I like Laura Dedering's comprehensive Lab diagrams at the link below:
http://www.cygnet-labs.com/folklaur/LabDiagrams.htm
See the Lab diagrams, the ones from Great Britain in particular.

According to the diagrams mentioned above, over angulation "may incline to cow or sickle hocks, produces poor hind action". Thank you Charlotte K. for posting this. I didn't know over angulation was the cause of cow hocks.

You are welcome. I do not think that overangulation always is the cause of cow hocks. It is often a LONG rear pastern or even just weak "couch potato" muscling that contributes to the the cow hocks. A dog with perfect angulation when crouching to spring for bait can also look cow hocked, temporarily. A cow hocked adolescent or bitch who has just weaned a litter can muscle up and have perfect angulation, even from the rear. True sickle hocks lack the working power of a springy cow hock in muscled haunches--the cow hocks can extend if not sickle hocks, too. Think how when you ride you can collect the horse with reins to put the weight on the rear of the horse to enhance the drive--kind of like a Cavalry horse maneuver. You can do it in a dog with a leash, to shift the weight back. It keeps the dog from pulling (young male dog!) and enhances the picture of the dog. I am not sure that my words are conveying what I'd like to say. No, I haven't bred a perfect rear--yet.