system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A patient complains of knee pain Routine investigations are unremarkable and still the patient is unsatisfied Urine turns black on standing what is the enzyme involved
assistant
The correct answer is  REF : LIPPINCOTT 6TH ED