Generalized joint laxity (GJL), a condition in which most joints of the body move beyond the accepted normal range of motion, is present in many ballet and modern dancers. It has been associated with an increased risk of injury, decreased muscle strength, and greater landing forces. Increased joint laxity results in joint instability and may precede the development of osteoarthritis, which is associated with a reduction in cartilage thickness. We hypothesized that dancers with GJL would have decreased hip cartilage thickness, as well as greater hip adduction angles and greater ground reaction force on landings. Twenty female ballet and modern dancers (mean age: 21.0 ± 1.79 years; mean weight: 57.0 ± 5.71 kg; mean years of dance experience: 14.6 ± 3.53 years; mean hours of training per week: 19.2 ± 7.24 hours) were recruited from college and local dance programs and screened for GJL. Each dancer performed three forward drop landings onto a force plate and received an MRI on their dominant hip. There was a significant difference in hip cartilage thickness, as viewed in the frontal plane (GJL group average: 2.66 ± 0.33 mm; control group average: 3.14 ± 0.48 mm; p = 0.0160), between the groups. There were no significant differences in peak hip adduction angle on landing (GJL group average: 80.9 ± 5.04 degrees; control group average: 77.9 ± 5.78 degrees; p = 0.2269) or peak landing ground reaction force (GJL group average: 5.56 ± 1.28 body weights; control group average: 5.17 ± 0.82 body weights; p = 0.4274) between the generalized joint laxity group and the control group. Dancers with GJL have thinner cartilage at the hip. These results suggest that dancers with GJL may be at a greater risk for injury. Therefore, these dancers may benefit from strength training programs, rather than flexibility training, to help counteract the joint instability that can lead to injury.

Syfte och frågeställningar: Syftet var att genom en tvärsnittsstudie ta reda på om det fanns asymmetrier mellan dominant och icke-dominant ben hos skadefria kvinnliga fotbollsspelare gällande sagittal knälaxitet. Frågeställningar i studien var: Hur stor är den anteriora och posteriora knälaxiteten i dominant respektive icke-dominant ben uppmätt med KT-1000 vid belastningar på 20 lb, 30 lb samt vid ett manuellt maxtest i anterior riktning? Föreligger det någon sidoskillnad mellan dominant och icke-dominant ben gällande knälaxitet uppmätt med KT-1000 vid anteriora och posteriora belastningar på 20 lb, 30 lb samt vid ett manuellt maxtest i anterior riktning? Hur stor andel av deltagarna uppvisar en sidoskillnad av sagittal knälaxitet på ≥ 2 mm respektive ≥ 3 mm uppmätt med KT-1000 och hur är frekvensen fördelad mellan dominant och icke-dominant ben hos dessa? Metod: För att besvara syfte och frågeställningar genomfördes en tvärsnittsstudie där 56 kvinnliga fotbollsspelare inom division 1-2 deltog. Samtliga deltagare var ≥ 18 år, skadefria och hade spelat fotboll i minst 5 år. Mätinstrumentet KT-1000 användes för att registrera knälaxitet mellan dominant och icke-dominant ben. Alla mätningar utfördes av samma testledare och med samma mätinstrument och genomfördes i en standardiserad position inför träning. Statistiska beräkningar utfördes på belastningarna P-20/30 lb, A-20/30 lb, Total AP-20/30 lb samt ett manuellt maxtest. Data för knälaxitet registrerades och analyserades utifrån bendominans genom ett Mann Whitney U-test. Resultat: Resultatet visade på en liksidig knälaxitet av dominant och icke-dominant ben vid anteriora och posteriora mätningar. Medelvärden varierade mellan 1,91–2,91 mm i posterior riktning med en spridning på 1-4 mm. Motsvarande mätvärden i anterior riktning var 4,03–9,53 mm med en spridning på 4-19 mm. Inga signifikanta sidoskillnader framkom mellan dominant och icke-dominant ben men en ökad knälaxitet uppmättes i dominant ben vid samtliga belastningar i anterior riktning. En sidoskillnad på ≥ 2 mm visade sig hos 16,6-51,8 % av deltagarna beroende på vilken belastning som testades. Av dessa registrerades en ökad anterior knälaxitet i det dominanta benet hos 62,1-81,2 %. Slutsats: Genomförda mätningar av sagittal knälaxitet visade inga signifikanta skillnader gällande asymmetrier mellan dominant och icke-dominant ben hos kvinnliga fotbollsspelare. Vid belastningen A-MMT uppvisade drygt hälften av deltagarna en individuell sidoskillnad på ≥ 2 mm. Studien belyser vikten av ytterligare forskning för att kartlägga individuella sidoskillnader gällande sagittal knälaxitet. / Aim: The aim of the cross-sectional study was to find out if there were asymmetries between the dominant and non-dominant leg in non-injured female soccer players regarding sagittal knee laxity. The aims were: What´s the anterior and posterior knee laxity in the dominant and non-dominant leg measured with KT-1000 at loads of 20 lb, 30 lb, and a manual maximum test in anterior direction? Is there side-to-side differences in knee laxity between the dominant and non- dominant leg measured with KT-1000 at the anterior and posterior loads of 20 lb, 30 lb and with a manual maximum test in anterior direction? How many of the participants show a side-to-side difference of sagittal knee laxity of ≥ 2 mm and ≥ 3 mm measured with the KT-1000 and how is the frequency between the dominant and non-dominant leg of these distributed? Method: In order to answer the aim of the cross-sectional study 56 female soccer players from division 1-2 participated. All participants were ≥ 18 years old, no previous knee injury and had played football for at least 5 years. The KT -1000 instrument was used to measure knee laxity between the dominant and non-dominant leg. All measurements were performed by the same test leader, with the same test-instrument and in a standardized position. Statistical calculations were performed on loads P-20/30 lb, A-20/30 lb, Total AP-20/30 lb and a manual maximum test. Data for knee laxity were measured and analyzed by leg dominance through the Mann Whitney U-test. Results: The results of all participants showed an equivalent of knee laxity of dominant and non-dominant leg at the anterior and posterior measurements. Mean values ranged from 1.91 to 2.91 mm in the posterior direction (range of 1-4 mm). The corresponding measured values in the anterior direction were 4.03 to 9.53 mm (range 4-19 mm). No significant side-to-side differences were revealed between the dominant and non-dominant leg but an increased knee laxity was documented in the dominant leg at all loads in the anterior direction. Depending on the load 16.6 to 51.8 % of the participated had a side-to-side difference ≥ 2 mm. 62.1 to 81.2 % of these registered increased anterior knee laxity in the dominant leg. Conclusions: The measurements of sagittal knee laxity revealed no significant differences in the asymmetries between the dominant and non-dominant leg in non-injured female soccer players. At the A-MMT load over half of the participants revealed a side-to-side difference ≥ 2 mm. The study highlights the need for further research to identify individual side-to-side differences regarding sagittal knee laxity.

Women are more likely to sustain knee injuries (e.g., ACL tears) than their male counterparts. The mechanisms responsible for this disparity are unclear. However fluctuating hormones during the menstrual cycle may be an influencing factor since more ACL injuries have been observed preceding ovulation when estrogen levels increase. Previous research shows females to have increased muscle strength and altered neuromuscular activation prior to ovulation. These findings have not been replicated in females using oral contraceptives (OC). To date, no study has examined all of these factors simultaneously. The purpose of this study was to determine the effect of sex, hormones, and contraceptive use on neuromuscular function at 3 points during a menstrual cycle. A prospective cohort design with independent variables of group [male (n=10), female no-OC (n=10), female OC (n=10)], and testing session (1,2,3) was used to assess knee function (i.e., tibial translation, isometric strength, vertical leg stiffness, and neuromuscular activation) on physically active college-aged participants. Three testing sessions were scheduled throughout a typical menstrual cycle. Tibial translation was measured at the start of each testing session to assess ACL laxity, for handgrip, knee extensors and knee flexors strength. Area EMG activity of the rectus femoris (representing quadriceps) and biceps femoris (representing hamstrings) was recorded over 3 46cm drop jumps, and vertical leg stiffness was calculated based on measurements obtained by a force plate. A 3 (group) x 3 (testing session) MANOVA (p ≤ 0.05) was used to assess knee function, as defined by tibial translation, strength, EMG activation and vertical leg stiffness. A significant difference was found with respect to strength, as males overall displayed greater strength than both female groups. No other significant differences were found. Although this study attempted to explain the effect of estrogen on strength and neuromuscular function with an improved design, no conclusive evidence was found to further explain this relationship. Future studies should use more sensitive and objective measures to explore this dynamic on a greater sample size over multiple menstrual cycle phases. / Kinesiology

Elbow joint laxity is a problem that normally comes with age; it increases up to critical levels due to rupture or damage to the ligaments of the elbow and affects the stability and capacities of the joint, interfering even with daily activities. This work investigates the kinematics of the elbow through in-vivo experimental measurement. To this end, a platform based on Stewart Platform mechanism was built and used at the bioengineering labs of Brunel University in West London, the UK, to measure the six degrees of freedom of the joint. This thesis aims to develop a method to simulate such motion which could be used for elbow implant design and manufacture. This work contributes to both the basic science of joint movement measurement and to the clinical applications of diagnosing elbow illness. In addition this research presents the preliminary results for a design for elbow implants. Tracking system developed in house was used to measure the degrees of freedom in healthy elbow motion. A pilot study was performed to assess the joint motion and its repeatability. A group of volunteers with normal elbow movement was used to carry out this study. A Stewart Platform mechanism based on the tracking system was used in this study as a non-invasive tool to capture elbow joint motion and track the trajectory and pattern of the motion in three-dimensional space. This thesis aimed to develop a method to simulate the elbow joint motion that could potentially be used for the elbow implants design and there manufacture. The goal of this study was achieved by in vivo measurement of the elbow movement. It was found that the results vary from person to person, but a healthy pattern of motion can be distinguished from an abnormal pattern. To ensure the result, the motion of the right and left hand of each person was compared,allowing the behaviour of the elbow motion to be judged and the results can help surgeons to analyze the motion of the elbow joint and follow up suspicions of abnormal behaviour in the joint or trace any possible joint laxity. Furthermore, the errors involved with the mechanism were calculated and appropriate factors were applied to correct them. As part of this study the manufacturing of medical implants was reviewed and discussed.

Le but de cette thèse a été de redéfinir le diagnostic d’hyperlaxité de l’épaule. Ce travail s’appui sur plusieurs études cliniques, chirurgicales et d’analyse du mouvement. Pour mener ce travail, nous avons tout d’abord défini l’hyperlaxité telle qu’elle est actuellement décrite dans la littérature, ainsi que ses liens avec l’instabilité de l’épaule et son traitement. Ce premier chapitre décrit également les moyens techniques d’analyse du mouvement qui seront utilisés dans cette thèse. Ensuite, plusieurs études ont été proposées. L’étude 2 est une étude chirurgicale, qui a cherché à corréler la laxité capsulaire étudiée en per opératoire et l’hyperlaxité clinique. L’étude 3 a ensuite rechercher les moyens de rendre plus reproductible la mesure de la rotation externe dans le cadre de l’hyperlaxité. Les études 4 et 5 sont des études utilisant l’analyse du mouvement. La première a cherché à fiabiliser la mesure clinique des amplitudes articulaires de l’épaule en tentant d’analyser les facteurs d’erreur de mesure. La deuxième étude a ensuite eut pour but de définir le volume articulaire global du complexe articulaire de l’épaule et de préciser la relation de ce volume avec les différents degrés de liberté de l’épaule. Une dernière étude (Etude 6) a enfin permis de corréler le volume articulaire de l’épaule et les signes cliniques d’hyperlaxité. Enfin, le chapitre « conclusions générales et perspectives » rassemble les éléments de conclusion de ces différents travaux et a pour ambition de redéfinir le diagnostic d’hyperlaxité de l’épaule. Ce chapitre ouvre plusieurs perspectives. La première est de proposer des modifications de l’examen clinique de l’épaule et notamment pour le diagnostic d’hyperlaxité. La seconde est d’utiliser la description volumétrique de l’épaule dans d’autres situations physiologiques ou pathologiques. Enfin, nous rapportons les résultats préliminaires d’une étude anatomique visant à identifier la place respective de chaque articulation dans cette définition volumétrique des amplitudes articulaires de l’épaule. / The aim of this study was to give a new definition to shoulder hyperlaxity. This work was conduced with clinical, surgical andmotion capture experimentations. We first gave a definition of hyperlaxity, as described actually in the literature, and its link with shoulder instability and treatment. Chapter 1 described also motion capture technics used along this work. Then, several studies were proposed. Study n°2 was a surgical one, and tempted to correlate peroperative capsular laxity and hyperlaxity. Therafter, study n°3 looked for an optimized way to examine external rotation of the shoulder. Studies N° 4 and 5 used motion capture analysis to assess clinical shoulder examination patterns and global reachable shoulder space volume. This volume was finally correlated to shoulder sign of hyperlaxity in study n°6. The last chapter, « general conclusions and perspectives » gather together conclusions of each study and redefine hyperlaxity. Finally, we report our prospect, giving first results of an anatomical study exploring the volumetric definition of shoulder range of motion described previously

No description available.

Rupture of the anterior cruciate ligament (ACL) increases anterior-posterior (AP) laxity. The treatment aims to reduce or teach the patient to control this instability. Altered kinematics due to absent ligament function may result in knee arthrosis. This study evaluated the clinical and functional results of reconstructive surgery. Roentgen stereophotogrammetry (RSA) was used to analyse the stabilising effect of knee braces, reconstructive surgery and the kinematics of the knee with and without weight-bearing. The stability of the knees were assessed in 86 patients with ACL injuries before and/or after reconstructive surgery with the RSA technique and with the KT-1000 arthrometer The KT- 1000 (89 N) recorded smaller side to side differences than the RSA set-up without any correlation between the methods. The effect of three different braces on the AP and rotatory laxity was studied on patients with ACL injuries. The ECKO and the modified Lenox Hill reduced the instability with about one third. The SKB had no significant effect. None of the braces decreased the internal rotatory laxity but the Lenox Hill reduced the external rotatory laxity. Thirty-two patients with old ACL tears were treated with surgical reconstruction using the over the top technique (OTT) with or without augmentation. A small reduction in AP laxity was observed at the 6 month follow-up, The AP laxity was almost the same two years after as before surgery. No correlation was observed between the stability and knee function. Fifty-four patients with old unilateral anterior cruciate ligament injuries were randomised either to the over the top (OTT) or the isometric femoral tunnel position (ISO) at ACL reconstructive surgery. Seven of 24 (ISO) and 9 of 25 (OTT) had "normal" laxity two years after surgery. The patients operated with the ISO technique did not have better subjective knee function, muscle strength, functional performance or knee stability than patients operated with the OTT technique. The knee kinematics in patients with chronic unilateral ACL ruptures were examined during active extension in the supine position (13 patients) and during extension and weight-bearing (13 patients). The tibia displaced at an average 1.9 mm more anteriorly and 0.8 mm distally in the injured than in the intact knees during active extension. During extension and weightbearing the tibia was about 2 mm more posteriorly positioned than in the intact knee. The ACL rupture did not affect tibial rotations. Conclusions: The RSA recorded larger side to side differences in ACL injured and reconstructed patients than the KT-1000 arthrometer. Some knee braces are able to reduce AP laxity in ACL injured knees. No correlation was observed after surgery between knee laxity and functional scoring or tests. ACL reconstructions with isometric graft position on the femoral side did not offer any advantages compared to the over the top placement. Altered knee kinematics in the ACL injured knees were observed during knee extension with and without weight-bearing. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 6 uppsatser</p> / digitalisering@umu

Gymnastics is noted for involving highly specialized strength, power, agility and flexibility. Flexibility is perhaps the single greatest discriminator of gymnastics from other sports. The extreme ranges of motion achieved by gymnasts require long periods of training, often occupying more than a decade. Gymnasts also start training at an early age (particularly female gymnasts), and the effect of gymnastics training on these young athletes is poorly understood. One of the concerns of many gymnastics professionals is the training of the spine in hyperextension—the ubiquitous ‘arch’ seen in many gymnastics positions and movements. Training in spine hyperextension usually begins in early childhood through performance of a skill known as a back-bend. Does practising a back-bend and other hyperextension exercises harm young gymnasts? Current information on spine stretching among gymnasts indicates that, within reason, spine stretching does not appear to be an unusual threat to gymnasts’ health. However, the paucity of information demands that further study be undertaken.

No description available.

No description available.