Gluteus Maximus: Everyone Needs a Butt
Tight psoas is a common cause of lower back pain.
Snapping hip syndrome
Here's a pic of how the nerves run through the shoulder down the arm. This is one of the situations that can cause pain further down the arm.
Painful muscles are debilitating but now you can have products to help at home. You don't need to see a specialist every time you have muscle knots.
Trigger Point Therapy For Myofascial Pain: The Practice Of Informed Touch
Julia Fullerton-Batten - Google Search