Has your student seen her doctor? What was the recommendation?
Any word that ends in "itis" means that a chronic inflammation response is occurring in that area: bursitis means inflammation in the bursa, in this case around the knee. Doctors will often recommend icing down the area, or will prescribe anti-inflammatories, which can cause problems if used constantly. I have written many times about another approach that is quite effective in dealing with chronic inflammation:
earthing. You may want to point your student to the web site
www.Earthing.com. She may really benefit from their simple bands or patches.
Regarding how she can do lunges or Dragons given her condition: if all the variations are painful, don't let her do them. Don't let her do any poses that makes the area painful or worse. Instead, remember why you want to do those postures in the first place, and find a different way to stress your targeted area. One option to offer instead of lunges/Dragon is Half-Happy Baby, which is basically a lunge turned upside down. If the targeted area is the quads, try Half-Saddle or Reclining Windshield Wipers. Can she do Pigeon or Swan? That may be an other option. Have you tried the variety of propping options to avoid pain in the knee in these poses? (See the video on
Using props in a Yin Yoga practice for ideas.)
With a
functional approach to your teaching, I am sure you will find ways to give your student the benefits of the lunges without aggravating her bursitis.
Cheers
Bernie