Ferdinand hid extent of injury from Ferguson
A course of spinal injections, physiotherapy and an orthopaedic cushion helped cure the problem which lasted for 18 months, fored Ferdinand to take painkillers to sleep and made him unable to train for up to five days.
He now expects to be fully fit for this year's World Cup finals in South Africa where he will captain England.
In an interview with the News of the World, Ferdinand said he was forced to tell the truth to Ferguson after United's 2-0 defeat at Liverpool last October, when Fernando Torres got away from him easily to score the opening goal.
"The day after a game I would waddle into the club like a duck, bent over like an old hunchback," Ferdinand said.
"I would be hobbling around, unable to train for four or five days. I would be OK to play the next game, but I must have missed 60-70 percent of training.
"If I'm honest, I didn't make it clear to the gaffer and the club physios that my injury was that serious. "But my back would go into spasm and I wouldn't be able to move.
"My fitness deteriorated but as a footballer you think you are superhuman. You don't think anything will stop you playing.
"I just had an incredible desire to play football and had never had to deal with an injury of this scale before but I was summoned into the manager's office after the Liverpool defeat.
"He told me: 'Last season, Torres would not have scored that goal against you'. As soon as he said that, you sit up and take notice.
The pair decided to rest the injury completely and Ferdinand missed three months of the season before returning to the first team in January.
"I'm still using the cushion, it helps my posture," he said. "I look daft when I'm sat on it in a restaurant - it makes me look really tall. But it has certainly helped."