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