Eddie Dupris claims that a knockout is caused when the neck turns a certain degree after which the human body takes over and shuts itself down for safety reasons. While generally unknown, it is widely believed that a knockout is actually caused by the rattling of the brain against the skull causing severe trauma resulting in a concussion.
When Eddie is reading a magazine, while on his bed, Frankie enters the Gym with a hamburger. Eddie throws the magazine on the bed to see who has entered. The magazine is seen on the pillow, wide open. The magazine is next seen closed and almost out of sight.
The first scene with Father Horvak is an overhead shot of him leaving the church talking with a parishioner. The parishioner has a bag in her right hand. The next shot switches to a head-on shot of them a second later but the parishioner has the bag in her left hand, too fast for her to have switched hands between the two shots.
When Maggie is taking her mother to the new home she just bought her, there are palm trees around the other houses in the neighborhood. This scene is supposed to be in a small town in Missouri, where palm trees do not grow.
When Frankie & Maggie leave Maggie's hometown of Theodosia, MO, they pass a road sign with "160" inside a Missouri outline, the correct sign for Missouri State Highway 160. However, the main highway through real-life Theodosia (in far southern Missouri, just north of the Arkansas border and east of Branson) is U.S. Highway 160.
Patients who are mentally competent and have the ability to communicate, have the right to refuse treatment, AKA "pull the plug". The entire late movie plot involving Maggie talking Frankie into performing euthanasia shows a complete lack of understanding of patient's rights. Maggie merely needed to tell her doctors to stop all life prolonging treatment.
Bedsores and infections leading to amputations are signs of poor medical care. If Frankie is so concerned with Maggie's care why he would have left in a situation where these preventable injuries could occur is never explained.
When Maggie is laid out on the mat after her neck injury, a doctor shines a penlight in her eye 5-6 times. The doctor is checking for pupillary reaction, but this would only take one, or at the maximum two, wrist flicks. The movie doctor does it repeatedly throughout the entire shot, not stopping until the scene cuts.
When Frankie is training Willy in the ring, Maggie walks in to begin training. She is carrying a new, expensive Ogio gym bag even though she's supposed to be so poor she has to scrape change together to buy a speed bag.
Death adrenaline overdose would have been agonizing and probably the worst way for a quadriplegic to die. If Frankie had performed ANY research prior to give the overdose shot, it's almost certain that he would have NOT done it.
Quadriplegics can and have lived for decades following their injury. This means that they will require expensive medical care for years to come. Why Maggie's family and their attorney would have thought there would be any money left over for them isn't clear as the hospital would have detailed the care that she required to them in advance.
The goof items below may give away important plot points.
When Frankie removes Maggie's ventilator to administer a lethal dose of adrenaline, she is clearly breathing on her own. Earlier in the movie, Eddie's voice-over noted that Maggie will never be able to breathe on her own again.
Sucker punching someone in boxing is a serious offense and will often result in a suspension of the offender. If it resulted in an injury like one suffered by Maggie, it would result in the arrest of the fouling fighter, the likely permanent revocation of their boxing license and a very hefty lawsuit against that fighter. SInce money to care of Maggie is a major portion of the film's narrative, it's surprising that very short shrift is giving to would obviously be a major concern: The offending fighter being punished for her actions.