Condition category
Musculoskeletal Diseases
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status

Plain English Summary

Background and study aims:
Total knee replacement (TKR) is the established way to treat end-stage osteoarthritis of the knee (when other treatment modalities have been exhausted). Currently more than 50,000 knee replacements are implanted every year in the UK. Over the past 30 years many new versions of knee replacements have been introduced with the development of technology supposedly leading to improvement in the function of the implant and hence the outcome for the patient. In current orthopaedic practice several different versions of TKR are in common use in the UK, and outcome studies using knee pain and functional scoring systems show similar results for most types of implants - around 90% survivorship at 10 years and generally good functional results. The aim of this study is to compare the outcome of a new type of knee replacement implant (Triathlon) which, it is claimed, allows greater movement of the knee and better function for patients than the current standard knee replacement implant (Kinemax). Both implants have received approval from the National Authorities and are currently used in this hospital. The surgeons involved in this study are experienced in using both types of knee replacement but it is not known whether one gives better results for patients.

Who can participate?
Patients with osteoarthritis on the waiting list for primary TKR

What does the study involve?
Participants are randomly allocated to receive one of the two implants (either Kinemax or Triathlon). All other aspects of the operation and post-operative care are the same as for those not taking part in this study. There is no technical difference in the surgery and no difference in the nursing care or rehabilitation. Participants are assessed at the pre-admission clinic visit (about 2 weeks before the surgery) and at 6 weeks, 6 months and then at 1, 3 and 5 years after the operation. The assessor does not know which type of knee has been used. Assessments involve questionnaires on issues such as the knee pain and stiffness, general health and daily activities. Knee movement, leg strength and ability to undertake some simple day to day tasks, such as walking up and down stairs, getting up from a chair and walking a measured distance, are all measured.

What are the possible benefits and risks of participating?
There should be no additional harmful effects caused by participation in this study in addition to those for people undergoing knee replacement surgery. Both types of implants have been routinely used. During the assessments participants are asked to perform normal activities of daily life such as climbing stairs which may cause some knee pain. However, they are asked to perform those activities in the same way as they would usually do, minimising the pain as much as possible. Participants can always at any moment withdraw from the tests. It is hoped that either treatment will help with pain and dysfunction. Both implants have been approved for use in the UK, but it is not known which implant will help the most and this is why this study is taking place. The information will help to plan treatment for future patients with osteoarthritis requiring a knee implant.

Where is the study run from?
University of Edinburgh and NHS Lothian. All operations and follow-up clinics will be carried out via the Royal Infirmary of Edinburgh (UK)

When is the study starting and how long is it expected to run for?
February 2008 to October 2015

Who is funding the study?
Styrker Orthopaedics (UK)

Who is the main contact?
Dr David Hamilton

Trial website

Contact information



Primary contact

Mr Paul Gaston


Contact details

Department of Orthopaedics and Trauma
Royal Infirmary of Edinburgh
Little France Crescent
EH16 4SB
United Kingdom

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Comparison of outcome in Total Knee Replacement (TKR) using a new design 'single-raduis-of-curvature' implant (TRIathlon) versus a traditional design 'multi-raduis' implant (KineMAX)



Study hypothesis

That a new implant designed based on modern kinematic theory of the knee would demonstrate enhanced functional outcome in comparison to a traditional design of knee prosthesis.

Ethics approval

Lothian Local Research Ethics Committee, 04/12/2006, ref: 06/S1103/50

Study design

Single-centre prospective double-blind randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details to request a patient information sheet


Osteoarthritis / total knee arthroplasty


Primary total knee arthroplasty - Patients randomised to either Triathlon or Kinemax implants

Intervention type



Drug names

Primary outcome measure

1. Change in Oxford Knee Score
2. Lower limb extensor mechanism power output (Leg Extensor Power Rig)
Measured pre-op, 6 weeks, 6 months, 12 months, 3 years and 5 years

Secondary outcome measures

1. Knee range of movement (flexion/extension)
2. Battery of timed functional performance tests (timed up-and-go, stairs climb, 8 metre walk)
3. Pain scores (0-10 numerical rating scale)
4. Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index
Measured pre-op, 6 weeks, 6 months, 12 months, 3 years and 5 years

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Diagnosis of osteoarthritis
2. Planned primary total knee arthroplasty with standard implants
3. Capacity to give informed consent

Participant type


Age group




Target number of participants

204 (102 patients per arm)

Participant exclusion criteria

1. Inability to fulfill the inclusion criteria
2. Comorbidities that would affect post operative recovery or subsequent physical performance

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Royal Infirmary of Edinburgh
EH16 4SB
United Kingdom

Sponsor information


University of Edinburgh (UK)

Sponsor details

Queen's Medical Research Institute
47 Little France Crescent
EH16 4JT
United Kingdom

Sponsor type




Funder type


Funder name

Stryker Orthopaedics (UK)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2015 results in:

Publication citations

Additional files

Editorial Notes

14/11/2017: Publication reference added.