I was told that i have an accessory bone in my foot, per x-ray. does this increase the likelihood of an accessory muscle/tendon near the ankle?

No.: Accessory bones are fairly common, and some are within the tendons. Unless there are symptoms of pain or limited use, these are not usually clinically important. There are some variations in the number of muscles and corresponding tendons, but these are less common, and usually do not cause any problems by themselves. These can be injured with trauma and mimic other disease processes.