Healthy Knee Research Articles

Varus-valgus native knee laxity in extension displays an almost rectangular pattern and does not correlate with lower limb alignment

Optimal ligament balance is crucial for successful total knee arthroplasty (TKA), which is a standard procedure for managing end-stage knee osteoarthritis. However, the reported values of ligament balance vary due to different methodologies and population differences, which requires further studies. This study aimed to investigate the varus-valgus ligament balance in healthy knees of Japanese individuals and its relationship with lower limb alignment. The studyanalyzed64 knees from 33 healthy young adults using stress radiographs to measure varus-valgus laxity. The mechanical hip-knee-ankle angle, medial proximal tibial angle, and lateral distal femoral angles were determined using digital long-leg radiographs. Varus and valgus laxities were compared, and the relationship between ligament balance and alignment parameters was analyzed. Mean varus laxity (3.6°± 1.3°) was significantly greater than mean valgus laxity(2.9°± 1.0°) (p<0.0001). No significant association was observed between ligament balance and alignment parameters. Healthy knees of Japanese individuals exhibited slightly greater varus laxity (0.7°) than valgus laxity, with no correlation observed between ligament balance and lower limb alignment. The finding underscores the importance of recognizing alignment diversity while noting that alignment does not influence ligament balance; this is particularly relevant in modern TKA techniques focusing on patient-specific joint and ligament reconstructions. The study’s findings could help formulate strategies benefiting knee osteoarthritis management.

Exploring healthy knee kinematic phenotypes obtained through dynamic CT imaging: A cluster analysis study

Dynamic Computed Tomography (CT) emerges as a pivotal imaging modality for the assessment of knee joint kinematics. However, integrating dynamic CT into clinical practice necessitates a thorough understanding of healthy knee kinematics, as large variation in kinematics has been described within healthy populations. Therefore, this study aims to identify and describe healthy phenotypes with homogenous knee kinematics using a clustering approach. A total of 120 healthy knees from 64 participants underwent dynamic CT scanning during knee extension and flexion. Eight tibiofemoral (TF) and patellofemoral kinematic parameters were extracted, after which K-means clustering was applied to identify homogenous kinematic clusters. Kinematic phenotypes were obtained by calculating the median and interquartile range (IQR) for all kinematic parameters per cluster. Two distinct clusters were found, comprising 53 (Cluster 1) and 67 (Cluster 2) knees. Statistically significant differences between the clusters were found in six out of eight kinematic parameters. The most notable differences were observed in TF rotations, with cluster 1 exhibiting a greater amount of internal and adduction rotation of the tibia compared to cluster 2. The two kinematic phenotypes provide new insights into the nuanced variation within a healthy cohort and can serve as reference for future studies evaluating pathological kinematic phenotypes using dynamic CT.

Assessment of meniscal extrusion with ultrasonography: a systematic review and meta-analysis

BackgroundMagnetic resonance imaging (MRI) is the imaging of choice for meniscal extrusion (ME). However, they may underappreciate the load-dependent changes of the meniscus. There is growing evidence that weight-bearing ultrasound (WB US) is more suitable, particularly in revealing occult extrusion. We therefore perform a systematic review and meta-analysis on the validity and reliability of US in diagnosing extrusion. Furthermore, we explored whether it detects differences in extrusion between loaded and unloaded positions and those with pathological (osteoarthritis and meniscal injury) and healthy knees.MethodsThe Cochrane Controlled Register of Trials, PubMed, Medline, and Embase were used to perform a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Data pertaining to intra- and interrater reliability of US in measuring meniscal extrusion (ME), its correlation with magnetic resonance imaging (MRI), and head-to-head comparison of potential factors to influence ME were included [loading versus unloading position; osteoarthritis (OA) or pathological menisci (PM) versus healthy knees; mild versus moderate–severe knee OA]. Pooled data were analyzed by random or fixed-effects models.ResultsA total of 31 studies were included. Intraclass correlation coefficients (ICC) for intra- and interrater reliability were minimum 0.94 and 0.91, respectively. The correlation between US and MRI was (r = 0.76). US detected ME to be greater in the loaded position in all knees (healthy, p < 0.00001; OA, p < 0.00001; PM, p = 0.02). In all positions, US detected greater extrusion in OA (p < 0.0003) and PM knees (p = 0.006) compared with healthy controls. Furthermore, US revealed greater extrusion in moderate–severe OA knees (p < 0.00001).ConclusionsThis systematic review suggests ultrasonography can play an important role in the measurement of meniscal extrusion, with results comparable to that of MRI. However, to what extent it can differentiate between physiological and pathological extrusion requires further investigation, with an absolute cutoff value yet to be determined. Nevertheless, it is an appropriate investigation to track the progression of disease in those with meniscal pathologies or osteoarthritis. Furthermore, it is a feasible investigation to evaluate the meniscal function following surgery.Level of evidence: IV, Systematic review of level III–IV evidence.

Finite element study of stress distribution in medial UKA under varied lower limb alignment

Knee osteoarthritis (KOA) has a high incidence among the elderly, significantly impacting their quality of life and overall health. Medial unicompartmental knee arthroplasty (UKA) is an excellent choice for treating knee single-compartment lesions, and lower limb alignment has a profound impact on medial UKA. To explore the influence of different lower limb alignments on medial UKA. In this study, we selected MR and CT data of healthy adult male knee joints to establish a complete finite element analysis (FEA) model of the knee joint. After validation, we established a finite element model of medial UKA. Subsequently, we created 60 sets of FEA models with different lower limb alignments to analyze the impact of different lower limb alignments on medial UKA. A vertical load of 1000 N was applied to the FEA models with different lower limb alignments. During the process of shifting the Mikulicz line from the midpoint of the knee joint towards the medial side, the lower limb load was primarily concentrated on the medial compartment. The stress values of the lateral meniscus, tibial cartilage, and femoral cartilage gradually decreased. ROI (region of interest) 1 and ROI 2 showed the maximum principal strain changes, while ROI 3 and ROI 4 exhibited less pronounced fluctuations, with the maximum principal strain roughly proportionally increased. During the process of shifting the Mikulicz line towards the lateral side from the midpoint of the knee joint, the stress on the lateral compartment increased observably. ROI 1, ROI 2, ROI 3, and ROI 4 showed decreased maximum principal strains, approximately inversely proportional changes, but the overall reduction was relatively small. Different lower limb alignments have a profound impact on the short- and long-term joint function after UKA. When the Mikulicz line is 10 mm inside the midpoint of the knee joint or slightly outside, there is a relatively lower risk of tibial component fractures, lower stress on the lateral compartment, and lower load on the prosthesis. During medial UKA, measures such as bone resection and prosthesis selection should be taken to ensure that the Mikulicz line is in the ideal position.

Long-term Prognosis of Patellar Tendinopathy (Jumper’s Knee) in Young, Elite Volleyball Players: Tendon Changes 11 Years After Baseline

Background: The long-term prognosis of jumper's knee and whether structural changes in the patellar tendon persist is unknown. Purpose: To investigate whether limitations in knee function and structural changes persisted beyond the athletic career of young elite volleyball players. Study Design: Cohort study; Level of evidence, 2. Methods: Volleyball players (mean ± SD age, 18 ± 0.8 years) enrolled in 2006-2011 in a prospective cohort study were invited in 2020-2022 to a follow-up study. Participants rated their knee function with the Victorian Institute of Sport Assessment–Patellar Tendon (VISA-P) score (baseline and follow-up) and the International Knee Documentation Committee (IKDC) score (follow-up) and reported if jumper's knee had influenced their decision to retire from sport. Tendon thickness and structural changes were assessed with ultrasound (baseline) and magnetic resonance imaging (MRI) (follow-up) of both patellar tendons. Results: We included 138 of 143 former athletes (97%) 11.4 ± 1.6 years after their baseline examination. At baseline, 37 persons (52 knees) had developed jumper's knee. At follow-up, participants reported lower knee function scores in knees diagnosed with jumper's knee at baseline than healthy knees (VISA-P scores: jumper's knee, 81 [95% CI, 70-92]; healthy, 90 [95% CI, 86-94]; P < .001; IKDC scores: jumper's knee, 82 [95% CI, 75-89]; healthy, 92 [95% CI, 91-95]; P < .001). Jumper's knee problems directly caused 7 of the 37 athletes (19%) with jumper's knee at baseline to retire from competitive volleyball. Of the 138 players included, 97 (70%) completed a bilateral MRI examination (194 knees). At follow-up, 38 of the 54 abnormal tendons (70%) had no structural changes (P < .001 vs baseline) while 22 of the 140 normal tendons (16%) had developed structural changes. Clinical symptoms were not correlated with tendon structure at follow-up (VISA-P scores for normal tendons: 85 [95% CI, 73-87]; abnormal: 89 [95% CI, 85-92]; P = .48). Conclusion: Jumper’s knee is not a self-limiting condition; volleyball players who had developed jumper's knee during adolescence reported persistent reductions in knee function 11 years later, leading one-fifth to retire from competitive volleyball. Although approximately 70% of tendons with structural changes at baseline were normal at follow-up, there was no clear relationship between structure and function.

Windswept deformity of the knee: prevalence and predictive factors in osteoarthritic and healthy populations.

This study examined windswept deformity (WSD) of the knee, comparing prevalence and contributing factors in healthy and osteoarthritic (OA) cohorts. A case-control radiological study was undertaken comparing 500 healthy knees (250 adults) with a consecutive sample of 710 OA knees (355 adults) undergoing bilateral total knee arthroplasty. The mechanical hip-knee-ankle angle (mHKA), medial proximal tibial angle (MPTA), and lateral distal femoral angle (LDFA) were determined for each knee, and the arithmetic hip-knee-ankle angle (aHKA), joint line obliquity, and Coronal Plane Alignment of the Knee (CPAK) types were calculated. WSD was defined as a varus mHKA of < -2° in one limb and a valgus mHKA of > 2° in the contralateral limb. The primary outcome was the proportional difference in WSD prevalence between healthy and OA groups. Secondary outcomes were the proportional difference in WSD prevalence between constitutional varus and valgus CPAK types, and to explore associations between predefined variables and WSD within the OA group. WSD was more prevalent in the OA group compared to the healthy group (7.9% vs 0.4%; p < 0.001, relative risk (RR) 19.8). There was a significant difference in means and variance between the mHKA of the healthy and OA groups (mean -1.3° (SD 2.3°) vs mean -3.8°(SD 6.6°) respectively; p < 0.001). No significant differences existed in MPTA and LDFA between the groups, with a minimal difference in aHKA (mean -0.9° healthy vs -0.5° OA; p < 0.001). Backwards logistic regression identified meniscectomy, rheumatoid arthritis, and osteotomy as predictors of WSD (odds ratio (OR) 4.1 (95% CI 1.7 to 10.0), p = 0.002; OR 11.9 (95% CI 1.3 to 89.3); p = 0.016; OR 41.6 (95% CI 5.4 to 432.9), p ≤ 0.001, respectively). This study found a 20-fold greater prevalence of WSD in OA populations. The development of WSD is associated with meniscectomy, rheumatoid arthritis, and osteotomy. These findings support WSD being mostly an acquired condition following skeletal maturity.

An Evaluation of Intra-articular Pathologies Accompanying Tibial Plateau Fractures Postoperatively.

Tibial plateau fractures are one of the most complex and common intra-articular fractures encountered in trauma surgery. This study aimsto evaluate the MRI intra-articular findings of patients with tibial plateau fractures treated surgically and the functional and radiological changes after surgical treatment. A total of 91 patients admitted to our clinic between 2010 and 2019 and operated for tibial plateau fracture were identified from the hospital information system. Patients were excluded fromthe study if aged <18 years, if the radiographs and MRIs were not suitable for the measurements, or if they could not be contacted by telephone. The study was completed with 49 operated knees and 49 healthy knees of 49 patients. The patients were evaluated with respect to demographic characteristics, KneeSocietyKneeScore (KSKS), KneeSocietyFunction Score (KSFS), KneeInjuryandOsteoarthritisOutcomeScore (KOOS) functional and clinical scores, Rasmussen, Kellgren-Lawrence, and Whole-OrganMagneticResonanceImagingScore (WORMS) radiological scoring, and meniscus and ligament pathologies examined on the follow-up MR images. The patients comprised 39 males and 10 females with a mean age of 45.9±11.89 years, and a mean follow-up of 58.2±30.7 months. The fractures were seen to be 49% (n=24)in the lateral plateau, 6.1% (n=4) in the medial plateau, and 42.9% (n=21) were bicondylar fractures involving both plateaux. The KSKS knee score was satisfactory in 85.7% of the patients, the KSFS functional score in 89.7%, and the Rassmussen radiological score in 93.8%. In the KOOS subjective questionnaire, the mean points obtained were 430.7, and the mean total WORMS points were 34.2. According to the Kellgren-Lawrence grades, severe osteoarthritis (grade 3-4) developed in 18.3% (n=9) of the patients. Meniscus injuries that are overlooked at the time of the first injury or which may develop in the subsequent process were not found to seriously affect the functional outcomes of tibial plateau fractures. It can be considered that even if a ligament injury is seen to be accompanying the fracture at the time of the first trauma, the effect is not great in terms of prognosis, and the treatment can remain conservative, especially for collateral ligament injuries.

The Distribution of Coronal Plane Alignment of the Knee Classification in a Sample of Spanish Southeast Osteoarthritic Population: A Retrospective Cross-Sectional Observational Study

Background and Objectives: The Coronal Plane Alignment of the Knee (CPAK) classification is a pragmatic distribution of nine phenotypes for coronal knee alignment that can be used on healthy and arthritic knees. Our study aimed to describe the CPAK distributions in a Spanish southeast osteoarthritic population and compare them to other populations’ published alignment distributions. Method and Materials: Full-leg standing X-rays of the lower limb from 528 cases originating from the so-called Vega Alta del Segura (southeast of the Iberian Peninsula) were retrospectively analysed. We measured the mechanical hip–knee–ankle, lateral distal femoral, and medial proximal tibial angles. We calculated the arithmetic hip–knee–ankle angle and the joint line obliquity to classify each case according to the criteria of the CPAK classification. Results: Based on the aHKA result, 59.1% of the cases were varus (less than −2°), 32.7% were neutral (0° ± 2°), and 8.2% were valgus (greater than +2°). Based on the JLO result, 56.7% of the cases had a distal apex (less than 177°), 39.9% had a neutral apex (180° ± 3°), and 3.4% had a proximal apex (greater than 183°). The most common CPAK distribution in our Spanish southeast osteoarthritic population was type I (30.7%), followed by type IV (25.9%), type II (21%), type V (11.2%), type III (5%), type VI (2.8%), type VII (2.4%), type VIII (0.6%), and type IX (0.4%). Conclusions: We described the distribution according to the CPAK classification in a sample of the osteoarthritic population from southeastern Spain. In our sample, more than 75% of the patients were classified as type I, II, and IV.

GNRB® Knee Arthrometer: Inter- and Intra-observer Reliability and Learning Curve.

Background Diagnosing anterior cruciate ligament rupture is challenging, particularly due to the subjective nature of clinical laxity assessments. Objective evaluation methods are necessary for consistency and publication in clinical research. This study aims to assess the reproducibility of the GNRB® knee arthrometer (GeNouRoB, Laval, France) across different examiners and to examine the associated learning curve for a junior examiner. Methods Anterior translation measurements were conducted on 20 healthy knees using the GNRB arthrometer. Two examiners, a senior and a junior, performed the measurements independently and were blinded to each other's results. Measurements were taken at two different push forces (134 N and 200 N). The study evaluated inter- and intra-observer reproducibility using Cohen's kappa coefficient and the intraclass correlation coefficient (ICC). The junior examiner also performed a thirdseries of measurements to assess the learning curve. Results The senior examiner demonstrated excellent reproducibility with an ICC greater than 0.75 for all measurements. The junior examiner's reproducibility varied from fair to good, with an ICC ranging from 0.45 to 0.75. Inter-observer reproducibility between the senior and junior examiners was excellent (ICC >0.75). Notably, the junior examiner's reproducibility improved to an excellent level (ICC >0.75) during the second series of measurements. Conclusion The GNRB system provides a reproducible method for evaluating anterior knee laxity across different examiners. A learning curve of approximately 20 knees is sufficient for a junior examiner to achieve statistically excellent reproducibility.

Alterations in mechanical properties of rabbit collateral ligaments eight weeks after anterior cruciate ligament transection

Anterior cruciate ligament (ACL) injury is a common knee ligament injury among young, active adults; however, little is known about its impact on the viscoelastic properties of the knee joint’s collateral ligaments. This study aimed to characterize and compare the viscoelastic properties of rabbit collateral ligaments in healthy control knees, injured knees, and knees contralateral to the injured knees.Unilateral anterior cruciate ligament transection was performed on six New Zealand white rabbits to create an ACL injury model. Medial and lateral collateral ligaments (MCL and LCL) were collected from the injured and contralateral knees eight weeks after ACL transection. Ligaments were also harvested from both knees of four unoperated rabbits. The ligaments underwent tensile stress-relaxation testing at strain levels of 2, 4, 6, and 8 %, and a sinusoidal loading test at 8 % strain with 0.5 % strain amplitude using frequencies of 0.01, 0.05, 0.1, 0.5, 1, and 2 Hz.The results showed that collateral ligaments of ACL-transected knees relaxed slower compared to control knees. Sinusoidal testing revealed that contralateral knee LCLs had significantly higher storage and loss modulus across all test frequencies.The results indicate that contralateral knee LCLs become stiffer compared to LCLs from control and ACL-transected knees, while LCLs from ACL-transected knees become less viscous compared to LCLs from control and contralateral knees. This study suggests that knee ligaments undergo adaptations following an ACL injury that may affect the mechanics of the ACL-transected knee, which should be considered in biomechanical and rehabilitation studies of patients with an ACL injury.

MRI analysis of the physiological patellofemoral joint morphology of adult knees.

The aim of the present study was to determine physiological reference values for the morphology of the patella and to analyse these parameters according to patella position in healthy knee joints. Healthy knee joints of 409 patients (mean age, 52.3years [± 16.8]) were analysed retrospectively on MRI images for Insall-Salvati index (ISI), sagittal patella thickness (PTS) and patella length (PLS) as well as axial patella thickness (PTA) and patella width (PWA). Differences between patellar diameters were analysed depending on ISI, side, age and gender. Mean PTS was 20.1 mm (± 2.4), PLS 44.0 mm (± 4.4), PTA 21.8 mm (± 2.4) and PWA 44.5 mm (± 4.7). Depending on the vertical patellar position (ISI), all patellar parameters (p < 0.01) showed significant differences between patients with a patella alta, norma and baja. In general, a smaller ISI showed higher measured values for the patellar parameters. There were no significant differences for the laterality. Only PTS showed a significant age difference (p = 0.031). All parameters were significantly larger in male compared to female knees (p < 0.001). Reference parameters for the patella morphology are reported. Concluding from the results, a relationship between vertical patellar position and patellar morphology seems to exist. This finding should be taken into account in diagnostics and therapy of patella disorders.

Nanomaterials: Recent Advances in Knee Osteoarthritis Treatment

AbstractOsteoarthritis (OA) of the knee is the most prevalent degenerative joint condition that places a substantial financial and medical burden on society. However, due to drawbacks such as inefficiency, adverse effects, and brief duration of action, the clinical efficacy of the current major therapies for knee OA is largely restricted. Therefore, novel medication development is highly required to address these issues. Numerous studies in recent years have established that nanomaterials can be a potential and highly effective way to overcome these challenges. In this review, the anatomical distinctions between healthy and OA knee joints, as well as novel advances in the field of nanomaterials for the treatment of knee OA are summarized. The limits of the present therapeutic strategies for treating knee OA are also highlighted, as well as the potential prospects of nanomaterials in the future.

Retention of the posterior cruciate ligament stabilizes the medial femoral condyle during kneeling using a tibial insert with ball-in-socket medial conformity.

Resecting the posterior cruciate ligament (PCL) increases posterior laxity and increases the flexion gap more than the extension gap in the native (i.e. healthy) knee. These two effects could lead to significant anterior displacement of the medial femoral condyle in kneeling following total knee arthroplasty even when using a tibial insert with a high degree of medial conformity. Using an insert with ball-in-socket medial conformity and a flat lateral articular surface, the primary purpose was to determine whether the medial femoral condyle remained stable with and without PCL retention during kneeling. Two groups of patients were studied, one with PCL retention (22 patients) and the other with PCL resection (25 patients), while kneeling at 90º flexion. Following 3D model-to-2D image registration, A-P displacements of both femoral condyles were determined relative to the dwell point of the medial socket. With PCL resection versus PCL retention, the medial femoral condyle was 5.1 ± 3.7mm versus 0.8 ± 2.1mm anterior of the dwell point (p < 0.0001). Patient-reported function scores were comparable (p ≥ 0.1610) despite a significantly shorter follow-up of 7.8 ± 0.9 months with PCL retention than 19.6 ± 4.9 months with PCL resection (p < 0.0001). Range of motion was 126 ± 8° versus 122 ± 6° with and without PCL retention, respectively (p = 0.057). Surgeons that use a highly conforming tibial insert design can stabilize the medial femoral condyle during kneeling by retaining the PCL. In patients with PCL resection, the 9mm high anterior lip of the insert with ball-in-socket medial conformity was insufficient to prevent significant anterior displacement of the medial femoral condyle when weight-bearing on the anterior tibia.

Anterior-Posterior Laxity in Midflexion After Posterior-Stabilized TKA Is Sensitive to MCL Tension in Passive Flexion: An in Vitro Biomechanical Study.

Knee instability in midflexion may contribute to patient dissatisfaction following total knee arthroplasty (TKA). Midflexion instability involves abnormal motions and tissue loading in multiple planes. Therefore, we quantified and compared the tensions carried by the medial and lateral collateral ligaments (MCL and LCL) following posterior-stabilized (PS) TKA through knee flexion, and then compared these tensions with those carried by the native knee. Finally, we examined the relationships between collateral ligament tensions and anterior tibial translation (ATT). Eight cadaveric knees (from 5 male and 3 female donors with a mean age of 62.6 years and standard deviation of 10.9 years) underwent PS TKA. Each specimen was mounted to a robotic manipulator and flexed to 90°. ATT was quantified by applying 30 N of anterior force to the tibia. Tensions carried by the collateral ligaments were determined via serial sectioning. Robotic testing was also conducted on a cohort of 15 healthy native cadaveric knees (from 9 male and 6 female donors with a mean age of 36 years and standard deviation of 11 years). Relationships between collateral ligament tensions during passive flexion and ATT were assessed via linear and nonlinear regressions. MCL tensions were greater following PS TKA than in the native knee at 15° and 30° of passive flexion, by a median of ≥27 N (p = 0.002), while the LCL tensions did not differ. Median tensions following PS TKA were greater in the MCL than in the LCL at 15°, 30°, and 90° of flexion, by ≥4 N (p ≤ 0.02). Median tensions in the MCL of the native knee were small (≤11 N) and did not exceed those in the LCL (p ≥ 0.25). A logarithmic relationship was identified between MCL tension and ATT following TKA. MCL tensions were greater following PS TKA with this typical nonconforming PS implant than in the native knee. Anterior laxity at 30° of flexion was highly sensitive to MCL tension during passive flexion following PS TKA but not in the native knee. Surgeons face competing objectives when performing PS TKA: they can either impart supraphysiological MCL tension to reduce anterior-posterior laxity or maintain native MCL tensions that lead to heightened anterior-posterior laxity, as shown in this study.

Centralization reduces meniscal extrusion, improves joint mechanics and functional outcomes in patients undergoing meniscus surgery: A systematic review and meta-analysis.

To perform a systematic review and meta-analysis of the existing literature on meniscal centralisation procedures, analysing its impact on meniscal extrusion, joint biomechanics and clinical and radiological outcome measures. The Cochrane Controlled Register of Trials, PubMed (MEDLINE) and Embase were used to perform a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Biomechanical studies on healthy animal or human cadaveric knee joints that assessed meniscal extrusion or tibiofemoral contact mechanics (contact area and pressure) following centralization for meniscal pathologies were included. For clinical studies, those that prospectively or retrospectively assessed patient-reported outcome measures (PROMs), postoperative knee motion, complications and radiological extrusion following centralization for meniscal pathologies were included. Fifteen studies were included in the analysis, comprising eight biomechanical, six clinical and one both. There were 92 knee specimens for biomechanical testing, of which 40 were human cadaveric and 52 porcine models. Biomechanical data revealed centralization to be commonly performed for posterior meniscal root tears and significantly reduced extrusion and contact pressure whilst improving contact area following a tear (p < 0.00001).Centralization restored extrusion to that of the native knee at all flexion angles described (0-90°, p = 0.25) and, compared to the torn state, brought tibiofemoral contact mechanics 3.2-5.0 times closer to the native state. Clinical data showed that 158 patients underwent centralization for extrusion. It improved postoperative Knee Injury and Osteoarthritis Outcome score (KOOS) (p = 0.006) and Lysholm scores (p < 0.00001) at 25.0 months, maintained extrusion reduction at 17.1 months (p < 0.00001) and preserved knee motion. Centralisation for various meniscal injuries associated with extrusion can reduce meniscal extrusion and improve joint biomechanics, along with clinical and radiological outcomes. Existing evidence is still scarce and exhibits a notable amount of methodological heterogeneity. Systematic review of Level IV evidence.

Mechano-adaptation: Exercise-driven Piezo1 & Piezo2 augmentation and chondroprotection in articular cartilage.

Chondrocytes in adult joints are mechanosensitive post-mitotic quiescent cells with robustly expressed both Piezo1 and Piezo2 ion channels. Here, we examined the mechano-adaptation and Piezo modulations in articular chondrocytes using a mouse exercise model. We first found differential expression patterns of PIEZO1 and PIEZO2 in articular chondrocytes of healthy knee joints; chondrocytes in tibial cartilage (T) exhibit significantly higher PIEZO1 and PIEZO2 than femoral chondrocytes (F). Interestingly, a few weeks of exercise caused both PIEZO1 and PIEZO2 augmentation in F and T compared to the sedentary control group. Despite the increased expression levels of these mechanosensors, chondrocytes in exercised cartilage exhibit significantly reduced mechanical susceptibility against 1mJ impact. PIEZO1 modulation was relatively more rapid than PIEZO2 channels post-exercise. We tested the exercise-induced effect using Piezo1-conditional knockout (Pz1-cKO; Agc1 CreERT2 ;Piezo1 fl/fl ). Pz1-cKO mice exhibit diminished exercise-driven chondroprotection against 1mJ impact, suggesting essential roles of Piezo1-mediated mechanotransduction for physiologic-induced cartilage matrix homeostasis. In addition, using a mouse OA model, we further found the modulated PIEZO1 in chondrocytes, consistent with reports in Ren et al., but without PIEZO2 modulations over OA progression. In summary, our data reveal the distinctly tuned Piezo1 and Piezo2 channels in chondrocytes post-exercise and post-injury, in turn modulating the mechanical susceptibility of chondrocytes. We postulate that Piezo1 is a tightly-regulated biphasic biomarker ; Piezo1 antagonism may increase cellular survival post-injury and Piezo1 (with Piezo2) agonism to promote cartilage ECM restoration.

Surgical parameters influence paediatric knee kinematics and cartilage stresses in anterior cruciate ligament reconstruction: Navigating subject-specific variability using neuromusculoskeletal-finite element modelling analysis.

Anterior cruciate ligament (ACL) rupture is increasingly common in paediatric and adolescent populations, typically requiring surgical ACL reconstruction (ACLR) to restore knee stability. However, ACLR substantially alters knee biomechanics (e.g., motion and tissue mechanics) placing the patient at elevated risk of early-onset knee osteoarthritis. This study employed a linked neuromusculoskeletal (NMSK)-finite element (FE) model to determine effects of four critical ACLR surgical parameters (graft type, size, location and pre-tension) on tibial articular cartilage stresses in three paediatric knees of different sizes during walking. Optimal surgical combinations were defined by minimal kinematic and tibial cartilage stress deviations in comparison to a corresponding intact healthy knee, with substantial deviations defined by normalized root mean square error (nRMSE) > 10%. Results showed unique trends of principal stress deviations across knee sizes with small knee showing least deviation from intact knee, followed by large- and medium-sized knees. The nRMSE values for cartilage stresses displayed notable variability across different knees. Surgical combination yielding the highest nRMSE in comparison to the one with lowest nRMSE resulted in an increase of maximum principal stress on the medial tibial cartilage by 18.0%, 6.0% and 1.2% for small, medium and large knees, respectively. Similarly, there was an increase of maximum principal stress on lateral tibial cartilage by 11.2%, 4.1% and 12.7% for small, medium and large knees, respectively. Knee phenotype and NMSK factors contributed to deviations in knee kinematics and tibial cartilage stresses. Although optimal surgical configurations were found for each knee size, no generalizable trends emerged emphasizing the subject-specific nature of the knee and neuromuscular system. Study findings underscore subject-specific complexities in ACLR biomechanics, necessitating personalized surgical planning for effective restoration of native motion and tissue mechanics. Future research should expand investigations to include a broader spectrum of subject-specific factors to advance personalized surgical planning. Level III.

Prof Analysis of CXCL12 and S100A12 levels in peripheral blood and synovial fluid and their correlation with severity in patients with knee osteoarthritis

Abstract: To investigate the expression of CXCL12 and S100A12 in peripheral blood (PB) and synovial fluid (SF) of patients with knee osteoarthritis (OS) and to analyze the correlation between them and the severity of knee OS. 60 patients with kneeOS treated in our hospital from January 2020 to December 2022 were selected as the experimental group, and 60 healthy knee joints with similar age were selected as the control group. The fasting venous blood of 120 subjects was drawn in the early morning, and the SF was extracted during joint operation or sodium hyaluronate injection. Put the collected PB and SF in the refrigerator at-80℃. The levels of CXCL12 and S100A12 in PB and SF were detected by enzyme linked immunosorbent assay (Elisa). The correlation between the levels of CXCL12 and S100A12 in PB and SF and Kmurl L grade and WOMAC score. The levels of CXCL12 and S100A12 in PB and SF in the observation group were raised than those in the control group. There were significant differences in the levels of CXCL12 and S100A12 in PB and SF in the experimental group. The higher the Kmurl grade of knee OS, the higher the concentration of CXCL12 and S100A12 in PB and SF. The levels of CXCL12 and S100A12 in PB of knee OS were positively correlated with WOMAC score (r = 0.767, 0.521 respectively, P &lt; 0.05), see figure 1. The levels of CXCL12 and S100A12 in SF of knee OS were positively correlated with WOMAC score (r = 0.663, 0.357 respectively, P &lt; 0.05). The levels of CXCL12 and S100A12 in PB and SF are positively correlated with the severity of knee OS. The levels of CXCL12 and S100A12 in PB and SF can provide basis for the evaluation and prognosis of knee OS.

Effects of different combinations of mechanical loading intensity, duration, and frequency on the articular cartilage in mice

BackgroundUnderstanding how healthy articular cartilage responds to mechanical loading is critical. Moderate mechanical loading has positive effects on the cartilage, such as maintaining cartilage homeostasis. The degree of mechanical loading is determined by a combination of intensity, frequency, and duration; however, the best combination of these parameters for knee cartilage remains unclear. This study aimed to determine which combination of intensity, frequency, and duration provides the best mechanical loading on healthy knee articular cartilage in vitro and in vivo.Methods and resultsIn this study, 33 male mice were used. Chondrocytes isolated from mouse knee joints were subjected to different cyclic tensile strains (CTSs) and assessed by measuring the expression of cartilage matrix-related genes. Furthermore, the histological characteristics of mouse tibial cartilages were quantified using different treadmill exercises. Chondrocytes and mice were divided into the control group and eight intervention groups: high-intensity, high-frequency, and long-duration; high-intensity, high-frequency, and short-duration; high-intensity, low-frequency, and long-duration; high-intensity, low-frequency, and short-duration; low-intensity, high-frequency, and long-duration; low-intensity, high-frequency, and short-duration; low-intensity, low-frequency, and long-duration; low-intensity, low-frequency, and short-duration. In low-intensity CTSs, chondrocytes showed anabolic responses by altering the mRNA expression of COL2A1 in short durations and SOX9 in long durations. Furthermore, low-intensity, low-frequency, and long-duration treadmill exercises minimized chondrocyte hypertrophy and enhanced aggrecan synthesis in tibial cartilages.ConclusionLow-intensity, low-frequency, and long-duration mechanical loading is the best combination for healthy knee cartilage to maintain homeostasis and activate anabolic responses. Our findings provide a significant scientific basis for exercise and lifestyle instructions.

Dilution of humoral immunity: Results from a natural history study of healthy total knee arthroplasty patients.

The incidence of prosthetic joint infection (PJI) following elective primary total knee arthroplasty (TKA) is very low but serious risk remains. To identify unknown risk factors, we completed a natural history study of IgG specific forStaphylococcus aureus antigens previously phenotyped as protective (anti-Atl) and pathogenic (anti-Isd). Twenty-five male and 25 female optimized patients 50-85 years of age and BMI 24-39 undergoing primary TKA were prospectively enrolled. Blood sampling was performed preoperatively, postoperative Day 1, and at 2, 6, and 12 weeks, to assess serum cytokine, anti-staphylococcal IgG levels and anti-tetanus toxoid IgG measured via custom Luminex assay. Clinical, demographic, and PROMIS-10 data were collected with outcomes to 2 years postop. All participants completed the study and 2-year follow-up. No patients were readmitted or noted to develop a surgical site infection or serious adverse event, and patient-reported outcomes were improved. Serology revealed a highly significant decrease in six out of eight antibody titers against specific S. aureus antigens on Day 1 (p < 0.0001), five of which normalized to preoperative levels within 2 weeks. These changes were commensurate with a decrease and recovery of anti-tetanus toxoid titers, and a 20% drop in hemoglobin 13.8 ± 1.7 at preop to 11.1 ± 1.8 mg/dL on Day 1 (p < 0.0001). After TKA, a significant decrease in humoral immunity commensurate with blood loss and hemodilution was recorded. This decrease in circulating anti-staphylococcal antibodies in the early postop period may represent a periprosthetic joint infection risk factor for patients.