hind leg lameness??

[natwood7]

Confused so any help appreciated! My horse has looked short on one of his hind legs for the last month or so. He does not look at all 'lame' in trot or canter just a shortened stride in walk. We have been successfully competing in be classes. I had the physiotherapist out to have a look and she said there was significant trauma to that side of his back and treated it. She is coming back to see him again this week to see if pain returns after he has been worked again. (by the way he had

 

[natwood7]

*****continued from above thread as computer playing up!!

(He had routine physio in march with only minor tension) As he is early teens my first thougt was that he may have bone spavin but would this have just appeared in the last 6 weeks? Also I assume he would look lame in trot/canter too. He has also been fine through the very cold winter and would have expected arthritic changes to show in colder weather not now it is warmer?? Don't know if i am worrying uneccessarily but it is definately noticable, however, dont want to put him through lots of vet exams if it is just soft tissue damage. Will see what physio finds this week. Just wondered if anyone has experienced similar symptoms??
Thanks.