Several years ago I was helping my son with building a shop. This meant upand down on a ladder then down on my hands and knees. After two days of thismy knees were so sore I could hardly walk. I was listening to Shell Busey onthe radio and he talked how SierraSil made all the difference with his kneesand elbows. I was sceptical but bought some SierraSil ( in the purplebottles) and after two weeks the soreness in my knees was gone. I have beentaking SierraSil ever since and no knee or elbow issues. Works great.