I'll throw in my 2 cents on glucosamine and personal experience. I suffered a bad tibial plateau fracture 5 years ago requiring plates and screws and have suffered terrible knee pain and stiffness since that point. It got to be so bad that I had surgery to remove the hardware and it allowed the doc to explore my knee joint while I was under. It was determined that I also had developed soft cartilage and that not much could be done. I had increased stiffness in the knee with the injury along with random pinching and stabbing pains in the joint and started to feel similar sensations in the other knee (possible soft cartilage as well). This resulted in me walking with a slight limp and impaired my ability to do several activities.
So... a friend mentioned glucosamine and I took it for a month. Nothing. Nada. No relief. After about 6 months I decided to try a different brand that was recommended by someone else and was told to stick with it for at least 6 weeks. I took the recommended dosage and carried on with life as usual (limping, knee pain). After about the 4th week I realized I was walking along without the familiar pinching sensation I had grown accustomed to. I was also walking without a limp. I remained skeptical but kept taking it. The pain never came back in a similar intensity. My flexibility increased and the stiffness improved. Being the type of person I am, I decided to quit taking it for a while and see what happened. The pain returned after about a week. I immediately started taking glucosamine again and never looked back.
I'm aware of the studies regarding glucoasime and have talked it over extensively with doctors, trainers, and physical therapists and nobody had any conclusive data or opinions on it. I'm also fully aware it could be a placebo effect but am too big of a skeptic (and pessimistic as well) to really believe that. I've looked everywhere for simple answers but nothing changed during the time I've been taking it. Shoes, my weight (155 lbs consistent), daily activities, diet, and everything else remained constant. All I know is that my quality of life has improved and I'm not looking back.
I'm only posting this to share my personal experience and not generate a debate. As previously mentioned, there is no solid evidence to back up either side of the argument but In know what works for me. All I can say is at the age of 43 it feels pretty damn good to be riding again.