Locking stifles and being cow hocked are two different issues. But both can be caused and resolved by one thing..... GROWTH.
Both conditions can be caused by either genetics OR growth issues. Each needs to addressed seperately.
Locking stifles, if genetic, can be resolved with a simple surgical procedure BUT the horse should NEVER be used for breeding. PERIOD. The horse can go on to lead a great life as cart/performance horse or a pet.
Sometimes a stifle problem can be a result of an enormous growth spurt. If it happens it's usually in their yearling year and very short lived. With proper nutrition and excersize the horse works it out and it never occurs again.
Cow-hocks can also be genetic. And again, if so, the horse should NOT be used for breeding. The problem can be corrected -- but only to a point -- with farrier work. A genetically cow-hocked horse is often used very well in driving cart and other performance activities.
Cow-hocks in a weanling AND in a very refined yearling can also be a nutrional and/or a weight issue. Once the young horse builds muscle and/or is given good groceries, the legs straighten on their own.....with or without corrective farrier work.....(occasionally corrective trimming can be detrimental in these cases.)
MA