If there is shouting on the grass courts at Wimbledon, it is typically a player’s tantrum, or the roaring of spectators for their favorites during tense tie-breaks.

Not so on Thursday, as American player Bethanie Mattek-Sands, who was a wild-card entrant to the women’s singles tournament, suffered a gruesome injury during the third set of her second-round match against Romanian opponent Sorana Cirstea.

Running towards the net, Mattek-Sands, 32, appeared to buckle and then cry out in agony. Cirstea jumped over the net, and seemed to immediately realize the gravity of her opponent’s injury.

Mattek-Sands repeatedly cried out, “Help me,” in agony.

Trainers and medics attended to Mattek-Sands on court, as distressed spectators looked on.

Mattek-Sands, who is one half of the number-one women’s doubles team in the world (with Lucie Šafárová), was later stretchered off court.

Šafárová was pictured in tears after the incident, and being comforted by their team-mates. The pair have won the last three Grand Slam tournaments: the U.S., Australian, and French Opens.

The incident took place on Court 17. Mattek-Sands had won the first set 6-4, Cirstea the second 7-6, and the pair had just begun the first game of the third set with Cirstea serving.

The Express reported that Mattek-Sands, who was born in Rochester, Minnesota, was treated for 25 minutes on court, with her husband and Šafárová at her side.

Cirstea said, “For me, I think she was too long on the ground. I mean, I was there for 10, 15 minutes, then I left and the stretcher was not there yet. It took a really long time not only for the stretcher to get there but, I mean, I don’t know for how long she was on the ground, but I would say ten, 15 minutes—for me, that’s really long.”

In a series of tweets, the official Wimbledon Twitter account, said: “The first response to Court 17 was within 1 minute, by a qualified ambulance technician. The player was kept on court while pain relief was given. The player was then transferred directly to an ambulance and taken under emergency conditions to a hospital.”

WTA Insider tweeted out that Mattek-Sands had “an acute knee injury.”

Cirstea said she had “never seen anything like this in my life, such an injury.” She thought it looked like Mattek-Sands’ “kneecap was out.”

Cirstea told of her shock at first seeing the injury. Mattek-Sands had repeated over and over again, “Sorana, help me.”

“I was trying, but of course I felt useless,” Cirstea said. “In this kind of moment when she is screaming so loud, you watch the knee, it was a very uncomfortable moment. I felt, yeah, a little bit useless. I wish I could have done more.”

Other players like Marion Bartoli, the 2013 Wimbledon women’s champion, tweeted their support to Mattek-Sands, and Cirstea herself tweeted: “I love you girl, you are strong, you will get through it! My thoughts are with you Beth.”