Hi, my Greyhound walks around 4 miles a day during the week, probably nearer 7miles at the weekend ( quite a lot for a couch potato), she loves her walks but for the past 2 Sundays she's become lame on her left back leg and left front leg, she lays down for around 10 mins and then gets up and starts bouncing around again, I have a vet appointment for her later in the week but wanted to know if anyone has any idea what is wrong with her (she's a retired, rescued racer, 8 yrs old). Thanks.