My friend bought a 7 yr old lovely ott that was over at the knee- his knees even shook at times. It never interfered with his gates or soundness and he went on to have a successful lower level eventing career. I wouldn't have bought him- but she was glad she did!
We had an old QH at my barn that had knees similar to that...only worse. He looked like he was walking on his tip toes.
That doesn't look like over at the knee to me. It looks like his knees are bowed out toward the front. When I think over at the knee, I think of a horse whose humerus is set slightly forward of its cannon bone at the knee joint. Posted via Mobile Device
That is over at the knee. If the horse is working sound I would not worry about it. Most horses over at the knee seem to adjust and do well as long as the leg doesn't buckle forward working.. such as on landing from a jump.
One of the best fox hunters I ever knew.. and I mean a horse that was ridden to hounds.. was a grey with non descript breeding that was as over at the knee as this picture. He never missed a landing or a jump... totally reliable and forward when you needed it.
I wish I could remember more about where I read about this. But the horses aren't born that way, it is a result of racing and something in their legs getting stretched or tore so the tendons pull the leg back because whatever normally keeps them straight is no longer doing so. And yes, it doesn't seem to give them trouble!
Maybe it was in Dr. Deb Bennet's conformation articles in Equus magazine?