The horse's face reports pain before his body does
A horse is a prey animal, and hiding pain is written into him, which is why the earliest signs are small, quiet and mostly facial. Learn to read the ears first: ears held stiffly back, turned out sideways, or moving asymmetrically when the horse is at rest suggest discomfort rather than mood, especially when they stay that way. Around the eyes, look for tightening of the skin so the eye takes on a worried, triangular shape, a visible tension and slight bulge above the eye, and a stare that is fixed rather than soft and blinking. The chewing muscles along the jaw stand out as if clenched. At the muzzle, a painful horse shows flared or pinched nostrils at rest, lips pressed and strained, and a chin that looks tight and pronounced instead of loose.
Behaviour changes that back up the face
The face is corroborated by what the horse stops doing and starts doing. Early pain commonly takes appetite first: hay left half-eaten by a horse who usually cleans up, or feed approached and then abandoned. Social behaviour shifts too: the horse who always greets you stands at the back of the stable, the herd animal drifts to the edge of the group, grooming and mutual scratching fall away, and restlessness or its opposite, an unusual dull stillness, replaces his normal pattern. Under saddle the same horse may be reluctant to go forward, resistant on one rein, or simply lacklustre in work he knows well.
Build a baseline so early means early
Every one of these signs is only readable against your own horse's normal. Spend a week deliberately learning his relaxed face at rest: how his ears sit when he dozes, how soft his eye is after turnout, how loose his muzzle hangs, how he stands, eats and greets on an ordinary good day. Then the deviations become measurable rather than arguable: ears back at a time he is usually soft, a muzzle strained through a whole morning, hay unfinished three feeds running. Record what you see and when, because patterns across days distinguish a passing mood from a developing problem.
What to do the day you spot the pattern
When the signs stack up, slow down and look the horse over before deciding anything. Check him standing square: is he shifting weight off one leg, resting a leg he does not usually rest, sweating without work, or breathing fast at rest? Run your hands over his back, legs and belly for heat, swelling or flinching, and take his temperature if you are equipped and he is settled enough. Rest him rather than working through it, and do not give leftover medicines from another occasion; masking pain destroys information and some products are dangerous for particular causes. Call the vet and describe the facial signs, the behaviour changes, and how long they have run. The more specific the description, the better the triage.
Pain signs that mean the vet now, not later
Some presentations skip the queue entirely. A horse who is rolling repeatedly, getting up and down, pawing and sweating, looking at his flanks and not passing droppings is showing the classic picture of severe gut pain and is an emergency call, not a watch-and-wait. A leg held off the ground with heat and a bounding pulse in the foot, sudden severe lameness, a horse who will not bear weight, laboured breathing at rest, or one who is down and reluctant to rise also need the vet immediately. For the slower patterns, the dated observations you file in KinsLe's Pet Passport, alongside farrier, dental and vet records, turn your early spotting into a history that speeds up every decision that follows.