As a vet, I have anatomy books with drawings/pictures of ruminant stifle (knee) joints that I can scan and send you if you think that will help. Email me if you are interested. Also, you can research the weight of an adult elk at several places including the Colorado Division of Wildlife. Go into their NDIS site. A rule of thumb is that 60-65% of an animal's weight is supported by the front legs (35-40 by the rear legs).

For a real one, check with private elk ranches.