A 77 year old male went in for a routine knee replacement surgery. Following this procedure, he began to decline in both his physical and mental capacities. The symptoms got progressively worse and about 4 years later, he was evaluated and given a brain imaging (SPECT) scan, and he was immediately given a diagnosis of dementia with major cognitive deficits and aphasia (the loss of ability to understand or express speech). It was determined that the cause of his dementia was a post-op complication from his previous knee surgery and began a course of 40 sessions inside of a hyperbaric oxygen chamber. After 5 months, both his physical and cognitive functions were substantially restored. The follow up brain imaging scan confirmed these results. Complications from major (and even minor) operations are not uncommon and sometimes not even diagnosed at the time, and in cases like this, 4 or 5 years after the surgical procedure. This study brings to light the benefits that can be achieved with hyperbaric oxygen therapy, even years after the surgery. <view study>