ASTM F2722-21

Standard Practice for Evaluating Mobile Bearing Knee Tibial Baseplate Rotational Stops

SIGNIFICANCE AND USE
4.1 Fundamental aspects of this practice include the use of dynamic rotational force and motion representative of the human knee joint during an activity of daily living (deep flexion) and the effect of these forces and motions on the design features which stop or limit rotation in a mobile bearing knee design.  
4.2 This test is required if rotational stops are designed to limit motion to ±20° or less; or there are other resistances to rotational motion with this ±20° range. In some instances, the rotational displacement could occur in both the inferior and superior interfaces.  
FIG. 1 Schematic of Test Setup
SCOPE
1.1 This practice covers a laboratory-based in-vitro method for evaluating the mechanical performance of materials and devices being considered for replacement of the tibio-femoral joint in human knee joint replacement prostheses in mobile bearing knee systems.  
1.2 Mobile bearing knee systems permit internal/external rotation to take place on one or both articulating surfaces. Some designs place physical limits or stops to the amount of rotation. Other designs may have increases of a resistance force with increases in rotation.  
1.3 Although the methodology describes attempts to identify physiologically relevant motions and force conditions, the interpretation of results is limited to an in-vitro comparison between mobile bearing knee designs and their ability to maintain the integrity of the rotational stop feature and tibial bearing component under the stated test conditions.  
1.4 This practice is only applicable to mobile knee tibial systems with a rotational stop.  
1.5 The values stated in SI units are regarded as standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Feb-2021
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.22 - Arthroplasty

Relations

• Refers: ASTM F2083-11 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Dec-2011
• Refers: ASTM F2083-10 - Standard Specification for Total Knee Prosthesis
• Effective Date: 15-Apr-2010
• Refers: ASTM F2083-08e1 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Jul-2008
• Refers: ASTM F2083-08 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Jul-2008
• Refers: ASTM F2003-02(2008) - Standard Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air
• Effective Date: 01-May-2008
• Refers: ASTM F2083-07 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Aug-2007
• Refers: ASTM F2083-06b - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Sep-2006
• Refers: ASTM F2083-06a - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Aug-2006
• Refers: ASTM F2083-06 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Mar-2006
• Refers: ASTM F2083-04 - Standard Specification for Total Knee Prosthesis
• Effective Date: 01-Nov-2004
• Refers: ASTM F2083-03 - Standard Specification for Total Knee Prosthesis
• Effective Date: 10-Apr-2003
• Refers: ASTM F2003-02 - Standard Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air
• Effective Date: 10-Dec-2002
• Refers: ASTM F2083-01a - Standard Specification for Total Knee Prosthesis
• Effective Date: 10-Jun-2001
• Refers: ASTM F2083-01 - Standard Specification for Total Knee Prosthesis
• Effective Date: 10-Jun-2001
• Refers: ASTM F2003-00 - Standard Guide for Accelerated Aging of Ultra-High Molecular Weight Polyethylene
• Effective Date: 10-Jan-2000

Overview

ASTM F2722-21: Standard Practice for Evaluating Mobile Bearing Knee Tibial Baseplate Rotational Stops provides a laboratory-based, in vitro methodology for testing the mechanical performance of materials and devices intended for use in the replacement of the tibio-femoral joint with mobile bearing knee systems. This international standard, developed by ASTM International, is critical for ensuring that the design features which restrict or stop rotation in mobile knee prostheses are robust and safe.

This standard is especially significant for prostheses where rotational motion is mechanically limited to ±20° or less, requiring stringent evaluation under dynamic conditions reflective of real-world knee movement, such as deep flexion during daily activities.

Key Topics

• Dynamic Rotational Testing: Focuses on applying forces and motions to simulate physiologically relevant activities, particularly deep bending or squatting, to evaluate the durability of tibial baseplate rotational stops.
• Applicability: Specifically intended for mobile bearing knee systems that incorporate a rotational stop, especially those engineered to limit motion to a defined angular range.
• Mechanical Test Parameters:
  • Utilizes a force representative of normal knee joint loading.
  • Requires cyclic rotational motion within a set frequency range.
  • Assesses both internal and external rotational stop performance if the design is asymmetric.
• Specimen Preparation and Test Conditions:
  • Emphasizes use of components reflecting final production geometries and materials, including aged polymeric components when applicable.
  • Details reporting requirements, including component sizes, material properties, test frequency, and documentation of any failure modes observed during testing.

Applications

ASTM F2722-21 is vital for:

• Prosthesis Manufacturers: Ensures that mobile bearing knee designs with rotational stops meet mechanical integrity and durability expectations before clinical adoption.
• Orthopedic Device Testing Laboratories: Provides a standardized in vitro approach for comparative evaluation of different mobile knee bearing designs.
• Regulatory Submission: Generates essential performance data required for demonstrating compliance with health authority and regulatory requirements for total knee replacement devices.
• Research and Development: Facilitates focused improvements in mobile bearing knee prosthesis design based on reliable, reproducible testing of rotational stop features.
• Risk Assessment: Informs on the expected longevity and safety of rotational stops under repetitive, physiologically-relevant motions, supporting preclinical risk management.

Related Standards

This standard is intended for use in conjunction with other ASTM and industry standards relevant to knee joint replacement prostheses, including:

• ASTM F2083 - Specification for Knee Replacement Prosthesis: Defines requirements and classifications for knee implants.
• ASTM F2003 - Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation: Guides preparation of polymeric components under test.
• Additional testing and safety standards relevant to orthopedic implant evaluation and quality assurance.

Practical Value

By adhering to ASTM F2722-21, stakeholders in the orthopedic device industry ensure an evidence-based, internationally recognized methodology for testing the reliability and performance of mobile bearing knee systems. This contributes to improved device safety, supports regulatory approval, and fosters innovation in total knee arthroplasty technology. For patients, it translates into enhanced confidence in the durability and functionality of their knee implants, particularly for those who require a high degree of mobility or are at higher risk for implant wear due to greater joint motion.

Keywords: ASTM F2722-21, mobile bearing knee, tibial baseplate, rotational stop, knee prosthesis testing, orthopedic implant standard, total knee replacement, mechanical performance, in vitro testing, rotational motion limit.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2722 − 21
Standard Practice for
Evaluating Mobile Bearing Knee Tibial Baseplate Rotational
Stops
This standard is issued under the fixed designation F2722; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers a laboratory-based in-vitro method
F2003Practice for Accelerated Aging of Ultra-High Mo-
for evaluating the mechanical performance of materials and
lecular Weight Polyethylene after Gamma Irradiation in
devices being considered for replacement of the tibio-femoral
Air
joint in human knee joint replacement prostheses in mobile
F2083Specification for Knee Replacement Prosthesis
bearing knee systems.
1.2 Mobile bearing knee systems permit internal/external 3. Terminology
rotation to take place on one or both articulating surfaces.
3.1 Definitions:
Some designs place physical limits or stops to the amount of
3.1.1 bearing axis—thelineconnectingthelowestpointson
rotation.Otherdesignsmayhaveincreasesofaresistanceforce
both the lateral and medial condyles of the superior surface of
with increases in rotation.
the mobile bearing.
3.1.2 inferior articulating interfaces—any interface in
1.3 Although the methodology describes attempts to iden-
which relative motion occurs between the underside of the
tify physiologically relevant motions and force conditions, the
mobile bearing component and the tibial tray.
interpretation of results is limited to an in-vitro comparison
3.1.3 mobile bearing—the component between fixed femo-
between mobile bearing knee designs and their ability to
ral and tibial knee components with an articulating surface on
maintain the integrity of the rotational stop feature and tibial
both the inferior and superior sides.
bearing component under the stated test conditions.
3.1.4 mobile bearing knee system—a knee prosthesis
1.4 This practice is only applicable to mobile knee tibial
system, comprised of a tibial component, a mobile bearing
systems with a rotational stop.
component that can rotate or rotate and translate relative to the
tibial component, and a femoral component.
1.5 The values stated in SI units are regarded as standard.
3.1.5 neutral point—midpoint of the bearing axis.
1.6 This standard does not purport to address all of the
3.1.6 rotational stop—a feature that prevents relative rota-
safety concerns, if any, associated with its use. It is the
tion between two articulating joint surfaces beyond a specific
responsibility of the user of this standard to establish appro-
angle of rotation or creates resistance to rotation beyond a
priate safety, health, and environmental practices and deter-
specific angel of rotation.
mine the applicability of regulatory limitations prior to use.
3.1.7 superior articulating interfaces—any interface in
1.7 This international standard was developed in accor-
whichrelativemotionoccursbetweenthetopsideofthemobile
dance with internationally recognized principles on standard-
bearing component and the femoral bearing component.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4. Significance and Use
mendations issued by the World Trade Organization Technical
4.1 Fundamental aspects of this practice include the use of
Barriers to Trade (TBT) Committee.
dynamic rotational force and motion representative of the
human knee joint during an activity of daily living (deep
ThispracticeisunderthejurisdictionofASTMCommitteeF04onMedicaland
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.22 on Arthroplasty. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 15, 2021. Published February 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2008. Last previous edition approved in 2015 as F2722–15. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/F2722-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2722 − 21
flexion) and the effect of these forces and motions on the 5.2.2 The system should be capable of maintaining an axial
designfeatureswhichstoporlimitrotationinamobilebearing force of 2000 N force as illustrated in Fig. 1. (Although this
knee design. force is representative of a normal range compressive force, it
is mainly intended as a uniform force to keep the components
4.2 This test is required if rotational stops are designed to
in contact during the test.)
limit motion to 620° or less; or there are other resistances to
5.2.3 The system should be capable of applying under
rotational motion with this 620° range. In some instances, the
torque control a peak torque of 14 N-m (2× the peak torque
rotational displacement could occur in both the inferior and
measured from a telemeterized knee study (1)) and cycling
superior interfaces.
back to near zero torque in both internal and external rotation
directions.
5. Apparatus and Materials
5.2.4 If the rotational stop geometries for internal and
5.1 Component Configurations:
external rotation are non-symmetrical, both the internal and
5.1.1 A test construct of the femoral component, mobile
external rotational stops should be tested. The same sample
bearing component, and tibial tray should be used to provide
may be used for both tests if the results of the first test do not
appropriate interface geometries.
cause any damage that could affect the results of the second
5.1.2 The knee joint tibial and femoral components should
test.
beassembledandorientedinamannersimilartothatinwhich
5.2.5 Rotational Test Frequency—Rotate the relative rota-
they would function in vivo as depicted in Fig. 1. The femoral
tional motion at a nominal rate of 0.5 to 3.0 cycles per second
component is mounted at the maximum flexion angle claimed
(0.5 to 3.0 Hz) per complete cycle to minimize viscoelastic
for the device by the manufacturer.
high frequency effects.
5.1.3 The tibial component is mounted at zero slope. This
5.2.6 Cycle Counter—Include with the mechanical testing
means that the flat portion of the superior tibial surface will be
system a method to monitor and count the number of cycles.
perpendicular to the force axis.
5.2.7 Lubricant—Lubricate the specimen by immersion in
water (for example, reverse osmosis (RO) water, deionized
5.2 Mechanical Testing Systems:
5.2.1 Test Chambers—Design each chamber entirely of (DI) water, or distilled water) and maintain at 37 6 2°C.
noncorrosivematerials,suchasacrylicplasticorstainlesssteel,
6. Specimen Preparation
and ensure that it is easily removable from the machine for
6.1 The geometry of the parts must be within the specified
thorough cleaning between tests. Design the chambers such
tolerance ranges of final production designs.
that the bearing surfaces are immersed in lubricant throughout
the test.
6.2 The metallic components should follow the complete
manufacturing process (machining, surface treatment, laser
marking, passivation, cleaning, and so forth) until the steril-
ization stage. Because sterilization has no known effect on the
mechanical properties for metallic components, it is not nec-
essary for these to be sterilized. The polymeric components
shouldbesterilizedinamannerconsistentwiththeclinicaluse
for such devices, as this may affect the mechanical properties
of the material.
6.3 The ultra-high molecular weight polyethylene(UHM-
WPE) components should be artificially aged according to
Practice F2003, except when the mechanical properties of the
UHMWPE have been proven not to be detrimentally affected
by the aging,
6.4 Because the cold flow of the bearing component de-
pends on its thickness, the thinnest bearing component in the
knee system should be used.
6.5 The tibial bearing size, including thickness, shall be
explicitlyspecifiedandreported,witharationaleofwhyitwas
chosen. It is good practice to also explicitly specify and report
the sizes and rationale of all other components of the implant
specimens used.
7. Procedure
7.1 Rigidly mount the femoral component at the maximum
flexion angle of the knee as determined in Specification F2083
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
FIG. 1 Schematic of Test Setup this standard.
F2722 − 21
to
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F2722 − 15 F2722 − 21
Standard Practice for
Evaluating Mobile Bearing Knee Tibial Baseplate Rotational
Stops
This standard is issued under the fixed designation F2722; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers a laboratory-based in vitroin-vitro method for evaluating the mechanical performance of materials and
devices being considered for replacement of the tibio-femoral joint in human knee joint replacement prostheses in mobile bearing
knee systems.
1.2 Mobile bearing knee systems permit internal external internal/external rotation to take place on one or both articulating
surfaces. Some designs place physical limits or stops to the amount of rotation. Other designs may have increases of a resistance
force with increases in rotation.
1.3 Although the methodology describes attempts to identify physiologically relevant motions and force conditions, the
interpretation of results is limited to an in vitroin-vitro comparison between mobile bearing knee designs and their ability to
maintain the integrity of the rotational stop feature and tibial bearing component under the stated test conditions.
1.4 This practice is only applicable to mobile knee tibial systems with a rotational stop.
1.5 The values stated in SI units are regarded as standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
F2083 Specification for Knee Replacement Prosthesis
F2003 Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air
F2083 Specification for Knee Replacement Prosthesis
This practice is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee F04.22
on Arthroplasty.
Current edition approved Jan. 15, 2015Feb. 15, 2021. Published February 2015.February 2021. Originally approved in 2008. Last previous edition approved in 20082015
as F2722F2722 – 15.-08. DOI: 10.1520/F2722-15.10.1520/F2722-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2722 − 21
3. Terminology
3.1 Definitions:
3.1.1 bearing axis—the line connecting the lowest points on both the lateral and medial condyles of the superior surface of the
mobile bearing.
3.1.2 inferior articulating interfaces—any interface in which relative motion occurs between the underside of the mobile bearing
component and the tibial tray.
3.1.3 mobile bearing—the component between fixed femoral and tibial knee components with an articulating surface on both the
inferior and superior sides.
3.1.4 mobile bearing knee system—a knee prosthesis system, comprised of a tibial component, a mobile bearing component that
can rotate or rotate and translate relative to the tibial component, and a femoral component.
3.1.5 neutral point—midpoint of the bearing axis.
3.1.6 rotational stop—a feature that prevents relative rotation between two articulating joint surfaces beyond a specific angle of
rotation or creates resistance to rotation beyond a specific angel of rotation.
3.1.7 superior articulating interfaces—any interface in which relative motion occurs between the topside of the mobile bearing
component and the femoral bearing component.
4. Significance and Use
4.1 Fundamental aspects of this practice include the use of dynamic rotational force and motion representative of the human knee
joint during an activity of daily living (deep flexion) and the effect of these forces and motions on the design features which stop
or limit rotation in a mobile bearing knee design.
4.2 This test is required if rotational stops are designed to limit motion to 620° or less; or there are other resistances to rotational
motion with this 620° range. In some instances, the rotational displacement could occur in both the inferior and superior interfaces.
5. Apparatus and Materials
5.1 Component Configurations:
5.1.1 A test construct of the femoral component, mobile bearing component, and tibial tray should be used to provide appropriate
interface geometries.
5.1.2 The knee joint tibial and femoral components should be assembled and oriented in a manner similar to that in which they
would function in vivo as depicted in Fig. 1. The femoral component is mounted at the maximum flexion angle claimed for the
device by the manufacturer.
5.1.3 The tibial component is mounted at zero slope. This means that the flat portion of the superior tibial surface will be
perpendicular to the force axis.
5.2 Mechanical Testing Systems:
5.2.1 Test Chambers—Design each chamber entirely of noncorrosive materials, such as acrylic plastic or stainless steel, and ensure
that it is easily removable from the machine for thorough cleaning between tests. Design the chambers such that the bearing
surfaces are immersed in lubricant throughout the test.
5.2.2 The system should be capable of maintaining an axial force of 2000 N force as illustrated in Fig. 1. (Although this force
is representative of a normal range compressive force, it is mainly intended as a uniform force to keep the components in contact
during the test.)
F2722 − 21
FIG. 1 Schematic of Test Setup
5.2.3 The system should be capable of applying under torque control a peak torque of 14 N-m (2× the peak torque measured from
a telemeterized knee study (1)) ) and cycling back to near zero torque in both internal and external rotation directions.
5.2.4 If the rotational stop geometries for internal and external rotation are non-symmetrical, both the internal and external
rotational stops should be tested. The same sample may be used for both tests if the results of the first test do not cause any damage
that could affect the results of the second test.
5.2.5 Rotational Test Frequency—Rotate the relative rotational motion at a nominal rate of 0.5 to 3.0 cycles per second (0.5 to
3.0 Hz) per complete cycle to minimize viscoelastic high frequency effects.
5.2.6 Cycle Counter—Include with the mechanical testing system a method to monitor and count the number of cycles.
5.2.7 Lubricant—Lubricate the specimen by immersion in deionized water, mineral oil, olive oil or other suitable lubricant and
maintainedwater (for example, reverse osmosis (RO) water, deionized (DI) water, or distilled water) and maintain at 37 6
2°C.2 °C.
6. Specimen Preparation
6.1 The geometry of the parts must be within the specified tolerance ranges of final production designs.
6.2 The metallic components should follow the complete manufacturing process (machining, surface treatment, laser marking,
passivation, cleaning, and so forth) until the sterilization stage. Because sterilization has no known effect on the mechanical
properties for metallic components, it is not necessary for these to be sterilized. The polymeric components should be sterilized
in a manner consistent with the clinical use for such devices, as this may affect the mechanical properties of the material.
6.3 The ultra-high molecular weight polyethylene (UHMWPE) components should be artificially aged according to Practice
F2003, except when the mechanical properties of the UHMWPE have been proven not to be detrimentally affected by the aging,
The boldface numbers in parentheses refer to the list of references at the end of this standard.
F2722 − 21
6.4 Because the cold flow of the bearing component depends on its thickness, the thinnest bearing component in the knee system
should be used.
6.5 The tibial bearing size, including thickness, shall be explicitly specified and reported, with a rationale of why it was chosen.
It is good practice to also explicitly specify and report the sizes and rationale of all other components of the implant specim
...