A most common cause of tarsal tunnel syndrome -: (A) Osteoarthritis, (B) Ankylosing spondylitis, (C) Psoriatic arthritis, (D) Rheumatoid arthritis
Answer is D. Amongst the given options, RA is the most common cause of tarsal tunnel syndrome.

Facts about etiology of tarsal tunnel syndrome

Most common origin of tarsal tunnel syndrome is idiopathic (21-36%).
When the cause is known, trauma is the most common cause.
Two most common systemic causes of tarsal tunnel syndrome are diabetes (m.c.) and RA (2nd m.c.)