John J. Brennan, MD

Sports Medicine, Joint Replacement

dr brennan

Contact Information:
Phone: (631) 689-4188
View Dr. Brennan on Google here

John Brennan, MD, received his medical degree from SUNY Health Science Center at Brooklyn after attending college at St. Louis University. He then performed a surgical internship at St. Luke’s-Roosevelt Hospital Center in Manhattan and followed with his orthopedic residency also at St. Luke’s-Roosevelt Hospital Center. During training, he completed rotations at Alfred I. DuPont Children’s Hospital in Delaware, Memorial Sloan-Kettering Cancer Center as well as The Blackrock Clinic in Dublin, Ireland.

Dr. Brennan is board certified in orthopedic surgery and is a member of the American Association of Hip and Knee Surgeons, Medical Society of the State of New York, Suffolk County Medical Society and the Irish-American Orthopedic Society. He also has an extra board certification in sports medicine from the American Board of Orthopedic Surgery. Dr. Brennan merged his practice with Orthopedic Associates of Long Island after being in practice in Southampton since 1999.

Dr. Brennan’s practice focuses on complete care of the shoulder, hip and knee with a particular emphasis on minimally invasive techniques. His philosophy is to avoid surgery if at all possible but when it is necessary, utilize the fastest, easiest recovery possibly. These techniques include arthroscopic shoulder and knee repairs including rotator cuff and labral tears in the shoulder and meniscus and ACL tears in the knee. When hip and knee replacements are needed, he uses the latest cutting edge technology with small incision techniques.

Patient Testimonial

"If it wasn’t for Dr. Brennan, I wouldn’t be able to enjoy life again at this level. I was in a lot of pain in my right shoulder, losing sleep, and having a lot of trouble just trying to do things that used to be easy. It’s been 8 months since my surgery and I’m playing golf and can’t wait to get back to bowling. The other and maybe the best part of Dr. Brennan is his friendly disposition and desire to help everyone. I can’t possibly thank him and his entire staff enough."

- LW



  • Rotator Cuff Repair
  • Labrum Repair
  • Dislocation
  • Bone Spurs


  • Meniscus Tears
  • Cartilage Tears
  • Arthritis
  • Knee Replacement
  • Partial Knee Replacement
  • ACL Tears


  • Arthritis
  • Hip Replacement


  • Southampton
  • Riverhead
  • East Setauket

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Our Offices


6 Technology Drive
Suite 100
East Setauket, NY 11733


500 Commack Road
Suite 150B
Commack, NY 11725


715 Roanoke Ave.
Building A, Ste. 3
Riverhead, NY 11901


6144 Route 25A
Building A Suite 4 & 5
Wading River, NY 11792


2112 Middle
Country Road
Centereach, NY 11720


55 Medford Avenue
Suite E
Patchogue, NY 11772


325 Meeting House Lane
Building One
Southampton, NY 11968


60 Fleets Point Drive
Suite 1
West Babylon, NY 11704

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