Major cartilage clean-up. No replacements, thankfully. His younger brother had both ACL & MCL replacement (about as serious as it gets for knees).
Certain medical conditions seem to run in families.. Knee, back, sciatia problems.. High BP, diabetes.. I have seen the trends in a lot of families...parents are wise to note these things & do what is necessary diet/conditioning wise to help their youngster minimize the onset etc.