Dog with luxating patellas in both knees

I have a 15 year old Shi tzu. Shes about 11 pounds. I've only had her for 7 years. She has always seemed to be deformed like her back legs are longer then the front. Then 4 years ago I was bathing her in the bath tub and when I was getting her out a disk in her back burst and she couldnt really walk with out her back end falling over. So when I took her to the vet they did ex-rays and saw the blown disk and had me put her on steriods and keep her still for 4 months of not walking up steps or anyting. after 4 months she healed they said the fluied went back in her disk. Well I've always noticed that her knees were weird but never knew what it was. so, in the past year I've noticed that something was really wrong. and When I took her to the vet he confirmed that she had luxating patellas in both her knees her right is worse then her left. And that they go out of joint really easily. This has helped made her very in active. She tries to go on walks but she hops like a rabbit with her back end or lift up her right leg when she walks for longer then a couple mins. I've been giving her springtime joint chews and fresh factors. Is there any remedies I can give her that might tighten her ligaments??

Thanks,
April