Alternative arthritis medications

My rescue lab has severe arthritis in her spine and both back legs. When she came to me (end of nov 2012) she was taking metacam, glucosamine and cod liver oil supplements. Although being told she had severe arthritis I saw no sign of it and concluded the medication was working well. However over the xmas period she was unable to get off her bed and cried in pain when she did. The vet changed her medication to PLT (NSAIDs) and Tramadol (a morphine based painkiller). This seemed to do the trick and all was fine until she was sick one morning early feb (1st time she'd ever been sick whilst with me). She carried on being sick and the vet told me to stop her meds and feed her chicken and rice. I did this and for a while she was okay without the meds but after about 5/7 days she was in pain and crying so I reluctantly put her back on the PLT and Tramadol. This helped again but a week later she started to be sick again. I took her off the meds and for a week she was on a chicken only diet as advised by the vet to help her lose weight. She has now been off her meds for 13 days but over the last few days she has gradually got stiffer and more reluctant to get off her bed. Yesterday and day before once she was up and moving she was fine and vet said if she can eventually get up then we can keep her off the meds. But today she can't get up and when she tried earlier she was trembling and crying. I'm really reluctant to put her back on the meds because I think thats what was making her sick before. But I don't really know enough about her condition. Could this just be a 'bad day' or is she going to get progressively worse if I keep her off the medication? I don't want her to suffer but I don't want her to be sick again either. Are there any alternatives out there that won't upset her stomach,which has probably been damaged by the NSAIDs?