I thought taking her on a few nice walking trail rides would be good for her. We had to go down a relatively steep grade for about 50 feet to start the ride and she was fine other than she wanted to stop and turn around halfway down...but that's not really uncommon for her so I didn't think anything of it. Then we did a few very gentle little rises and then another 50 feet slight grade on uneven ground. All at the walk on a loose rein and she didn't have any problems. Then when we turned around after about 30 minutes she refused to go back down the last grade we had come up. She would either try to run down the hill or slam on the breaks, when I tried to collect her and ask her to move slowly down the hill she would paw, crow hop and do little bucking fits that were more to show her irritation than to actually dislodge me. We were out with a group and they were crowding her on the grade so I hopped off and walked her down the hill since I had remained on top and had her calmed down at a halt when I got off her. I didn't want her or I to get hurt because she was not fit enough to be able to act up on that kind of surface and not injure herself and I didn't want any innocent bystanders to get in the way. Anyway, I hand walked her down the hill with her trying to get ahead of me and charge down the hill or stopping and making me drag her along. I remounted when we were back on level-ish ground and we continued our ride until we came to an even more gradual grade. She got 4 or 5 steps down and lost her mind, she tried to jump up on a bank and was pawing at it, was trying to sidepass down the hill and would not stay straight and walk down it. She was flinging her feet everywhere and doing more of the mini-bucks as well as had her eyes rolling and everything. There were two horses in front of her and more behind her and she just lost her mind. Again, to preserve the other riders and my mare's health I got off and walked her down the grade and was going to walk her up the last grade and just walk her home but at that point she was gone mentally. She was charging around, would not match her walk to me and was just totally non-responsive unless I got in her face and made her back up. Needless to say it was a long, tiring walk home and I didn't want to end there but we both needed a break. I put her in the ring to cool out and went to get myself a drink and breather. Then I went out to do some in hand and lunging work. She was totally calm, came right up to me and did everything I asked when I worked her in the ring. Although at this point she was stiff and sore from all the flailing, flinging and bucking she had done earlier but not lame or unsound in any way. My question is that it's not enough that the vet will be able to do anything but tell me to bute her and stall rest her, which I don't think will work. As when she is pastured she is less stiff because she is moving, however I'm not totally convinced she wasn't just being a pissy mare (she was just coming out of heat) and didn't want to go down the hill and behave herself. Anyone have any similar experiences? Was it pain or behavioral? I'm baffled because this all happened on the way home and she was fine going up and down hills on the way out. I've never had a horse lose it so bad going home, although she did just want to run home regardless of how steep the grade was. I'm also in search of exercises to help strengthen those back legs and hips again very slowly so I don't overdo it, because she has never had this problem before. Any insights you might have would be appreciated. Thanks.