[SquishyHelium]

I have an elderly Syrian (Domino) who I adopted a little over a year ago. He is at least two years old though could be considerably older than this.

Perhaps about 2 months or so ago he gradually developed a slight weakness in his rear end. When he is standing, his back legs don't hold him up as high as they used to and at times his rear end touches the ground. Additionally he can no longer lift his back legs to itch his ears, he ends up just scratching mid air or scratching the ground. Sometimes he'll topple sideways because he's trying so hard to reach. At times I think his back legs are stiff and don't always do what he wants them to do.

He is still extremely bright and alert and always keen to come out and play.
What I am wondering is, what could be the cause (I think it is perhaps arthritis or stiffening of the joints due to age) and if there is anything I can do to improve his range of movement and make things easier for him? Suggestions appreciated.