Hi again,Thank you for your patience. There are a few things that could have happened to Hercules, and as you mentioned, we definitely have to consider whether he has overheated a little while he was playing outside. Given he wasn't putting weight on his hind leg, we also have to consider whether he has a musculoskeletal issue in this limb (such as a ligament problem for example - the cranial cruciate ligament). Hopefully he is putting weight on that back leg without an issue now, and hopefully he is settled, calm and relaxed. Definitely continue to keep a close eye
on Hercules now if you can, and in particular, please keep a close eye on his mucus membranes, capillary refill time and respiratory rate as follows:Mucus membranes - flip his lip and look at the color of his gums. They should maintain a nice salmon pink color. Get him to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.Respiratory Rate - if he is continuously panting throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet. Good on you for cooling him down. If you think he could still be hot, I would recommend checking his temperature. If you have a thermometer you are willing to keep for him, you could do this now via a rectal temperature check. There are details of how to do this online here: http://www.pedigree.com/all-things-dog/article-library/how-to-take-your-dog-s-temperature.aspx . A temperature of 100.5° to 102°F degrees is normal and if he is more than 102, then you are best to get him checked by your local ER vet tonight. I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!Kind Regards,Dr EPS: If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. E..." or "Pet-doc..." and others will leave the questions for me.