Obviously, I can not say what the cause is .. but if you have tried EFT and there is absolutely no change, then we could assume that this is not an emotional imbalance.
Here are things to try (from my own experience they helped a LOT)
1. Cod Liver Oil - really helps any type of inflammation in a dog. Not sure the size of your dog, but when one of mine bruised his leg, I gave him a teaspoon each day and he is 20lbs in weight. The inflammation died down very quickly and that was all that was needed.
2. I used a Canine Osteopath after a horrific incident at the groomers. He must have really been under stress because when I got him home, he was all lop sided and his tail did not hang straight. (I no longer send my dogs to groomers but my partner and I have learnt to do it all ourselves). The Canine Osteo was amazing. Within 30 minutes with gentle massage, it was all corrected. He said the problem was similar to sciatica. We only needed the one session (cost me £40 = approx $65)
3. This is not something I use, but I saw it on iherb and recommended it to a few dog owners I've met as the ingredients are fantastic for joints and inflamatory issues and these have helped their dogs regain more mobilty. It's called: 'Sea Mobility' by Ark Naturals. There are 2 flavours in this brand that I would recommend (Venison jerky and the Lamb jerky) - the other ones have ingredients I wouldn't recommend.
You can use the discount code "MAY985" to get $5 off your first order from iherb.
Lamb jerky: http://www.iherb.com/Ark-Naturals-Sea-Mobility-Lamb-Jerky-Approx-22-ct-9-oz-2...
Venison jerky: http://www.iherb.com/Ark-Naturals-Sea-Mobility-Venison-Jerky-Approx-22-CT-9-o...
4. You can also try a 1 part apple cider vinegar 2 parts water spray on his legs and let air dry - that can also help ease pain/inflammation - and/or 3% h2O2 spray.
If you are absolutely sure there are no broken bones or something that would require immediate attention, then please try the above.
Hopefully others will have further suggestions.
Best wishes, I hope you find your solution soon.