We all know how important Quidditch is in the world of Harry Potter and beyond. Even in real life, many fans of the series play their own games of Quidditch aboard broomsticks and everything. Although unfortunately in the Muggle world, we can't be up in the air. However, Quidditch is also a very dangerous game. There have been many injuries across the series and several that were hinted at in the past history of the franchise.
When you're playing a game in midair and have a bunch of deadly balls flying around, two with the specific intent to knock you off your broom, things are guaranteed to get ugly. The game is competitive and it's common for players to take things too far. Of everyone in the books, none has suffered quite as many injuries as our hero, Harry Potter, out on that field.
Harry almost chokes on the Snitch
Way back in Harry Potter and the Sorcerer's Stone when Harry first becomes a Seeker, his life was immediately at risk. At the time we didn't know it but Professor Quirrell was actually possessed by Lord Voldemort. At one point during a match, Harry was being bucked off of his broomstick over and over again while suspended in midair. At one point he even fell off his broom and was only hanging on by one hand.
Luckily, Harry had Snape in his corner attempting to counteract Quirrell's jinx, although again, Hermione, Harry, and Ron were unaware of Snape's intentions. Regardless, Harry was eventually able to clamber back on his broomstick and complete the game. But when he spotted the Snitch and zoomed towards the ground, he accidentally swallowed it and nearly choked on it before raising it in the air for everyone to see. Out of the many injuries Harry has received, this was the mildest as it didn't leave any lasting impact, but still, what a way to kick things off!
Harry loses all the bones in his arm
Perhaps the worst and most unforgettable instance of Quidditch trauma occurs in the second book of the series. Harry is targeted by a rogue Bludger and has to do his best to avoid it while also trying to beat Malfoy to get the Snitch. Eventually, Harry is unable to fend off the Bludger any longer and receives a horrific smash in the arm from the heavy ball.
We learn later that Dobby was behind the Bludger in an effort to protect Harry but he winds up with a broken arm because of it. To make matters worse, Professor Lockhart attempts to fix Harry's arm, only to rid his limb of bones completely. Harry is escorted to the hospital wing with a rubber sock of an arm as Madam Pomfrey tries to fix him up over a long and painful night.
Quidditch World Cup crash
In an incident that was not related to Harry, for once, during the fourth book and the Quidditch World Cup between Ireland and Bulgaria, things get pretty nasty on the field. In one particularly terrifying moment, the two Seekers from their respective teams, Viktor Krum and Adrian Lynch, crash into one another on the field. Based on the book's description, it's a pretty nasty and severe incident between the two of them.
When Krum pulls away he is dripping blood all down the front of his robes. Krum winds up catching the Snitch anyway, despite losing the game, but it's no wonder Krum's nose is crooked when he deals with injuries to that drastic extent.
Harry faints off his broomstick
In Harry Potter and the Prisoner of Azkaban, we are introduced to the chilling Dementors. No one likes Dementors. But no one is affected by them quite the same way that Harry is. Upon his initial encounters with the dreadful creatures, Harry faints. This happens during a Quidditch match in the book when a swarm of Dementors arrives onto the field in their search for Sirius Black. Harry winds up fainting off his broomstick and spiraling down to the ground.
Some people even thought Harry had died in the process given how far his fall was but luckily Dumbledore was there to keep Harry from hitting the ground at full-force. This was one of the few games Harry lost as Cedric Diggory wound up catching the Snitch instead of him, unaware that Harry had been taken out of the game. To Cedric's credit, he did try to call for a rematch.
A referee died in the past
While there aren't many deaths in Quidditch, surprisingly, especially in modern times when they've become increasingly rare due to natural magical evolution and stricter regulations, there was at least one notable death where a referee died in 1357.
His name was Cyprian Youdle and it is believed he was killed by a curse as the game was a friendly match. There was another incident where a referee's broomstick was turned into a Portkey without him being aware of it and as a result, he resurfaced months later in the middle of the Sahara Desert.
Numerous Bludger injuries
Aside from the earlier Bludger incident that we are all very familiar with from the second book in the series, there have been a few other incidences involving Bludgers over the years. Generally in the matches involving Slytherin, there was always someone getting whacked too hard with a Bludger due to the team playing dirty.
But one of the worst incidents came from someone on Harry's own team when he was Captain. During Quidditch tryouts, Harry was hit in the back of the head by a Bludger by accident. His skull fractured in the process and he was knocked unconscious.
Intervention of Veelas
Veela are magical beings that take the shape of beautiful women but their true form is more like a hideous harpy of some kind. The Veela are also present at the Quidditch World Cup in Harry Potter and the Goblet of Fire, they are present at the game as the mascots of Bulgaria, their homeland. The Veela cause several problems during the game as they distract several of the men in the vicinity, as is their ability, and lash out when rebuked by the referee.
Despite the fact the Veela are not necessarily the cause of on-field Quidditch injuries, they still cause a great deal of drama and get into a fight with the Ireland mascots, the Leprachauns.