Former world middleweight champion Sergio Martinez plans to retire from boxing within the next few weeks because his "knee is shattered".

"I am a boxer, my knee is shattered. I am 40-years-old, I'm getting wrinkles and my hair is falling out," Martinez was quoted as saying in Argentina's La Nacion daily on Monday.

"I've already made up my mind, but in a few weeks I will have a final meeting with doctors and make my announcement then."

The Argentine boxer, whose career spanned almost 20 years, lost his World Boxing Council (WBC) middleweight title to Puerto Rican Miguel Cotto in June.

In his crushing defeat to Cotto in Madison Square Garden, Martinez appeared struggled to move freely around the ring because of the knee injury, experts said.

Since then, Martinez has remained out of the limelight.

"Now I cannot play a game of soccer with my mates, like when I was a kid, let alone return to fight at the top level," Martinez added.

During his fighting career the Argentine notched up 51 wins, including 28 knockouts, lost three bouts and drew two.