Patient presents with complaints of chronic left knee pain, stiffness, and functional limitation consistent with osteoarthritis.  Symptoms include significant pain with weight-bearing, crepitus, reduced range of motion, and morning stiffness lasting greater than 30 minutes.  Conservative treatments including physical therapy, nonsteroidal anti-inflammatory drugs (NSAIDs), and viscosupplementation have failed to provide adequate relief.  Radiographic imaging of the left knee demonstrates advanced degenerative joint disease characterized by joint space narrowing, osteophytes, and subchondral sclerosis.  Based on the patient's history, physical examination findings, and radiographic evidence, a diagnosis of osteoarthritis of the left knee is confirmed.  Surgical intervention in the form of a total left knee replacement (TKR), also known as total knee arthroplasty (TKA), is indicated to alleviate pain, improve function, and enhance quality of life.  Risks and benefits of the procedure, including potential complications such as infection, deep vein thrombosis (DVT), and prosthetic loosening, were discussed with the patient.  The patient understands the risks and benefits and consents to proceed with total left knee replacement surgery.  Preoperative clearance, including electrocardiogram (ECG) and laboratory tests, will be obtained.  Postoperative care will involve physical therapy, pain management, and close monitoring for complications.  ICD-10 code M17.1 (primary osteoarthritis left knee) and CPT code 27447 (total knee arthroplasty) are relevant for this encounter.  Medical necessity for total knee replacement is supported by the patient's persistent pain, functional limitations, and failed conservative management.