FILE PHOTO: Winnie Madikizela Mandela,ex-wife of former South African president Nelson Mandela, attends the inauguration ceremony of South African President Jacob Zuma at the Union Buildings in Pretoria, South Africa, May 24, 2014. REUTERS/Mujahid Safodien/Pool/File Photo

JOHANNESBURG (Reuters) - South African anti-apartheid veteran Winnie Madikizela-Mandela, ex-wife of the late President Nelson Mandela, is “in high spirits” after being admitted to hospital for minor surgery, her spokesman said on Thursday.

Victor Dlamini said in a statement the 81-year-old former first lady was admitted to hospital on Tuesday for minor surgery on her knee and doctors had decided to keep her in for the next two weeks as she recovers.

“I visited her at the hospital this afternoon and she was in high spirits,” Dlamini said.

“In our conversation (she) said that her health problems go back to the time when she was banished to Brandfort by the apartheid government and during this period her knee first gave her trouble.”

Madikizela-Mandela spent several weeks in hospital last year for back surgery.

During her ex-husband’s 27-year incarceration for his fight against apartheid, Madikizela-Mandela campaigned for his release and for the rights of black South Africans, undergoing detention, banishment and arrest.