What pillow is best to sit on after doing a BBL?

Sitting should be avoided or at least done very briefly and only when it is necessary.  Take note that it will take three weeks for the fat grafts to form their new blood supply and the extra-cellular matrix holding them together with the rest of the tissue to become strong enough to tolerate pressure and tension from sitting, squatting, sleeping in supine position, and stretching.

During this critical period of recovery, pillows that allow you to sit on your thigh and back of the knee are highly ideal.  You may use Boppy pillow, donut-shaped cushion, or cigar-shaped pillow.  As long as your buttocks "hang" from them, you're good.

Good luck and best wishes. 

Dear triciasam,I instruct my patients not to sit for 2 solid weeks. We provide them a specialized pillow that our patients can sit on during that time. They can sleep on their stomachs or sides. Every plastic surgeon has his own postoperative protocol which he recommends to his patients. I would suggest you to discuss this with your plastic surgeon.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

Hello and thank you for your excellent question. Our practice recommends the "BBL Pillow", although there are many similar devices on the market. Of course, you will need an in-person consultation to
evaluate you for this procedure. Preoperative visualization and surgical
simulation with the Crisalix system may help with your decision. I suggest that
you find a board-certified plastic surgeon with whom you are comfortable. Be
sure to have all of your questions answered during a face-to-face meeting with
your surgeon, and review before and after pictures of patients who have had
similar procedures. Good luck!
Best,
Jon Ver Halen, MD FACS
Harvard educated plastic surgeon
Texas “Top Doc”