Glucosamine is the most commonly used supplement.There are others, chondroitin and msm to name a coulple.I have used glucosamine with good results.Dont expect overnight results,it could take a month or longer before you notice anything.
get some glucosamine, chondroitin, or some MSM. and dont forget the flax oil
it will take a while to notice the effects b/c the tendons are avascular which means they dont not recieve a direct flow of blood. the nutrients just seep to it. this is why it takes a Loooooong time for joints and tendons to heal. give the glucosamine and chondroitin time, i guarentee you will feel the difference