Can your employer videotape you in a medical office, where patients will also be seen?

Videotaping employees in the workplace is legally permissable as long as it is limited to their work activities/job performance. Accordingly, an employer may videotape employees to prevent vertain behavior, such as employee theft or, as in your case, too much socializing with co-workers. Additionally, employers must provide notice (typically in writing) to all employees that video surveillance is being conducted and where it is being used, as well as state the areas that are off limits from surveillance. That having been said, videotaping may violate employees' rights to privacy if they are taped in areas considered private and personal (i.e. bathrooms, locker rooms, etc.).
As for voice recording, there is no “expectation of privacy” in public areas (i.e. the lobby, stairwells, conference rooms, etc.), so recording conversations in those areas is legal. Otherwise, recording employees without their consent is illegal unless the person recording the conversation is also a party to the conversation, although in some states all parties must consent to the recording. 
As for the patients, since a waiting room is considered to be a "public area", their rights are not being violated so long as they are given notice (e.g. a sign) informing them of the videotaping. Any audio recording is sublect to that stated above.

If employees are aware of the video camera, there is no violation: the law does *not* give employees any rights to avoid being videoed at work, so long as they are aware that they may be or are being recorded, either through being told of the camera, a sign, etc. warning of it, or the camera being open and obvious.
Similarly, videoing patients in a common or waiting room (not an examination room) is not illegal or any violation of their rights so long as there is some notice (e.g. a sign or warning) of videotaping, or they can see the camera. Anyone may be videoed in either public areas or someone else's space (office or home) as long it is not done surreptitiously, in  a way that might violate the normal expectations for being observed in such a location.