Always feel free to introduce yourself to your instructor and describe any injuries you might have. He or she will then be able to advise you as to how to “work around” your problem area to avoid further injury. The instructor may also be able to suggest particular exercises that might help to bring increased mobility and healing to your injuries. In any event, listen to your body’s feedback. If anything you do in yoga feels painful or uncomfortable, you should “back off”. Your instructor will most likely be able to recommend an appropriate alternative pose for you during the class.