BONO could have been left permanently paralysed if it wasn't for emergency back surgery, it was revealed.
The U2 frontman went under the knife after collapsing during rehearsals for a US tour.
While the surgery went well, the band have had to postpone or cancel the shows as the singer recuperates.
Dr Hans-Wilhelm Muller-Wohlfahrt, a sports injury specialist, said Bono "suffered severe compression of the sciatic nerve".
On his recommendation, the singer was then taken for emergency surgery with neurosurgeon Professor Joerg Tonn at the Germany's Munich hospital.
Prof Tonn said Bono was "already in severe pain with partial paralysis in the lower leg" when he arrived at the hospital.
"The exact details of the injury revealed the ligament surrounding the disc had an 8mm tear," he explained.
During surgery, it was discovered fragments had travelled into the spinal canal.
"This surgery was the only course of treatment for full recovery and to avoid further paralysis," Prof Tonn said.
"Bono is now much better, with complete recovery of his motor deficit.
"The prognosis is excellent but to obtain a sustainable result, he must now enter a period of rehabilitation," he added.
Doctor and author Carol Cooper, said the singer "obviously had a very badly slipped disc".
"The discs in your back act as shock absorbers between each bone in the spine. When they rupture, it puts pressure on the nerves and this can cause pain right down to the foot or in extreme cases it can paralyse the leg," Dr Cooper said.
She added if Bono did not have surgery he could have been paralysed in that leg.
"His injury affected his sciatic nerve, which is the biggest nerve in the body and damaging it can cause severe disability," Dr Cooper said.
She warned that recovery "is not always plain sailing" and it will take time. Doctors indicated the singer may be laid up for longer than the minimum two-month rehabilitation period.
The 50-year-old was discharged from hospital yesterday.