United States women's national team World Cup winner Sam Mewis has opened up on her difficult decision to retire from the game aged 31, saying she is hoping to move on from the repetitive knee injury that hampered her career in recent years.

"The decision to step away was really difficult and clearly it took me a really long time to accept but overall I think that prioritizing my health as a person became really important to me," Mewis said.

- Stream on ESPN+: LaLiga, Bundesliga, more (U.S.)

"After about two, two and a half years of really just rehabbing my knee every day it became clear to me my knee couldn't handle the impact that elite soccer requires.

"I've had a cartilage injury in my knee for seven years now and actually feel really fortunate that I was able to play on it as long as I did.

Sam Mewis won 83 caps for the USWNT. Getty Images

"I went through some surgeries, I talked to a dozen doctors and physical therapists and people who could have an option about how to fix this cartilage issue in my knee.

"It just took a lot of time and a lot of acceptance that physically I was unable to return to the game at the level required.

"[I had] a lot of mixed emotions honestly and a lot of long conversations with my family and close friends. It's been a tough couple of years."

Mewis won the World Cup in 2019, helped the U.S. claim bronze at the Tokyo Olympics and scored 24 goals in 83 caps.

Mewis also scored 16 goals in 32 games between 2020-21 for Manchester City, and was on the scoresheet as they beat Everton in the 2020 FA Cup Final. She was also named in the Women's Super League PFA Team of the Year.

Asked when the former midfielder thinks she was in her prime, Mewis said her time with City came to mind.

"Maybe some time in 2020 which is crazy to say with the pandemic, into 2021, I was at Man City I felt I was playing really well," Mewis said.

"I think unfortunately I just had to step away and have this surgery and haven't really gotten back since."

Mewis also won four NWSL titles and played for the North Carolina Courage, Kansas City Current and the now defunct Western New York Flash.