ESR essentials: MRI of the knee-practice recommendations by ESSR.

Many studies and systematic reviews have been published about MRI of the knee and its structures, discussing detailed anatomy, imaging findings, and correlations between imaging and clinical findings. This paper includes evidence-based recommendations for a general radiologist regarding choice of imaging sequences and reporting basic MRI examinations of the knee. We recommend using clinicians' terminology when it is applicable to the imaging findings, for example, when reporting meniscal, ligament and tendon, or cartilage pathology. The intent is to standardise reporting language and to make reports less equivocal. The aim of the paper is to improve the usefulness of the MRI report by understanding the strengths and limitations of the MRI exam with regard to clinical correlation. We hope the implementation of these recommendations into radiological practice will increase diagnostic accuracy and consistency by avoiding pitfalls and reducing overcalling of pathology on MRI of the knee. CLINICAL RELEVANCE STATEMENT: The recommendations presented here are meant to aid general radiologists in planning and assessing studies to evaluate acute and chronic knee findings by advocating the use of unequivocal terminology and discussing the strengths and limitations of MRI examination of the knee. KEY POINTS: • On MRI, the knee should be examined and assessed in three orthogonal imaging planes. • The basic general protocol must yield T2-weighted fluid-sensitive and T1-weighted images. • The radiological assessment should include evaluation of ligamentous structures, cartilage, bony structures and bone marrow, soft tissues, bursae, alignment, and incidental findings.

Ex vivo evaluation of the soft tissue components of the equine stifle using 3 Tesla magnetic resonance imaging under flexion, extension, and loading.

High-field MRI of the equine stifle provides high-resolution information about soft tissues that is useful in the diagnosis of stifle lameness. The aim of this prospective anatomic study was to describe the appearance, position, size, and shape of the equine femorotibial ligaments, meniscal ligaments, and menisci using 3 Tesla MRI under extended, extended-loaded, and flexed conditions. Additionally, histologic examination of the collateral and cruciate ligaments (CLs) of a single stifle was performed to compare with MRI images. In extension, mild variations in MRI signal intensity were apparent in the CLs, and the cranial had two distinct longitudinal regions indicating two ligament bundles. Flexion had minor effects on CL signal intensity and altered the tibial angles of attachment. Histology indicated that both CLs were comprised of two fiber bundles. The collateral ligaments were the same low-signal intensity. The medial collateral ligament had a smaller cross-sectional area than the lateral, and flexion increased the length of the medial collateral ligament and the cross-sectional area of the lateral. Low loads in extension did not affect the MRI appearance of stifle soft tissues. Flexion of the stifle impacted cruciate ligament insertion angles and the size and shape of collateral ligaments. This study provides support for the use of MRI to understand the anatomy and function of stifle ligaments.

Knee joint laxity is restored in a bi-cruciate retaining TKA-design.

PURPOSE: The goal is to evaluate the passive stability of a bicruciate retaining, cruciate retaining and bicruciate substituting TKA design in relation to the native knee stability in terms of the laxity envelope. A bicruciate retaining knee prosthesis was hypothesized to offer a closer to normal knee stability in vitro. METHODS: Fourteen cadaveric knee specimens have been tested under passive conditions with and without external loads, involving a varus/valgus and an external/internal rotational torque, distraction/compression force and an anteroposterior shear force. Subsequently, the native knee, bicruciate retaining, cruciate retaining and finally a bicruciate substituting total knee arthroplasty were tested. RESULTS: Through the range of motion, the width of the varus/valgus and internal/external laxity envelope for the native knee and the bicruciate retaining knee were almost equivalent, whereas the cruciate retaining and the bicruciate substituting knee displayed less laxity and more joint distraction. In all prosthetic knees, an equal anteroposterior laxity was seen for the lateral and medial side whereas in the native knee, a difference in laxity was seen between the stable medial side and the more mobile lateral side. CONCLUSION: Bicruciate retaining knee prostheses can restore normal laxity and thus have the potential to offer more normal knee function. Restoration of natural peri-articular soft-tissue tension is clinically important because of its obvious effects on joint stability and range of motion. Furthermore, the results of this study could help to establish the ideal ligament tension and laxity in more conventional implants by approaching the normal values for passive knee evaluation as presented here.

In Vivo Kinematic Comparison of a Bicruciate Stabilized Total Knee Arthroplasty and the Normal Knee Using Fluoroscopy.

BACKGROUND: The bicruciate stabilized (BCS) total knee arthroplasty (TKA) features asymmetrical bearing geometry and dual substitution for the anterior cruciate ligament and posterior cruciate ligament (PCL). Previous TKA designs have not fully replicated normal knee motion, and they are characterized by lower magnitudes of overall rollback and axial rotation than the normal knee. METHODS: In vivo kinematics were derived for 10 normal knees and 40-second generation BCS TKAs all implanted by a single surgeon. Mobile fluoroscopy and three-dimensional-to-two-dimensional registration was used to analyze anterior-posterior motion of the femoral condyles and femorotibial axial rotation during weight-bearing flexion. Statistical analysis was conducted at the 95% confidence level. RESULTS: From 0° to 30° of knee flexion, the BCS subjects exhibited similar patterns of femoral rollback and axial rotation compared to normal knee subjects. From 30° to 60° of knee flexion, BCS subjects experienced negligible anterior-posterior motions and axial rotation while normal knees continued to rollback and externally rotate. Between 60° and 90° the BCS resumed posterior motion and, after 90°, axial rotation increased in a normal-like fashion. CONCLUSION: Similarities in early flexion kinematics suggest that the anterior cam-post is supporting normal-like anterior-posterior motion in the BCS subjects. Likewise, lateral femoral rollback and external rotation of the femur in later flexion provides evidence for appropriate substitution of the PCL via the posterior cam-post. Being discrete in nature, the dual cam-post mechanism does not lend itself to adequate substitution of the cruciate ligaments in mid-flexion during which anterior cruciate ligament tension is decreasing and PCL tension is increasing in the normal knee.

High field magnetic resonance imaging is comparable with gross anatomy for description of the normal appearance of soft tissues in the equine stifle.

High field magnetic resonance imaging (MRI) is increasingly used for horses with suspected stifle disease, however there is limited available information on normal imaging anatomy and potential incidental findings. The aim of this prospective, anatomic study was to develop an optimized high field MRI protocol for evaluation of the equine stifle and provide detailed descriptions of the normal MRI appearance of the stifle soft tissues, using ultrasound and gross pathological examination as comparison tests. Nine cadaver limbs were acquired from clinically normal horses. Stifles were evaluated ultrasonographically and then by an extensive 1.5 T MRI protocol. Subsequently, all stifles were evaluated for gross pathologic change. Findings were compared between gross evaluation and MRI imaging and described. No soft tissue structure abnormalities were identified on any evaluation. Specific descriptive findings of the meniscotibial, meniscofemoral, collateral, patellar and cruciate ligaments, and the menisci were reported. The high field MRI protocol described in this study provided high spatial and contrast resolution of the soft tissue structures, and this in turn allowed visualization of detailed structural characteristics, such as striations and variations in signal intensity. Findings supported the use of high field MRI as a modality for the evaluation of the soft tissues of the equine stifle. As clinical availability of this modality increases in the future, authors anticipate that new stifle diseases will be detected that have not previously been identified with other imaging modalities.

Where does magnetic resonance imaging stand in the diagnosis of knee injuries?

BACKGROUND: The aim of this study was to determine the diagnostic value of magnetic resonance imaging (MRI) in the diagnosis of knee injuries. MATERIALS AND METHODS: Ninety-eight consecutive patients were enrolled in the study. In all patients, MRI and arthroscopy were performed and the results were compared. RESULTS: MRI was most sensitive in the detection of medial meniscus injuries, and the highest specificity and negative predictive value (NPV) were found in the detection of posterior cruciate ligament injuries. CONCLUSION: MRI is a valuable tool, and according to its high NPV, normal MRI can prevent unnecessary arthroscopic interventions.

Mapping the quadriceps tendon: an anatomic and morphometric study to guide tendon harvesting.

INTRODUCTION: The quadriceps tendon (QT) may be used in first-line knee ligament surgery (Anterior and Posterior Cruciate Ligaments), surgical revision and multiligament surgery. There are few published anatomic guides to QT harvesting. The present anatomic study sought to determine the ideal harvesting site and exa mined possible correlation between patellar and graft sizes. MATERIALS AND METHODS: A descriptive morphometric anatomic study was performed on 12 cadaveric knees. The reference anatomical landmark was the center of the superior edge of the patella. The QT was dissected and sliced longitudinally into five 5-mm strips. The central strip corresponded to the anatomic center of the patella. QT thickness was measured every 10 mm over a length of 100 mm. Data were analyzed on Pearson correlation test and Student, Bartlett and Fisher tests (α risk = 0.05). RESULTS: QT thickness ranged from 0.7 to 9.78 mm, for a mean 4.94 mm. Mean thickness in the lateral, central and medial strips was, respectively, 3.464, 6.040 and 3.899 mm. Central and centromedial strips were thicker than medial, centrolateral and lateral strips; central and centromedial strips were similar at, respectively, 6.040 and 6.041 mm (non-significant: p = 0.95), and significantly thicker than lateral strips. QT thickness showed significant correlation with patellar length (r = 0.75; p = 0.0048; 95% CI [+0.31; +0.93]). CONCLUSION: The present anatomical study confirmed that QT should be harvested from the central and centromedial regions. Mean thickness was 7.84 mm at the patellar insertion, 7.37 mm at 20 mm from the insertion, 6.41 at 40 mm, 5.61 at 60 mm and 4.33 at 100 mm.

A New Methodology for the Accurate Measurement of Tibiofemoral Kinematics in Human Cadaveric Knees: An Evaluation of the Anterior-Posterior Laxity Pre- and Post-Cruciate Ligament Resection.

Anterior-posterior (AP) stability is an important measure of knee performance after total knee arthroplasty (TKA). To improve the stabilizing effect of implants designed to compensate for the loss of the cruciate ligaments, it is important to understand the tibiofemoral contact situation within the native ligamentous situation of the knee and how it changes after cruciate ligament resection. This in vitro study introduces a new approach to accurately measure the tibiofemoral kinematics in a six-degrees-of-freedom joint motion simulator by tracking landmark-based coordinate systems and their corresponding bone geometries. The tibiofemoral contact situation was investigated by projecting the medial and lateral flexion facet centers onto the tibial plateau under AP shear forces across various flexion angles in thirteen knees. Tests were conducted pre- and post-cruciate ligament resection. Post-cruciate ligament resection, the femoral condyles shifted closer to or even exceeded the posterior border of the tibial plateau, but only slightly closer to the anterior border. This study presents a new methodology for measuring the tibiofemoral kinematics that can be applied to multiple loading profiles. It provides a basis for further investigations, including passive or active muscle forces, to enhance the design of total knee protheses and improve surgical outcomes.

Pediatric Anterior Cruciate Ligament Reconstruction.

The incidence of anterior cruciate ligament (ACL) injuries in children and adolescents has been growing recently. This problem is a challenge for the treating orthopedic surgeon, especially when the patient is in the prepubertal period with a high growth potential. Since reconstructive procedures require interventions close to active growth plates, they are associated with the risk of postoperative limb length discrepancies and limb deformities. Postponing ACL reconstruction until the end of growth is not a solution, as persistent knee instability increases the risk of secondary intra-articular damage. The key to success is not only knowledge of the anatomy and biomechanics of the pediatric knee but also the ability to predict the remaining growth potential and familiarity with a wide range of reconstructive surgical procedures available for patients at different ages.

Magnetic Resonance Imaging of Internal Derangements and Other Knee Pathologies in Adult Nigerians.

Background: Knee joint pathologies/injuries are one of the most common musculoskeletal complaints in adults worldwide. The aetiologies of knee joint disorders are diverse. Magnetic resonance imaging (MRI) is a sophisticated method of detecting and characterizing knee pathologies. This study was conducted to document the clinical presentation and MRI patterns of knee joint abnormalities in a group of adults in Lagos, Nigeria, and to juxtapose it with reports from other climes. Methodology: A retrospective hospital-based analysis of the knee MRI of 158 adult Nigerians was conducted in a single health facility. The clinical history and knee MRI findings were extracted, analyzed, and documented. Statistical significance was established at P≤0.05. Results: There were 158 participants comprising 92 males (58.2%) and 66 females (41.8%) between the ages of 18 and 79. The mean age of the males was 44.75 ± 14.41 years, while that of the females was 47.76 ± 13.72 years (P = 0.19). A history of previous trauma was elicited in 135 (85.4%) participants. Eighty-two right knees (51.9%) and 76 left knees (48.1%) were examined. The dominant joint pathologies detected include effusion (77.2%), medial meniscopathy (48.1%), tibial abnormalities (46.2%), femoral abnormalities (46.2%), patella abnormalities (46.2%), anterior cruciate ligament disorders (37.3%), lateral meniscopathy (27.2%), medial collateral ligament disorders (22.2%), and popliteal (Baker's) cysts (15.8%). ACL abnormalities were significantly more prevalent in male subjects. Knees with ruptured sACL had significantly more joint effusion and injuries to the medial meniscus, lateral meniscus, posterior cruciate ligament (PCL), medial retinacular ligament (MRL), femur, tibia, and fibula. There was no significant difference in the frequency of abnormalities between the right and left knees. Conclusion: Joint effusion, medial meniscopathy, osseous abnormalities (tibia, femur, patella), ACL abnormalities, lateral meniscopathy, and MCL abnormalities, in decreasing order, were the most frequent pathologies in the knee joints evaluated.

Age-related changes in microRNAs expression in cruciate ligaments of wild-stock house mice.

Cruciate ligaments (CL) of the knee joint are injured following trauma or aging. MicroRNAs (miRs) are potential therapeutic targets in musculoskeletal disorders, but there is little known about the role of miRs and their expression ligaments during aging. This study aimed to (1) identify if mice with normal physical activity, wild-stock house mice are an appropriate model to study age-related changes in the knee joint and (2) investigate the expression of miRs in aging murine cruciate ligaments. Knee joints were collected from 6 and 24 months old C57BL/6 and wild-stock house mice (Mus musculus domesticus) for ligament and cartilage (OARSI) histological analysis. Expression of miR targets in CLs was determined in 6-, 12-, 24-, and 30-month-old wild-stock house mice, followed by the analysis of predicted mRNA target genes and Ingenuity Pathway Analysis. Higher CL and knee OARSI histological scores were found in 24-month-old wild-stock house mice compared with 6- and 24-month-old C57BL/6 and 6-month-old wild-stock house mice (p < 0.05). miR-29a and miR-34a were upregulated in 30-month-old wild-stock house mice in comparison with 6-, 12-, and 24-month-old wild-stock house mice (p < 0.05). Ingenuity Pathway Analysis on miR-29a and 34a targets was associated with inflammation through interleukins, TGFß and Notch genes, and p53 signaling. Collagen type I alpha 1 chain (COL1A1) correlated negatively with both miR-29a (r = -0.35) and miR-34a (r = -0.33). The findings of this study support wild-stock house mice as an appropriate aging model for the murine knee joint. This study also indicated that miR-29a and miR-34a may be potential regulators of COL1A1 gene expression in murine CLs.

Current strategies for enhancement of the bioactivity of artificial ligaments: A mini-review.

Background and objective: Anterior cruciate ligament (ACL) reconstruction calls for artificial ligaments with better bioactivity, however systematic reviews regarding bioactivity enhancement strategies, technologies, and perspectives of artificial ligaments have been rarely found. Methods: Research papers, reviews, and clinical reports related to artificial ligaments were searched and summarized the current status and research trends of artificial ligaments through a systematic analysis. Results: Having experienced ups and downs since the very first record of clinical application, artificial ligaments differing in material, and fabrication methods have been reported with different clinical performances. Various manufacturing technologies have developed and realized scaffold- and cell-based strategies. Despite encouraging in-vivo and in-vitro test results, the clinical results of such new designs need further clinical examinations. Conclusion: As the demand for ACL reconstruction dramatically increases, novel artificial ligaments with better osteoinductivity and mechanical performance are promising. The translational potential of this article: To develop novel artificial ligaments simultaneously possessing excellent osteoinductivity and satisfactory mechanical performance, it is important to grab a glance at recent research advances. This systematic analysis provides researchers and clinicians with comprehensive and comparable information on artificial ligaments, thus being of clinical translational significance.

Morphometry of Anterior Cruciate Ligament in Knee joint. A Cadaveric Study.

Objectives: The journey of Anterior Cruciate Ligament (ACL) reconstruction surgery has long way from open surgery to arthroscopy. Therefore, the anatomical features of the ACL and its two bundles description rewarded as good outcome of procedure. Material and methods: Fifty fresh knees were dissected. The insertion position, length and diameter of ACL and patellar tendon length were measured and determines the range of normality according to sex and side. Results: The average lengths of Antero- medial (AM) and postero- lateral (PL) bundle of the ACL were 35.35 mm and 26.11mm in male on right side, respectively while 34.21mm and 25.53 mm in female. Patellar tendon length was 45.24 mm in right side of male and 43.38 mm in female obtained. The average lengths of AM and PL bundle of the ACL were 35.47 mm and 26.04 mm in male on left side, respectively while 34.23 mm and 25.38 mm in female. Conclusion: The length of ligaments was higher in male than female. There was strong correlation between height and length of ligaments but no correlation with age.

Outcomes of Repair and Reconstruction of the Acute Posterolateral Corner Injuries of the Knee Combined with Cruciate Ligaments Injuries.

Background: This study aimed to report objective and subjective knee stability scores for patients who underwent acute repair of avulsed posterolateral corner (PLC) structures or acute reconstruction of midsubstance tears combined with delayed reconstruction of cruciate ligaments. Methods: A total of 48 sport and vehicle accident traumatic patients were enrolled in a three-year follow-up study. The patients were investigated by clinical exams, subjective and objective International Knee Documentation Committee (IKDC) score, Tegner score, Lysholm score, and stress imaging. All scores were compared between the reconstruction and repair groups. Results: Subjective IKDC scores were obtained at 83.3±9.6 and 88.3±4.39 for the reconstruction and repair groups, respectively. Only two patients in the reconstruction group had abnormal objective IKDC scores. Based on the Tegner score, 15 out of 18 patients in the repair group and 20 out of 24 patients in the reconstruction group regained their pre-injury functional level. Mean Lysholm scores for the reconstruction and repair groups were estimated at 83.4±8.2 and 88.2±4.1, respectively. Mean lateral joint opening differences between two knees in the reconstruction and repair groups were -0.2±0.1mm and 0.5±0.1mm, respectively. There were no statistically significant differences between groups outcomes. We had no failure of treatment at the final follow-up. Conclusion: Acute intervention within 3 weeks after PLC injuries combined with delayed cruciate ligaments reconstructions showed favorable outcomes. Both repair and reconstruction are effective when deciding based on the type of injury (i.e., avulsion and midsubstance tear).

Outcomes of Bi-unicompartmental Versus Total Knee Arthroplasty for the Treatment of Medial and Lateral Knee Osteoarthritis: A Systematic Review and Meta-analysis of Comparative Studies.

Purpose: The aim of this meta-analysis was to evaluate differences in functional outcomes between simultaneous bi-unicompartmental knee arthroplasty (Bi-UKA) and total knee arthroplasty (TKA) for the treatment of medial and lateral knee osteoarthritis. Material and Methods: According to the PRISMA statement, a comprehensive search was conducted to identify studies reporting comparative results of the Bi-UKA versus the TKA. Of 953 titles, 6 studies met the inclusion criteria. Results: A total of 286 patients were identified, of which 137 underwent Bi-UKA and 149 TKA. TKA reported a mean hip-knee-ankle (HKA) angle of 179.4 ± 2.4 compared to that in Bi-UKA measuring 177.2 ± 2.7 (p = 0.0001, 95% CI - 3.02 to - 1.38). No difference was found in the Western Ontario and McMaster Universities (WOMAC) pain (4 ± 1.6 and 4.2 ± 1.3 for Bi-UKA and TKA, respectively; p = 0.4996, 95% CI - 0.86 to 0.43). Bi-UKA was favorable in terms of WOMAC function (7.5 ± 1.9 and 9 ± 1.9 for Bi-UKA and TKA, respectively; p = 0.001, 95% CI - 2.29 to - 0.61) and WOMAC stiffness (1.6 ± 1 and 2.4 ± 0.7 for Bi-UKA and TKA, respectively; p = 0.0001, 95% CI - 1.18 to - 0.42). Bi-UKA showed a better Knee Society Score (KSS) in comparison to TKA (79.7 ± 7.8 and 75.4 ± 10.5 for Bi-UKA and TKA, respectively; p = 0.0021, 95% CI 1.58-7.02). The differences in postoperative outcomes scores between Bi-UKA and TKA were lower than their respective minimum clinically important differences. Conclusions: When Bi-UKA and TKA are compared for the treatment of medial and lateral knee osteoarthritis, Bi-UKA are favorable in terms of WOMAC and KSS even though these values are lower than the minimum clinically important differences; moreover, similar postoperative hip-knee-ankle angle can be expected 3 years after Bi-UKA and TKA.

Anatomical feature of knee joint in Aachen minipig as a novel miniature pig line for experimental research in orthopaedics.

BACKGROUND: The pig is a commonly used large animal model, since pigs share anatomical and physiological similarities with humans. In contrast to other experimental pig lines the Aachen minipig, as a robust novel minipig does not require housing with any barrier. To estimate transferability of results to human conditions, pig lines should be thoroughly characterized. PURPOSE: Therefore, we analyzed the anatomical pecularities of the knee joint of the novel "Aachen minipig" line raised for experimental conditions. METHODS: Eight knee joints of four adult Aachen minipigs were dissected measuring the dimensions of typical landmarks using a digital caliper. Hybrid pig and human knee joints served as controls. Cartilage of the Aachen minipig (trochlear groove, femoral condyles, menisci) were assessed histologically. RESULTS: The Aachen minipig shared its knee joint anatomy with the hybrid pig. In comparison to humans, peculiarities of the pig were demonstrated in the Aachen minipig: the lateral meniscus and the lateral tibial joint surface were significantly longer than the medial counterparts. The fibular head was covered by fibrocartilage and completely integrated into the lateral lower joint surface. The cartilage at the joint areas usually used for cartilage repair studies was in average 0.66±0.04mm thick. The porcine anterior cruciate ligament (ACL) attached with two bundles at the anterior tibial plateau separated from each other by the lateral anterior meniscotibial ligament. Aachen minipig articular and meniscal cartilage presented the typical histoarchitecture. CONCLUSIONS: The Aachen minipig reflects porcine anatomical peculiarities, which should be considered, especially for meniscus and ACL reconstruction.

Viscoelastic characteristics of the canine cranial cruciate ligament complex at slow strain rates.

Ligaments including the cruciate ligaments support and transfer loads between bones applied to the knee joint organ. The functions of these ligaments can get compromised due to changes to their viscoelastic material properties. Currently there are discrepancies in the literature on the viscoelastic characteristics of knee ligaments which are thought to be due to tissue variability and different testing protocols. The aim of this study was to characterise the viscoelastic properties of healthy cranial cruciate ligaments (CCLs), from the canine knee (stifle) joint, with a focus on the toe region of the stress-strain properties where any alterations in the extracellular matrix which would affect viscoelastic properties would be seen. Six paired CCLs, from skeletally mature and disease-free Staffordshire bull terrier stifle joints were retrieved as a femur-CCL-tibia complex and mechanically tested under uniaxial cyclic loading up to 10 N at three strain rates, namely 0.1%, 1% and 10%/min, to assess the viscoelastic property of strain rate dependency. The effect of strain history was also investigated by subjecting contralateral CCLs to an ascending (0.1%, 1% and 10%/min) or descending (10%, 1% and 0.1%/min) strain rate protocol. The differences between strain rates were not statistically significant. However, hysteresis and recovery of ligament lengths showed some dependency on strain rate. Only hysteresis was affected by the test protocol and lower strain rates resulted in higher hysteresis and lower recovery. These findings could be explained by the slow process of uncrimping of collagen fibres and the contribution of proteoglycans in the ligament extracellular matrix to intra-fibrillar gliding, which results in more tissue elongations and higher energy dissipation. This study further expands our understanding of canine CCL behaviour, providing data for material models of femur-CCL-tibia complexes, and demonstrating the challenges for engineering complex biomaterials such as knee joint ligaments.

Role of Magnetic Resonance Imaging in Classifying Individuals Who Will Develop Accelerated Radiographic Knee Osteoarthritis.

We assessed whether adding magnetic resonance (MR)-based features to a base model of clinically accessible participant characteristics (i.e., serological, radiographic, demographic, symptoms, and physical function) improved classification of adults who developed accelerated radiographic knee osteoarthritis (AKOA) or not over the subsequent 4 years. We conducted a case-control study using radiographs from baseline and the first four annual visits of the osteoarthritis initiative to define groups. Eligible individuals had no radiographic KOA in either knee at baseline (Kellgren-Lawrence [KL] grade <2). We classified two groups matched on sex (i) AKOA: at least one knee developed advanced-stage KOA (KL = 3 or 4) within 48 months and (ii) did not develop AKOA within 48 months. The MR-based features were assessments of bone, effusion/synovitis, tendons, ligaments, cartilage, and menisci. All characteristics and MR-based features were from the baseline visit. Classification and regression tree analyses were performed to determine classification rules and identify statistically important variables. The CART models with and without MR features each explained approximately 40% of the variability. Adding MR-based features to the model yielded modest improvements in specificity (0.90 vs. 0.82) but lower sensitivity (0.62 vs. 0.70) than the base model. There was consistent evidence that serum glucose, effusion-synovitis volume, and cruciate ligament degeneration are statistically important variables in classifying individuals who will develop AKOA. We found common MR-based measures failed to dramatically improve classification. These findings also show a complex interplay among participant characteristics and a need to identify novel characteristics to improve classification. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2420-2428, 2019.

Osteoarthritis of the Anterior Cruciate Ligament and Medial Tibial Plateau: A Cadaveric Study.

The objective of this study was to analyze morphometric anatomy and damages with aging in cadaveric knee specimens specific to the cruciate ligaments, the articular cartilage of the tibial plateau, and the menisci. Morphometric analyses to cadaveric anatomy of the knee were performed using Image-Pro® software on 3 age populations: <70 years old, 70 to 79 years old, and ≥80 years old. An average thickness of the cruciate ligaments was assessed with 5 circumferential measurements per specimen using nylon thread. Percent degeneration of the tibial plateau's articular cartilage and coverage by menisci was assessed with surface area measurements. The articular cartilage of the medial tibial plateau in ≥80 years old specimens showed a 1.7-fold increase in surface area degeneration (mm2) compared to 70 to 79 years old specimens ( P < 0.05). The medial meniscus also experienced degenerative changes with aging, which were expressed as decreases in tibial plateau coverage. The anterior cruciate ligament (ACL) experienced substantial degenerative thinning with aging. The 70 to 79 years old specimens had a 1.2-fold (10.5%) decrease in average ACL circumference (mm) compared to the <70 years old specimens ( P < 0.001). The ≥80 years old specimens had a 1.24-fold (19%) decrease in ACL circumference compared to the <70 years old specimens ( P < 0.001). ACL thinning during aging may be leading to substantial articular cartilage and menisci degeneration given the cruciate ligaments are a primary restraint that combats shearing forces at the knee joint.

Knee Forces During Landing in Men and Women.

Sex differences in biomechanics may provide one explanation for the greater incidence of knee injuries in women, but few studies have compared internal forces. In this study, a musculoskeletal model was used to compare male and female, bilateral and unilateral landings based on motion capture and force plate data. Participants were classified as landing medially or laterally loaded based upon the mediolateral load share at the knee (bilateral: p < 0.001, η2=0.452; unilateral: p < 0.001, η2 = 0.444). Knee kinematics and ground reaction forces were not different between the two groups (p > 0.05, η2 = 0.001 - 0.059), but there were differences in muscular recruitment. Landing strategy did not appear to be dependent on sex. However, for both medially and laterally loaded bilateral landings men had greater gluteal (p = 0.017, η2 = 0.085) and hamstrings forces (p < 0.001, η2 = 0.183), whereas women had greater quadriceps forces (p = 0.004, η2 = 0.116). This study demonstrates an association between muscular recruitment and medially loaded landings. Landing strategy seems to be a function of skill not sex; however, within a particular landing strategy there may be sex differences in muscular activation that contribute to the difference in injury rates.