An orthopedic surgery expert witness opines on a case happened in New Mexico where an orthopedic surgeon carried out bilateral knee replacement surgery and fit the patient with the wrong size prosthesis. This case involves a seventy-eight-year-old male patient with a past medical history of osteoarthritis and hypertension. The patient was under the care of his primary care physician for treatment of his arthritis which was being managed conservatively with pain medications and glucosamine supplements. The patient’s condition worsened to the extent that the patient was suffering chronic pain and was unable to mobilize without assistance. The patient’s primary care physician referred him to an orthopedic surgeon for further evaluation. Following imaging of the affected joints which revealed extensive degenerative disease, the treating orthopedic surgeon recommended that the patient undergo bilateral knee replacement surgery. The surgery was carried out with no complications reported and the patient tolerated the surgical procedure and made a good recover post-operatively. However, a few days after discharge from hospital the patient began to complain of severe pain in one of his knees. The patient followed up with the operating surgeon at routine post-operative appointments who assured him that the pain was a normal part of recovery after a knee replacement. The pain persisted and the patient complained to the treating surgeon several times who reiterated that it was normal on each occasion. After some time passed the patient decided to seek a second medical opinion from another orthopedic surgeon. After an evaluation including imaging of both knees it was determined that the original knee replacement surgery was performed incorrectly; the two replacement sizes were not congruent with one size being a 9 and the other a size 13. The patient had to go undergo a corrective surgery to remove the incorrectly fitting prosthesis and replace it with another one.