Myalgia, defined as any pain perceived in muscle, is very common in the general population and a frequent cause for referral to neurologists, rheumatologists and internists in general. It is however only rarely due to primary muscle disease and often referred from ligaments, joints, bones, the peripheral and central nervous system. A muscle biopsy should only be performed if this is likely to be diagnostically useful. At present no 'guidelines' exist.
European Journal of Neurology : the Official Journal of the European Federation of Neurological Societies, 2013, Vol 20, Issue 7, p. 997-1005