In May each year, as the football season comes to a close with titles won, promotions secured or relegations narrowly avoided, fans spill onto pitches in stadiums across Europe to celebrate with their players.
Traditionally, pitch invasions are spontaneous outpourings of emotion, expressions of unity and common cause between players and supporters at the end of a long season.
This year, however, the phenomenon has brought with it a series of incidents which have been unwarranted, dangerous and even criminal.
Crush at Schalke
When Schalke recently secured its promotion to the Bundesliga and fans stormed onto the pitch, DW observed a serious crush at the bottom of the Nordkurve terrace.
As fans pressed forward toward the pitch, a crush developed, and police, stewards and medical teams were soon pulling fans out of the stand. Despite increasingly desperate pleas from the stadium announcer for fans to move back, several people were injured and taken to hospital.
Sexual assault in Nuremberg
A week later, an even more serious incident occurred when a Nuremberg fan was sexually assaulted during a joint pitch invasion after the game against Schalke to celebrate the latter's promotion (Nuremberg and Schalke share a fan friendship).
"I felt a hand on my bottom … and thought it must have been an unintentional brush in the melee," Cosima Müller told Nuremberg's official website.
"Shortly after, I felt a hand behind me again which grabbed toward my groin … and ran up and down my body. I finally managed to get to the front [of the crowd] but the attacker followed me, grabbed my hips, pulled my shirt out of my pants and reached under it. I was overwhelmed by the whole situation, shocked and not able to defend myself," she said.
FC Nuremberg and the police are working to identify the assailant, but it's not just in Germany where pitch invasions have had undesirable, and indeed criminal, side effects.
Head-butt in England
In England this week, following the playoff semifinal second leg between Nottingham Forest and Sheffield United, Forest fans stormed the pitch to celebrate reaching the final and the chance of winning promotion to the Premier League.
While the vast majority ran to celebrate with the players or each other, one fan made a beeline for Sheffield United captain Billy Sharp, who was standing by the bench, having missed the game through injury. Entirely unprovoked, and caught live on camera, the fan knocked Sharp to the ground with a vicious head-butt, causing an injury which required stitches.
The fan, Nottingham Forest season ticket holder Robert Biggs, 30, was sentenced to six months in prison after pleading guilty to assault causing actual bodily harm.
Pitch invasions have little to do with fan culture
Now, to be clear: fans are the lifeblood of football, and fan culture is an integral part of the sport — especially in Germany, where the 50+1 rule means that fans are not just fans; they're voting members who technically own their clubs. This writer is a big an advocate of that as any.
German fan culture is vibrant, active, engaged, participatory and inclusive — but pitch invasions aren't. Not in this current form, anyway.
Rather than being spontaneous outbursts of emotion and shared experience, recent pitch invasions have been predictable, planned and even unofficially announced in advance. And rather than being occasions of communal celebration, they feature fans who are more interested in selfies and content for their individual social media profiles.
In the great scheme of things, such behavior isn't really of great importance. But dangerous crushes, sexual molestation and physical assaults are.
There are so many more genuine ways of expressing fan culture than pitch invasions.