Lady Gaga has undergone hip surgery. The 'Bad Romance' hitmaker recently cancelled her 'Born This Way Ball' tour and revealed she is using a wheelchair after contracting a painful injury and inflammation of her joints, known as synovitis, and has now gone under the knife to help her back to health. She tweeted yesterday (20.02.13): "Going in for surgery now. Thank you so much for sending me love and support. I will be dreaming of you." Following the operation, she thanked her fans for giving her the strength to get through her ordeal and put her problems in perspective. In an open letter to fans, she wrote: "Thank You Monsters, You really gave me a lot of strength today. Everything happened so fast, but when it came time to face it I reflected on the many stories and experiences you've shared with me about your lives. Meeting you backstage, reading your letters, watching you communicate with fans from around the globe to form a community that supports one another--You have completely blown my mind. "As they wheeled me into surgery today, I thought about all of your pain and perseverance, your unique family situations, school environments, health issues, homelessness, identity struggles - sometimes you are so brave that it terrifies me. I wonder how it's even possible.”