I highly recommend Dr. Beale at Gulf Coast Veterinary Specialists in Houston. Their website is:
www.gcvs.com I have heard that Dr. Whitney is also great with knees.
Their surgeons are Board Certified and Dr. Beale has operated on two of my fosters. One was a complicated case with his legs and one knee. Both pups have done very well. If you would like more detailed information, feel free to PM me!
They also have a terrific physical therapy department!