My legs are bowing. i had gastric bypass surgery 10 years ago. could this be the cause.

Most unlikely as I -: Am sure you probably have arthritic knees which are a common cause of the bowing, in middle ages.

No: Bowing of your legs is due, most likely, to arthritis, not to the gastric surgery. Increased weight can cause increased joint wear and changes in your mechanical axis. The weight reduction likely is currently reducing your symptoms, but arthritis and mechanical axis malalignment is common in the general population in your age group.