This case report highlights the importance of including a comprehensive and continuous differential diagnostic process throughout the treatment period, looking for those risk factors (i.e. red flags) that warrant further investigation and referral to the appropriate physician. Physiotherapy diagnosis should include clinical reasoning, clinical presentation, and symptom behavior in addition to appropriate referral for medical assessment and diagnostic imaging when appropriate. Physiotherapists working within a direct access environment have the competence and responsibility to participate with other health professionals in the differential diagnose process especially for patients presenting with serious pathology mimicking musculoskeletal disorders.