Factual error: Before Cameron goes surfing the girls mention that there's a hurricane off the coast causing good waves. There are no hurricanes in the Pacific Ocean, only typhoons.
Continuity mistake: When Madison and the Angels are fighting on the rooftop, Madison throws Natalie (which you can tell is a stunt double) through some glass and the glass breaks. But when Natalie stands up the glass is still intact.
Continuity mistake: At the end of the movie, in the scene where Madison is flying through the air, when she lands she is wearing stiletto heels. However, when she runs up the back of the car to jump in it she is wearing flat shoes, almost like black tennis shoes.
Continuity mistake: When Dylan leaves the Angels, she returns the stuff that she has borrowed throughout the years. This includes a letter. Look carefully at the position of the writing on the letter. When Natalie and Alex find the box just after, the writing is upside down.
Continuity mistake: When the bombs go off on top of the rooftop, Madison's telescope has disappeared.
Other mistake: In the scene where Bosley is driving the truck into the O'Grady's workyard he is stopped by a man who asks him for I.D. The man says that he has never seen a black Irishman before, but he says this in a Scottish accent. Surely working for an Irish gang he should be Irish?
Revealing mistake: When Natalie is thrown into the rooftop frame by Madison, Cameron Diaz's stunt double is visible.
Answer: It is making fun of the show CSI. Even still, there are ways of telling if someone had a knee problem by the way they walk and put pressure on the foot. Being able to tell if it was a torn tendon, I don't think so. Check out the way people run and you can tell if they have hurt something in the past because of which leg they favor.