Okay, I'm not sure if this should be in health, but I'll put it here. I'm taking care of my neighbors dog, a yellow lab, female, about 3-4 years old. she loves to play fetch so I hit the ball for her. but for some reason, after playing for about 10 minutes, she'll start limping. Yesterday, she was making these weird crying/ yelping noises. She collapsed right on her face and couldn't get up. It was like she had no control over her back legs. Three to seven minutes later, she gets right up and bounds around like nothing happened. This is the third time this has happened. I'm going to talk to my neighbors about it. What do you think I should say? What do you think this is?