Labrador with a previous history of an elbow microfracture here. The elbow was noticeably stiff after rest, and she limped noticeably, especially the evening and next morning after a day's work. Vet's advice was painkillers (prescribed by them) on an ad-hoc basis. They also suggested a joint supplement, so I got Nutramax Cosequin DS plus MSM. Not cheap, but after the initial bedding in period she no longer limps. She has one a day, and has done for the last 20 months. Touching wood, she hasn't limped or appeared stiff for about 18 months. I also keep her weight low, she's about 26.5kg, which probably also helps, although she was always kept lean and fit.
Placebo effect? Yes of course. I sat the dog down and read her the list of ingredients, and the various bits of stuff you can get online telling you of the benefits of Glucosamine. She as much as told me that because I was spending the extra 30p a day on her that she would join in the deception and has promised not to limp, even if we do overdo it.