Hello, so my 16 year old horse has been standing with his back legs streched out, usually after bieng worked. It has been almost a year since his hocks have been injected, about a month away. Which I am making an appointment for around that time of course to see if he needs it done again. Last year before I got him injected for the first time he was having gate issues, at this time I have not had gate issues and he still seems to be running normal like he did when he first got his hocks injected (I did have issues a few months after but I got the angle of his feet changed and after that he has been golden) so I am not sure if I should make an appointment sooner than a month? I have a show tomorrow I am going to so of course if he acts different I will make the appointment sooner but if he does just fine should I still wait until next month instead like I planned? TIA. 

Probably hocks. Or if they hurt enough that he's been compensating then it could be his back. Or stifles. Once the hocks are sore everything gets thrown out of whack. Most injections only last 6-8 months at most, so I would suggest doing it more often. 

Oh okay, when we went back after my vet advised he could wait a year so that's why I waited. Thank you!

Always go with what your horse says, not the vet. My horse needs trims every 4 weeks, not six like both vet and farrier recommend, although now the farrier agrees with 4. He can go longer than a year on his teeth floats, unless he tells me otherwise. Now that he is on a forage only diet he can go over a year, but if tells me otherwise I'll do it more often. 
The vet can't feel the horse's pain, just like the doctor can't feel ours. Nothing is ever set in stone. 

Could be front foot pain also.