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True KneeInstitute

Surgeon education · Evidence

Published evidence. Defined limits.

Original papers, study designs, findings, and limitations relevant to the surgical discussion.

An established foundation.

This education is grounded in Stephen Howell’s unrestricted kinematic alignment: restoring each knee’s pre-arthritic joint lines through measured reconstruction and verification.

The papers below address surgical access, alignment, anatomic landmarks and activity after arthroplasty. Anatomical rationale and radiographic accuracy are different questions from patient-reported benefit, implant survival and return to sport, and are kept apart here.

Howell · 2019

Technical description · Calipered unrestricted KA technique

Describes calipered unrestricted kinematic alignment, measured resections and verification to restore native joint lines while preserving healthy ligaments.

Interpretation. A technical description is not a randomized comparison or proof of superior outcomes.

Howell · 2019 · Read the original paper ↗

Howell et al. · 2018

Single-arm clinical cohort · 222 knees; ten-year follow-up; patient-specific instrumentation

Ten-year survivorship free of revision for any reason was 97.5%; mean Oxford Knee Score was 43/48.

Interpretation. No randomized comparator. Results from the studied cohort do not establish universal safety or superiority across surgeons, implants and deformities.

Howell et al. · 2018 · Read the original paper ↗

Dossett et al. · 2014

Randomized trial · 88 patients; two years; patient-specific KA guides versus conventional MA instruments

KA versus MA: Oxford Knee Score 40 vs 33; flexion 121° vs 113°; WOMAC 15 vs 26, favoring KA.

Interpretation. Small trial with different instrumentation between groups. Later follow-up of the same cohort did not show persistent superiority.

Dossett et al. · 2014 · Read the original paper ↗

Dossett et al. · 2023

Long-term randomized-trial follow-up · Original 88-patient trial; mean follow-up approximately 13 years

At approximately 13 years, patient-reported outcomes, reoperations and complications were comparable.

Interpretation. Same cohort as Dossett 2014, not independent replication. Long-term attrition and sample size limit interpretation of uncommon events.

Dossett et al. · 2023 · Read the original paper ↗

Gibbons et al. · 2025

Randomized trial · 99 patients; ten years; KA patient-specific blocks versus MA navigation

Revision-free survival was 96% for MA and 91% for KA (p=0.38); patient-reported outcomes did not differ significantly.

Interpretation. Selected eligibility, different instruments and limited power for rare failure. A nonsignificant difference does not prove equivalence.

Gibbons et al. · 2025 · Read the original paper ↗

Koutp et al. · 2026

Randomized trial · 100 patients; two years; conventional instruments and same medial-pivot implant

FJS-12 65.64 for unrestricted KA vs 57.24 for MA; difference 8.4 points, below the study’s cited MCID of 16.6. Most between-group differences did not exceed clinical-importance thresholds.

Interpretation. Single surgeon and implant design; two-year follow-up. Subgroup findings require confirmation. Published online in 2025, issue dated 2026.

Koutp et al. · 2026 · Read the original paper ↗

Scott and Horton · 2025

Technical accuracy cohort · 385 consecutive patients; single experienced surgeon

Mean absolute femoral resection errors were approximately 0.1–0.3 mm depending on the surface.

Interpretation. Resection accuracy is not proof of native-anatomy reconstruction accuracy or superior patient outcomes. Experience and disclosed industry relationships matter.

Scott and Horton · 2025 · Read the original paper ↗

Selected sources checked 2026-10-10. This is a curated review, not a systematic review. Clinical studies of the underlying principles are separate from the results of any one program. Read original papers for complete methods and disclosures.

Additional surgical and recovery questions

Exposure, implant design, rehabilitation and activity are separate questions. Their findings cannot be added together to establish a benefit for the complete program.

Activities after surgery

Activities after surgery

Umbrella review of seven systematic reviews of total and partial knee replacement.

The review supports return to low-impact activities, including cycling and golf. Moderate-impact sports require individual consideration; long-term evidence for high-impact sport is insufficient.

Limits. Mixed procedures and underlying studies. This is not a comparison of anatomic resurfacing, and it does not establish a pickleball-specific recommendation or a guaranteed return date.

Return to sport post-knee arthroplasty: an umbrella review for consensus guidelines ↗

Lester D, et al. Bone Jt Open. 2022;3(3):245–251.

Early recovery

Early recovery

Meta-analysis of 20 randomized trials involving 1,893 knee replacements.

Subvastus access was associated with earlier straight-leg raise (1.7 days), less day-one pain (0.8 points on a 10-point scale), and greater motion at one week (7°). Knee Society Scores did not differ at six weeks or one year; operating time was longer.

Limits. Results concern surgical access, not implant alignment or the complete anatomic resurfacing technique. Study methods varied; early differences do not establish a lasting functional advantage.

Medial subvastus versus the medial parapatellar approach for total knee replacement: A systematic review and meta-analysis of randomized controlled trials ↗

Berstock JR, et al. EFORT Open Rev. 2018;3(3):78–84.

Implant alignment

Implant alignment

Single-center randomized trial comparing kinematic and mechanical alignment at ten years.

The trial found no statistically significant difference in patient-reported outcomes or revision-free survival at ten years.

Limits. One trial using specific implants and instrumentation. A nonsignificant difference is not proof of equivalence; the findings cannot settle every personalized alignment strategy or rare complication risk.

No Difference in 10-year Clinical or Radiographic Outcomes Between Kinematic and Mechanical Alignment in TKA: A Randomized Trial ↗

Gibbons JP, et al. Clin Orthop Relat Res. 2025;483(1):140–149. Published online 2024.

Anatomic landmarks

Anatomic landmarks

Retrospective case-control study: 34 landmark-guided and 34 matched conventional knee replacements.

Landmark guidance reduced the proportion of tibial angle measurements outside the study’s target range.

Limits. Small, single-surgeon study of early radiographic accuracy. It does not demonstrate better patient-reported function, faster recovery, return to sport, or longer implant survival.

Specific tibial landmarks to improve to accuracy of the tibial cut during total knee arthroplasty. A case control study ↗

Parratte S, et al. Arch Orthop Trauma Surg. 2024;144:4101–4108.

References for the surgical illustrations.

The [S] markers beside the teaching sections match the sources below. Study type and scope are stated so an anatomy study, technical report, or illustration is not mistaken for a clinical outcome trial. Selected sources checked September 17, 2026.

The 20 sources, with study type, scope and limits

  1. [S1] Retrospective radiographic comparison

    Better restoration of joint line obliquity in tibia first restricted kinematic alignment versus mechanical alignment TKA. ↗

    Shichman I, Hadad A, Brandstetter AS, Ashkenazi I, Warschwaski Y, Gold A, Snir N. Arch Orthop Trauma Surg. 2024;144(9).

    DOI: 10.1007/s00402-024-05551-8

    Scope & limitations. 200 patients; between-group difference in joint-line obliquity change did not reach statistical significance (p=0.09). Does not establish better clinical outcomes.

  2. [S2] Resection accuracy cohort

    Femoral resection accuracy and precision in manual caliper-verified kinematic alignment total knee arthroplasty. ↗

    Scott DF, Horton EN. J Exp Orthop. 2025;12(2).

    DOI: 10.1002/jeo2.70234

    Scope & limitations. 385 consecutive patients. Supports caliper verification of femoral resections; does not compare patient outcomes or establish a universal resection thickness.

  3. [S3] MRI anatomy study

    Femoral bone and cartilage wear is predictable at 0° and 90° in the osteoarthritic knee treated with total knee arthroplasty. ↗

    Nam D, Lin KM, Howell SM, Hull ML. Knee Surg Sports Traumatol Arthrosc. 2014;22(12).

    DOI: 10.1007/s00167-014-3080-8

    Scope & limitations. 208 osteoarthritic knees. Distal and posterior wear differ; cohort means are not patient-specific cartilage measurements.

  4. [S4] Prospective multicenter cartilage study

    Validation of Articular Cartilage Depth in Total Knee Arthroplasty. ↗

    Johnson EP, Brown NM, Hellman MD, Calkins TE, Hou N, Crockarell JR, Guyton JL, Holland CT, Mihalko WM, Ford MC. Arthroplast Today. 2025;35.

    DOI: 10.1016/j.artd.2025.101869

    Scope & limitations. 806 TKA cases. Cartilage thickness varies by location and patient factors; a fixed thickness is not appropriate for every knee.

  5. [S5] Retrospective case-control study

    Specific tibial landmarks to improve to accuracy of the tibial cut during total knee arthroplasty. A case control study. ↗

    Parratte S, Azmi Z, Daxelet J, Argenson JN, Batailler C. Arch Orthop Trauma Surg. 2024;144(9).

    DOI: 10.1007/s00402-024-05428-w

    Scope & limitations. 34 landmark-guided and 34 matched controls; two-month radiographs. Accuracy evidence, not proof of superior function or survivorship.

  6. [S6] Radiographic classification and randomized balance comparison

    Coronal Plane Alignment of the Knee (CPAK) classification. ↗

    MacDessi SJ, Griffiths-Jones W, Harris IA, Bellemans J, Chen DB. Bone Joint J. 2021;103-B(2).

    DOI: 10.1302/0301-620x.103b2.bjj-2020-1050.r1

    Scope & limitations. 500 healthy and 500 arthritic knees; 138 randomized TKAs in the balance comparison. Phenotype frequencies and intraoperative balance are not long-term patient outcomes.

  7. [S7] Radiographic classification study

    Surgically Relevant Knee Phenotypes: The Modified Coronal Plane Alignment of the Knee System-A Deep Learning-Based Classification. ↗

    Burgio C, Zepeda KE, Karasavvidis T, Jang SJ, Mayman DJ, Jerabek SA, Sculco PK, Debbi EM, Vigdorchik JM. J Arthroplasty. 2026;41(S1).

    DOI: 10.1016/j.arth.2026.04.010

    Scope & limitations. 1,944 knees classified using automated radiographic measurements. Distinct from original CPAK; does not validate the animation or establish clinical superiority.

  8. [S8] Retrospective CT anatomy study

    Phenotyping the knee in young non-osteoarthritic knees shows a wide distribution of femoral and tibial coronal alignment. ↗

    Hirschmann MT, Moser LB, Amsler F, Behrend H, Leclercq V, Hess S. Knee Surg Sports Traumatol Arthrosc. 2019;27(5).

    DOI: 10.1007/s00167-019-05508-0

    Scope & limitations. 308 young, non-osteoarthritic knees. Describes anatomical variation; applicability to older arthritic knees requires judgment.

  9. [S9] Cadaveric CT axis study

    Difference between the epicondylar and cylindrical axis of the knee. ↗

    Eckhoff D, Hogan C, DiMatteo L, Robinson M, Bach J. Clin Orthop Relat Res. 2007;461.

    DOI: 10.1097/blo.0b013e318112416b

    Scope & limitations. 23 specimens. Anatomical axis differences do not by themselves establish an optimal surgical target or outcome benefit.

  10. [S10] Anatomical methods report

    Three-dimensional mechanics, kinematics, and morphology of the knee viewed in virtual reality. ↗

    Eckhoff DG, Bach JM, Spitzer VM, Reinig KD, Bagur MM, Baldini TH, Flannery NM. J Bone Joint Surg Am. 2005;87 Suppl 2.

    DOI: 10.2106/jbjs.e.00440

    Scope & limitations. Related to the 2007 Eckhoff axis report; matching sample and statistics are not counted as independent confirmation.

  11. [S11] Cadaveric kinematics study

    The axes of rotation of the knee. ↗

    Hollister AM, Jatana S, Singh AK, Sullivan WW, Lupichuk AG. Clin Orthop Relat Res. 1993;(290).

    Scope & limitations. Six specimens. A distinct axis model; should not be merged with other models into a single validated surgical prescription.

  12. [S12] Normal-knee stress MRI study

    The flexion gap in normal knees. An MRI study. ↗

    Tokuhara Y, Kadoya Y, Nakagawa S, Kobayashi A, Takaoka K. J Bone Joint Surg Br. 2004;86(8).

    DOI: 10.1302/0301-620x.86b8.15246

    Scope & limitations. 20 knees at 90° showed greater lateral opening under stress. These are native-knee observations, not prescribed TKA gap sizes.

  13. [S13] Retrospective TKA cohort

    Lateral Laxity in Flexion Influences Patient-Reported Outcome After Total Knee Arthroplasty. ↗

    Okamoto N, Nakamura E, Masuda T, Hisanaga S, Miyamoto T. Indian J Orthop. 2024;58(1).

    DOI: 10.1007/s43465-023-01045-8

    Scope & limitations. 98 knees. Excessive lateral laxity was associated with worse symptom scores; satisfaction and activity scores did not differ. Measurement load and implant context matter.

  14. [S14] Unloaded cadaver MRI study

    Tibiofemoral movement 1: the shapes and relative movements of the femur and tibia in the unloaded cadaver knee. ↗

    Iwaki H, Pinskerova V, Freeman MA. J Bone Joint Surg Br. 2000;82(8).

    DOI: 10.1302/0301-620x.82b8.10717

    Scope & limitations. Six knees. Supports asymmetric native motion as a teaching reference, not an invariant pattern for every living knee.

  15. [S15] Living-knee MRI study

    Tibiofemoral movement 2: the loaded and unloaded living knee studied by MRI. ↗

    Hill PF, Vedi V, Williams A, Iwaki H, Pinskerova V, Freeman MA. J Bone Joint Surg Br. 2000;82(8).

    DOI: 10.1302/0301-620x.82b8.10716

    Scope & limitations. 13 unloaded and seven loaded knees. Loading altered movement, including medial forward translation; medial stability does not mean zero motion.

  16. [S16] Living-knee loaded and unloaded MRI study

    Tibio-femoral movement in the living knee. A study of weight bearing and non-weight bearing knee kinematics using 'interventional' MRI. ↗

    Johal P, Williams A, Wragg P, Hunt D, Gedroyc W. J Biomech. 2005;38(2).

    DOI: 10.1016/j.jbiomech.2004.02.008

    Scope & limitations. Describes load-dependent motion and deeper-flexion changes. Animation values are illustrative, not measurements from the displayed model.

  17. [S17] Anatomy and kinematics review

    The movement of the normal tibio-femoral joint. ↗

    Freeman MA, Pinskerova V. J Biomech. 2005;38(2).

    DOI: 10.1016/j.jbiomech.2004.02.006

    Scope & limitations. Synthesizes native motion studies; not an independent clinical trial or evidence of implant superiority.

  18. [S18] In-vivo fluoroscopy study

    In vivo fluoroscopic analysis of the normal human knee. ↗

    Komistek RD, Dennis DA, Mahfouz M. Clin Orthop Relat Res. 2003;(410).

    DOI: 10.1097/01.blo.0000062384.79828.3b

    Scope & limitations. Five normal knees during five activities. Individual and activity-dependent differences include a lateral-pivot subject.

  19. [S19] 3D component morphology study

    Differences in Trochlear Morphology of a New Femoral Component Designed for Kinematic Alignment from a Mechanical Alignment Design. ↗

    Hull ML, Simileysky A, Howell SM. Bioengineering (Basel). 2024;11(1).

    DOI: 10.3390/bioengineering11010062

    Scope & limitations. Two component designs aligned on ten femur-cartilage models. Geometric differences suggest a design rationale; the study did not measure clinical tracking or complication reduction.

  20. [S20] Retrospective clinical comparison

    The Influence of Femoral Internal Rotation on Patellar Tracking in Total Knee Arthroplasty Using Gap Technique. ↗

    Ko DO, Lee S, Kim JH, Hwang IC, Jang SJ, Jung J. Clin Orthop Surg. 2021;13(3).

    DOI: 10.4055/cios20168

    Scope & limitations. 245 TKAs. With the gap technique and ligament balance, the internally rotated group did not have significantly greater patellar tilt. Rotation alone does not explain all tracking behavior.

For the separate bearing-design evidence collection, see 16 papers on medial stabilization. Those papers retain their author–year labels and individual findings and limitations. Reviews may include studies also listed individually.

Clinical outcomes.

How the knee feels, how long the reconstruction lasts and what can go wrong: each answers a different question.

Interactive: published study results, not an individual outcome prediction.

Selected reading

Medial stabilization.

16 papers on bearing geometry, measured motion, and clinical outcomes. Reviews may include the primary studies listed here.

Motion · Moonot et al. · 2009Tibiofemoral kinematic analysis of knee flexion for a medial pivot knee

Fluoroscopy · 13 patients / 15 knees

Medial-centered motion during lunge and kneeling, with less tibial rotation than reported for native knees.

Small, activity-specific series; no comparative patient-outcome claim.

Read published paper ↗
Outcomes · Scott & Gray · 2022Outcomes are Better With a Medial-Stabilized vs a Posterior-Stabilized Total Knee Implanted With Kinematic Alignment

Randomized trial · 200 patients · KA · 2 years

MS had greater maximum flexion (132° vs 124°) and a higher Forgotten Joint Score (68.3 vs 58.3).

Single center and specific implant systems. Not every enrollee completed every two-year measure; results do not isolate the polyethylene alone.

Read published paper ↗
Motion · Alesi et al. · 2022No kinematical difference between ultra-congruent and medial-congruent total knee arthroplasty when implanted with mechanical alignment

Dynamic RSA · 8 MC / 8 UC · MA

No detected difference in medial-pivot behavior during sit-to-stand; clinical flexion was greater with MC.

Small sample; absence of a detected difference is not proof of equivalence.

Read published paper ↗
Outcomes · Hoskins et al. · 2022Medial Pivot Designs Versus Conventional Bearing Types in Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Systematic review · 8 randomized trials · 725 knees

Pooled MP-versus-PS comparisons found no clear advantage in measured clinical outcomes.

One high-risk-of-bias trial excluded from pooling; insufficient randomized evidence for other bearing comparisons.

Read published paper ↗
Overview · Romano et al. · 2025Medial Congruent and Medial Pivot Inserts in Total Knee Arthroplasty: A Scoping Review

Scoping review · 39 articles · 6,143 TKAs

Generally favorable outcomes with both MC and MP constructs; terminology and surgical approaches vary.

Heterogeneous evidence does not establish equivalence, a universal PCL strategy, or comparative longevity.

Read published paper ↗
Motion · Nelson-Tranum et al. · 2025Implant design may influence knee flexor activation patterns during stair ascent and descent

Biomechanics and EMG · 52 patients · 1 year

Greater medial AP constraint was associated with lower biceps femoris activation during stair tasks.

Muscle activation is not proof of easier stairs, reduced fatigue, or superior patient outcomes.

Read published paper ↗
Outcomes · French et al. · 2020A Single Surgeon Series Comparing the Outcomes of a Cruciate Retaining and Medially Stabilized Total Knee Arthroplasty Using Kinematic Alignment Principles

Prospective comparison · 90 patients · KA · 1 year

Higher FJS and selected quality-of-life scores with MS; most other measures were comparable.

Small, nonrandomized, single-surgeon comparison with short follow-up.

Read published paper ↗
Outcomes · Jones et al. · 2023Better flexion and early recovery with medial-stabilized vs single-radius total knee arthroplasty with kinematic alignment: Two-year clinical results

Retrospective cohort comparison · 210 patients · KA

MS had greater flexion from six months to two years and selected early pain advantages.

Comparison across separate trials, not a direct randomized comparison. The MS cohort overlaps the Scott–Gray trial.

Read published paper ↗
Outcomes · Chang et al. · 2021A Prospective Randomized Controlled Trial Comparing Medial-Pivot versus Posterior-Stabilized Total Knee Arthroplasty

Randomized trial · 88 patients · 2 years

No detected differences in ROM or measured patient-reported outcomes between MP and PS.

Findings apply to the studied devices and follow-up; no significant difference does not establish equivalence.

Read published paper ↗
Motion · Tsubosaka et al. · 2021Mid-flexion stability in the anteroposterior plane is achieved with a medial congruent insert in cruciate-retaining total knee arthroplasty for varus osteoarthritis

Intraoperative comparison · 30 varus OA knees · CR-TKA

MC reduced AP translation under manual stress at 45° compared with CR inserts. Varus–valgus laxity was comparable.

Intraoperative mechanics, not evidence that MC prevents long-term clinical instability.

Read published paper ↗
Motion · Kaneda et al. · 2022Kinematically Aligned Total Knee Arthroplasty Using Medial Pivot Knee Prosthesis Enhances Medial Pivot Motion

Comparative kinematics · 13 knees / 9 patients · 1 year

KA knees showed greater lateral posterior travel and femoral external rotation than MA knees with the studied MP implant.

Exploratory: 8 KA and 5 MA knees. Does not establish clinical superiority.

Read published paper ↗
Outcomes · Tso et al. · 2021Clinical and Patient-Reported Outcomes of Medial Stabilized Versus Non-Medial Stabilized Prostheses in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

Systematic review · 21 studies / 13 pooled

FJS favored MS by 13.83 points, just below the review’s chosen clinical-importance threshold of 14; other differences were absent or not clinically important.

Thresholds and study populations vary; statistical significance alone is not clinical importance.

Read published paper ↗
Outcomes · Frye et al. · 2021A Medial Congruent Polyethylene Offers Satisfactory Early Outcomes and Patient Satisfaction in Total Knee Arthroplasty

Retrospective cohort · 327 TKAs · 1 year

MC improved selected early pain, FJS, and satisfaction measures; KOOS/PROMIS and MC-versus-PS satisfaction were similar.

Observational, short-term evidence; does not establish a universal satisfaction advantage.

Read published paper ↗
Motion · Schütz et al. · 2019Kinematic Evaluation of the GMK Sphere Implant During Gait Activities: A Dynamic Videofluoroscopy Study

Dynamic fluoroscopy · 3 groups of 10 patients

The studied Sphere construct limited medial AP excursion while permitting lateral travel and axial rotation.

Selected good-outcome patients and specific devices; industry-supported study.

Read published paper ↗
Motion · Delman et al. · 2021The posterolateral upslope of a low-conforming insert blocks the medial pivot during a deep knee bend in TKA: a comparative analysis of two implants with different insert conformities

Bilateral comparison · 25 patients · KA

The medial ball-in-socket/flat lateral construct maintained a medial pivot. A posterolateral upslope was proposed to explain different motion with the low-conforming CR construct.

Different implant systems, PCL management, and follow-up. No difference in median patient-reported outcomes.

Read published paper ↗
Motion · Gray et al. · 2020Comparison of posterior-stabilized, cruciate-retaining, and medial-stabilized knee implant motion during gait

Randomized implant groups · gait imaging · 74 patients

MS showed less AP drawer/paradoxical translation and a medial center of rotation.

All three implant designs still differed from healthy knees. Motion is not a patient-outcome measure.

Read published paper ↗

Implant selection · focused reading

Design differences and clinical outcomes

Ten primary studies selected for the three evidence views. Several also appear in the existing polyethylene library; these are curated comparisons, not ten new independent datasets.

Randomized clinical comparison · Less drawer at 30°; no detected PROM advantage

The Effect of Implant Design on Sagittal Plane Stability: A Randomized Trial of Medial- versus Posterior-Stabilized Total Knee Arthroplasty

Edelstein AI, Bhatt S, Wright-Chisem J, Sullivan R, Beal M, Manning DW.

J Knee Surg · 2020 May

PubMed ↗ · Published article ↗

Medial-stabilized vs posterior-stabilized TKA · 50 patients analyzed (25 per group) · 2 years · KT-1000 arthrometer

Mean sagittal laxity at 30° was 5.6 vs 10.2 mm (P < .0001). At 90°, the difference was not significant (4.1 vs 5.3 mm; P = .14). Standard patient-reported scores did not differ.

Small trial. Laxity at one angle is not a clinical instability rate. Results do not identify a universal stability target or rank current company products.

Randomized groups · in-vivo motion · A medial center of rotation during walking

Comparison of posterior-stabilized, cruciate-retaining, and medial-stabilized knee implant motion during gait

Gray HA, Guan S, Young TJ, Dowsey MM, Choong PF, Pandy MG.

J Orthop Res · 2020 Aug

PubMed ↗ · Published article ↗

MS (26), PS (23), and CR (25) knees · 74 patients · biplane X-ray imaging during a walking cycle

MS showed less AP drawer and paradoxical anterior translation, with a medial rather than lateral center of rotation. All three groups still differed from healthy knees.

Task-specific kinematics do not establish better pain relief, satisfaction, or implant survival. Our model does not replay the measured trajectories.

Laboratory · cadaveric · Geometry changes laxity in a controlled test

Total knee replacement designs have differing stability under novel robotic testing method in vitro

Holthof SR, Nejima S, Rock M, vanArkel RJ, Brivio A, Barrett D, Amis AA.

Knee Surg Sports Traumatol Arthrosc · 2025 Nov

PubMed ↗ · Published article ↗

Modified designs based on ATTUNE MS, Persona MC, and symmetrical Triathlon · 8 cadaveric knees · same bone cuts · robotic loading: 710 N compression and ±90 N drawer

The single-radius symmetrical design had a larger mean AP laxity envelope than the other tested designs and native knees. Rollback did not differ significantly.

DePuy-funded study using modified test implants. This is not a trial of Triathlon MS, a patient-outcome comparison, or a basis for ranking brands.

Clinical · retrospective comparison · Less crepitus in one historical-control study

Femoral Implant Design Modification Decreases the Incidence of Patellar Crepitus in Total Knee Arthroplasty

Martin JR, Jennings JM, Watters TS, Levy DL, McNabb DC, Dennis DA.

J Arthroplasty · 2017 Apr

PubMed ↗ · Published article ↗

ATTUNE PS vs PFC Sigma PS · 728 ATTUNE / 1,165 PFC Sigma participants · minimum 1 year

Crepitus at 2 years was 0.83% with ATTUNE and 9.4% with PFC Sigma (P < .001). Score and motion differences were not clinically meaningful.

Historical controls cannot isolate trochlear geometry from other changes. Crepitus is not the same endpoint as anterior knee pain. This is ATTUNE PS, not ATTUNE MS.

Clinical · retrospective comparison · A second comparison found no pain advantage

Comparison Between the Attune and PFC Sigma in Total Knee Arthroplasty: No Difference in Patellar Clunk and Crepitus or Anterior Knee Pain

Bateman DK, Preston JS, Mennona S, Gui E, Kayiaros S.

Orthopedics · 2020 Nov

PubMed ↗ · Published article ↗

ATTUNE vs PFC Sigma · 103 ATTUNE / 114 PFC Sigma implants · mean 3.2 years

Anterior knee pain occurred in 15.5% vs 9.7% (P = .219). The study also found no significant overall difference in clunk / crepitus.

Single-surgeon series with bearing-subtype differences. A nonsignificant result does not demonstrate equivalence. Do not pool these rates with a different study’s crepitus endpoint.

Randomized clinical comparison · A positive signal with kinematic alignment

Outcomes are Better With a Medial-Stabilized vs a Posterior-Stabilized Total Knee Implanted With Kinematic Alignment

Scott DF, Gray CG.

J Arthroplasty · 2022 Aug

PubMed ↗ · Published article ↗

Medial-stabilized vs posterior-stabilized TKA · both KA · 200 randomized patients (101 MS / 99 PS) · minimum 2 years

Two-year Forgotten Joint Score was 68.3 vs 58.3 (P = .02); maximum flexion was 132° vs 124° (P < .0001), favoring MS.

Single center and specific constructs. Not every participant completed every outcome measure. The comparison does not isolate the insert or establish a class-wide advantage.

Randomized clinical comparison · Another trial found similar patient scores

A Prospective Randomized Controlled Trial Comparing Medial-Pivot versus Posterior-Stabilized Total Knee Arthroplasty

Chang JS, Kayani B, Moriarty PD, Tahmassebi JE, Haddad FS.

J Arthroplasty · 2021 May

PubMed ↗ · Published article ↗

Medial-pivot vs single-radius posterior-stabilized TKA · 88 patients (43 MP / 45 PS) · 2 years

Oxford Knee Score was 42.7 vs 42.3 (P = .18). ROM, WOMAC, and Knee Society scores also showed no significant between-group differences.

Different trial, constructs and outcome instruments. No detected difference is not proof of equivalence. Do not compare the numerical size of OKS and FJS across trials.

Clinical · registry comparison · Similar ten-year survival in one registry

Long-term survivorship of a medial-pivot total knee system compared with other cemented designs in an arthroplasty registry

Bordini B, Ancarani C, Fitch DA.

J Orthop Surg Res · 2016 Apr

PubMed ↗ · Published article ↗

ADVANCE Medial-Pivot vs other cemented TKA designs · 506 ADVANCE / 20,446 comparator knees · mean follow-up 6.6 years · 10-year estimate

Estimated implant survival was 96.3% vs 95.7%; the difference was not statistically significant.

Observational data; one author was affiliated with the manufacturer. Survival concerns revision, not whether the knee feels normal. This older ADVANCE device is not a current-device class benchmark.

Clinical · registry comparison · A registry counterpoint: revision risk varied

Decreased Survival of Medial Pivot Designs Compared with Cruciate-retaining Designs in TKA Without Patellar Resurfacing

Øhrn FD, Gøthesen Ø, Låstad Lygre SH, Peng Y, Lian ØB, Lewis PL, Furnes O, Röhrl SM.

Clin Orthop Relat Res · 2020 Jun

PubMed ↗ · Published article ↗

Five MP brands vs common CR controls · no patellar resurfacing · 6,310 MP / 70,870 CR knees · Australia and Norway · 2005–2017

Adjusted revision hazard was higher for MP in Australia (HR 1.4; 95% CI 1.2–1.7). Norway’s estimate was uncertain (HR 1.5; CI 0.9–2.4). Results differed by brand.

No patellar resurfacing; observational confounding and variable follow-up. Includes GMK Sphere, not SpheriKA. These historical findings cannot rank current MS products.

Clinical · exact-device cohort · SpheriKA: a short-term trochlear-height cohort

Restoration of the trochlear peaks is unnecessary with a kinematic alignment-optimized femoral component as under-stuffing results in equivalent or better patient-reported outcome scores

Howell SM, Zabiba A, Sadoghi P, Nedopil AJ, Hull ML.

Knee Surg Sports Traumatol Arthrosc · 2025 Dec

PubMed ↗ · Published article ↗

Trochlear peak-height subgroups within GMK SpheriKA KA TKA · 115 knees · retrospective cohort · mean 22 months (12–28)

The cohort compared peak under-stuffing greater than 2 mm with restoration within ±2 mm. Several patient scores favored under-stuffing; over-stuffing was too uncommon for analysis.

No competing-implant control or long-term survival comparison. Associations do not prescribe a resection target. Authors disclosed manufacturer consulting, royalties or research support.

Focused PubMed review: 27 September 2026. Not a systematic review. Abstract-level summaries except the laboratory study, SpheriKA cohort and registry papers, for which full text was reviewed; existing Scott and Chang source reviews were retained.

Reference library

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Publications

448 references · Organized by clinical topic

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448 of 448 references

Anatomy & joint-line geometry36 references
Ligaments & soft-tissue balance32 references
Kinematics, gait & knee motion34 references
Patellofemoral joint & trochlear tracking92 references
Implant design & polyethylene geometry40 references
Surgical technique & instrumentation20 references
Component rotation & positioning7 references
Comparative studies33 references
Patient outcomes & recovery25 references
Implant survivorship & complications20 references
General reference & perspectives109 references

Broader reference material and papers whose filenames do not identify a specific subject. Topics are based on available filenames and collection labels, not a full-text review.

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This library includes research articles and supporting reading. Inclusion is not an endorsement of a study’s conclusions; filenames are not verified citations.

Polyethylene and insert design · 1,876 references, 711 PDFs

Polyethylene

1,876 references · 711 PDF links

Knee insert design: medial congruence, medial stabilization and constraint, with related bearing designs listed separately.

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Collection scope and sources

Imported from the supplied knee insert reference collection, compiled September 11, 2026. Citations and design tags are preserved from that collection. Its search covers PubMed/MEDLINE; categories reflect indexed terms and are not a full-text assessment of each paper.

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