8month old male puppy

Question
Please could you help me. We have a 8 month old black labrador puppy who on two seperate occasions over the last month has hurt his back leg. On the first occasion he was scrathing his neck early one morning and without warning began whimpering / screaming and would not lower his rear leg to the floor instead favouring to keep it tucked up in his undercarrage. The second time this happened he was in the middle of a walk and again the same happened. On both occasions the whimpering and holding up of his leg in his under carrage only last for a few minutes and after this he will limp for about half an hour before returning to his normal self. My wife has best described it as having a muscle cramp (in humans). Is it possible for puppies to get muscle cramps and have you had this in any of your puppies over the years. if so is there any dietary changes we need to make or is this just part of his growth.

Answer
You really need to talk to the vet about this.  As for diet, if you are feeding a puppy chow, switch to adult.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them.  Each dog is different.  Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx  The slower growth and lower weight means less stress on developing joints.  

They do seem to hurt themselves sometimes.  As long as it goes away by the next day, I wouldn't worry too much.