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Open research questions in Total Knee Arthroplasty Outcomes

66 unresolved questions extracted from the limitations and future-work sections of 494 Total Knee Arthroplasty Outcomes papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • 1. Routine measurement of adherence using a validated instrument (e.g., EARS) may be considered at Day 5 and discharged as a structured post-operative mobility- adherence measure. risk integrate stratification educational level, serum albumin, and total protein to identify patients at risk for low adherence and constrained recovery. 2. Pre-operative should 3. Targeted pre-operative interventions for at-risk patients, including structured patient education and nutritional optimization, warrant evaluation in prospective trials. 4. Future research in acute post-operative orthopedic settings should consider alternative patient-reported outcome measures (e.g., Lower Extremity Functional Scale, Timed Up and Go) better suited to detecting variation functional recovery, given the demonstrated WOMAC floor effect. in early Authors’ contributions: PNT: Conceived and designed the study, conducted research, provided research materials, and collected and organized data; GHTH: Analyzed and interpreted data; DMV: Contributed to data interpretation, wrote the initial and final draft of the article, and provided logistical support. All authors have critically reviewed and approved the final draft and are responsible for the manuscript’s content and similarity index.

    Adherence to early mobilization and acute functional recovery after lower-limb orthopedic surgery: A longitudinal cohort study · 2026 · DOI

  • Finally, regression estimates for sparse subgroups (ASA II/III, hypertension n = 22) are inherently unstable; the bootstrap analysis for hypertension and the directionally consistent arthroplasty subset analysis partially address this concern, but caution is warranted.

    Adherence to early mobilization and acute functional recovery after lower-limb orthopedic surgery: A longitudinal cohort study · 2026 · DOI

  • Monocular two-dimensional pose estimation (2D-PE) apps represent an emerging low-threshold solution; however, their accuracy against established reference systems remains insufficiently validated.

    Gait assessment using a 2D video-based pose estimation app in comparison to a markerless motion capture system in subjects with osteoarthritis of the knee – a pilot study · 2026 · DOI

  • A limitation of this study is that HILT and telerehabilitation were administered concurrently. Therefore, the independent contribution of each intervention could not be determined, and the observed benefits may reflect their synergistic effects.

    Effectiveness of Combined High-Intensity Laser Therapy (HILT) and Telerehabilitation in Patients with Primary Knee Osteoarthritis Following Total Knee Replacement Surgery: A Randomized Controlled Study · 2026 · DOI

  • Future work should investigate why the observed muscle activation patterns are altered, what the consequences are for other joints in the kinetic chain, whether similar patterns are present in other activities of daily living, and assess the ability of rehabilitation interventions to address neuromuscular impairments and improve overall physical performance after TKA.

    MUSCLE ACTIVATION DURING CYCLING AFTER TOTAL KNEE REPLACEMENT: A PATIENT-CONTROL STUDY · 2026 · DOI

  • This review is limited by the available literature, which primarily consists of case reports with minimal follow-up, making it challenging to assess complications and longterm outcomes. Despite millions of TKAs performed during the study period, the small number of reported incidental findings suggests likely underreporting, as many incidental findings may go undocumented if they do not alter surgical SurgiColl 8 Intraoperative Incidental Findings In Total Knee Arthroplasty: A Systematic Review Table 4.

    Intraoperative Incidental Findings In Total Knee Arthroplasty: A Systematic Review · 2026 · DOI

  • The database we used did not include information on some potential risk factors for manipulation such as BMI, preopera- tive range of motion, and smoking. Additionally, we did not analyze the use of a tourniquet during primary TKA. More- over, the case-level indication for TKA (at the population level about 95% of cases had osteoarthritis as an indication) was missing, and the laterality of manipulation remained unclear in 163 (4.1%) cases. Additionally, the register data did not include the specific indications for revisions after manipulation.

    Risk factors for manipulation under anesthesia after total knee arthroplasty and subsequent revision arthroplasty: a Finnish register-based study of 154,883 patients · 2026 · DOI

  • Prior histologic series have reported similar prevalence rates of 15–25%, indicating that subclinical inflammation may be underrecognized in standard OA evaluation [6, 7, 10].

    Inflammatory changes in osteoarthritis knees undergoing total knee arthroplasty: a prospective clinical and histopathological study · 2026 · DOI

  • The findings highlight the need for targeted healthcare policy adjustments in Germany. While centralization in primary arthroplasty has progressed, revision care remains fragmented and should be addressed through minimum vol- ume requirements and specialized centre structures. Demo- graphic changes and increasing patient complexity require expansion of high-volume, multidisciplinary centres. In par- allel, reimbursement systems must be adapted to support shorter hospital stays and the transition toward outpatient and hybrid care models, that still have to be developed in Germany. Acknowledgements The authors did not receive any direct financial support, grants, or personal remuneration for the preparation of this manuscript. However, data acquisition for this study was commissioned and funded by the German Society for Orthopaedics and Orthopaedic Surgery (Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie—DGOOC), which contracted hcb (Institute for Health Care Business GmbH, Essen Germany) for the data collection process. The authors would like to thank the hcb, for their support in the initial data processing and visualization. In particular, we gratefully acknowledge the contributions of Sabine Finke, Vivian Hölzner and Dr. Michaela Lemm (hcb) for their valuable work in preparing the initial datasets. The scientific analysis, as well as the final data processing, interpreta- tion, and visualization, were performed independently by the author team. Author contribution I.S. and B.M.H. conceived and supervised the study and were substantially involved in study design, data interpreta- tion, manuscript preparation, and critical revision of the manuscript. D.L. contributed to data acquisition, data analysis, and manuscript drafting. G.B. contributed to data processing, statistical analysis, and visualization. S.M.-W. contributed to data interpretation and critical revision of the manuscript. M.R. and B.K. contributed to study design, interpretation of the results, and critical revision of the manuscript. All authors reviewed and approved the final version of the manuscript. Funding Open Access funding enabled and organized by Projekt DEAL. Data acquisition for this study was commissioned by the Ger- man Society for Orthopaedics and Orthopaedic Surgery (Deutsche Gesellschaft für Orthopädie und Orthopädische Chirurgie – DGOOC), which contracted hcb (Institute for Health Care Business GmbH, Essen, Germany) for the data collection process. Data availability The data used in this study were obtained from pub- licly available datasets provided by the German Federal Statistical Office (Destatis) and hospital quality reports of the German Federal Joint Committee (G-BA). Processed data supporting the findings of this study are available from the corresponding author upon reason- able request.

    Diverging trends in primary and revision arthroplasty in Germany: projections and implications for healthcare delivery for the next ten years · 2026 · DOI

  • Continued expansion of TJA in resource-limited environments will depend on advancement of collaborative infrastructure, outcome measurement, and sustainable supply models. As institutional experience grows, opportunities exist to refine patient selection, optimize perioperative pathways, and expand locally led surgical capacity. Development of prospective arthroplasty registries focused on low-resource settings represents a critical next step. Standardized collection of demographic data, implant utilization, complications, and patient-reported outcomes would enable objective performance assessment, support Journal of Orthopaedic Experience & Innovation 8 High-Volume Total Joint Arthroplasty in Resource-Limited Settings: A Systems-Based Framework for Inter… Table 3.

    High-Volume Total Joint Arthroplasty in Resource-Limited Settings: A Systems-Based Framework for International Surgical Collaboration · 2026 · DOI

  • Of the 2,842 screened patients, we have data only from the 280 patients in the RCT sample and 373 in the observational sample. Of the 1,713 patients that met the inclusion and exclusion criteria, we do not know why 1,433 (84%) declined to participate in the RCT, and of those who declined the RCT, 1,060 (74%) also declined to participate in the observational sample. We do not know anything about their psychological status or their levels of knee symptoms and knee awareness. Hence, we were unable to evaluate the nature of possible responder bias. The relatively small effect sizes of the reported associations (FABQ Physical activity scale OR for participation 0.96–0.97 and HADS Anxiety 1.05 with 95% confidence intervals close to null) means that there is no evidence that these associations translate into clinically meaningful differences in participation behavior. Because the MCID for the FABQ not has been explored for patients with knee OA, we used the value of an MCID of 4 NJK, AL, MFL, TKN, AA, and SH conceived and designed the study. NJK, SE, TKN, AA, SH, and TR collected the data. NJK and CLG performed the statistical analyses. NJK drafted the manuscript. All authors had access to all data, participated in analysis and interpretation of the data, revision of the manuscript, and gave final approval of the version to be published. Handling co-editors: Taco Gosens and Robin Christensen Acta thanks Troels Christensen and for help with peer review of this manuscript. The authors would like to thank the patients in this study for their participation. Further, they wish to acknowledge Lovisenberg Diaconal Hospital, the Coastal Hospital in Hagevik, and Martina Hansens Hospital for accessibility to the outpatient and physiotherapy clinics. This paper is a product stemming from the Norwegian research project “The MultiKnee trial.” Dr Maren Falch Lindberg is the Principal Investigator (PI) and Drs Anners Lerdal and Arild Aamodt are Co-PIs. Ingvild Buset Bergvad, Alexander Eikrem-Lüthi, and Turid Rognsvåg are PhD students supervised by the seniors Drs Anners Lerdal, Jon Magnussen, Maren Falch Lindberg, Mona Badawy, Ove Furnes, and Søren T. Skou. The other members of the MultiKnee research team are Drs Caryl L. Gay, Stig Heir, Inger Holm, Nina Jullum Kise, Tor Kjetil Nerhus, Milada C. Småstuen, and Jan Stubberud. Katrine Rutledal, Deputy Director for Lovisenberg User Board, provided user participation. 1. Steers W, Richter H, Nyberg L, Kusek J, Kraus S, Dandreo K, et al. Challenges of conducting multi-center, multi-disciplinary urinary incontinence clinical trials: experience of the urinary incontinence treatment network. Neurourol Urodyn 2009; 28: 170-6. doi: 10.1002/nau.20653. 2. Dickson S, Logan J, Hagen S, Stark D, Glazener C, McDonald A M, et al.

    Psychological factors associated with trial participation among patients eligible for total knee arthroplasty with a non-surgical treatment arm: a comparative cross-sectional study · 2026 · DOI

  • However, it is important to critically note that no included study performed a formal head-to-head comparison between simple and complex models using identical datasets, identical outcome definitions, and identical validation strategies. The observed comparability between simple and complex models is therefore inferred from cross-study comparisons rather than within-study evidence. This substantial, as differences in patient populations, outcome definitions, and these validation approaches across studies may confound comparisons. For instance, the simple three-variable model by Bozic et al. (5) was developed on a US national registry dataset with 28,661 patients, while the complex deep learning models were trained on different institutional datasets with varying sample sizes and predictor sets. Without rigorous within-study comparisons controlling for these variables, the conclusion that simple models perform comparably to complex ones remains tentative and should be interpreted with caution. is Similarly, the BMI paradox warrants attention: while Class III obesity (BMI ≥40) is associated with higher perioperative risk, these in patient- patients demonstrated the greatest improvements (13). This reported outcomes at 90 days postoperatively counterintuitive of distinguishing between risk prediction and expected benefit— patients at highest risk may derive the most value from intervention, a nuance that simple risk stratification tools fail to capture. underscores importance finding the Robotic-Assisted TKA: technical outcomes and cost considerations Twelve studies (25.5% of all included studies) specifically examined RA-TKA outcomes, while the remaining 35 studies (74.5%) addressed general TKA populations. Among the RA- TKA-specific studies, robotic systems demonstrated improved component alignment accuracy, with outliers (>3 degrees from neutral) reduced from 25.8% to 10.1% compared to conventional techniques (14). However, the clinical significance of improved alignment remains debated, as some studies failed to demonstrate corresponding improvements in functional outcomes or implant survival. Within the general TKA studies, several models were developed using datasets that included both conventional and robotic-assisted procedures, but did not perform subgroup analyses stratified by surgical approach, limiting the ability to draw RA-TKA-specific conclusions from these studies. This distinction is important for interpreting the prediction model results presented above, as their generalizability to RA-TKA- specific populations may vary depending on the proportion of RA-TKA patients included in the training data. To further clarify the distinction between general TKA and RA-TKA ML applications, it is important to note that none of the 47 included studies developed or validated a dedicated ML prediction model exclusively for RA-TKA-specific outcomes. The 12 RA-TKA studies primarily focused on evaluating the accuracy of robotic systems (e.g., component alignment, soft tissue balance) rather than developing predictive algorithms. Conversely, the 35 general TKA ML studies developed prediction models using datasets that predominantly included conventional TKA patients, with variable and often unspecified proportions of RA-TKA patients. This gap represents a significant limitation: the prediction models reported in this review may not be directly generalizable to RA-TKA populations, as RA-TKA patients may differ systematically from conventional TKA patients in terms of preoperative functional status, deformity severity, and surgical complexity. We strongly advocate for future studies to develop and externally validate ML prediction models specifically in RA-TKA cohorts using robotic-systems-generated intraoperative data. Cost-effectiveness analyses presented conflicting results. While RA-TKA was associated with higher hospital charges ($154,673 vs. $125,467 for conventional TKA) (15), the potential for reduced revision rates and complications could theoretically offset these costs. However, no study to date has demonstrated that ML prediction models can identify patients most likely to benefit from robotic assistance, representing a critical gap in the literature. The question remains: can preoperative risk stratification guide resource allocation, directing RA-TKA toward patients who will derive maximal benefit?.

    From data to decisions: machine learning in predicting outcomes of robotic-assisted total knee arthroplasty · 2026 · DOI

  • Finally, the positioning assistance sheet was designed based on a specific medial left-sided implant model; therefore, its direct applicability to other UKA implant types, such as lateral models or those from different manufacturers, remains to be validated.

    Optimization of postoperative unicompartmental knee arthroplasty radiography using a phantom-based ray-summation positioning sheet · 2026 · DOI

  • IA is not universally applicable to all TKA patients, and optimizing GA-related outcomes may serve as an alternative strategy to shorten LOHS, requiring further investigation.

    The role of anesthesia in TKA length of stay: a data-driven analysis using Boruta algorithm · 2026 · DOI

  • Although Boruta feature selection yielded stable results across 100 and 1,000 iteration runs, this Random Forest-based method has inherent limitations in small datasets with potential risk of inflated feature importance estimates and compromised accuracy of importance measures.

    The role of anesthesia in TKA length of stay: a data-driven analysis using Boruta algorithm · 2026 · DOI

  • The current literature, however, brings contradictory reports as to its effectiveness, which, at least in part, should be attributed to the diversity of methods for producing the concentrate, including the use of various volumes of whole blood, single vs double centrifugation vs filtration, use of thrombin vs calcium chloride to activate the process, and, finally, the use of an anticoagulant.

    High Volume PRP Therapy · 2022 · DOI

  • Insufficient evidence of the benefits provided by costlier microprocessor knees (MPKs) over nonmicroprocessor knees (NMPKs) often causes concern when considering MPK prescription.

    Comparison of mobility and user satisfaction between a microprocessor knee and a standard prosthetic knee: a summary of seven single-subject trials · 2017 · DOI

  • Despite the considerable number of patients suffering from chronic postsurgical pain after TKA, available data is scarce, and well controlled prospective studies are lacking.

    Predicting Persistent Unclear Pain Following Primary Total Knee Arthroplasty · 2016 · DOI

  • However, there is limited information available regarding whether such nonsystemic risk factors could also be responsible for the increased risk of knee OA after traumatic, unilateral lower limb amputation in young military Service Members.

    A Narrative Review of the Prevalence and Risk Factors Associated With Development of Knee Osteoarthritis After Traumatic Unilateral Lower Limb Amputation · 2016 · DOI

  • Adding intermittent pneumatic compression to pharmacological thromboprophylaxis is suggested to reduce venous thromboembolism risk in surgical settings broadly, but specific direct evidence for total knee replacement patients is lacking.

    In adults undergoing total knee replacement, does adding intermittent pneumatic compression to pharmacological thromboprophylaxis reduce the incidence of postoperative venous thromboembolism compared to pharmacological thromboprophylaxis alone? · 2026 · DOI

  • Background Aseptic sleeve failure in revision total knee arthroplasty (TKA) is rare, and associated risk factors remain poorly understood.

    Aseptic Failure of Tibial Components With Sleeves in Revision Total Knee Arthroplasty: A Novel Radiographic Assessment of Zonal Fixation · 2026 · DOI

  • In the literature, there are some studies on the muscle recruitment pattern during cycling in healthy subjects, especially in competitive and professional cyclists, however, to our knowledge, no studies have been performed in patients.

    MUSCLE ACTIVATION DURING CYCLING AFTER TOTAL KNEE REPLACEMENT: A PATIENT-CONTROL STUDY · 2026 · DOI

  • Future research should explore institutional stewardship, standardized discharge protocols, and multidisciplinary engagement to reduce unnecessary postoperative exposure to EROs.

    A Population-based Cross-sectional Analysis of Extended-release Opioid Dispensing Incidence, Prognostic Factors, and Variation after Total Joint Arthroplasty · 2026 · DOI

  • Although robotic assistance has demonstrated efficacy in primary TKA, its application in partial revision procedures remains poorly understood.

    Robotic‐Assisted Partial Revision of Total Knee Arthroplasty: First Case Report and Literature Review · 2026 · DOI

  • Although the direction and magnitude of ankle joint realignment are well studied, the knee deformity threshold beyond which the ankle will align outside the accepted neutral coronal plane alignment remains incompletely defined.

    In knee osteoarthritis, what is the knee deformity threshold after which the ankle realigns beyond the neutral zone? · 2026 · DOI

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