what exactly causes "over at the knee"

[paintjumper]

and does it REALLY matter to performance? A friend just rescued a 4 y/o QH gelding recently off the track. In the videos he moves perfectly sound so she agreed to take him, when he arrived he is over at the knee, both knees but worse on the right. He is sound, yet the knees are more noticeable after he gets a little tired and is standing. I told her about a horse I was familiar with many years ago that was WAY over at the knees and he was super fast and sound well into his 20's and probably until he died, so she feels better, but I did not have the actual reason for the conformation problem.

[Androcles]

It depends.

Meaning, it can be conformational or can be caused by heel pain from poor trimming, causing the horse to 'buckle over' at the knee to avoid the pain. Eventually the knee joint can become adapted to this position. The younger the horse the more likely it can be corrected if it is from bad trimming (less adaptation to correct). OTOH the fact the he already gets tired from standing would be cause for concern IMO. If it does become more or less 'set' a perfect, balanced trim is that much more essential because there is less room for error. I'm thinking of a horse I know with one knee 'over' who was trimmed badly by two less than knowledgeable people and became lame on that leg after the two trims, and was pretty much sound again after two expert trims. Presumably the added stress from the poorly balanced foot on the already wonky joint caused enough stress to cause the lameness. So in other words, it's not just something you live with but an 'issue' that requires being aware of and good farrier/vet care throughout the horse's life.

[Amwrider]

I think scar tissue on a check ligament can also cause this. I have an Amish rescue horse that we think has this problem.

[JetsBuddy]

Our gaming horse is over at the knee. He is a Mexican Mustang that was used hard in his former lives. He's got a line of white dots down his spine to his tail which we think was from pack saddles. That horse is the most broke, most responsive horse I have ever ridden and is super smooth to ride. He had horrible feet before we got him and had had therapeutic bar shoes at one point. The farrier was trying to overcompensate for the knees by leaving his heels really high. I am very diligent about trimming him no later than every 3 weeks. He's got great feet now and they are super hard. When we got him the vet thought that his legs may straighten some in time as the ligaments stretched but he's 18 so he'll always have some bow to his legs.

[paintjumper]

I never thought about the feet being the problem, I'll tell her to keep a close check on that.