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A Pedigree with Heritage and Clinical Data

  • The original ball-and-socket knee portfolio
  • Over 25 years of clinical heritage and ODEP 13A[1]
  • Low revision rates, better high-end activity
  • Better patient-reported success and satisfaction
  • A step further for the ‘forgotten knee’

The Medial Rotation Knee™ (MRK™) is the most successful total knee replacement on the market; this is demonstrated in The National Joint Registry alongside comparative studies on other products.

The MRK™ was patented by Finsbury Orthopaedics in 1990 and developed based on the company’s vast knowledge of anatomy and structures of the knee dating back to 1978. This anatomical approach along with a desire to meet the patients’ growing needs has resulted in a revolutionary and very successful knee design that resembles the movement of the natural knee – we refer to this as the medial-ball- and-socket design.

The MatOrtho SAIPH® Knee is a modern update of the MRK™, it has been developed using the same principles and it is presenting the same high levels of satisfaction.

For more information please visit the product pages to freely download literature or arrange to speak with your local representative.

  1. Orthopaedic Data Evaluation Panel (ODEP). Latest ODEP ratings can be found at

Natural Asymmetry

  • Anatomical and functional asymmetry
  • Physiological medial stability
  • Lateral freedom to move AP
  • Physiologically lateralised trochlea
  • Normal feeling of stability and movement

In normal healthy knees, the shapes of the medial and lateral tibial condyles are different: the medial side is concave; the lateral side is convex. Stability is provided collectively by the collateral ligaments (ACL and PCL) and the menisci.

The resulting pattern of movement during flexion is asymmetric: the medial condyle is stable throughout the range of motion; on the lateral side there is limited freedom to move anterior-posterior (tibia with respect to the femur).

The anatomy of the patellofemoral articulation is also asymmetric: the femoral trochlea is lateral to the midline and the patella has a larger lateral facet compared to the medial facet. As a result, normal patellar tracking is asymmetric.

The Medial Rotation Knee™ (MRK™) and the SAIPH® Knee were both designed on the principle that by providing this asymmetry in all three components, better function and increased patient satisfaction can be achieved. The clinical data supports this philosophy.

Complete Stability

  • Substitutes for the ACL, PCL and meniscus
  • Full-range Posterior Stabilised
  • No mid-stance instability or paradoxical motion
  • Physiological lateral stability from extensor mechanism

A ‘medial pivot’ design implies that a TKR is intended to conform to the idea that the normal knee always exhibits a medial centre of rotation. This is not the case: the normal knee centre of rotation is not static and in some activities, lateral AP translation is suppressed. Normal knees are however stable throughout flexion. The provision of stability by the articular shapes and constraining tissues is greatest on the medial side but both the lateral and patellofemoral compartments also contribute to stability. If any compartment is neglected, the outcome is compromised.

As such, the defining principle of MatOrtho® ball-and-socket knees is the provision of full-ROM stability. Because this is achieved with a medial deep-dish ball-and-socket articulation the concept is better termed ‘medially stabilised’. However overall stability is achieved with appropriate constraint in all compartments and this is demonstrated by the assessment of total knee AP stability throughout ROM.

The defining principle of MatOrtho® ball-and-socket knees is provision of full-ROM stability.

Designed Without Compromise

  • Combines the design attributes of all four basic philosophies in Total Knee Replacement
  • Highly conforming, low contact stress for low wear
  • Proportional flexion radii for the patient population
  • Tibia locking mechanism eliminates micromotion

The MatOrtho® medial ball-and-socket knee design consistently achieves superior functional performance and excellent survivorship. With a heritage of low revision rates, the fixation design and tibiofemoral constraint work with normal knee function and preserve fixation longevity.

Proven materials are used with long-standing clinical evidence to support its design. The design provides the right balance for natural freedom of movement and stability for every compartment (medial, lateral and patellofemoral).

The medial-ball-and-socket knee provides the benefits of all other bearing designs rolled into one: fixed condylar, bicruciate substituting, posterior stabilised and mobile bearing.

The unique and proven tibia locking mechanism eliminates micromotion, which can be experienced with alternative designs, and offers excellent femoral and tibial contact throughout ROM resulting in low stresses and wear on the implant components.

Patient Satisfaction

  • Improved range-of-motion
  • Increased high-end function
  • Better physical outcome
  • Less pain

The MatOrtho® medial ball-and-socket knees provide more inherent stability than comparator devices. When combined with a lateralised trochlea, a medial ball-and-socket knee exhibits a more normal patellar function and better restoration of range-of-motion (ROM) when compared to a standard PS knee design and mean ROM is equal to that of a ‘high-flex’ knee.

The medial ball-and-socket knee provides better high-end function for categories of daily living, sport and exercise, movement and lifestyle compared to the most commonly used standard PS knee in the UK using the total knee function questionnaire (TKFQ).

Views by MatOrthoPatients with a MatOrtho® medial ball-and-socket knee are less likely to modify their lifestyle to accommodate their knee replacement, more likely to ‘forget’ their knee in everyday life and report better quality of life 1-year after their surgery.

When compared to all TKR designs the benefits of the medial ball-and-socket knee are reflected in higher functional scores and improved rates of success and satisfaction.

A More Natural Patella Function

  • A physiologically lateralised trochlea, like the normal knee
  • 40+ years of successful clinical heritage to support the design
  • Cemented and cementless patella options

Total knee replacement surgery replaces the patellofemoral joint, whether or not the patella itself is resurfaced. The patellofemoral joint is as important for a high-functioning knee replacement as the tibiofemoral joint, but it is often neglected or ‘second-place’ in TKR design. All three compartments of the MatOrtho medial ball-and-socket knees have been optimised – including the PF joint.

The normal trochlea is lateral to the midline and with an asymmetric patella, the normal patella tracks laterally in flexion. The lateralised patella also plays a role in stabilising the lateral tibiofemoral articulation. Most standard TKR devices are restricted to a centrally located trochlea – a necessity given standard femoral condylar design and the resulting patella tracking does not compare well to that of the normal knee.

The MatOrtho medial ball-and-socket Knees feature a physiologically lateralised trochlea which exhibits a similar amount of lateral translation of the patella in flexion as patients without a total knee replacement.

With the right trochlea design, choosing not to replace the patella has not been shown to influence outcomes. Nevertheless, the MatOrtho Medial ball-and-socket knees are available with the same unique saddle-shaped patella, which can rotate to match the femur for a fully conforming interface and has 40 years of successful clinical heritage to support its use.

The clinical data supports this information.

Authentic Engineering Based on Real Science and Knowledge

  • Based on our philosophy for a safe introduction of new technology
  • 40+ years of successful clinical heritage to support the design
  • Evolved design based on clinical experience!

The SAIPH® Knee is a 2nd generation medial ball-and-socket knee. It is an evolved design based on the clinical successful Medial Rotation Knee™ (MRK™) that has been used since 1994.

The MatOrtho philosophy for the safe introduction of new technology was applied to the SAIPH Knee and for 10 years it was closely monitored through limited availability.

Over 6,000 procedures are currently recorded in the National Joint Registry and the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Data up to 31st  December 2019 is reported in the respective annual reports and further demonstrates the success of this  2nd generation medial ball-and-socket knee.

Information relating to our knee portfolio can be found on the relevant product page.

A useful document for your reference is the SAIPH® Clinical Rationale – Click here


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