Releases from liability are usually accompanied by warnings about how a person can become injured when on or near a horse. These warnings are just as important as the release from liability and in some states–where releases from liability are invalid or at best shaky–they are more important.
First, the release from liability can operate only as to risks that are in some sense known by the person signing the release. The warnings prove that the person signing the release was aware of those risks because they were explained in black and white.
Second, even if releases from liability are invalid in your state in some or all situations, if you can prove the rider was informed of typical horse hazards and chose nevertheless to ride at your stable, you can sometimes show that the rider by his or her own conduct has assumed the risk of such an accident occurring.
Third, those warnings may become important in assessing to what extent, if any, the injured person was in part at fault in the accident. If a riding hazard is explained in a warning and the rider nevertheless engaged in the warned-against conduct, then a good case can be made that he was at fault in the accident. In many states, if the injured person was more at fault than the stables, the stables wins.
Fourth, even if the judge or jury concludes that the stable was more at fault than the rider, the amount of the money awarded as damages is reduced in accordance with the assessment of fault. Thus, if the damages were assessed at $100,000 and the judge or jury found that the rider had 40% of the fault and the stables 60%, the stables and/or insurer would be required to pay $60,000 instead of $100,000.