscle in the buttock area. The name means pear-shaped - piri is pear and formis being shape.

The muscle is quite small and it is quite deep in, under the gluteus maximus. However this muscle when tight or has trigger points can emulate the symptoms associated with sciatica which can run up the lower back or down into the legs. It is believed that when there is hypertension in the muscle it can create soft tissue pressure on the sciatic nerve and indeed in some people the sciatic nerve passes directly through the muscle rather than the muscle laying next to it. When it causes problems that are like sciatica but are not then this may be diagnosed as piriformis syndrome.

https://www.youtube.com/watch?v=0Zlplpt6jEM

https://www.youtube.com/watch?v=UaG3eY_wNQg