An unusual cause of knee pain discovered at a nurse practitioner clinic.

PURPOSE: To describe an interesting and instructive case of knee pain from nurse practitioner (NP) practice and discuss the epidemiology, pathophysiology, clinical evaluation, and treatment of osteosarcoma.

DATA SOURCES: Findings from the history, physical examination, diagnostic testing, and follow-up of the case of an 18-year-old male who first presented with nontraumatic, diffuse left knee pain of 2.5-month duration.

CONCLUSIONS: At follow-up, after a trial of conservative treatment, a lesion suspicious for osteosarcoma was seen in the proximal tibia. Osteosarcoma is a rare but dangerous cause of chronic extremity pain, especially in children and adolescents.

IMPLICATIONS FOR PRACTICE: NPs must consider malignant bone tumors in the differential diagnosis of traumatic and nontraumatic extremity pain of extended duration, especially in children and adolescents. Thorough, persistent follow-up on recommended tests and referrals is necessary to ensure that important findings are not missed. The care of uninsured patients requires particular attention to cost concerns and access issues.