London (AFP) - Bethanie Mattek-Sands admitted on Saturday that she had endured a "painful and emotional 36 hours" after suffering a sickening knee injury which shocked Wimbledon.

The 32-year-old American is being treated in a nearby private hospital where she was taken on Thursday after her knee appeared to buckle as she approached the net in her second round clash with Sorana Cirstea on Court 17.

She was left screaming in pain: "Please, help me, please, please" in scenes so distressing that TV cameras panned away from the stricken star.

On Saturday, Mattek-Sands said she would hold a Facebook Live session to provide an update on her condition.

"To the best family, friends and fans a girl could ask for, it's been a painful & emotional 36hrs but THANK YOU for all the love and support," tweeted the winner of 24 doubles titles including seven at the Majors.

Romanian player Cirstea was visibly upset by the incident and said Mattek-Sands's knee was "out... and in a very weird position".

"I freaked out. I have never seen such an injury before, the knee was really in a bad position. It was like something you see only in the movies," said Cirstea. "I tried to comfort her but I panicked. I felt useless. All she kept saying was 'Sorana, help me, help me."

Concerns were also raised over the amount of time it took a medical crew to reach Mattek-Sands even though Court 17 is just a stone's throw from the tournament's Centre Court.

Cirstea said only she, her physio and Justin Mattek-Sands, the player's husband, attended to the American star and said it took around 10-15 minutes for a stretcher to arrive.

However, the All England Club insisted in a statement: "The first response to Court 17 was within one minute, by a qualified ambulance technician".