I worked with Cookie during the last 4 years of her life.  Cookie was an off-the track standardbred mare.  Like many retired racehorses, Cookie had tight stifles and asymmetry between her left and right sides.  Cookie had four foals after she was done racing.  While she was still able to be ridden, her stifle sensitivity increased with each pregnancy.  Cookie had a series of medical problems in her senior years that made her unsound for riding.  It was difficult for Cookie to maintain her weight and muscle tone.  As Cookie transitioned between different homes and horse rescue she developed an aggressive personality.  She took over-the-counter calming supplements to temper her moods.