Complex sentence: As the horse and rider passed the unfortunate recipient of the thrust, the sword would be very difficult to drag clear of the body, leaving the the rider at best disarmed or at worst unhorsed or with a broken wrist.
Split into simpler sentences: As the horse passed the unfortunate recipient of the thrust, the sword would be very difficult to drag clear of the body. This could leave the rider at best disarmed or at worse unhorsed or with a broken wrist.