OsteoarthritisFLEX-UNINCT04913987
Unicompartmental Versus Total Knee Replacement for Medial Compartment Knee Osteoarthritis
A study testing Persona Partial Knee (PPK) and Triathlon cruciate-retaining total knee system. in people with Osteoarthritis and Knee, run by Golden Jubilee National Hospital at 1 site in United Kingdom.
Trial summary
For patients with osteoarthritis affecting only the inner part of the knee, surgeons can offer either a partial knee replacement, which resurfaces the worn compartment alone, or a total knee replacement. Both are recommended treatments, but there is no agreement on when to choose one over the other. Read more about this study
- Who is it for?
- Ages 18 to 75 years
- Conditions the study is for
- Osteoarthritis, Knee, Arthroplasty
- What is being tested?
- Persona Partial Knee (PPK) and Triathlon cruciate-retaining total knee system.
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 26 Apr 2021to 15 Oct 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Suitable for medial unicompartmental knee arthroplasty
- Aged between 18 and 75 years inclusive
- Taller than 1.5m in height (the 10th percentile for the population)
- Functionally intact anterior cruciate ligament
- Able to give informed consent
- Able to return to the study centre for follow-up
- BMI under 40
Who cannot join
- Inflammatory joint disease e.g. rheumatoid arthritis
- Previous hip procedure within the previous twelve months
- Previous knee surgery other than arthroscopy and medial menisectomy
- Previous ankle surgery
- Symptomatic foot, hip or spinal pathology
- Any medical condition limiting normal ambulation e.g. stroke, Charcot-Marie-Tooth disease, severe lymphedema, advanced cardiac disease
- Unable to read and understand English and follow verbal and visual instructions unless they can bring a relative or friend to all study assessments to act as a translator
Trial locations and contacts
1 site in 1 country.
United Kingdom1 site
Golden Jubilee National Hospital
Clydebank, West Dunbartonshire, G81 4DY
About this study
Official title: A Functional, Clinical, and Biomechanical Examination of Unicompartmental Versus Total Knee Arthroplasty for Medial Compartment Knee Osteoarthritis (FLEX-UNI): A Randomized Controlled Trial
For patients with osteoarthritis affecting only the inner part of the knee, surgeons can offer either a partial knee replacement, which resurfaces the worn compartment alone, or a total knee replacement. Both are recommended treatments, but there is no agreement on when to choose one over the other. Partial knee replacement preserves the anterior cruciate ligament and more of the natural knee, and recovery is usually quicker, but it is used in only about one in ten knee replacements in the United Kingdom.
Studies comparing the two have mostly relied on patient questionnaires, which may not be sensitive enough to detect differences in how the knee actually functions. Studies that have measured movement directly have concentrated on level walking, which is not demanding enough to separate the two operations. Difficulty with stairs is one of the longest lasting problems patients report after knee replacement.
The FLEX-UNI trial will compare the two operations using three-dimensional motion analysis during more demanding everyday activities. Forty patients who are suitable for a partial knee replacement will be randomly allocated to receive either a partial or a total knee replacement. Patients and the researchers measuring their movement will not know which operation was performed. The main measurement is how far the operated knee bends while stepping down from a 20 cm step, measured one year after surgery. Movement during walking, stair climbing, slopes, sitting and standing, and balance will also be measured, along with questionnaires, x-rays, and complications. Results will be compared against measurements from people with healthy knees.
Read the detailed description
FLEX-UNI is a single-centre, prospective, randomized, double-blinded, controlled superiority trial comparing medial unicompartmental knee arthroplasty (UKA) with total knee arthroplasty (TKA) in patients with anteromedial knee osteoarthritis. Forty participants will be randomized 1:1. The trial is conducted at a high-volume elective arthroplasty centre and participants are followed for 12 months.
Participants are identified from the clinic lists of participating consultant orthopaedic surgeons and screened against the eligibility criteria by a member of the research team and by the treating consultant. Following written consent and baseline assessment, participants are randomized using sequentially numbered, opaque, sealed envelopes prepared and opened by a member of the research team not involved in screening, recruitment, or outcome assessment.
Participants allocated to UKA receive a cemented medial fixed-bearing Persona Partial Knee (Zimmer Biomet, Warsaw, Indiana, USA), implanted using a spacer block technique that resurfaces the medial compartment without deliberate correction of limb alignment. Participants allocated to TKA receive a cemented Triathlon cruciate-retaining total knee system without patellar resurfacing (Stryker, Mahwah, New Jersey, USA), implanted using a measured resection technique with a mechanical alignment target. Both procedures use conventional manual instrumentation, without robotic assistance or computer navigation, and are performed by the same group of consultant surgeons, each of whom performs both operations.
Suitability for medial UKA is confirmed intraoperatively at arthrotomy in all participants, including those allocated to TKA. Participants allocated to UKA who are found at arthrotomy to be unsuitable, principally because of disease progression beyond anteromedial osteoarthritis or a deficient anterior cruciate ligament, undergo TKA.
Participants are blinded to allocation. A standard-size sterile dressing is applied to the surgical wound by an independent healthcare support worker before biomechanical testing to conceal scar length, and participants are not shown their postoperative radiographs unless there is a clinical need. Research staff performing biomechanical assessment, outcome scoring, and statistical analysis are blinded to allocation, with unblinding only after analysis is complete. The treating surgeon cannot be blinded.
Assessments take place preoperatively, immediately postoperatively, and at six weeks, six months, and 12 months. Biomechanical assessment is performed in the centre's Motion Analysis Laboratory using a Vicon motion capture system (Vicon Motion Systems Ltd, Yarnton, UK) and two AMTI force plates (Advanced Mechanical Technology Inc., Watertown, Massachusetts, USA). Tasks are level walking, incline walking, decline walking, step ascent, step descent, sit-to-stand-to-sit, and single-leg balance.
A matched healthy control group is drawn from an existing motion analysis database held at the study centre, comprising individuals without known knee pathology previously assessed using an identical protocol under separate ethical approval. Control data do not contribute to the primary comparison between arms and are used only to contextualize findings against values expected in a healthy population. Healthy controls are not prospectively enrolled in this trial.
The sample size was calculated for the primary outcome, assuming 95 degrees for the UKA group and 89 degrees for the TKA group with a pooled standard deviation of 5.5 degrees, two-sided alpha of 0.05, and 80% power, giving 15 participants per group for an analysis of covariance with baseline as a covariate. Allowing for an estimated 10% intraoperative conversion from UKA to TKA and 15% loss to follow-up, the recruitment target is 20 per group. The trial is powered for the primary outcome alone, and all secondary outcomes are exploratory.
The primary analysis is performed on the per-protocol population, defined as participants who received their randomized implant and completed the 12-month biomechanical assessment. Participants found intraoperatively unsuitable for UKA at arthrotomy are excluded from the primary analysis regardless of allocation.
The trial is funded by Zimmer GmbH (Winterthur, Switzerland).
- Conditions
- Osteoarthritis, Knee, Arthroplasty, Replacement, Knee
- Being tested
- Persona Partial Knee (PPK), Triathlon cruciate-retaining total knee system.
- Keywords
- Total knee arthroplasty, Partial knee arthroplasty, Unicondylar knee arthroplasty, Randomised controlled trial, Functional biomechanical assessment, Movement analysis, Gait analysis, Step descent, Knee kinematic, randomized controlled trial
- Medical subject headings
- Osteoarthritis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Persona Partial Knee (PPK)Device
Cemented medial fixed-bearing unicompartmental knee arthroplasty using the Persona Partial Knee (PPK; Zimmer Biomet, Warsaw, Indiana, USA).
Triathlon cruciate-retaining total knee system.Device
Cemented Triathlon cruciate-retaining total knee system without patellar resurfacing (Stryker, Mahwah, New Jersey, USA).
| Study group | Role | What they receive |
|---|---|---|
| Unicompartmental knee arthroplasty (UKA) | Experimental | Description: Cemented medial fixed-bearing unicompartmental knee arthroplasty, implanted using a spacer block technique that resurfaces the medial compartment without deliberate correction of limb alignment, using conventional manual instrumentation Receives: Device: Persona Partial Knee (PPK) |
| Total knee arthroplasty (TKA) | Active comparator | Cemented cruciate-retaining total knee arthroplasty without patellar resurfacing, implanted using a measured resection technique with a mechanical alignment target, using conventional manual instrumentation. This is the standard total knee implant used at the study centre. Receives: Device: Triathlon cruciate-retaining total knee system. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Maximum knee flexion of the operated knee during step descent
Peak flexion angle of the operated knee in the sagittal plane, in degrees, during descent from a 20 cm step with the operated limb acting as the trailing limb, measured using three-dimensional motion analysis.
Measured: 12 months post-operatively
Secondary outcomes (8)
Maximum knee flexion during step descent, operated limb as trailing limb
Measured: 6 months post-operatively
Knee kinematics and kinetics
Knee kinematics: sagittal, coronal, and transverse plane joint angles during level walking, incline walking, decline walking, step ascent, step descent, and sit-to-stand-to-sit.
Knee kinetics: knee joint moments and ground reaction forces during tasks performed on force plates.
Measured: baseline, 6 months, 12 months
Spatiotemporal and balance
Spatiotemporal gait parameters: walking speed and step length. Single-leg balance: time to failure, in seconds.
Measured: baseline, 6 months, 12 months.
Patient satisfaction
Patient satisfaction on a Fpur-point Likert scale.
Measured: 6 weeks, 6 months, 12 months
Radiographic assessment
- Radiographic assessment of implant position, alignment, and signs of loosening or migration, using a modified Knee Society Roentgenographic Evaluation and Scoring System. No summary score is produced.
Measured: to 12 months postoperatively
Complications and adverse events
- Complications and adverse events, including deep and superficial infection, thromboembolic events, intraoperative fracture, neurovascular injury, wound complications, and any reoperation or revision.
Measured: to 12 months postoperatively
Implant survivorship
Implant survivorship, reported as the number of implants in situ.
Measured: 12 months
Intraoperative conversion from unicompartmental to total knee arthroplasty, reported as the number of participants.
Measured: day of surgery
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Jun 2021
- Study start26 Apr 2021
- Primary completion15 Oct 2027 (estimated)
- Study completion15 Oct 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (13)Papers the sponsor has linked to this study.
- Other trials for OsteoarthritisStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Parallel Assignment. Participants considered suitable for medial unicompartmental knee arthroplasty are randomized 1:1 to receive either a medial unicompartmental knee arthroplasty or a total knee arthroplasty. Allocation uses sequentially numbered, opaque, sealed envelopes prepared and opened by a member of the research team not involved in screening, recruitment, or outcome assessment.
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Golden Jubilee National Hospital
- Sponsor type
- Other government
- Responsible party
- Sponsor
- Investigators
- Nicholas Ohly, FRCS Ed, Principal investigator, Golden Jubilee University National Hospital
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04913987
- Sponsor's protocol ID
- Ortho 18-03
- Other IDs
- 251071, 19/SS/0124
- Acronym
- FLEX-UNI
- Status last verified
- Sep 2026
- First submitted
- 17 Jul 2019
- Last updated
- 24 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Publications
Kuntze G, Panjavi S, Henning E, Korley R, Abelseth G, Ronsky J, Johnston K. Preserving Patient-Specific Knee Motion: A Randomized Clinical Trial of Unicompartmental and Total Knee Arthroplasty. J Orthop Res. 2025 Dec;43(12):2203-2211. doi: 10.1002/jor.70077. Epub 2025 Oct 3.
PubMed 41044992Jung MC, Chung JY, Son KH, Wang H, Hwang J, Kim JJ, Kim JH, Min BH. Difference in knee rotation between total and unicompartmental knee arthroplasties during stair climbing. Knee Surg Sports Traumatol Arthrosc. 2014 Aug;22(8):1879-86. doi: 10.1007/s00167-014-3064-8. Epub 2014 May 24.
PubMed 24859731Bjerke J, Ohberg F, Nilsson KG, Foss OA, Stensdotter AK. Peak knee flexion angles during stair descent in TKA patients. J Arthroplasty. 2014 Apr;29(4):707-11. doi: 10.1016/j.arth.2013.07.010. Epub 2013 Aug 9.
PubMed 23937925Copp EH, Gale TH, Byrapogu VKC, Urish KL, Anderst WJ. Unicompartmental knee arthroplasty approximates healthy knee kinematics more closely than total knee arthroplasty. J Orthop Res. 2024 Nov;42(11):2514-2524. doi: 10.1002/jor.25926. Epub 2024 Jul 2.
PubMed 38956422Komnik I, David S, Funken J, Haberer C, Potthast W, Weiss S. Compromised knee internal rotation in total knee arthroplasty patients during stair climbing. PLoS One. 2018 Oct 10;13(10):e0205492. doi: 10.1371/journal.pone.0205492. eCollection 2018.
PubMed 30304032Komnik I, Peters M, Funken J, David S, Weiss S, Potthast W. Non-Sagittal Knee Joint Kinematics and Kinetics during Gait on Level and Sloped Grounds with Unicompartmental and Total Knee Arthroplasty Patients. PLoS One. 2016 Dec 21;11(12):e0168566. doi: 10.1371/journal.pone.0168566. eCollection 2016.
PubMed 28002437Dong M, Fan H, Yang D, Sun X, Yan C, Feng Y. Comparison of spatiotemporal, kinematic, and kinetic gait characteristics in total and unicompartmental knee arthroplasty during level walking: A systematic review and meta-analysis. Gait Posture. 2023 Jul;104:58-69. doi: 10.1016/j.gaitpost.2023.06.005. Epub 2023 Jun 7.
PubMed 37321113Bayram JM, Clement ND, Hall AJ, Walmsley P, Clarke JV. Are Current Patient-Reported Outcome Measures Fit for Purpose to Evaluate Unicompartmental Knee Arthroplasty? J Clin Med. 2025 Jan 2;14(1):203. doi: 10.3390/jcm14010203.
PubMed 39797286Eckhard L, Munir S, Wood D, Talbot S, Brighton R, Walter B, Bare J. The ceiling effects of patient reported outcome measures for total knee arthroplasty. Orthop Traumatol Surg Res. 2021 May;107(3):102758. doi: 10.1016/j.otsr.2020.102758. Epub 2020 Dec 11.
PubMed 33316442Mohammad HR, Liddle AD, Judge A, Murray DW. A Matched Comparison of Long-Term Outcomes of Total and Unicompartmental Knee Replacements in Different Ages Based on National Databases: Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man. J Arthroplasty. 2022 Feb;37(2):243-251. doi: 10.1016/j.arth.2021.09.018. Epub 2021 Oct 5.
PubMed 34619307Bin G, Jinmin L, Cong T, Yuchen T, Xiaohui Z, Yayi X. Surgical interventions for symptomatic knee osteoarthritis: a network meta-analysis of randomized control trials. BMC Musculoskelet Disord. 2023 Apr 22;24(1):313. doi: 10.1186/s12891-023-06403-z.
PubMed 37087428Beard DJ, Davies LJ, Cook JA, MacLennan G, Hudson J, Price AJ, Carr AJ, Little M, Leal J, Fitzpatrick R, Murray DW, Campbell MK; TOPKAT Study Group. Assessing clinical and cost effectiveness of total versus partial knee replacement (TOPKAT): 10-year follow-up of a multicentre, randomised controlled trial. Lancet Rheumatol. 2026 Feb;8(2):e116-e126. doi: 10.1016/S2665-9913(25)00250-4. Epub 2025 Nov 18.
PubMed 41270774Beard DJ, Davies LJ, Cook JA, MacLennan G, Price A, Kent S, Hudson J, Carr A, Leal J, Campbell H, Fitzpatrick R, Arden N, Murray D, Campbell MK; TOPKAT Study Group. The clinical and cost-effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT): 5-year outcomes of a randomised controlled trial. Lancet. 2019 Aug 31;394(10200):746-756. doi: 10.1016/S0140-6736(19)31281-4. Epub 2019 Jul 17.
PubMed 31326135
Study at a glance
From the registry record, last updated by the sponsor on 24 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Functional, Clinical, and Biomechanical Examination of Unicompartmental Versus Total Knee Arthroplasty for Medial Compartment Knee Osteoarthritis (FLEX-UNI): A Randomized Controlled Trial
- ClinicalTrials.gov ID
- NCT04913987
- Acronym / sponsor ID
- FLEX-UNI / Ortho 18-03
- Conditions
- Osteoarthritis, Knee, Arthroplasty, Replacement, Knee
- Keywords
- Total knee arthroplasty, Partial knee arthroplasty, Unicondylar knee arthroplasty, Randomised controlled trial, Functional biomechanical assessment, Movement analysis, Gait analysis, Step descent
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Golden Jubilee National HospitalOther government
- Study start
- 26 Apr 2021 (actual)
- Primary completion
- 15 Oct 2027 (estimated)
- Study completion
- 15 Oct 2027 (estimated)
- First posted
- 4 Jun 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
For patients with osteoarthritis affecting only the inner part of the knee, surgeons can offer either a partial knee replacement, which resurfaces the worn compartment alone, or a total knee replacement. Both are recommended treatments, but there is no agreement on when to choose one over the other. Partial knee replacement preserves the anterior cruciate ligament and more of the natural knee, and recovery is usually quicker, but it is used in only about one in ten knee replacements in the United Kingdom.
Studies comparing the two have mostly relied on patient questionnaires, which may not be sensitive enough to detect differences in how the knee actually functions. Studies that have measured movement directly have concentrated on level walking, which is not demanding enough to separate the two operations. Difficulty with stairs is one of the longest lasting problems patients report after knee replacement.
The FLEX-UNI trial will compare the two operations using three-dimensional motion analysis during more demanding everyday activities. Forty patients who are suitable for a partial knee replacement will be randomly allocated to receive either a partial or a total knee replacement. Patients and the researchers measuring their movement will not know which operation was performed. The main measurement is how far the operated knee bends while stepping down from a 20 cm step, measured one year after surgery. Movement during walking, stair climbing, slopes, sitting and standing, and balance will also be measured, along with questionnaires, x-rays, and complications. Results will be compared against measurements from people with healthy knees.
Detailed description
FLEX-UNI is a single-centre, prospective, randomized, double-blinded, controlled superiority trial comparing medial unicompartmental knee arthroplasty (UKA) with total knee arthroplasty (TKA) in patients with anteromedial knee osteoarthritis. Forty participants will be randomized 1:1. The trial is conducted at a high-volume elective arthroplasty centre and participants are followed for 12 months.
Participants are identified from the clinic lists of participating consultant orthopaedic surgeons and screened against the eligibility criteria by a member of the research team and by the treating consultant. Following written consent and baseline assessment, participants are randomized using sequentially numbered, opaque, sealed envelopes prepared and opened by a member of the research team not involved in screening, recruitment, or outcome assessment.
Participants allocated to UKA receive a cemented medial fixed-bearing Persona Partial Knee (Zimmer Biomet, Warsaw, Indiana, USA), implanted using a spacer block technique that resurfaces the medial compartment without deliberate correction of limb alignment. Participants allocated to TKA receive a cemented Triathlon cruciate-retaining total knee system without patellar resurfacing (Stryker, Mahwah, New Jersey, USA), implanted using a measured resection technique with a mechanical alignment target. Both procedures use conventional manual instrumentation, without robotic assistance or computer navigation, and are performed by the same group of consultant surgeons, each of whom performs both operations.
Suitability for medial UKA is confirmed intraoperatively at arthrotomy in all participants, including those allocated to TKA. Participants allocated to UKA who are found at arthrotomy to be unsuitable, principally because of disease progression beyond anteromedial osteoarthritis or a deficient anterior cruciate ligament, undergo TKA.
Participants are blinded to allocation. A standard-size sterile dressing is applied to the surgical wound by an independent healthcare support worker before biomechanical testing to conceal scar length, and participants are not shown their postoperative radiographs unless there is a clinical need. Research staff performing biomechanical assessment, outcome scoring, and statistical analysis are blinded to allocation, with unblinding only after analysis is complete. The treating surgeon cannot be blinded.
Assessments take place preoperatively, immediately postoperatively, and at six weeks, six months, and 12 months. Biomechanical assessment is performed in the centre's Motion Analysis Laboratory using a Vicon motion capture system (Vicon Motion Systems Ltd, Yarnton, UK) and two AMTI force plates (Advanced Mechanical Technology Inc., Watertown, Massachusetts, USA). Tasks are level walking, incline walking, decline walking, step ascent, step descent, sit-to-stand-to-sit, and single-leg balance.
A matched healthy control group is drawn from an existing motion analysis database held at the study centre, comprising individuals without known knee pathology previously assessed using an identical protocol under separate ethical approval. Control data do not contribute to the primary comparison between arms and are used only to contextualize findings against values expected in a healthy population. Healthy controls are not prospectively enrolled in this trial.
The sample size was calculated for the primary outcome, assuming 95 degrees for the UKA group and 89 degrees for the TKA group with a pooled standard deviation of 5.5 degrees, two-sided alpha of 0.05, and 80% power, giving 15 participants per group for an analysis of covariance with baseline as a covariate. Allowing for an estimated 10% intraoperative conversion from UKA to TKA and 15% loss to follow-up, the recruitment target is 20 per group. The trial is powered for the primary outcome alone, and all secondary outcomes are exploratory.
The primary analysis is performed on the per-protocol population, defined as participants who received their randomized implant and completed the 12-month biomechanical assessment. Participants found intraoperatively unsuitable for UKA at arthrotomy are excluded from the primary analysis regardless of allocation.
The trial is funded by Zimmer GmbH (Winterthur, Switzerland).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
- Model description
- Parallel Assignment. Participants considered suitable for medial unicompartmental knee arthroplasty are randomized 1:1 to receive either a medial unicompartmental knee arthroplasty or a total knee arthroplasty. Allocation uses sequentially numbered, opaque, sealed envelopes prepared and opened by a member of the research team not involved in screening, recruitment, or outcome assessment.
| Arm | Type | Receives |
|---|---|---|
| Unicompartmental knee arthroplasty (UKA) | Experimental | Device: Persona Partial Knee (PPK)Description: Cemented medial fixed-bearing unicompartmental knee arthroplasty, implanted using a spacer block technique that resurfaces the medial compartment without deliberate correction of limb alignment, using conventional manual instrumentation |
| Total knee arthroplasty (TKA) | Active comparator | Device: Triathlon cruciate-retaining total knee system.Cemented cruciate-retaining total knee arthroplasty without patellar resurfacing, implanted using a measured resection technique with a mechanical alignment target, using conventional manual instrumentation. This is the standard total knee implant used at the study centre. |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- Suitable for medial unicompartmental knee arthroplasty
- Aged between 18 and 75 years inclusive
- Taller than 1.5m in height (the 10th percentile for the population)
- Functionally intact anterior cruciate ligament
- Able to give informed consent
Key exclusion criteria (7 listed)
- Inflammatory joint disease e.g. rheumatoid arthritis
- Previous hip procedure within the previous twelve months
- Previous knee surgery other than arthroscopy and medial menisectomy
- Previous ankle surgery
- Symptomatic foot, hip or spinal pathology
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Persona Partial Knee (PPK)Cemented medial fixed-bearing unicompartmental knee arthroplasty using the Persona Partial Knee (PPK; Zimmer Biomet, Warsaw, Indiana, USA). | Device | Unicompartmental knee arthroplasty (UKA) |
| Triathlon cruciate-retaining total knee system.Cemented Triathlon cruciate-retaining total knee system without patellar resurfacing (Stryker, Mahwah, New Jersey, USA). | Device | Total knee arthroplasty (TKA) |
Primary outcome
Maximum knee flexion of the operated knee during step descent
Time frame: 12 months post-operatively
Peak flexion angle of the operated knee in the sagittal plane, in degrees, during descent from a 20 cm step with the operated limb acting as the trailing limb, measured using three-dimensional motion analysis.
8 secondary outcomes
Maximum knee flexion during step descent, operated limb as trailing limb
Time frame: 6 months post-operatively
Knee kinematics and kinetics
Time frame: baseline, 6 months, 12 months
Spatiotemporal and balance
Time frame: baseline, 6 months, 12 months.
Patient satisfaction
Time frame: 6 weeks, 6 months, 12 months
Radiographic assessment
Time frame: to 12 months postoperatively
Complications and adverse events
Time frame: to 12 months postoperatively
Implant survivorship
Time frame: 12 months
Intraoperative conversion from unicompartmental to total knee arthroplasty, reported as the number of participants.
Time frame: day of surgery
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Sep 2026.
- Background: PubMed 41044992Kuntze G, Panjavi S, Henning E, Korley R, Abelseth G, Ronsky J, Johnston K. Preserving Patient-Specific Knee Motion: A Randomized Clinical Trial of Unicompartmental and Total Knee Arthroplasty. J Orthop Res. 2025 Dec;43(12):2203-2211. doi: 10.1002/jor.70077. Epub 2025 Oct 3.
- Background: PubMed 24859731Jung MC, Chung JY, Son KH, Wang H, Hwang J, Kim JJ, Kim JH, Min BH. Difference in knee rotation between total and unicompartmental knee arthroplasties during stair climbing. Knee Surg Sports Traumatol Arthrosc. 2014 Aug;22(8):1879-86. doi: 10.1007/s00167-014-3064-8. Epub 2014 May 24.
- Background: PubMed 23937925Bjerke J, Ohberg F, Nilsson KG, Foss OA, Stensdotter AK. Peak knee flexion angles during stair descent in TKA patients. J Arthroplasty. 2014 Apr;29(4):707-11. doi: 10.1016/j.arth.2013.07.010. Epub 2013 Aug 9.
- Background: PubMed 38956422Copp EH, Gale TH, Byrapogu VKC, Urish KL, Anderst WJ. Unicompartmental knee arthroplasty approximates healthy knee kinematics more closely than total knee arthroplasty. J Orthop Res. 2024 Nov;42(11):2514-2524. doi: 10.1002/jor.25926. Epub 2024 Jul 2.
- Background: PubMed 30304032Komnik I, David S, Funken J, Haberer C, Potthast W, Weiss S. Compromised knee internal rotation in total knee arthroplasty patients during stair climbing. PLoS One. 2018 Oct 10;13(10):e0205492. doi: 10.1371/journal.pone.0205492. eCollection 2018.
- Background: PubMed 28002437Komnik I, Peters M, Funken J, David S, Weiss S, Potthast W. Non-Sagittal Knee Joint Kinematics and Kinetics during Gait on Level and Sloped Grounds with Unicompartmental and Total Knee Arthroplasty Patients. PLoS One. 2016 Dec 21;11(12):e0168566. doi: 10.1371/journal.pone.0168566. eCollection 2016.
- Background: PubMed 37321113Dong M, Fan H, Yang D, Sun X, Yan C, Feng Y. Comparison of spatiotemporal, kinematic, and kinetic gait characteristics in total and unicompartmental knee arthroplasty during level walking: A systematic review and meta-analysis. Gait Posture. 2023 Jul;104:58-69. doi: 10.1016/j.gaitpost.2023.06.005. Epub 2023 Jun 7.
- Background: PubMed 39797286Bayram JM, Clement ND, Hall AJ, Walmsley P, Clarke JV. Are Current Patient-Reported Outcome Measures Fit for Purpose to Evaluate Unicompartmental Knee Arthroplasty? J Clin Med. 2025 Jan 2;14(1):203. doi: 10.3390/jcm14010203.
- Background: PubMed 33316442Eckhard L, Munir S, Wood D, Talbot S, Brighton R, Walter B, Bare J. The ceiling effects of patient reported outcome measures for total knee arthroplasty. Orthop Traumatol Surg Res. 2021 May;107(3):102758. doi: 10.1016/j.otsr.2020.102758. Epub 2020 Dec 11.
- Background: PubMed 34619307Mohammad HR, Liddle AD, Judge A, Murray DW. A Matched Comparison of Long-Term Outcomes of Total and Unicompartmental Knee Replacements in Different Ages Based on National Databases: Analysis of Data From the National Joint Registry for England, Wales, Northern Ireland, and the Isle of Man. J Arthroplasty. 2022 Feb;37(2):243-251. doi: 10.1016/j.arth.2021.09.018. Epub 2021 Oct 5.
- Background: PubMed 37087428Bin G, Jinmin L, Cong T, Yuchen T, Xiaohui Z, Yayi X. Surgical interventions for symptomatic knee osteoarthritis: a network meta-analysis of randomized control trials. BMC Musculoskelet Disord. 2023 Apr 22;24(1):313. doi: 10.1186/s12891-023-06403-z.
- Background: PubMed 41270774Beard DJ, Davies LJ, Cook JA, MacLennan G, Hudson J, Price AJ, Carr AJ, Little M, Leal J, Fitzpatrick R, Murray DW, Campbell MK; TOPKAT Study Group. Assessing clinical and cost effectiveness of total versus partial knee replacement (TOPKAT): 10-year follow-up of a multicentre, randomised controlled trial. Lancet Rheumatol. 2026 Feb;8(2):e116-e126. doi: 10.1016/S2665-9913(25)00250-4. Epub 2025 Nov 18.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Nicholas Ohly, FRCS Ed principal investigator
Golden Jubilee University National Hospital
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Persona Partial Knee (PPK) and Triathlon cruciate-retaining total knee system. in people with Osteoarthritis and Knee, run by Golden Jubilee National Hospital at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 24 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Maximum knee flexion of the operated knee during step descent (time frame: 12 months post-operatively). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04913987, which also lists 13 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Sep 2026; AzTrials last refreshed its copy on 7 Nov 2026.