Horses did not evolve specifically to carry weights on their backs, and modern competition places even more strain upon their skeletal structure.
Musculoskeletal problems may be caused by an accident or a single event (acute injury) or by a problem that has been present and worsened over time (chronic injury).
Acute injuries include:
Trips, falls or slips
Chronic injuries may be caused by:
Overwork or repetitive work
Getting cast in the stable
Common signs of back pain include:
Resistances: bucking, rearing, napping or bolting
Unlevelness, particularly behind
Reduced quality of paces, inability to extend / collect the stride
Temperamental changes, such as loss of interest in work, lethargy, or grumpiness
Inability to stand square
Refusal to jump, running out, or rushing jumps
Hollowing of the back and inability or refusal to work on the bit
Uneven shoe wear caused by toe dragging or scuffing
Most horses will benefit from a maintenance check every 6-8 months and for performance horses, treatment is recommended at the beginning and end of a competition season (see my MOT Clinics). Mares will also benefit from treatment after foaling, as this can affect the pelvis.