Dr. Jan Ahrens

Fields of expertise

  • / Special orthopedic surgery
  • / Chiropractic
  • / Cartilage surgery


Dr. Ahrens is an experienced specialist in joint-preserving operations, artificial joint replacement (endoprosthetics) and revision endoprosthetics, i.e. prosthesis replacement operations of the hip and knee joint.

As a “special orthopedic surgeon”, Dr. Ahrens is one of the few physicians in the region to combine joint-preserving operations, such as arthroscopies and so-called conversion operations, with regenerative cartilage operations or cartilage replacement procedures.

The surgical focus is on artificial joint replacement of the knee joint, i.e. complete knee joint endoprosthetics.

Here, primary care is largely performed using the so-called ” PSI knee prostheses” (PSI=Patient Specific Instruments”).

“Minimally invasive hip arthroplasty” with so-called cementless short-shaft prostheses as well as classical hip prosthesis operations are part of the daily operative routine of the experienced surgeon.

For many years, Dr. Ahrens has successfully performed complex replacement operations on knee and hip joints, the so-called revision endoprosthetics.

The third surgical focus is the complete surgical treatment of the shoulder joint.

The spectrum ranges from arthroscopic shoulder surgery, with reconstruction of tendon injuries and shoulder stabilization operations, to endoprosthetic treatment of shoulder arthrosis. Using state-of-the-art surface replacement prostheses and so-called “inverse” shoulder prostheses, Dr. Ahrens can help patients.

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Dr. Ahrens began his medical career at the Clinic for Orthopedics at Münster University Hospital under the direction of Prof. Dr. med. W. Winkelmann where he concentrated on the sub-areas of endoprosthetics, revision endoprosthetics and foot surgery.

For further specialization in these operative areas, he moved to the Auguste-Viktoria-Klinik (orthopedic specialist hospital) in Bad Oeynhausen in April 2008 under the direction of Prof. Dr. med. Chr. Götze. In 2009 he received his doctorate.

To complete the entire spectrum of trauma surgery and intensive care medicine, Dr. Ahrens moved to the Marienhospital Osnabrück, Clinic for Trauma, Hand and Reconstructive Surgery under the direction of Prof. U. Joosten in July 2010.

Dr. Ahrens joined ONZ as a partner in 2016 and as an associate in 2020 and is a specialist in orthopedics and trauma surgery.

Dr. Ahrens holds the following additional designations:

Special orthopedic surgery
Manual therapy and chiropractic therapy


Accident physician of the professional associations


Association of South German Orthopedists
– North German Orthopedic Association
– German Society for Manual Medicine (DGMM-MWE)
– German Society for Sports Medicine
– German Association for Orthopedic Foot Surgery (D.A.F)

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