Anatomy and biomechanics of the menisci

The shape of the menisci and the orientation of the collagen fibers are optimal for weight bearing and shock absorption. The menisci are of clinical importance to knee biomechanics as they function to maintain knee joint stability and congruity, resist capsular and synovial impingement during knee motion, support the screw home mechanism, and distribute load over a large area of the articular surface. Because of these vital roles, an attempt should be made to save viable meniscus when performing knee surgery.     

Function of the normal meniscus and consequences of meniscal resection

The principal functions of the meniscus are load transmission and shock absorption, based on the meniscal collagen architecture, the biochemical fluid composition, and the proteoglucan-collagen meshwork. The mobile menisci transmit 50-90% of load over the knee joint, depending on knee flexion angle, femoral translation and rotation. The meniscus contributes to knee joint proprioception and probably also to joint stability. Late consequences of total and partial meniscectomy are radiographic osteoarthritis, with a varying percentage of these patients having symptoms. Malalignment, concomitant articular cartilage lesions, and ligament instability are absolute risk factors, while age, lateral compartment, and continued sport activity are relative risk factors. Acute reinsertion of meniscal tears in the red-red or red-white zones can be performed successfully by arthroscopic technique. Also in chronic tears stable healing can be expected in most cases, if the scar tissue is resected.     

Biomechanics of the meniscus-meniscal ligament construct of the knee

The menisci of the knee act primarily to redistribute contact force across the tibio-femoral articulation. This meniscal function is achieved through a combination of the material, geometry and attachments of the menisci. The main ligaments that attach the menisci to the tibia (insertional ligaments, deep medial collateral ligament), the femur (meniscofemoral ligaments, deep medial collateral ligament) and each other (the anterior intermeniscal ligament) are the means by which the contact force between tibia and femur is distributed into hoop stresses in the menisci to reduce contact pressure at the joint. This means that the functional biomechanics of the menisci cannot be considered in isolation and should be considered as the functional biomechanics of the meniscus-meniscal ligament construct. This article presents the current knowledge on the anatomy and functional biomechanics of the meniscus and its associated ligaments. Much is known about the function of the meniscus-meniscal ligament construct; however, there still remain significant gaps in the literature in terms of the properties of the anterior intermeniscal ligament and its function, the properties of the insertional ligaments, and the most appropriate ways to reconstruct meniscal function surgically.     

Anatomic variations of the shape of the menisci: a neonatal cadaver study

Meniscal injuries in children and adolescents are being seen with increased frequency. The menisci are two crescentic lamellae whose functions are to deepen the articular surfaces of the tibial plateu for reception of the condyles of the femur. In our study, our aim is to determine the variations of the shapes and attachments of the menisci in newborns. This study was performed on 11 neonatal cadavers, 22 knee joints that were obtained from the anatomy laboratory. The variations of the shape of the menisci were noted. We found that 77% of the lateral menisci were discoid. This percent is higher than the previously reported percents of the lateral discoid menisci. The different shapes of the menisci were determined as horse shoe, sickle, sided U, sided V and C shaped. We did not determine any discoid medial menisci. We believe that our study will provide support to the neonatal anatomy of the knee, concerning with the surgical procedures and arthroscopy of the knee joint.This study was presented at the 6th international symposium of clinical anatomy, Varna, Bulgaria, 8–10 October 2004     

The anatomy and biomechanics of thelateral aspect of the knee

The lateral and posterolateral aspects of the knee are complex and often confusing anatomic regions. The structures that comprise the lateral aspect of the knee are the lateral knee retinaculum, which is comprised of the iliopatellar band, and iliotibial tract. The complicated posterolateral corner is an integrated complex that includes the lateral collateral ligament, the popliteus tendon, the fabellofibular ligament, the arcuate ligament, the popliteofibular ligament, and the short lateral ligament. It is only recently that a much clearer understanding of the anatomic structures of the lateral and posterolateral aspects of the knee have been delineated. As a result a more accurate determination of the biomechanical contributions of each these structures has occurred. The lateral collateral ligament is the primary restraint to varus rotation at all degrees of knee flexion. The posterolateral structures, of which the popliteofibular ligament has been shown to play a major role, are also a primary restraint to external rotation. These same structures play a secondary role in the control of anterior and posterior translation of the knee. It is the hope that this improved understanding of the anatomy and biomechanics of the lateral and posterolateral aspects of the knee will translate into improved clinical management of the instabilities that are often so debilitating and clinical challenging.     

Normal anatomy and biomechanics of the knee

Functionally, the knee comprises 2 articulations-the patellofemoral and tibiofemoral. Stability of the joint is governed by a combination of static ligaments, dynamic muscular forces, meniscocapsular aponeurosis, bony topography, and joint load. The surgeon is ill equipped to undertake surgical treatment of a dislocated knee without a sound footing in the anatomic complexities of this joint. We review the normal anatomy of the knee, emphasizing connective tissue structures and common injury patterns.     

MRI after patellofemoral replacement: the preserved compartments

Introduction

The aim of this study was to assess the reproducibility of magnet resonance imaging (MRI) analysis of preserved anatomic structures of the knee after patellofemoral replacement (PFR). It was hypothesized that evaluation of cartilage, ligaments, meniscus and tendons would result in high inter-observer reliability after PFR.

Material and methods

MRI, tailored to reduce metallic artefacts of the knee, after PFR was performed in seven patients. Two independent investigators evaluated cartilage, menisci, collateral and cruciate ligaments, the quadriceps and patellar tendons and the presence of joint effusion. The reviewers used a five-point scale to give a degree of confidence to their evaluation of each parameter. Inter-observer reliability was determined by calculation of Cohen's Kappas.

Results

Artefact provoked by the implants was not observed. For all assessed structures, there was excellent inter-observer reliability, with high Cohen's Kappas. There were also high levels of inter-observer agreement and observer confidence in the evaluation of cartilage, meniscus, tendons, ligaments and joint effusion.

Conclusion

Tailored MRI allows reproducible analysis of the preserved knee joint structures after PFR. It might prove helpful in assessment of painful knee joints after PFR.     

Effects of prolonged walking with body borne load on knee adduction biomechanics

BackgroundSoldiers that suffer a service-related knee musculoskeletal injury routinely develop joint osteoarthritis. Knee osteoarthritis is a substantial and costly problem among soldiers, yet it is unknown how body borne load and duration of walking impact knee adduction biomechanics linked to progression and severity of osteoarthritis.Research questionThis study determined the adaptations in magnitude and variability of knee adduction joint angle (KAA) and moment (KAM) during prolonged walking with body borne load.MethodsThirteen recreationally active participants had knee biomechanics quantified while walking over-ground for 60-min at 1.3 m/s with three body borne loads (0, 15, and 30 kg). Magnitude and variability of KAA and KAM measures were quantified and submitted to a RM ANOVA to test the main effect and interactions between load (0, 15 and 30 kg) and time (0, 15, 30, 45 and 60 min).ResultsBody borne load increased peak KAM (p < 0.001), whereas time increased peak and range of KAA (both: p < 0.001). Specifically, peak KAM increased with each addition of body borne load (all: p < 0.025), and peak and range of KAA increased after 30 min of walking (both: p < 0.040). Neither body borne load, nor time had a significant effect on KAA or KAM variability (both: p > 0.05).SignificanceProlonged walking with heavy body borne load increased knee adduction biomechanics related to osteoarthritis. Adding heavy body borne load increased in peak KAM whereas duration of walking increased KAA, knee biomechanics that may increase loading of the medial knee joint compartment and risk of OA at the joint.     

Pitfalls in knee arthrography.

Sources of error in performing and interpreting knee arthrograms are discussed. Normal anatomic structures and technical factors can simulate tears in most areas of both the medial and lateral menisci. These pseudotears, as well as unrecognized true tears, occur more commonly in the posterior horn of the medial meniscus. Inferior meniscal recesses and coronary ligament irregularities of the posterior medial meniscus often represent incomplete tears. Diagnostic, etiologic, and therapeutic aspects of these recesses, or pseudorecesses, are discussed. Excessive intra-articular positive contrast medium may become localized and simulate a loose body in the joint.     

Tibial meniscal dynamics using three-dimensional reconstruction of magnetic resonance images.

The human knee joint represents a complex biomechanical system of which the menisci are an integral component. At present, little data exists describing the meniscal kinematics of the intact knee. Accordingly, a three-dimensional reconstruction magnetic resonance image model was used to explore this issue. Five fresh cadaveric knees were examined by magnetic resonance imaging throughout a full range of motion at 10 degrees intervals. Computer three-dimensional images of the menisci were generated and evaluated for anteroposterior excursion and deformation. During flexion, the posterior excursion of the medial meniscus was 5.1 mm, while that of the lateral meniscus was 11.2 mm. The anterior horn segments were shown to be more mobile than the posterior horn segments bilaterally. Prior limitations of meniscal kinematic assessment may be overcome with advanced imaging techniques such as magnetic resonance imaging and three-dimensional reconstruction. The menisci are highly mobile and easily deformed structures within the intact, cadaveric knee. This imaging technique may prove useful in the elucidation of meniscal dynamics. In the future, similar techniques may be applied clinically to aid in the diagnosis of joint dysfunction.     

Combined meniscal allografttransplantation and autologous chiondrocyte implantation

The knee, with complex injury involving the meniscus and articular cartilage, presents a challenging situation forboth physician and patient. The utilization of meniscal transplantation for replacement of the meniscus deficiency has been used successfully. Autologous chondrocyte implantation (ACI) has been utilized to successfully treat the presence of chondral defects in the knee joint. By combining these two procedures the knee homeostasis can be replaced and the knee salvaged, retarding the future growth of degeneration. Initial results appear to be promising, although long-term follow-up will be critical to evaluate.     

Meniscal tears, repairs and replacement: their relevance to osteoarthritis of the knee

The menisci of the knee are important load sharers and shock absorbers in the joint. Meniscal tears are common, and whenever possible meniscal tears should be surgically repaired. Meniscectomy leads to a significant increased risk of osteoarthritis, and various options now exist for replacing missing menisci, including the use of meniscal scaffolds or the replacement of the entire meniscus by meniscal allograft transplantation. The field of meniscal surgery continues to develop apace, and the future may lie in growing new menisci by tissue engineering techniques.     

MR arthrography of the lower extremity

MR arthrography by virtue of its ability accurately to demonstrate intra-articular structures and abnormalities of these structures has become an important tool for the evaluation of a variety of articular disorders. Although not necessary in all patients, MR arthrography may facilitate the evaluation of patients with suspected intra-articular pathology in whom conventional MRI is not sufficient for an adequate therapy planning. MR arthrography combines the advantages of arthrography, like joint distention and delineation of intra-articular structures, with the superior spatial resolution of MRI. This technique improves diagnostic confidence, particularly in the assessment of subtle lesions and of complex anatomic structures. MR arthrography is of high value in the evaluation of osteochondral defects, loose bodies, previously operated menisci, and acetabular labral lesions.     

Meniscal reconstruction using allograft tissue: An arthroscopic technique

The treatment of meniscal pathology has changed dramatically over the last decade. This change in treatment has been brought about by our increased knowledge of the functions of the human meniscus: force transmission, increase contact area, decrease contact stress, shock absorption, joint lubrication, nutrition of chondrocytes, and stabilization. Meniscal transplantation has been developed in an attempt to interrupt or retard the progressive joint deterioration that develops in the postmeniscectomy knee. The author's arthroscopically assisted technique for meniscal reconstruction using fresh frozen allograft tissue without disruption of the extensor mechanism or collateral ligaments is described. This technique emphasizes visualization of specific landmarks for each meniscal horn insertion site with creation of osseous tunnels at these corresponding sites to allow for anatomic placement of the meniscal inplant. Only if normal anatomy and kinematics is established can one assume that the transplanted meniscus will provide a beneficial function. The author's believe that the operation should be limited to a select group of individuals who meet specific inclusion criteria in study groups and investigational protocols until long-term results are determined.     

MR imaging,MR arthrography,and specimen correlation of the posterolateral corner of the knee: an anatomic study

OBJECTIVE: We sought to evaluate the anatomy of the posterolateral aspect of the knee with anatomic dissection, MR imaging, MR arthrography, and sectional anatomy. MATERIALS AND METHODS: We assessed the posterolateral corner of the knee during dissection of one gross anatomic specimen. MR imaging and MR arthrography were performed in seven additional knee specimens. T1-weighted spin-echo MR images were obtained in the standard imaging planes as well as in the coronal oblique plane. The specimens underwent T1-weighted spin-echo MR imaging after administration of intraarticular contrast material and were sectioned into planes corresponding to those of the MR images. RESULTS: At anatomic dissection, the following posterolateral structures were identified: the arcuate ligament (medial and lateral limbs), fabellofibular ligament, popliteofibular ligament, popliteus tendon and its two posterior attachments to the lateral meniscus, fibular collateral ligament, direct and anterior arms of the tendon of the long head of the biceps femoris muscle, and direct and anterior arms of the tendon of the short head of the biceps femoris muscle. Correlation of MR imaging and anatomic findings showed that the popliteofibular ligament and oblique popliteal ligament were found in 57% and 100% of specimens, respectively. At least one of the two limbs of the arcuate ligament was identified in 71% of specimens. The fabellofibular ligament was not identified on MR images in any of the specimens. The anteroinferior and posterosuperior popliteomeniscal fascicles were identified in all specimens. CONCLUSION: The posterolateral corner of the knee comprises complex and variable anatomic structures. Recognition of these variations is important in the assessment of MR images of the knee.     

An anatomic-arthrographic study of the relationships of the lateral meniscus and the popliteus tendon.

The anatomy of the posterior lateral knee joint is studied through photography and radiography of plastic corrosion casts of the knee joint. The images thus obtained are compared to in vivo arthrograms. This anatomic-arthrographic correlation clearly demonstrates how the bursal extensions of the joint space about the popliteus tendon dictate the location and arthrographic appearance of the peripheral attachments of the posterior lateral meniscus. The casts also serve to illustrate a discussion of anatomic variation, embryology, and function of the popliteus apparatus. The largely unappreciated direct action of the popliteus muscle on the lateral meniscus is emphasized.     

Tibial slope changes following dome-type high tibial osteotomy

The tibial slope is essential in knee biomechanics, both for ligament function and knee kinematics. High tibial osteotomy (HTO) designed primarily to correct frontal plane malalignment in osteoarthritis of the knee joint can cause unintentional tibial slope changes. We evaluated tibial slope changes in 40 knees in patients with medial compartment osteoarthritis treated by dome-type HTO and external fixation on one side, and followed up for 55 months on average. Four different tibial slope measurement methods (anterior tibial cortex, proximal tibial anatomic axis, posterior tibial cortex, and proximal fibular anatomic axis) were used preoperatively and postoperatively on both sides. Patients were allocated into three groups according to their final frontal plane alignment of the knee joint (hypercorrection, normocorrection, and undercorrection groups) based on tibiofemoral anatomic axis angle. As a whole, preoperative slope values (11.2°, 7.5°, 5.6°, and 8.2° for the four methods, respectively) displayed a significant decrease postoperatively (on average 7.9°, 4.8°, 2.2°, and 3.7°, respectively). Patients with undercorrection (or recurrence of deformity) had a more remarkable decrease in slope than those with normocorrection or hypercorrection. The higher the degree of postoperative mechanical axis valgus, the higher the degree of posterior tibial slope that resulted. Sagittal plane changes after dome-type HTO basically decreasing the tibial slope should be taken into account for subsequent reconstructive procedures such as total knee arthroplasty.     

关节镜下治疗半月板囊肿的疗效评价

目的探讨关节镜下治疗半月板囊肿的临床疗效。方法 2007年5月—2010年11月,我科共收治15例半月板囊肿患者,其中男10例,女5例,年龄19～37(22.6±4.1)岁。术前行膝关节MRI明确诊断,采用关节镜下囊肿切除、半月板成形术治疗。结果平均随访(12.3±2.4)个月,14例患者膝关节疼痛、肿胀消失,活动范围恢复正常,膝关节间隙表面包块消失,无关节交锁及弹响。1例多房性囊肿因遗留复发。术前Lysholm评分平均为(68.7±5.4)分,末次随访时Lysholm评分平均为(93.5±3.7)分,差异有统计学意义(P<0.01);术后Glasow评分优良率为86.7%。结论关节镜下治疗半月板囊肿具有创伤小、膝关节稳定性好及生理功能干扰小等优点,是治疗半月板囊肿的理想方法。     

Current concepts review: comprehensive physical examination for instability of the knee

A careful history and physical examination are the cornerstones of orthopaedic sports medicine. When evaluating a patient for ligamentous instability of the knee joint, an understanding of the contribution of anatomic structures to stability enhances a practitioner's ability to achieve an accurate clinical diagnosis. This article reviews the various types of knee instability and the associated anatomic structures. Ultimately, information must be obtained from multiple tests to reach the final diagnosis. We describe in detail the pathologic and biomechanical basis of the tests for both tibiofemoral and patellofemoral instability of the knee joint and provide recommendations for performance and interpretation of these physical examinations.     

Clinical biomechanics of the patellofemoral joint

Anatomic variations of the knee extensor mechanism may result in predisposition to maltracking or instability ofthe patella and quadriceps mechanism. In addition to these anatomic variations, individuals may subject their knees to a wide variety of activities and stresses. Each case of patellofemoral dysfunction, which may range from only anterior knee pain to patellar dislocation, must be considered individually. In the presence of maltracking or patellar instability that is recalcitrant to rehabilitation, there is no single structure which can be surgically altered, repaired, or reconstructed in each case to expect a satisfactory result. The purpose of this article is to describe recent work on the anatomy and biomechanics of the patellofemoral joint to aid the reader in understanding, assessing, and determining the method of treatment most likely to result in improvement in symptoms associated with patellofemoral dysfunction.