I used to get knots the size of golf balls first in the neck,then the traps and then the back. It was bad enough to bring me to my knees at times but then again I am only a man. It is caused during contraction of the muscles. If it is somewhat small then you need it stretched. Monthly massage helps the best. Work with a physical therapist, kinesiologist, accumpuncturist, etc., to get it worked out while still small and remember to do any stretches or excercises suggested often and forever or it could get bigger. It is possibly effects of radiation and there is blockage of either blood and/or current. A Chirpractor that uses ART releases the knot. It is similar to myofascial release, accupressure, trigger point release. If left alone calcium can build up with scar tissue and cause more complicated issues. It can be caused by scar tissue in the nerve casing that restricts electrical impulses.

Ed