Let’s take a look at piriformis syndrome.
AKA deep gluteal syndrome (DGS).
Piriformis syndrome is a form of sciatica where the sciatic nerve is compressed or irritated by the piriformis muscle. The piriformis muscle is a muscle deep in the buttocks and is a primary stabilizer for the hip, lifting and rotating the thigh away from the body. It is used whenever we walk, shift our weight from one foot to another, or maintain balance. Care needs to be taken with diagnosis to rule out the possibility of other structures compressing the nerve, or of simple trigger points with the muscles of the buttock which can cause pain mimicking piriformis syndrome.
Piriformis syndrome can be either a primary or a secondary condition; and sometimes both at the same time. This means that it can happen of its own accord, and potentially cause other issues such a sprain in one of the joints of the pelvis; or it can be a reaction to another problem, such as a sprain in one of the joints in the pelvis. This can, of course, be a self-repeating cycle, creating chronicity.
Pain is usually felt in one buttock, going down the back of the leg into the calf and foot; the leg and foot pain is often accompanied by numbness and a tingling sensation. You can even experience weakness in the muscles as well; it is often worse in the morning, whilst sitting or walking up slopes or stairs.
The single most common cause of piriformis syndrome in men is sitting with the wallet in the back pocket. If you do this, please stop (or continue, and then pay me to tell you to stop).