Medial Rotation Knee™

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The knee that became a philosophy

Medial Rotation Knee™

The Medial Rotation Knee™ (MRK™) is the original medial ball-and-socket knee and has been in clinical use for over 25 years. The MRK™ design was based on the principle that by providing natural functional and anatomical asymmetry in all three knee compartments (medial tibiofemoral, lateral tibiofemoral and patellofemoral articulations), better function and increased patient satisfaction can be achieved without the compromises of traditional TKRs.

The result is complete inherent stability throughout the range of motion, coupled with allowance for physiological rotation during flexion. The design also features a physiologically asymmetric patellofemoral joint for a more natural feel and ease of flexion.

When compared to all other knees, the MRK™ medial ball-and-socket knee design consistently achieves superior functional performance and excellent survivorship. Clinical data for the MRK™ shows that patients can expect:

  • Inherent full ROM stability [1-3], like the normal knee [4];
  • An excellent range of motion [1,5,6], with a device that permits over 140° flexion [1];
  • Significant health gains and improvements in function [3,5,7]; and
  • Excellent survivorship [7-9] with a device that has an ODEP 15A rating [10].
  1. Moonot P, Mu S, Railton GT, Field RE, Banks SA. Tibiofemoral kinematic analysis of knee flexion for a medial pivot knee. Knee Surg Sports Traumatol Arthrosc. 2009; 17(8):927-34.
  2. Molloy D, Jenabzadeh R, Walter W and Hasted T. Sagittal Stability in Three Different Knee Designs. A Single Centre Independent Review. Bone Joint J 2013; 95-B SUPP 15 85 (presented ISTA 2012; The Great Debate 2013)
  3. Jonas SC, Argyropoulos M, Al-Hadithy N, Korycki M, Lotz B, Deo SD, Satish V. Knee arthroplasty with a medial rotating total knee replacement. Midterm clinical findings: A district general experience of 38 cases. The Knee. 2015; 22(2): 122-125.
  4. Johal P, Williams A, Wragg P, Hunt D, Gedroyc W. Tibio-femoral movement in the living knee. A study of weight bearing and non-weight bearing knee kinematics using ‘interventional’ MRI. J Biomech. 2005; 38(2):269-76.
  5. Hossain F, Patel S, Rhee SJ, Haddad FS. Knee arthroplasty with a medially conforming ball-and-socket tibiofemoral articulation provides better function. Clin Orthop Relat Res. 2011; 469(1):55-63
  6. Kooijman CM and van Stralen GMJ. Having the confidence to change for a more stable future. June 2013. Presented at The Great Debate, London.
  7. National Joint Registry. Implant Summary Report: August 2016. Ref: Summary.Report.KP_Femoral_MRK.15/08/2016.20:41 (held by MatOrtho Ltd.)
  8. National Joint Registry. 14th Annual Report, 2017:
  9. Mannan K and Scott G. The Medial Rotation total knee replacement: a clinical and radiological review at a mean follow-up of six years. J Bone Joint Surg Br. 2009; 91(6):750-6.
  10. Orthopaedic Data Evaluation Panel (ODEP). Latest ODEP ratings can be found at The MRK™ has  been awarded a 15A rating when used with the patella and 13A for use without a patella.