I recommend that your son be examined by an orthopedic doctor, so that the extent of the injury can be assessed and proper therapy administered. During a routine examination, my doctor seemed perturbed because she found my liver to be slightly enlarged. A CT scan revealed fat, but no tumor. Now she wants me to have a liver biopsy. I have no symptoms and, at 57, enjoy excellent health.
All surgery carries certain risks.
The hazards of liver biopsy include hemorrhage, peritonitis and infection. I believe that you would be better served by insisting on more non-invasive testing. For example, blood tests of liver function and the possibility of hepatitis would be helpful in delineating the cause of your fatty liver. Therefore, try an experiment. Then have another exam.