Early triage of a patient with metastatic melanoma presenting as mechanical knee pain - a case report.

Physical therapists (PTs) working in primary care settings commonly encounter mechanical causes of knee pain. Non-mechanical causes of knee pain, such as bone tumors, are rare, and therefore, PTs often have a low index of suspicion regarding sinister pathology. The purpose of this case report is to describe the physical therapist's clinical reasoning process for a 33-year-old female presenting with medial knee pain and a subsequent history of metastatic melanoma. Initially, subjective and objective testing pointed to a mechanical internal derangement of the knee. However, symptom progression and poor treatment responses between physical therapy visits 2 and 3 raised suspicions as to the cause of the knee pain. This prompted an orthopedic referral and medical imaging, revealing a large bone tumor invading the medial femoral condyle, which was further characterized as metastatic melanoma by a specialty oncology team. Further imaging revealed several metastatic subcutaneous, intramuscular and cerebral lesions. This case highlights the importance of the ongoing medical screening process, including the monitoring of symptoms and treatment responses.