Continuity mistake: After the fight with Seamus O'Grady, the Angels burst through the roof. Drew Barrymore grabs a short piece of wood to slide down the rope with. When she slides down the rope, the wood is longer. When they land, the wood is even longer. (00:56:35)
Factual error: When Lucy L. is using the gas pipe as a flamethrower, it is suddenly turned off afterward. This could be because of one of the other characters turning the handle, but if they turned it off in that way (or any way), the flame would go inside the tube and make the tank blow up. (00:58:40)
Continuity mistake: When Natalie jumps into the boat she is wearing flat heeled shoes, but in the earlier fire scene she is wearing black stiletto boots. (This is visible in zoom and slo-mo.) (00:58:55)
Continuity mistake: When the Angels find the photos on Emmet's body at the coal bowl, the picture of Helen Zaas shows her holding her Lucky lighter. If you look closely, you can see that it is completely different to the Lucky lighter which Dylan carries. The stars part of the 'Stars and Stripes' design cover the whole lid on Dylan's lighter, but on Helen Zaas's lighter it only covers half of the lid. (00:59:50)
Continuity mistake: When Nat has the record in her hand from all the stuff Dylan left, in the next shot, she is holding a picture of the Angels with both hands, and the record is on the table behind her. (01:06:05)
Deliberate mistake: Bosley is a school crossing guard trying to help the Angels. The children behind them say they are gonna be late for school. Of course they're going to be late because there is not a school within 10 miles of where they are standing. There's trees and what looks like a huge mountainside on the other side of the street. You can see this more visibly as the car that is about to run over Bosley is approaching. Done for a gag, but still ridiculous. (01:09:05)
Continuity mistake: When Alex and Natalie are chasing the man in the car, the headrest changes from black to red. (01:10:20 - 01:11:15)
Continuity mistake: When Bosley (as a crossing guard) is in the middle of the road, attempting to stop Ray Carter in his car, the waiting children disappear and reappear between shots. (01:10:40)
Visible crew/equipment: When Bosley is a crossing guard and is yelling 'Stop' at the oncoming car, lighting equipment is seen reflected in his glasses. It can also be seen reflected in the cars after the children have crossed. (01:10:40)
Continuity mistake: When Bosley holds up the stop sign it is unmarked on both sides, but when Carter drives away there is a large scratch down through the 'O'. (01:10:45)
Revealing mistake: When Madison is shooting at the Angels at the observatory the gun in her left hand is empty and the slide is locked open. She then continues to shoot with both guns. (01:14:45)
Continuity mistake: When Madison Lee is at the top of that dome after she shoots Carter, she says "You know, I never really got that whole partner thing" and she has nude lips, then she comes down and she is answering Alex's question "Why?" and she has red lip gloss on. (01:14:50)
Factual error: When Dylan tries to kick Madison and she catches her foot Madison twists Dylan's foot straight down and you hear bones popping, but after getting flipped and kicked she gets up without so much as a limp. Her ankle should have been broken/dislocated at this point. (01:15:00)
Continuity mistake: When Dylan tries to roundhouse kick Madison from behind, Madison catches her foot and twists it so her toes are pointing down. In the next frame just before Madison throws Dylan over her shoulder, Dylan's toes are pointing up. (01:15:25)
Continuity mistake: When the Angels encounter Madison at the observatory they are supposedly wearing bullet-proof vests. You can tell through Nat's shirt she isn't wearing one. After they are shot, you can see the shirt is bulky from the vest. (01:17:00 - 01:20:00)
Continuity mistake: When Demi Moore shoots the Angels off the side of the observatory, the bullet intended for Drew Barrymore hits her in the lower abdomen. Later in the movie when the Angels wake up on the lawn below the observatory, the only bullet hole in Drew's shirt is on her upper left chest. (01:17:05 - 01:20:25)
Continuity mistake: When the Angels get shot off the observatory, Natalie is between Alex and Dylan. When the next shot shows them on the ground, Natalie is on the far right, past Dylan. (01:17:15)
Continuity mistake: When the Angels are walking through the sprinklers after getting shot, you can see the bullet holes in each one of the Angels' shirts. When they get to the car, and it blows up, Cameron Diaz's bullet hole disappears. (01:20:00 - 01:21:30)
Revealing mistake: Whenever a car explodes in the movie, the car splits exactly in half, with each half having a straight edge. (01:21:25)
Continuity mistake: When the Angels are walking through the sprinklers, they get soaked. But after their car blows up and they are lying on the ground Drew Barrymore's hair is dry along with Lucy Liu's. (01:21:30)
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.