2 yrs ago I got a cyst in my ankle and had to get surgery which required metal plates, I rencently got another on my wrist. What's causing the cysts?

Cause is not known. Causes of unicameral bone cysts are unknown. One theory is that the cysts result from a disorder in the growth plate at the ends of bones. Another theory is that the cysts result from problems with blood circulation in the bone due to some abnormal blood vessels. Whether trauma influences the formation of these bone cysts is not known. A orthopedic (bone) surgeon can take care of the problem.
Dr. Kwok is correct. Other causes of bone cysts can be a vascular abnormality (aneurysmal bone cyst) and things that look like cysts but are actually benign tumors (e.g. Giant cell tumor of bone). Ask the orthopaedic surgeon who has taken care of you to see if a sample was sent from your surgery for a tissue diagnosis.