You don't know this horse!! He has well and truly learned that if he limps he gets out of work - on more than one occasion I have gone and got him out of the paddock, he has been three-legged lame, and I've therefore checked him all over [no signs of anything] and chucked him back in the paddock, only to watch him "miraculously" become sound and start bolting around like an idiot with no sign of any pain. He is 17, and a teeny bit arthritic in his hind end [we think, based on the fact that giving him Pentosan peps him up and helps him use himself better], but invariably when he is faking it he goes "lame" in the front end, not the hind which he is genuinely arthritic in, AND when he's faking it he will occasionally switch legs, so I know that when he's lame consistently on the same leg he is actually genuinely hurting and not trying to get out of work. I have learned not to trust him on matters of ouchy in the front end because of this - if I can see something, sure, he's lame, but if not, I call his bluff, and invariably he "miraculously comes good" within 30 seconds.
He is genuinely lame at the moment after getting himself kicked... so he's off work... there have been three times in the time I have had him that front end lameness has been real, this time after the kick being one of them... another being because he injured himself in the transport truck on his way to me... and the third being the time he nearly ripped a heel bulb off being an idiot in the pasture.
He gets a bit stiff in the hind end/loins at times and I can't let heavier riders on him because he will walk like he's 30 the next day so I would think it was his hind causing leg yield to be so difficult, if he wasn't so good at everything else I know how to ask for! As mentioned in a previous post he can be hard to get and keep together and working from behind but one look at his conformation will tell you that's not something that would come naturally to him anyway - he has a VERY long back and loin, and less than ideal hindquarters!