Apparently Bipasha was going through the knee pain as she had injured her knee badly few days before the shoot of the item number. Her physiotherapist advised her to take complete rest but the actress chose to work.
A unit hand informs us that Bipasha attended rehearsals a day before the shoot. Being a professional, Bipasha made sure that her knee pain shouldn't affect her work schedule thus she used to visit her physiotherapist during the shoot breaks.
Now that's what we call sheer dedication.