Carolina Marin - "I'll be back stronger"
The Spaniard posted a photo message on Twitter from hospital in Madrid after the operation.
Marin was forced to retire from the final of the Indonesia Masters on Sunday (29th January) when she ruptured the anterior cruciate ligament in her right leg.
The Spaniard faces at least six months on the sidelines, but tweeted a positive message on the eve of her hospital visit.
Marin was leading London 2012 bronze medallist Saina Nehwal 9-2 when her right knee buckled on landing after a routine overhead shot.
She tried to continue, even winning a point, but eventually retired in tears with the score at 10-4.
Top of her game
In recent months, Marin has been playing her best badminton since winning Olympic gold at Rio 2016.
Marin makes badminton history for Spain
Marin makes badminton history for SpainCarolina Marin beats India's PV Sindhu in three sets to become the first non-Asian woman to win an Olympic Games gold.
The 25-year-old left-hander beat Rio silver medallist PV Sindhu to claim her third world title last August in Nanjing, and followed that up with victories in the Japan Open and China Open.
Marin had made a good start to 2019 as well, reaching the final of the Malaysia Masters where she lost out to Thailand's 2013 world champion Ratchanok Intanon.
In Jakarta last week, she brushed aside Sindhu in the quarter-finals before edging out China's Chen Yufei 23-21 in the third to reach the final.
The road back
A rupture of the anterior cruciate ligament, also known as torn ACL, was once a career-ending injury. It now results in an absence of somewhere between six months and a year.
Surgery involves reconstructing the damaged ACL, usually with a strip of tissue taken from the patient's own patellar (kneecap) tendon or hamstring tendon.
Initial bruising from the surgery takes a week to subside with the patient often wearing a padded knee brace containing cooling fluid.
According to the UK National Health Service guide, there then follows extensive rehab with activities involving twisting, jumping or turning to be avoided while the grafted tissue anchors itself in place inside the knee.
Swimming and cycling are recommended from early on in the rehab process with six months considered the minimum time before a return to full training.
In good company
The injury is most commonly associated with football and skiing.
Aksel Lund Svindal tore his ACL in a big crash at Kitzbuehel in January 2016 but was back on the podium the following December.
Olympic champion Lindsey Vonn suffered the injury at the World Championships in February 2013, before partially tearing it again nine months later.
Although Vonn did return to World Cup action the following month, further complications forced her to miss the defence of her downhill title at Sochi 2014.