In this article, the six major studies of soccer injury epidemiology are reviewed. Strengths and weaknesses of each epidemiologic design are critiqued and the crucial importance of the definition of injury is emphasized. The effect of age, sex, and intensity of play on injury rates is discussed. Our present knowledge of injury rate by anatomical site, player position, and the type of playing surface are reviewed. We examined the importance of player factors such as flexibility, joint laxity, weakness, and incomplete rehabilitation from other injuries. In addition, we reviewed the role played by inadequate equipment, field conditions, and rule violations. A successful program for soccer injury prevention is described, and guidelines for future soccer injury epidemiology research are proposed.

Adolescent↗

PubMed1988

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures.

We applied specific forces and moments to the knees of fifteen whole lower limbs of cadavera and measured, with a six degrees-of-freedom electrogoniometer, the position of the tibia at which the ligaments and the geometry of the joint limited motion. The limits were determined for anterior and posterior tibial translation, internal and external rotation, and varus and valgus angulation from zero to 90 degrees of flexion. The limits were measured in the intact knee and then the changes that occurred with removal of the posterior cruciate ligament, the lateral collateral ligament, the popliteus tendon at its femoral attachment, and the arcuate complex were measured. The cutting order was varied, allowing us to determine the changes in the limits that occurred when each structure was cut alone and the amount of motion of the joint that was required for each structure to become taut and to limit additional motion when the other supporting structures had been removed. Removal of only the posterior cruciate ligament increased the limit for posterior tibial translation, with no change in the limits for tibial rotation or varus and valgus angulation. The additional posterior translation was least at full extension and increased progressively, reaching 11.4 millimeters at 90 degrees of flexion. The progressive increase in posterior translation with flexion was apparently due to slackening of the posterior portion of the capsule, as the translation nearly doubled when the posterolateral structures subsequently were removed. Removal of only the posterolateral extra-articular restraints increased the amount of external rotation and varus angulation. The average increase in external rotation depended on the angle of flexion; it was greatest at 30 degrees of flexion and decreased with additional flexion. At 90 degrees of flexion, the intact posterior cruciate ligament limited the increase in external rotation to only 5.3 degrees, less than one-half of the 13.0-degree increase that occurred at 30 degrees of flexion. Subsequent removal of the posterior cruciate ligament markedly increased external rotation at 90 degrees of flexion, resulting in a total increase of 20.9 degrees. The limit for varus angulation was normal as long as the lateral collateral ligament was intact. When the lateral collateral ligament was cut, the limit increased 4.5 degrees (approximately 4.5 millimeters of additional joint opening) when the knee was partially flexed (to 15 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗

PubMed1988

Foreword: Sports injury research.

Explore the source record for details and available documents.

Athletic Injuries↗

PubMed1987

The use of computerized thermography in the evaluation of non-traumatic anterior knee pain.

Computerized thermography was used to evaluate eight patients with the complaint of non-traumatic anterior knee pain. Computerized thermograms were recorded before and after subjects performed a specific rehabilitation program. Thermographic imaging was then repeated 4 weeks to 8 weeks after the initial thermogram. Among the subject group, thermal asymmetries were noted in the involved knees, but a specific abnormal thermal pattern could not be recognized. Changes in temperature and thermal patterns after exercise and over time were consistent within each subject, but were not consistent between subjects. Thermal asymmetries did not appear to resolve over time. It is felt that the pathology investigated by this study may involve many etiologies, therefore making it difficult to establish a single abnormal thermal pattern with regard to non-traumatic anterior knee pain.

Adolescent↗

PubMed1987

Classification of ligament injuries: why an anterolateral laxity or anteromedial laxity is not a diagnostic entity.

To interpret clinical laxity tests, the clinician must apply the kinematic and biomechanical concepts listed in Figure 12-13. These concepts have been briefly introduced here and are discussed in greater detail elsewhere. Figure 12-13 illustrates the importance of first selecting a laxity test to diagnose a specific ligament structure abnormality. The test selected, and the diagnostic information gained, is based on an understanding of the primary and secondary ligamentous restraints which are being tested. It is difficult to guess which ligaments are resisting specific joint displacements; therefore, biomechanical tests must first experimentally determine the restraints. Performing these tests obviates the first level of disagreement that existed when interpretations of clinical laxity tests were based only on "clinical impressions." The results of the laxity tests must be understood and communicated in terms of the six degrees-of-freedom system that determines abnormalities in motion. Resultant joint subluxations are readily understood by examining the medial and lateral tibiofemoral compartments separately. Our bumper model illustrates the different types of anterior subluxations that occur after anterior cruciate disruption. The final diagnosis of a ligament defect must be made in precise anatomic terms. In cases of partial disruption, or after healing occurs, the clinician must analyze the remaining functional capacity of the ligaments. In the future, newer diagnostic machines will provide even more detailed information enabling clinicians to determine the different types of compartmental subluxations under defined loading conditions. These machines will also provide measurements of ligament and joint stiffness. In this way, the functional deficits of the individual ligaments, and the joint as a whole, can be more readily characterized. The concepts that we have presented here can be applied qualitatively by the clinician, and in the future, they can be quantitatively applied. Our goal is to provide the basic scientific and clinical principles upon which the diagnosis and classification of ligament injuries should be based.

Humans↗

PubMed1986

Levels of knee joint research. How do we bridge the gap?

Explore the source record for details and available documents.

Biomechanical Phenomena↗

PubMed1985

The variable functional disability of the anterior cruciate ligament-deficient knee.

The goal of the authors has been to define the syndrome of the anterior cruciate ligament-deficient knee. These concepts have been applied to pertinent articles in order to explain the discrepancies and contrasting opinions in the literature. The authors have suggested guidelines for treatment based on the quantification of risk factors and a method for the prediction of the functional disability level of patients. Functional disability is activity level-related and is also related to the type of sport and the intensity level of play. Functional disability is symptomatically expressed by pain, swelling, and giving way, which must be correlated with a specific activity level.

Biomechanical Phenomena↗

PubMed1985

On the interpretation of our anterior cruciate ligament data.

Design of a synthetic replacement or selection of a biologic substitute requires detailed knowledge of the mechanical properties of the normal ligament. Femur-anterior cruciate ligament-tibia unit (ACL) data have been frequently used for this purpose, although not always properly. Mechanical properties of the human ACL-bone unit are reviewed. Ligament stiffness, elongation, and energy results are based on grip-to-grip motion and thus include ligament and limited bone deformations. Maximum bone-ligament-bone force in young donors (1730 +/- 66N) is higher than reported previously and represents only ligamentous failures. Methods for measuring tissue dimensions are provided and must be duplicated for obtaining accurate material property data. Bone-ligament-bone strain data are higher than those in reports where midsubstance collagen strains are measured and differ from data obtained on isolated ligaments. The authors have examined many factors that affect ligament-bone unit response. Increasing age weakens the tissue-bone preparation, and only when testing is performed at high rates will ligamentous failures predominate. Use of the authors' data in prosthetic ligament evaluation requires that the material be selected based on ligament bundle properties, the prosthesis be examined under similar testing conditions, and anticipated functional loads and margins of safety be determined.

Humans↗

PubMed1985

Controversy about treatment of the knee with anterior cruciate laxity.

A complete tear of the anterior cruciate ligament represents the initiation of a clinical syndrome characterized by a continuum of functional disability. The authors present here a risk factor checklist, based on statistics drawn from their previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofemoral factors, rehabilitation, and patient compliance. They also present their subjective and functional rating system in which six activity levels are related to pain, swelling, and giving way. The functional disability of the anterior cruciate insufficient knee is activity-level related. Thus, activity levels must be rigorously and comprehensively defined for adequate appreciation of the degree of existing disability. The authors also examined the reasons for the conflicting opinions on the functional disability of the anterior cruciate ligament syndrome that exists in the literature. Differences in subjective and objective rating systems; failure to specifically define preinjury and postinjury activity levels and associated symptoms; and different populations as to laxity, giving way episodes, and type of athletic activity (jumping, twisting activities versus light recreational pursuits) are but a few of the important differences that make comparisons between studies often invalid. Long-range treatment guidelines are necessary for management of the acute and chronic anterior cruciate ligament insufficient knee.

Disability Evaluation↗

PubMed1984

Effects of structure and strain measurement technique on the material properties of young human tendons and fascia.

It is generally recognized that the organization of collagen bundles in soft tissues strongly influences their material properties. To study this, sixty failure tests were conducted on double-layered fascia lata, 'isolated' parallel-bundled tendons (gracilis and semitendinosus) and parallel-bundled bone-patellar tendon-bone units taken from about the knees of eighteen young human donors (mean age of 26 yr). Surprisingly, most material parameters for the two-layered fascia lata did not differ significantly from corresponding values for the isolated tendons and tendon-bone preparations, suggesting their longitudinal fibers predominated during loading. Differences were present however between the gracilis tendon and all other tissues for both modulus and maximum stress. The large variations in reported maximum and failure strains for tendons, fascia and other collagenous tissues prompted the other phase of the study. During 15 of the 60 failure tests, surface markers were simultaneously filmed to determine; differences between local surface strains and grip to grip values; the amount of tissue slippage and/or failure occurring in the grips; and the effect of strain measurement technique on tissue moduli and failure energy densities. Maximum local strains were found to be 25-30% of grip strains for all tissues tested. Some slippage and/or failure could be seen in all isolated tissues which were gripped directly although their maximum grip strains were similar to values for tendon-bone units. For all tissues, two to three fold differences were also found in moduli and failure energy densities between grip and midregion measurements.

Adult↗

PubMed1984

Advances in the understanding of knee ligament injury, repair, and rehabilitation.

Knee injuries continue to present a complex set of clinical problems. The answers to these problems have recently been redefined by the application of sophisticated biomechanical research methods to the study of knee ligaments and joint function. This manuscript reviews contributions which our laboratory has made to the understanding of knee injury, highlighting those research findings which form the basis for our clinical treatment of knee ligament injuries. High strain-rate techniques for studying knee ligament failure have replaced the previous low strain-rate methods and distinguish the failure mechanism of ligaments from that of bone. Ligament function is now further defined by measuring the restraining force provided by specific ligaments, adding to the information provided by cutting studies. The development of the 6-degrees-of-freedom concept and the instrumented kinematic chain now permit precise analysis of joint position, motion, and laxity. Biomechanical evaluation of intra-articular anterior cruciate ligament substitution has emphasized the importance of selection of a high-strength graft material, meticulous surgical technique with attention to graft vascularity, precise location of graft fixation sites, judicious adjustment of graft tension, post-operative protection during tissue remodelling, and a carefully conceived rehabilitation program. Newer biomechanical research methods have provided a sound scientific foundation on which to base clinical decisions concerning the care of knee ligament injuries.

Adrenal Cortex Hormones↗

PubMed1984

Biomechanical analysis of human ligament grafts used in knee-ligament repairs and reconstructions.

Virtually all types of collagenous tissues have been transferred in and around the knee joint for intra-articular and extra-articular ligament reconstructions. However, the mechanical properties (in particular, strength) of such grafts have not been determined in tissues from young adult donors, where age and disuse-related effects have been excluded. To provide this information, we subjected ligament graft tissues to high-strain-rate failure tests to determine their strength and elongation properties. The results were compared with the mechanical properties of anterior cruciate ligaments from a similar young-adult donor population. The study indicated that some graft tissues used in ligament reconstructions are markedly weak and therefore are at risk for elongation and failure at low forces. Grafts utilizing prepatellar retinacular tissues (as in certain anterior-cruciate reconstructions) and others in which a somewhat narrow width of fascia lata or distal iliotibial tract is utilized are included in this at-risk group. Wider grafts from the iliotibial tract or fascia lata would of course proportionally increase ultimate strength. The semitendinosus and gracilis tendons are stronger, having 70 and 49 per cent, respectively, of the initial strength of anterior cruciate ligaments. The bone-patellar tendon-bone graft (fourteen to fifteen millimeters wide, medial or central portion) was the strongest, with a mean strength of 159 to 168 per cent of that of anterior cruciate ligaments. Patellar tendon-bone units, based on grip-to-grip motions, were found to be three to four times stiffer than similarly gripped anterior cruciate ligaments, while gracilis and semitendinosus tendon preparations had values that were nearly identical to those of anterior cruciate ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

Biomechanics of the knee-extension exercise. Effect of cutting the anterior cruciate ligament.

UNLABELLED: We conducted this study to determine the effective moment arm of the knee extensor mechanism and the conditions under which the anterior cruciate ligament is loaded during knee-extension exercises. The moment arm was calculated from measurement of the quadriceps force required to extend the knee with and without resistive weights placed at the foot, the leg weight, and the location of its center of gravity. Changes in three-dimensional joint motion after the anterior cruciate ligament was removed were considered to be an indication that the ligament was loaded. The quadriceps force rose during the initial phase of knee extension and remained nearly constant at an average value of 177 newtons between 50 and 15 degrees. With extension past 15 degrees it rose rapidly, reaching an average of 350 newtons at zero degrees of extension, and continued to increase with hyperextension. The addition of thirty-one newtons (seven pounds) at the foot approximately doubled the quadriceps force that was required to extend the knee. The effective moment arm of the extensor mechanism increased with knee extension, peaked at approximately 20 degrees, and rapidly decreased with further extension. No change was found in the quadriceps force or its effective moment arm when the anterior cruciate ligament was sectioned except in hyperextension, where the quadriceps force decreased in two of five specimens. There was, however, an increased anterior tibial displacement in the range of 30 degrees to full extension, suggesting that the anterior cruciate ligament is loaded in that flexion arc. CLINICAL RELEVANCE: This study demonstrates that very large quadriceps forces are required to accomplish the last 15 degrees of extension during leg-raising exercises, typically twice those required to reach 30 degrees of flexion. The large forces that are required to obtain full extension explain why an extensor lag occurs with quadriceps weakness even though a full passive range of motion is possible. Since thirty-one newtons (seven pounds) of resistive weight added at the foot approximately doubles the quadriceps forces required to extend the leg alone, using such weights can produce very large quadriceps forces and concurrent patellofemoral and tibiofemoral contact forces. Because the quadriceps force increases little as the leg is extended from 50 to 15 degrees, in patients with patellofemoral chondroses for whom a full range of joint motion is not desired, quadriceps exercises can be limited to the amount of extension without decreasing quadriceps force.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗

PubMed1983

Error analysis of a system for measuring three-dimensional joint motion.

In the past ten years there has been increased use of six-degree-of-freedom instrumented spatial linkages for the measurement of biological joint motions. In spite of the increased popularity, little information has been reported on the accuracy of these devices. In this paper, we present a two-part investigation of the accuracy of the instrumented spatial linkage when used to measure knee joint kinematics. In the first part, we present the results of a theoretical analysis and an experimental determination of the errors associated with spatial linkage systems. In the second part, we describe the errors associated with a bi-planar X-ray system used to obtain the coordinate transformation between the linkage ends and coordinate systems located in the bones comprising the joint. We found that the theoretical error analysis consistently overestimated the actual measurement error, thus providing an unreliable estimate of errors. The experimental study of both the linkage system and the bi-planar X-ray system demonstrated that the accuracy of displacement measurement is insensitive to large systematic errors in position measurement.

Biomechanical Phenomena↗