If you are interested in releasing these "knots" aka trigger points, I recommend Claire Davies The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief. Mr. Davies explains the trigger point phenomenon and muscle pain in everyday language. But what makes this book worth its weight in gold are the individual muscle trigger point treatments that Davies has compiled. His diagrams and step by step instructions help you locate which muscles are contributing to your pain, how to find the trigger point and treat it. It takes time and practice to master finding trigger points, but once you learn you have a tool and method to help relieve muscle pain throughout the body. Relieving trigger points in iliocostalis muscle have helped many people resolve upper body pain issues. This book is a must-have for anyone interested in finding the cause and treating muscle pain.