My potential new lease horse is lame on the left front leg, only obvious in trot. She’s moving great on the right, but obviously lame on the left rein. Owner said I just need to ride her in an outline, and it only masks lameness. She says horse has been like that for a year. So lameness is only obvious on the left front leg when she goes to the left. Do you have any experiences? Like where to look for a problem? No heat/swelling and has front shoes on. Mare is 14.