Circulation, aka constipation or the lack of it is always the cause of all pains in the body.
The pain is always 100% created in the mind. Matter, such as the knee, the foot, etc. blood/skin/bones, etc. all are matter, matter feels NOTHING, it can not, only the brain creates what we know as pains, it creates what we call love/hate.
The breaking of the laws creates the constipated body and the Mind being the caretaker of the body creates pains to punish the sin of wrongful eating, wrongful diet.