Walker undergoes abdominal surgery
The 24-year-old, who missed the World Cup in Brazil, has not played for the club since March and it is unclear when he is likely to return.
Tottenham released a short statement to confirm the news on Tuesday.
"The England right-back's pre-season preparations were disrupted by the abdominal injury and the decision to have surgery was taken following further medical assessment by specialists," it read.
Speaking last month, head coach Mauricio Pochettino said: "Kyle is good some days. On other days he has a bad feeling.
"We believe he may recover soon but we need to be calm with him because it is an injury that he has had for five months."
Walker made his Spurs debut in March 2010 following after moving to the club from Sheffield United the previous year.
He has earned 10 England caps.