Eighty patients with primary knee osteoarthritis scheduled for unilateral TKA were randomized to receive hyperbaric oxygen therapy (HBOT) added to standard care (n=40) or normobaric oxygen therapy (n=40). The primary outcome was serum muscle-injury biomarkers (CK, Mb, LDH, GOT). Secondary outcomes included IL-6, CRP, VAS pain (rest/motion), knee ROM, quadriceps strength, swelling ratio, and HSS scores; outcomes were measured pre-op and on post-op days (POD) 1, 2, 3, and 14 (HSS also at 6 and 12 weeks). Overall, the results revealed lower muscle-injury biomarkers at POD3 with HBOT along with less inflammation, less pain, less swelling, better early ROM, and stronger quadriceps; adverse events were similar. These findings suggest early adjunctive HBOT improves early recovery markers after TKA without increasing complications.