The painful knee after total knee arthroplasty

Clinical Efficacy of 2-Needle Joint Lavage for Osteoarthritis-Related Knee Pain and Predictors of Response Based on Knee MRI Osteoarthritis Knee Score: A Medical Records Review Study

BACKGROUND

Knee osteoarthritis (OA) is notoriously difficult to treat. Pain is the key symptom for patients to seek medical attention. This study aimed to evaluate the therapeutic efficacy of joint lavage (JL) for OA-related knee pain and to explore the knee pathological changes detected by magnetic resonance imaging that may affect the prognosis of patients who received JL.

METHODS

Eighty-two hospitalized patients who were diagnosed with knee OA and received JL in our department were finally enrolled in this study. The patients' clinical data including Numeric Rating Scale (NRS), Western Ontario and McMaster Osteoarthritis Index pain subscale, analgesic medication usage, adverse events, and magnetic resonance imaging data of the affected knee joint scored by the MRI Osteoarthritis Knee Score were recorded and analyzed.

RESULTS

The NRS scores significantly decreased after JL and remained steady until 6 months ( p < 0.001). The Western Ontario and McMaster Osteoarthritis Index pain scores and the percentage of patients who needed analgesic medication significantly decreased at 6 months compared with baseline ( p < 0.001). At 6 months after JL, 51 of the 82 patients experienced ≥50% improvement in their NRS scores (effective). Multivariate binary logistic regression analysis revealed that duration of pain (odds ratio [OR], 1.022; 95% confidence interval [CI], 1.003-1.042; p = 0.024), bone marrow lesion score (OR, 1.221; 95% CI, 1.028-1.450; p = 0.023), and cartilage loss score (OR, 1.272; 95% CI, 1.021-1.585; p = 0.032) significantly influenced the therapeutic efficacy of JL.

CONCLUSIONS

JL treatment can significantly alleviate the OA-related knee pain in at least 6 months. JL tends to provide limited benefit for patients with long duration of pain, serious bone marrow lesions, and severe cartilage loss.

Robotic-assisted mechanically aligned total knee arthroplasty does not lead to better clinical and radiological outcomes when compared to conventional TKA: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

Robotic-assisted total knee arthroplasty (R-TKA) has emerged as an alternative to improve the results of the conventional manual TKA (C-TKA). The aim of this study was to analyse the high-level studies comparing R-TKA and C-TKA in terms of clinical outcomes, radiological results, perioperative parameters, and complications.

METHODS

The literature search was conducted on three databases (PubMed, Cochrane, and Web of Science) on 1 February 2023 according to the guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Inclusion criteria were: randomized controlled trials (RCTs), written in English language, published in the last 15 years, focusing on the comparison of C-TKA and R-TKA results. The quality of each article was assessed using the Cochrane risk-of-bias tool for randomized trials version 2 (RoB 2). The statistical analysis was carried out using random effects (DerSimonian & Laird) for weighted mean difference (MD) of the continuous variables and Peto method for odds ratios of the dichotomous variables.

RESULTS

Among the 2905 articles retrieved, 14 RCTs on 12 series of patients treated with mechanically aligned implants were included. A total of 2255 patients (25.1% males and 74.9% females; mean age 62.9 ± 3.0; mean BMI 28.1 ± 1.3) were analysed. The results of this systematic review and meta-analysis showed that R-TKA did not provide overall superior results compared to C-TKA in mechanically aligned implants in terms of clinical and radiological outcomes. R-TKA showed longer operative time (MD = 15.3 min, p = 0.004) and similar complication rates compared to C-TKA. A statistically significant difference in favour of R-TKA was found in the posterior-stabilized subgroup in terms of radiological outcomes (hip-knee-ankle angle MD = 1.7, p < 0.001) compared to C-TKA, although without resulting in appreciable difference of clinical outcomes.

CONCLUSION

R-TKA did not provide overall superior results compared to C-TKA in terms of clinical and radiological outcomes, showing longer operative time and similar complication rates.

LEVEL OF EVIDENCE

Level I.

Anterior Knee Pain Following Primary Unilateral Total Knee Arthroplasty With Posterior-Stabilized Prosthesis and Patellar Resurfacing: Prevalence and Clinical Implications

BACKGROUND

Anterior knee pain following total knee arthroplasty (TKA) is associated with patient dissatisfaction. Factors related to postoperative anterior knee pain and its impact on patient outcomes are poorly understood. The following are the aims of this study: (1) to report the prevalence of anterior knee pain before and after TKA using a posterior-stabilized prosthesis with routine patellar resurfacing; (2) to investigate the association of preoperative clinical factors with the presence of anterior knee pain after TKA; and (3) to explore the association of postoperative anterior knee pain with postoperative self-reported function and quality of life.

METHODS

This retrospective study included 506 patients who had undergone elective primary unilateral TKA with a posterior-stabilized prosthesis and patellar resurfacing. Outcome measures prior to and 12 months after TKA included self-reported anterior knee pain, knee function, and quality of life.

RESULTS

Prevalence of anterior knee pain was 72% prior to and 15% following TKA. Patients who had preoperative anterior knee pain had twice the risk of experiencing anterior knee pain after TKA than patients who did not have preoperative anterior knee pain (risk ratio: 2.37, 95% CI 1.73-2.96). Greater severity of preoperative anterior knee pain and worse self-reported function were associated with the presence of postoperative anterior knee pain (rho = 0.15, P < .01; rho = 0.13, P < .01, respectively). Preoperative age, gender, and quality of life were not associated with postoperative anterior knee pain. Greater severity of postoperative anterior knee pain was associated with worse knee function at 12 months postoperative (rho = 0.49, P < .01).

CONCLUSION

One in 7 patients reported anterior knee pain 12 months following posterior-stabilized and patella-resurfaced TKA. The presence of preoperative anterior knee pain and worse self-reported function are associated with postoperative anterior knee pain.

Resection of Infrapatellar Fat Pad during Total Knee Arthroplasty Has No Impact on Postoperative Function, Pain and Sonographic Appearance of Patellar Tendon

Routine resection of the infrapatellar fat pad (IFP) during total knee arthroplasty (TKA) is controversial, as it may result in shortening of the patellar tendon (PT) and anterior knee pain. This prospective study examined whether IFP excision during TKA affects joint function, anterior knee pain, PT dimensions and sonographic structure. A total of 65 consecutive patients undergoing TKA for osteoarthritis were randomized into two groups: IFP was resected in one and retained in the other. Patients were examined preoperatively, at 6 weeks and 6 months postoperatively: pain (Numerical Rating Scale-NRS), range of motion (ROM) and knee function (Knee Injury and Osteoarthritis Outcome Score-KOOS score) were evaluated; sonographic examination determined the length, structure and vascularity of the PTs. In both groups there were postoperative improvements in NRS and KOOS scores, although IFP resection did not influence clinical outcomes or sonographic parameters. At 6 weeks and 6 months postoperatively for both groups there were no differences between NRS scores (Mann-Whitney test, p = 0.511 and p = 0.579), ROM scores (Mann-Whitney test, p = 0.331, p = 0.180) or all KOOS subscores. IFP excision had no effect on sonographic parameters. This study suggests that IFP resection during TKA does not influence postoperative functional outcomes, pain scores, patellar tendon length and thickness, or sonographic structure.

Stress Radiographs in the Posterior Drawer Position at 90° Flexion Should Be Used for the Evaluation of the PCL in CR TKA with Flexion Instability

The purpose of this study was to define a cut-off value for the posterior drawer position in stress radiography that confirms an insufficiency of the posterior cruciate ligament (PCL) in cruciate-retaining (CR) total knee arthroplasty (TKA). In this retrospective study, 20 symptomatic patients with flexion instability and suspected PCL insufficiency in CR TKA were included. Asymptomatic patients served as an age- and sex-matched control group. All of the patients had undergone stress radiography, and the posterior translation was measured in a posterior drawer position at 30° and 90° flexion. The two groups were compared using t-tests and chi-square tests. The stress radiographs showed significantly more posterior translation in the symptomatic group (p < 0.01). Stress radiographs at 90° flexion more effectively discriminated between the patients with and without PCL insufficiency compared with those carried out at 30° flexion. Sensitivity and specificity testing revealed the best sensitivity (90.5%) and the best specificity (94.7%) at 90° posterior drawer radiographs at a cut-off value of 10 mm. Stress radiographs including the posterior drawer position at 90° flexion should be part of the diagnostic algorithm in patients with suspected flexion instability. A posterior translation of more than 10 mm in CR TKA strongly indicates an insufficiency of the PCL.

Additional nerve blocks are not superior to multiple-site infiltration analgesia in total knee arthroplasty under adductor canal block

Background

Adductor canal block (ACB) with additional nerve blocks (ANBs) is reported to provide adequate analgesia and enhanced functional rehabilitation in total knee arthroplasty (TKA). The present study aims to evaluate whether ANBs are superior to multiple-site infiltration analgesia (MIA) in patients undergoing TKA under ACB.

Methods

We enrolled 530 patients undergoing primary TKA from 2015 to 2019 at our institution in this retrospective cohort study. Patients were divided into two groups: Group A was treated with ANBs + ACB; Group B was treated with MIA + ACB. Primary outcomes were pain scores and morphine consumption. Functional recovery was the secondary outcome. Other outcomes included satisfaction score, cost-effectiveness, adverse events, and length of hospital stay (LOS).

Results

Pain scores at rest and morphine consumption were slightly lower in the ANBs + ACB group than in the MIA + ACB group. No significant difference was found in functional recovery, post-operative complications or LOS between the groups. Meanwhile, the cost of analgesic intervention in the MIA + ACB group was less than that in the ANBs + ACB group.

Conclusion

The present study suggests that ANBs do not provide superior pain relief compared to MIA for patients undergoing TKA under ACB.

Trial registration

Chinese Clinical Trial Registry, ChiCTR2100043227. Registered 9 February 2021, https://www.chictr.org.cn/showproj.aspx?proj=121745.

Diagnostic Algorithm in Patients with Flexion Instability after Cruciate-Retaining Total Knee Arthroplasty: A Case Report

A posterior flexion instability due to insufficiency of the posterior cruciate ligament (PCL) in cruciate retaining (CR) total knee arthroplasty (TKA) is an important but underdiagnosed problem. We hereby suggest a diagnostic algorithm, as demonstrated by a case report of a male patient suffering from anterior knee pain and instability after CR TKA. Clinical examination was followed by standard anterior–posterior and lateral radiographs. Stress radiographs in 30° and 90° posterior drawer position enabled a dynamic examination of the instability. SPECT/CT was used to determine the TKA component position in all planes and investigate bone tracer uptake (BTU) patterns. At revision surgery, an absent PCL after CR TKA was noted and a semi-constrained TKA was implanted.

Factors Associated With the Risk of Developing Moderate to Severe Acute Postoperative Pain After Primary Total Knee Arthroplasty: Results From the PAIN OUT Registry

BACKGROUND

Total knee arthroplasty (TKA) is one of the most common procedures in orthopedic surgery and not always matches with patient's expectations of pain relief and function improvement. The aim of this study was to assess risk factors for developing moderate to severe acute postoperative pain (APOP) after TKA using the PAIN OUT questionnaire.

METHODS

Prospective, multicentre, international cohort study within the PAIN OUT project. Patients' outcomes were measured with 11-point numerical rating scales (0 = null, 10 = worst possible). Patient and analgesic/anesthetic treatment were assessed. Odds ratio for moderate-severe pain was calculated for each variable and if they were statistically significant in the univariate logistic model, variables were fitted into a multivariate logistic regression model. The effect size was assessed by Cohen's d coefficient.

RESULTS

In total, 968 patients were evaluated. The multivariate model identified chronic preoperative pain (P < .001), general anesthesia (P = .020), and receiving chronic opioids before (P = .020) or after the surgery (P < .001) as factors associated with moderate-severe APOP. No protective factors were observed.

CONCLUSIONS

Our model identified several risk factors for APOP. From our results, preoperative chronic pain, general anesthesia and the use of opioid analgesics could be predictors for higher APOP. These findings may help establish new strategies for the treatment of pain in TKR. More studies should be carried out to identify acute pain predictors and to develop better strategies of pain management for risk patients.

Diagnostic accuracy of SPECT/CT arthrography in patients with suspected aseptic joint prostheses loosening

Purpose

To evaluate the diagnostic accuracy of SPECT/CT arthrography in patients with suspected aseptic prosthesis loosening following hip and knee arthroplasty.

Methods

A retrospective review of 63 SPECT/CT arthrogram studies (36 knees and 27 hips) between February 1, 2013, and July 1, 2018, was conducted. All patients underwent clinical and radiologic evaluation as part of their assessment for persistent pain following hip and knee arthroplasty. The detection of tracer activity along the bone-prosthetic interface on SPECT/CT suggests aseptic loosening. Operative assessment as well as clinical/radiologic follow-up at a minimum of 1 year was used as the reference standard.

Results

The sensitivity and specificity of SPECT/CT for detection of aseptic loosening was 6/7 (86%) and 55/56 (98%), respectively. This gives a positive predictive value (PPV) of 6/7 (86%), a negative predictive value (NPV) of 55/56 (98%), and a diagnostic accuracy of 61/63 (97%).

Conclusion

SPECT/CT arthrography has a high diagnostic accuracy (97%) in the evaluation of loosening of both hip and knee arthroplasties in patients with persistent post-procedural pain.

Why do knees after total knee arthroplasty fail in different parts of the world?

Objective

The aim of this narrative review was to provide an overview of failure modes after total knee arthroplasty in different parts of the world based on data from worldwide representative studies and National Joint Registries.

Methods

A review of the available literature was performed using the keyword terms “total knee arthroplasty”, “revision”, “failure”, “reasons”, “causes”, “complications”, “epidemiology”, “etiology”; “assessment”, “painful knee”, “registry” and “national” in several combinations. The following databases were assessed: Pubmed (https://pubmed.ncbi.nlm.nih.gov), Cochrane Reviews (https://www.cochrane.org), Google Scholar (https://scholar.google.com). In addition, registry data were obtained directly from national registry archives. Due to the heterogeneity of available data it was decided to present the review in a narrative manner.

Results

Current literature report that infection has become the primary acute cause of TKA failure, while aseptic loosening and instability remain the overall most frequent reasons for revisions. Based on national registries certain tendencies can be deducted. The predominant overall failure mode of aseptic loosening is particularly found in Japan, United Kingdom, New Zealand and Switzerland. Leading early TKA failure mode represents infection with percentages of 20–30% in Sweden, Australia, New Zealand, Japan and the United States. Higher numbers could only be found in clinical studies on the Asian continent such as Korea (38%), China (53%), Iran (44%) and India (87%).

Conclusion

Although there are regional differences in TKA failure modes, TKA fails worldwide especially due to infections and aseptic loosening. It is important to diagnose these in good time and reliably using appropriate, standardized diagnostics in order to recommend the best possible therapy to the patient.

Bone SPECT/CT has excellent sensitivity and specificity for diagnosis of loosening and patellofemoral problems after total knee arthroplasty

PURPOSE

The primary purpose of this retrospective study with prospectively collected data was to evaluate the clinical value of SPECT/CT, in particular its impact on clinical diagnosis and patient management, in patients with pain, stiffness, or swelling after primary total knee arthroplasty (TKA). The secondary purpose was to determine the sensitivity and the specificity of SPECT/CT for different pathologies such as loosening and patellofemoral overloading.

METHODS

A retrospective analysis was carried out on 214 knees in 202 consecutive patients (mean age 69 ± 11 years) with persistent or recurrent knee pain after TKA. All patients underwent clinical examination, standardised radiographs, and 99mTc-hydroxymethane diphosphonate (HDP) SPECT/CT as part of a routine diagnostic algorithm. The diagnoses before and after SPECT/CT and final treatment were recorded. TKA component position was routinely measured on 3D-reconstructed images. Intensity and anatomical distribution of bone tracer uptake were determined.

RESULTS

SPECT/CT changed the clinical diagnosis and final treatment in 139/214 (65%) knees. In 117 (54.7%) out of 214 patients, revision surgery was proposed following SPECT/CT. Early onset of pain was significantly (p = 0.011) correlated with tibiofemoral stress pattern in SPECT/CT. A total of 86 knees (40.2%) were surgically revised using semi-constrained or fully constrained TKA. In 35 patients, a secondary patellar resurfacing was performed. SPECT/CT showed the clinical diagnosis to be incorrect for suspicion of tibial component loosening in 56 patients (26.2%), femoral component loosening in 53 patients (24.8%), and patellofemoral overloading/progressive patellofemoral osteoarthritis in 26 patients (12.1%) and provided different underlying causes of persistent knee pain after TKA. Likewise, SPECT/CT identified tibial component loosening in 8 patients (3.7%), femoral component loosening in 4 patients (1.9%), and patellofemoral OA in 71 patients (33.2%) without prior clinical suspected diagnosis. The sensitivity and specificity of SPECT/CT for detection of patellofemoral OA was 96.5% and 96.2%, respectively. The sensitivity and specificity for detection of tibial component loosening was 96.0% and 100%, respectively. The sensitivity and specificity for detection of femoral component loosening was 95.0% and 100%, respectively.

CONCLUSION

The diagnostic benefits of SPECT/CT in the challenging and complex cohort of patients with pain after primary TKA have been proven. The excellent sensitivity and specificity for detection of tibial or femoral component loosening and diagnosis of patellofemoral OA have been surgically confirmed. Due to the benefits in establishing the correct diagnosis, SPECT/CT should be implemented as part of the routine diagnostic algorithm for patients with pain after primary TKA.

LEVEL OF EVIDENCE

II.

Chronic, Active Inflammation in Patients With Failed Total Knee Replacements Undergoing Revision Surgery

Chronic pain and restricted knee motion is a significant problem following the total knee arthroplasty (TKA). The molecular pathogenesis of pain post-TKA is not known and no targeted therapeutic intervention is available. The aim of this study was to investigate whether pro-inflammatory mediators are elevated in revision knee patients, indicating an active, ongoing inflammatory process that may contribute to pain. Twelve key markers (pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor [GM-CSF], interleukin 5 [IL-5], IL-8 and IL-10, chemokines CCL2, CCL3, CCL4, and CCL13, mediators of angiogenesis Flt-1, vascular endothelial growth factor, and cell migration vascular cell adhesion molecule 1 and intercellular adhesion molecule 1) were measured in knee tissue and synovial fluid (SF) from primary TKA (n = 29) and revision patients (n = 32). Indications for surgery were osteoarthritis (OA) for primary TKA, and component loosening (n = 11), stiffness (n = 11), laxity pattern (n = 8), or progression of OA in patella resurfacing (n = 3) for revision surgery. Pain levels (WOMAC score) were higher in revision than primary patients (p ≤ 0.05). Time from primary to revision ranged from 8 months to 30 years (median 10 years). All markers were elevated in revision TKA; there was no trend toward decreasing levels with greater time from primary surgery for any marker studied in SF. Similar results were seen in knee tissue. We found no differences comparing indications for revision surgery (p ≥ 0.05). The elevation of inflammatory mediators in painful post-TKA knees requiring revision suggests active, chronic inflammation. Characterization of upregulated markers provides rationale for targeted therapy, even many years from the primary surgery. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2316-2324, 2019.

Different Factors Conduct Anterior Knee Pain Following Primary Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BACKGROUND

A systematic review and meta-analysis was performed to investigate the risks associated with anterior knee pain (AKP) following primary total knee arthroplasty (TKA).

METHODS

A computerized search was performed of the following databases: MEDLINE, Embase, and Cochrane Central (published prior to July 2017). A total of 37 studies, which included 1641 cases of AKP and 168,090 TKAs, were included in the meta-analysis.

RESULTS

A subgroup analysis revealed that compared with those without the following medical conditions, patients who had an infrapatellar fat pad excision and more than 12 months of follow-up (odds ratio [OR] 12.58, 95% confidence interval [CI] 3.245-48.781) were more likely to have AKP after TKA. Circumpatellar electrocautery (>12 months: OR 0.50, 95% CI 0.326-0.760; ≤12 months: OR 0.59, 95% CI 0.408-0.867) and patellar resurfacing (OR 0.25, 95% CI 0.131-0.485) may decrease the risk of AKP. Other factors, including the prosthesis bearing type (mobile bearing or fixed bearing) and the approach (midvastus compared with the medial parapatellar approach), were not significant risk factors for AKP.

CONCLUSION

The use of strategies such as patellar denervation and patellar resurfacing in primary TKA is recommended because they are safe and result in good clinical outcomes in preventing AKP. Caution should be taken when using an infrapatellar fat pad excision, because there is an increased risk of AKP at long-term follow-up (>12 months). Future studies should investigate these different strategies to confirm the underlying mechanisms and help prevent the occurrence of AKP after TKA. The timing of AKP onset remains unclear and requires further research.

[Total knee arthroplasty. Patient-specific instruments and implants]

This article describes the concept and surgical technique of patient-specific total knee arthroplasty. Patient-specific implants and instruments are designed and fabricated based on computed tomography (CT) data of the leg. The disposable patient-specific drill guides and cutting-jigs are manufactured taking into consideration the anatomical and biomechanical axes of the knee joint and mediating the efficient pre-navigation of the osseous saw-cuts, without the need for additional navigation or balancing aids. The surgical plan is made on the basis of the CT data. The implantation technique comprises the following steps: distal femoral resection, tibial resection, balancing and femur preparation, tibia preparation, optional patellar resurfacing, trialling of the test components, and implantation of the final components. By using this patient-specific implant system, which includes not only personalized, single-use instruments, but also individualized implants, the surgeon is able to provide endoprosthetic treatment that broadly restores the patient's own knee anatomy and knee kinematics. Preliminary studies have proven the concept and data on this technology are promising so far; however, like a new implant, they are usually limited. In particular, comparative long-term clinical data are still to come.

Persistent pain after knee replacement: do factors associated with pain vary with degree of patient dissatisfaction?

OBJECTIVE

Up to 20% of patients experience long-term pain and dissatisfaction following knee replacement. The aim of this study was to investigate factors associated with persistent pain following knee replacement and their implications for patient satisfaction.

DESIGN

A case-controlled analysis compared patients with established persistent pain with patients who were pain-free. 2:1 frequency matching for age, gender, time from surgery and prosthesis was performed. 1310 patients were approached and 100 patients with persistent pain and 200 matched pain-free controls were included. Variables assessed included mechanical, biological, psychosocial and generalised factors.

RESULTS

The study found that the degree of dissatisfaction experienced by the patient with persistent pain following knee replacement affected the factors associated with pain. In the most dissatisfied patients, pain was associated with instability in the coronal plane (OR 19.8, 95% CI 3.8-104.0), stiffness (OR 6.4, 95% CI 2.3-18.4) and negative social support (OR 3.3, 95% CI 1.1-10.0). In patients who were less dissatisfied, pain was associated with patellofemoral problems (OR 10.3, 95% CI 3.6-29.6), elevated BMI (OR 2.8, 95% CI 1.4-5.7) and reduced local pain thresholds (OR 4.4, 95% CI 2.0-9.6). Depression (OR 13.6, 95% CI 1.9-96.6) and presence of proximal tibial tenderness (OR 23.5 95% CI 7.8-70.7) were strongly associated with pain regardless of level of satisfaction.

CONCLUSIONS

Patients with persistent pain after knee replacement are dissatisfied. This study identifies factors associated with the worst pain outcomes, which lead to the greatest levels of dissatisfaction. Particular efforts with a holistic multidisciplinary approach should be focused towards these "red flag" factors in order to minimise persistent pain after knee replacement.

[Individualized total knee arthroplasty]

This article describes the rationale and the surgical technique of patient-specific uni-, bi-, or three-compartmental knee arthroplasty using the second generation (G2) of ConforMIS™ technology. The patient-individual implants and instruments are designed and fabricated based on data from a preoperative computed tomography of the lower limb. The disposable patient-specific drill guides and cutting-jigs are manufactured under consideration of the anatomical and biomechanical axes of the knee joint and mediate efficient pre-navigation of the saw-cuts on the femoral and tibial bone without the need for an additional navigation or balancing device. The surgical technique for all types of knee resurfacement comprises the steps of cartilage removal, knee balancing in extension and flexion, sparing bony cuts, final preparation of femur and tibia, trialling, cementing of components and final choice of tibial insert. The use of individualized three-dimensional image-derived resurfacing implants, as well as personalized single-use instrumentation, facilitates the surgeon to perform an almost anatomical knee resurfacement that has the potential to restore almost normal knee kinematics. The limited data on this novel technology is promising, however long-term clinical data is needed for final evaluation of this technology.

Anterior knee pain following primary total knee arthroplasty

Despite improvements in technique and technology for total knee arthroplasty (TKA), anterior knee pain impacts patient outcomes and satisfaction. Addressing the prosthetic and surgical technique related causes of pain after TKA, specifically as it relates to anterior knee pain, can aid surgeons in addressing these issues with their patients. Design features of the femoral and patellar components which have been reported as pain generators include: Improper femoral as well as patellar component sizing or designs that result in patellofemoral stuffing; a shortened trochlear groove distance from the flange to the intercondylar box; and then surgical technique related issues resulting in: Lateral patellar facet syndrome; overstuffed patella/flange combination; asymmetric patellar resurfacing, improper transverse plane component rotation resulting in patellar subluxation/tilt. Any design consideration that allows impingement of extensor mechanism anatomical elements has the possibility of impacting outcome by becoming a pain generator. As the number of TKA procedures continues to increase, it is increasingly critical to develop improved, evidence based prostheses that maximize function and patient satisfaction while minimizing pain and other complications.

[Rare cause of knee pain after total knee arthroplasty]

A painful knee after total knee arthroplasty may have various causes. In addition to commonly occurring causes, such as infections, aseptic loosening, implant failure or typical anterior knee pain, rare causes also have to be taken into account. We report a previously unknown cause of knee pain after total knee replacement involving a non-resected medial meniscus, which was sandwiched between the medial condyle of the femur and the inlay of the prosthesis and caused pain typical for a medial meniscus. After arthroscopic meniscectomy the patient was symptom-free.