In the guidelines of your ICD-10 book under chapter 13 there is a paragraph labeled Site and Laterality. It states "Most of the codes within Chapter 13 have site and laterality designations. The site represents the bone, joint or the muscle involved. For some conditions where more than one bone, joint or muscle is usually involved, such as osteoarthritis, there is a "multiple sites" code available. For categories where no multiple site code is provided and more than one bone, joint or muscle in involved, multipel codes should be used to indicate the different sites involved.
The code for multiple sites is M15.3, if that does not fit I would code each site individually. I hope this helps, have a great day.
Angela Pommarane, CPC