No, stenosis is the narrowing of the space for the spinal cord and wouldn't be affected by those supplements. However, it'd be great to give them to support all the other joints... hips, knees, etc. When my oldster had trouble standing/walking last Nov., my vet recommended a trial of Pred to see if there was an inflammatory process in her back which could be calmed down. She was on 5 to 10 mg. for about 3 weeks, tapered off and has been doing great since!
Dr. Stack's article indicated that none of that stuff would work for LS. Helps for arthritis, so if your guy has that too, just keep using it.
Good Luck.