Avoiding anchoring bias in unexplained chronic pain: an unexpected diagnosis of synovial osteochondromatosis

Unconscious biases may influence clinical decision making, leading to diagnostic error. Anchoring bias occurs when a physician relies too heavily on the initial data received. We present a 57-year-old man with a 3-year history of unexplained right thigh pain who was referred to a physiatry clinic for suggestions on managing presumed non-organic pain. The patient had previously been assessed by numerous specialists and had undergone several imaging investigations, with no identifiable cause for his pain. Physical examination was challenging and there were several 'yellow flags' on history. A thorough reconsideration of the possible diagnoses led to the discovery of hip synovial osteochondromatosis as the cause for his symptoms. Over-reliance on the referral information may have led to this diagnosis being missed. In patients with unexplained pain, it is important to be aware of anchoring bias in order to avoid missing rare diagnoses.