Lester Wood alleges that the actor gave his permission for a trail to be used for horse riding on his estate in the Pacific Palisades area of California, but blames its poor design for a sprinkler system going off, alarming Wood's animal and causing him a number of injuries.
The 70-year-old was left in a critical condition in hospital, according to TMZ.
Wood told the local weekly Palisadian-Post that he suffered concussion and a shattered pelvis, in addition to internal bleeding and damage to both his liver and bladder.
He has also claimed that the accident left him with broken ribs, fractures to his shoulder blade and lower back and a torn meniscus in his knee.
Wood was not wearing a helmet and said that he was looking at his watch when the incident happened, but he has complained that his treatment cost him $500,000 (£308,199) in medical bills during the two months he was in hospital.
What to Expect When You're Expecting star Quaid no longer owns the property in question, and has yet to comment on the lawsuit.