I have had a few clients over the age of 80, one even 99 years old. I have needled them for back pain, hip pain and neck pain with vague radicular symptoms as well. They were all thin with limited muscle mass. I had really good success with needles that were slightly shorter than I would have anticipated needing to reach the bony landmark below. I did not notice any increase in tendency to bruise, and they generally had minimal muscle soreness after.