Pete I have been getting the shots in my knee for 3 or 4 years. They worked really well up until last April. All of the sudden my knee was really hurting at certain times. I had surgery to clean it out. There were a couple of bone chunks floating around (1cm x 2 cm) and the inside of my knee looked like moon craters. He cleaned it out and buffed it. I was good for 6 months now it is acting up again. The shots were certainly beneficial. Mine worked for 6 months per shot. Definately worth trying them.