The singer, 42, has arthritis in his back, which has forced him to tone down his usually-energetic dance routines.
Speaking to the Evening Standard, the dad of two opened up about his health: 'I've got arthritis in my back so I can't put my foot through a ball.'
When asked how it was affecting his dancing, he said: 'I have very tight hamstrings, barely existent calves. I dance like a drunk dad at a wedding. But I've got to do something to fill the time on stage.'
Arthritis is a common condition affecting around 10 million people in the UK, and causes pain and inflammation in a joint. It usually develops in adults who are in their late 40s or older, and symptoms include joint pain and stiffness, restricted movement of the joints and weakness and muscle wasting.
Robbie has said he'll be toning down his stage moves
The former Take That star shared his diagnoses just ahead of World Arthritis Day on 12th October, which hopes to encourage people to live their lives to the fullest by sharing personal stories from those successfully living with arthritis.
Liam O'Toole, Arthritis Research UK's Chief Executive Officer, says: 'We are sorry to hear that Robbie Williams is experiencing back pain caused by arthritis.
'By talking about his experiences, he is shining the spotlight on the condition affecting over 10 million people in the UK. Today is World Arthritis Day, and our new campaign Share your Everyday is calling for people affected by arthritis to share their day-to-day experiences, like Robbie has done, to help push back the limits of arthritis by visiting arthritisresearchuk.org/shareyoureveryday'
Robbie, who has spoken publicly about his past battles with depression and substance abuse, now lives in Los Angeles with his wife Ayda, four-year-old daughter Teddy, and two-month-old son Charlie.
He said: 'Having kids has completely focused my attention away from my neuroses and addictions. My life is tenfold better for it. Daddy goes to work and it all makes sense. This is my job. It's not a normal job. And having children has made it all make sense.'
Robbie with wife Ayda
Robbie isn't the only celeb to battle the condition - former Emmerdale star Claire King also suffers from arthritis, telling the Mirror: 'It feels like my whole body is falling apart. I have elderly parents and they've got problems too, so I want to be around to help them.
'I don't want to be a helpless old woman who can't do anything for anyone because all my joints are falling apart.'