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Purpose Bilateral involvement is common in patients with patellar instability. The management of bilateral patellar instability is associated with increased complication rate. The higher complication rate in this cohort may be related to the presence of underlying anatomic risk factors. The purpose of the study was to evaluate the presence and side-to-side differences in risk factors between knees in bilateral patellar instability. Methods In a retrospective study (2008–2017), demographic information, characteristics of patellar dislocation and anatomic risk factors on MRI (trochlear dysplasia, patellar height, tibial tubercle lateralization, patellar tilt, sulcus angle, bump height) were evaluated in both knees of all patients ( n  = 32, 15 males and 17 females) with bilateral patellar instability. The risk factors were analyzed based on established cut off values and were compared between gender, laterality and more symptomatic (index) knee. Knee symmetry and absolute differences between risk factors for both knees were analyzed. Results The mean age of 32 patients was 14.6 ± 2.3 years. Of the 4 major anatomic risk factors, the most common were trochlear dysplasia in 59/64 (92.1%) knees and patella alta in 51/64 (79.7%) knees. Tibial tubercle lateralization was the least common risk factor being present in 8/64 (12.5%) knees. Of 64 knees, 55 (85.9%) had 2 or more risk factors and 30 (46.8%) had 3 or all 4 risk factors present. There were no significant differences in risk factors based on gender, laterality or index knee. There was symmetry between paired knees for 31/32 (96.8%) patients for trochlear depth, 29/32 (90.6%) for patellar tilt, 27/32 (84.3%) for TT–TG distance and 25/32 (78.1%) for patellar height. There were no significant differences in absolute measurements between knees for any of the risk factors. Conclusion Patients with bilateral instability had multiple risk factors, with trochlear dysplasia being the most common and increased TT–TG distance being the least common. Majority of patients had 2 or more risk factors and about half had 3 or 4 risk factors in each knee. There was symmetry between paired knees for each risk factor without any significant differences between the index knee compared to the contralateral knee. Level of evidence Level III.

Purpose To assess measurement equivalence, inter- and intra-rater reliability, standard error of measurements (SEM) and false positive measurements (FPM) of four different knee arthrometers (KLT,Karl Storz; KiRA, I + ; KT-1000 MEDmetric Corp; Rolimeter, Aircast) in healthy patients. Methods Four different investigators (two advanced (AR) and two beginners (BR)) examined 12 participants with healthy knees at two time points with regards to anterior tibial translation (ATT) and side-to-side difference (SSD). Test equivalence was assessed using the TOST (two-one-sided t test) procedure with ± 1 mm equivalence boundaries. Intraclass correlation coefficients (ICCs) were calculated using two-way mixed effects models. Furthermore, false positive-(SSD > 3 mm) and SEMs were assessed. Results A total of 2304 Lachman Tests were performed. Between-rater SSDs were equivalent between AR and BR raters for the Rolimeter only. Inter-rater ICC values (SSD, ATT) were graded as “poor” to “moderate” for all devices. Equivalent test–retest results were observed for all raters using the Rolimeter, KLT and KT-1000, whereas measurement consistency with KiRA was given in the advanced examiners group only. Intra-rater ICC values (Range: SSD, ATT) were graded as “poor” to “moderate” for SSD values and “moderate” to “good” for ATT. SEMs were lowest for the Rolimeter and highest for KiRA. FPM were never obtained with the Rolimeter (0%), twice (2.1%) with the KT-1000, three times (3.1%) with the KLT and 33 times (34.4%) using KiRA. Conclusion There is acceptable intra-rater but poor inter-rater reliability with all tested arthrometers. Measures of knee laxity are comparable between Rolimeter, KLT and KT-1000 but higher for KiRA. Clinically, the present study shows that repeated arthrometry measurements should always be performed by the same investigators.

Background Non-contact injuries such as anterior cruciate ligament ruptures often occur during physical load toward the end of a match. This is ascribed to emerging processes due to exercise-induced fatigue. Moreover, non-contact injuries often occur during dynamic actions such as landing or cutting movements. Inter-limb asymmetries are suggested as one possible cause for those injuries based on findings indicating that asymmetries between limbs are associated with a higher injury risk. Hence, assessing inter-limb asymmetry during physical load in the condition of exercise-induced fatigue is warranted to identify potentially relevant precursors for non-contact injuries. Objective The objective of this study was to overview the current state of evidence concerning the influence of exercise-induced fatigue on inter-limb asymmetries through a systematic review. Methods A systematic literature search was conducted using the databases Web of Science, Scopus, PubMed, SURF, and SPONET to identify studies that assessed inter-limb asymmetries of healthy people, calculated with an asymmetry equation, before and after, or during a loading protocol. Results Thirteen studies were included in the systematic review. The loading protocols involved running, race walking, jumping, squatting, soccer, rowing, and combinations of different exercises. Moreover, different tasks/procedures were used to assess inter-limb asymmetries, e.g., squats, single-leg countermovement jumps, gait analysis, or isokinetic strength testing. The results seem to depend on the implemented loading protocol, the tasks/procedures, and the measured parameters. Conclusions Future research needs more systematization and consistency, assessing the effect of exercise-induced fatigue on inter-limb asymmetries. Moreover, the emergence of inter-limb asymmetries should be regarded in the context of sport-specific movements/tasks. Testing before, after, and during a physical loading protocol is advisable to consider the influence of exercise-induced fatigue on sport-specific tasks and to identify the possible mechanisms underlying load-dependent inter-limb asymmetries with regard to risk of non-contact injury.

Physical examination of the knee joint is used to diagnose the type and severity of knee ligament injury; however, these exams are qualitative and subjective. To perform common physical examinations, we developed an arthrometer which quantitatively measures the load–displacement response in anterior-posterior (AP) translation, internal-external rotation (IER) and varus-valgus (VV) rotation. Here we describe safety, reliability, minimum detectable changes (MDCs), and absolute side-to-side differences in twenty young, healthy subjects (ten male, ten female, mean age: 28 ± 6 years). The arthrometer consists of an instrumented mechanical linkage, a force-moment sensor, and software for real-time visualization and recording of the load–displacement responses. During testing, the subject sits reclined in a chair with their knee fixed at 30° of flexion. Two examiners tested both knees of each subject twice to assess reliability via intraclass correlation coefficients (ICC). All subjects completed the test protocol with minimal pain and stated that they would volunteer to be tested again. Each knee required on average five minutes to test. All intra-test reliabilities were excellent (≥0.91). Intra-examiner reliabilities ranged from good to excellent (0.62–0.89), and inter-examiner reliabilities were good to excellent (≥0.72). MDCs for repeat measures were ≤ 4.5 mm, 4.6°, and 2.3° for AP, IER, and VV, respectively. The absolute side-to-side differences for this cohort averaged 3.8 mm in AP, 5.5° in IER, and 2.2° in VV. Our arthrometer was safe, testing was time-efficient, and MDCs in our cohort of healthy subjects support utilization of this device for clinical research.

Purpose Previous investigations suggested that femoral side-to-side differences were located in the upper femur anatomy. However, little is known about the asymmetry between distal femur and patella. The degree of bony asymmetry in the patellofemoral joint was evaluated using pairs of CT-scans with emphasis on morphometric measurements and risk factors relevant to patellofemoral disorders. Methods Patellofemoral morphometric parameters and anatomical risk factors were analyzed from 345 pairs of CT scans to evaluate side-to-side differences for each patient. All measurements were automatized using previously published algorithm-calculated bone landmarks. We analyzed asymmetry based on absolute differences (AD) and percentage asymmetry (AS%). Significant asymmetry was defined as AS% > 10%. Results Patellar height was found to be highly symmetric (mean AD 0.1 for both Insall-Salvatti and Caton-Deschamps methods, AS% 8% and 9%, respectively). Patellar and femoral morphometric parameters were found highly symmetric, except for the trochlear groove depth. Substantial asymmetry was reported in two patellofemoral risk factors: the lateral trochlear inclination (mean AD 2°, AS% 16%) and the tibial tuberosity-trochlear groove distance (1 mm, 116%). Patellar and femoral morphometric asymmetries were independent of demographics, including age, gender, height, weight and ethnicity. Conclusion Patellar height was found to be highly symmetric and is, therefore, a reasonable index for contralateral templating. While very few patellofemoral morphometric parameters and anatomical risk factors were asymmetric, the mean differences were clinically negligible and independent of demographics. Level of evidence III.

Background The presence of inter-limb asymmetry in the human body has traditionally been perceived to be detrimental for athletic performance. However, a systematic review addressing and comprehensively assessing the association of asymmetry between the lower limbs and middle- and long-distance running performance-related metrics is currently lacking. Objective The main purpose of this systematic review was to examine the relationship between lower inter-limb asymmetry and determinants of running performance in healthy middle- and long-distance runners. The secondary objective was to identify possible avenues for further research in this area. Methods PubMed, Web of Science and SPORTDiscus were systematically searched for studies investigating the relationship between lower inter-limb asymmetry and (determinants of) running performance in healthy and injury-free middle- and long-distance runners. The quality of studies eligible for inclusion was assessed using the Downs and Black Quality Index Tool. Results Out of 4817 articles screened, 8 studies were included in this review which assessed the association between functional, morphological, kinematic and kinetic asymmetry and running performance-related metrics. The quality score of the included research varied between 5/10 and 9/10. Our results revealed mixed findings, showing both significant negative (n = 16) and positive (n = 1) associations as well as no significant associations (n = 30) between inter-limb asymmetry and running performance-related metrics. Conclusions A high heterogeneity across study methods and outcomes was apparent, making it difficult to draw a straightforward conclusion. Our results indicate that the majority of metrics of functional, morphological, kinematic and kinetic inter-limb asymmetry are negatively or not associated with running performance (and/or its determinants). Thus, a more extensive high-quality body of research using standardised asymmetry magnitude metrics is essential to determine whether, and to what extent asymmetry between the lower limbs could affect middle- and long-distance running performance. Future studies should establish potential trade-off values to help practitioners develop evidence-based training programs. Key Points In the majority of the metrics, the magnitude of lower inter-limb asymmetry was negatively or not associated with middle- and long-distance running performance. Coaches, athletes and researchers should be attentive of the task, time- and metric-specificity as well as the inter- and intra- individual variability of magnitude outcomes, when assessing inter-limb asymmetries.

Background As a recently available arthrometer, the Ligs arthrometer has been gradually used in clinical practice to assess knee stability. However, its reliability has not been fully established in this regard. The aim of this study was to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for measuring anterior tibial translation (ATT) and the corresponding side-to-side difference (SSD) in healthy subjects. Methods A total of 40 healthy male subjects were recruited for this study between June 2023 and September 2023. Three examiners with different levels of experience tested the subjects with the Ligs arthrometer for ATT and SSD measurements. ATT values for both knees and the corresponding SSD at 90 N, 120 N, and 150 N were recorded for analysis. Statistical significance was determined using Student’s t test or one-way analysis of variance (ANOVA). The intraclass correlation coefficient (ICC) was used to assess the intra-rater and inter-rater reliability of the Ligs arthrometer for ATT and SSD measurements. Results No subject asked to stop any test due to pain or discomfort. There was no significant difference among the three examiners in ATT measurements of the subjects’ ipsilateral knees and SSD measurements at the same load ( P  > 0.05 for all). Furthermore, ATT measurements for the subjects’ left and right knees measured by the same examiner were comparable ( P  > 0.05 for all). The Ligs arthrometer showed excellent intra-rater reliability (ICCs = 0.930–0.982) for ATT measurements and moderate to good intra-rater reliability (ICCs = 0.705–0.862) for SSD measurements. Similarly, its inter-rater reliability was excellent (ICCs = 0.911–0.930) for ATT measurements, but moderate (ICCs = 0.684–0.737) for SSD measurements. Conclusion The Ligs arthrometer had moderate to excellent intra-rater and inter-rater reliability for ATT and SSD measurements in healthy knees. As compared with ATT measurements, SSD measurements showed lower intra-rater and inter-rater reliability at the same load. It is recommended that the tests be performed by the same examiner when using the Ligs arthrometer for SSD measurements.

Background Inter-limb asymmetry is commonly regarded as a potential limitation for athletic performance and a contributor to injury risk. However, the influence of training status and sex on asymmetry in judokas remains poorly understood. Therefore, this study aimed to: (1) quantify inter-limb asymmetry in lean mass, bone mineral density, bone mineral content, and fat mass, and (2) examine how inter-limb morphological asymmetry varies across competitive levels (national vs. European) and sexes among young competitive judokas. Methods Lean mass, bone mineral density, bone mineral content, and fat mass were assessed using Dual-energy X-ray Absorptiometry in 27 male and 21 female competitive judokas aged 13–17 years. Comparisons between limbs were performed using paired-samples t-tests. Differences in asymmetry across competitive levels (national vs. European) and sexes were analyzed using Mann-Whitney U tests. Results Inter-limb asymmetry magnitudes ranged from 1.47% to 8.24% across groups. Overall, judokas showed greater values in the dominant limb compared to the non-dominant limb for most measures ( p  ≤ 0. 010). Mann-Whitney U tests identified significant differences in asymmetry between competitive levels only in lower-limb fat mass for both males ( p  = 0.015) and females ( p  = 0.033), and in lower-limb bone mineral content for females ( p  = 0.039). No significant differences in asymmetry were observed between sexes. Conclusion While inter-limb differences were present, the magnitude of asymmetry was generally small (≤ 8%) and did not differ significantly between competitive levels or sexes. These findings suggest that reducing morphological asymmetry in judokas may not be a priority, regardless of competition level or sex.

Background: The kneeling stress radiograph is valuable for quantifying posterior cruciate ligament (PCL) injuries. However, this method presents drawbacks, including patient discomfort during filming, radiation exposure, variability attributable to patient cooperation, and technician skill requirements. The modified Lachmeter technique offers an alternative approach. Its notable advantages are reproducibility, less patient pain or discomfort, and reduction of radiographic exposure. Purpose: To compare and find the correlation of the side-to-side difference (SSD) value between the modified Lachmeter technique and the kneeling stress radiograph. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A total of 33 patients with isolated PCL injury were measured for the SSD value using a modified Lachmeter technique and a kneeling stress radiograph. Demographic data and SSDs were collected from each method and analyzed. Results: The sample entailed 26 men and 7 women, with a mean of 37.58 years (range, 15-65 years). There were 14 patients with right knee injuries and 19 patients with left knee injuries. The mean difference in absolute values between the 2 methods was 2.32 ± 2.29 mm. Interobserver and intraobserver intraclass correlation coefficients of the modified Lachmeter showed almost perfect agreement (0.909 and 0.977, respectively). Conclusion: The SSD showed an excellent correlation between the modified Lachmeter technique and kneeling stress radiographs. Consequently, the modified Lachmeter technique holds promise as an alternative to stress radiography for patients with isolated PCL injuries.

Purpose To compare clinical and radiological outcomes and failure rates between anatomical and high femoral tunnels in remnant-preserving single-bundle posterior cruciate ligament (PCL) reconstruction. Methods 63 patients who underwent remnant-preserving single-bundle PCL reconstruction between 2011 and 2018 with a minimum 2-year follow-up were retrospectively reviewed. Patients were divided into two groups according to the femoral tunnel position: group A (33 patients with anatomical femoral tunnel) and group H (30 patients with high femoral tunnels). The femoral tunnel was positioned at the center (group A) or upper margin (group H) of the remnant anterolateral bundle. The position of the femoral tunnel was evaluated using the grid method on three-dimensional computed tomography. Clinical and radiological outcomes and failure rates were compared between the groups at the 2-year follow-up. Results The position of the femoral tunnel was significantly high in group H than in group A (87.4% ± 4.2% versus 76.1% ± 3.7%, p  < 0.001). Clinical outcomes were not significantly different between the two groups in terms of the clinical scores (International Knee Documentation Committee subjective, Lysholm, and Tegner activity scores), range of motion, and posterior drawer test. Radiological outcomes also showed no intergroup differences in the side-to-side differences of posterior tibial translation and osteoarthritis progression. Side-to-side difference on the Telos stress radiograph was 5.2 ± 2.9 mm in group A and 5.2 ± 2.7 mm in group H (n.s.). There were four failures in group A (12.1%) and one in group H (3.3%). The differences between the groups were not statistically significant. Conclusion The clinical and radiological outcomes and failure rates of the high femoral tunnels were comparable with those of the anatomical femoral tunnels at the 2-year follow-up after remnant-preserving single-bundle PCL reconstruction. The findings of this study suggest that high femoral tunnels can be considered an alternative in remnant-preserving single-bundle PCL reconstruction. Level of evidence III.