We have a BC/Sheltie cross we adopted at 1 year old within a couple months she blew out her left knee playing with a ball on the lawn. What can you do, $900 later she was good as new. Wife started her in Flyball and a year later she blew out the other knee playing with a ball in the driveway. Well another Grand and she was as good as new, again. She went on to have an 11 year career as a Flyball dog earning her "Iron Dog" award among many other honors. She is now 14 and still runs in practice to help train young upcoming dogs and handlers, granted not as fast as she once was but the attitude is still strong.
No sign of joint problems in hips or knees, some arthritis in her spine and front legs but is still very active but in shorter intervals.
From our experience the surgery works very well.
Good luck with your puppy.
Tinbender