Many times they can see arthritic changes on the Xray. I have had PT a number of times, for a herniated disc, post-tibial tendon dysfunction(foot and ankle PT), thumb joint replacement(!), whiplash, and a badly sprained knee. In each and every case, PT has restored my to full function or nearly full function. It works if you work it. They will show you exercises and probably will see you twice a week. At the first visit they will probably take measurements to see how much flexibility you have and if there is swelling or a difference in strength. Then the fun begins. They will give you exercises to do at home and if you do them you ought to progress fairly steadily. Every few weeks they will repeat their measurements to see if you're improving.
I say go for it. You have nothing to lose by trying it.