Adele, 34, has been taking Las Vegas by storm since mid November, and will continue to croon for fans until March - but her rescheduled concert dates have been far from easy, as she admitted onstage recently.The Set Fire To The Rain singer has been battling a secret bout of sciatica, and is now forced to "waddle" around the stage.She let slip the impact that the painful nerve condition has had on her after fans spotted her struggling to walk smoothly."I’ve got two more, I’ve just got to get over to the other side of the stage," she announced as she attempted to hand out T-shirt launchers to the audience.She added: "I have to waddle these days as I have really bad sciatica.”According to the NHS website, the condition is most commonly caused by a slipped disc which compresses the sciatic nerve, and it causes intense shooting pain that flows from the lower back all the way down to the feet.Numbness, tingling, and pins and needles sensations are among the other uncomfortable symptoms.Sufferers typically recover within around six weeks but Adele hasn't been so lucky - in fact, the songstress previously admitted that she has endured back pain for years.Shockingly, she admitted that she had slipped her first disc due to sneezing aggressively at the age of 15 - and it was the same way that subsequent discs "flew out", too.She lamented that, by the time she had a C-section, her core had become "useless"."I’ve been in pain with [it] for, like, half of my life, really," she agonised to The Face."It flares up, normally due to stress or from a stupid bit of posture."Adele has certainly been through her fair share of stress in life, including a painful divorce from charity boss Simon Konecki, who is the father of her son Angelo, now.