Insurance carriers have a variety of plans.
The HMO and PPO varieties both require contracts between the insurance company and the physician. The carrier agrees to pay the money directly to the physician in a quick fashion and recommend the physician to large groups of patients that may not otherwise know of the doctor. The physician in turn helps hold costs down by accepting a contracted rate for services and by handling the billing and many referral issues for the patient. Contracts are signed and expire often, so if you have an HMO or PPO check this site often to make sure Boulder Medical Center is still contracted with your carrier. If you have medical insurance, know your policy.