To describe the successful treatment of a Baker's cyst in the setting of post-traumatic osteoarthritis using ultrasound-guided injection of platelet-rich plasma. Outpatient sports clinic. 29-year old male basketball player. The patient presented with 2-months history of right knee pain, 17 months after undergoing right knee anterior cruciate ligament reconstruction surgery. Exam revealed medial joint line and medial collateral ligament tenderness with posterior knee swelling. After aspiration, a corticosteroid injection was administered with temporary symptom relief. Diagnostic ultrasound examination confirmed the Baker's cyst. The patient then underwent two serial leukocyte-rich platelet-rich plasma injections into his right knee. The patient reported complete resolution of pain and cyst size. Leukocyte-rich platelet-rich plasma may be considered as a treatment option for patients with Baker's cysts in the setting of post-traumatic osteoarthritis.
