I'm also a big believer in just putting your hands on your horse - feeling legs and feet, one at a time and compared to another leg, and knowing where all the little existing lumps and irregularities are so you know when there's a new one, and also doing a little massage to check for tension or soreness. Some horses initially like this more than others, but most of them get so they appreciate it, and many will get so they "ask" for specific areas that they want to be rubbed or massaged.
All that said, Noble wasn't quite right this morning. One of the most important things I do when I feed the horses and turn them out in the morning is watch them, and notice when anything isn't normal for each horse. Each horse has its own routine and practices during feeding and as I turn out, and often the first clue that something is wrong is when a horse does something a little bit differently. In the case of Noble, he started eating from the residue in his hay bag before I offered him new hay. This meant he didn't turn towards the door, as he usually does, but kept his butt towards me. Then, when I gave grain about ten minutes later, although he nickered while I was feeding - he's usually quite vocal - he was very slow to turn from his hay to come to his feed bin.
When I took him outside, he was slow moving - he's usually pretty forward. I stood him outside and scraped off yesterday's mud and picked his feet. He was fine with that, and picked up his feet normally - he's usually stiff behind, which isn't surprising considering that he's about to turn 29. The PM feeders yesterday (I couldn't come to the barn yesterday PM because I was elsewhere) had reported that he seemed a little sore on his right front - which could have been because he was banging on the gate with his foot when he wanted in, or because the mud was slippery. Since, when I asked, they also said that they had picked his feet (in case of rocks) and that he was weighting all four feet, as well as eating normally, I wasn't too worried. But when I looked this morning, both front legs and feet were normal - his right knee is permanently larger due to an earlier injury but it doesn't bother him.
I'm sort of beginning to think back or hind end - he's somewhat arthritic behind - mostly hocks - and has had some difficulty lately in getting up after rolling on his left side, due to soreness/weakness in his left hind. Nothing was obvious as I ran my hands over him, so we went to the pasture and I let him loose. He didn't move far from the gate, and started doing little paws and head bobs, which are signs for him that something was bothering him. He was also looking around to the left, but it didn't look to me like he was colicing - he seemed to be looking at his hindquarters, not his belly. If it was a soreness issue, I wanted to give him a little bute to see if that would help, but didn't want to do that if it were digestive (horses that are colicing will often paw or indicate pain in other ways). I went back inside and checked his stall - I do this for all the stalls after I turn out - he had eaten his hay and grain, and the poop and pee amounts and distribution in the stall were normal for him and there was no sign that he had been agitated - no signs of unusual movement or pawing. So I got the bute and took it to the dry lot and gave him 1 gram to see if it would make a difference. I went inside and kept making up feed and doing my regular barn chores.
I checked on him again about 15 minutes later. He was standing quietly in the sun, which he sometimes does after turn out when it's warmer. He had also moved away from the gate. His stance wasn't quite normal for him, though - he usually stands very square, with his four legs at the corners. He was standing square in front, but had his hind legs under him a ways with the left hind farther forward. But he wasn't pawing or head-bobbing, so the bute seems to have helped. So I went out to him to do some more feeling around, and give him a bit of a massage.
I started at his poll, and the muscles in his forehead over his eyes, applying pressure to see if there was tension, and massaging a bit and then releasing - he was loose and unhaltered for this, because I wanted him to be able to move if he needed to or had something to tell me. His poll was tight, but as I massaged he lowered his head and licked and chewed - so that felt good. Then I worked my way down his neck and back, pressing and massaging on both sides. I think he was a little sore in the sacral area, and when I "bounced" his hips, the left one wasn't moving very much in comparison to the right. I'm really thinking sacrum/left hind now (which would also explain the perceived soreness on the right front). I carefully felt both hind legs, including stifles, all the way to the ground, but didn't find much.
I also, as a test, took his face in one hand and put my other hand on his side and asked him to rotate in place, in both directions. He was able to turn to the left fairly well, but was reluctant and had trouble moving his hindquarters when we turned to the right - he did a little side-step instead of crossing over behind and avoided moving the left hind any more than he had to.
I'm guessing at this point that he wrenched something, but as he seemed to be more comfortable, I left him, after a bit more massaging of head, neck and shoulders. I'll check on him later.