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Concept: Sartorius muscle


BACKGROUND: A common goal of persons post-stroke is to regain community ambulation. The plantar flexor muscles play an important role in propulsion generation and swing initiation as previous musculoskeletal simulations have shown. The purpose of this study was to demonstrate that simulation results quantifying changes in plantar flexor activation and function in individuals post-stroke were consistent with (1) the purpose of an intervention designed to enhance plantar flexor function and (2) expected muscle function during gait based on previous literature. METHODS: Three-dimensional, forward dynamic simulations were created to determine the changes in model activation and function of the paretic ankle plantar flexor muscles for eight patients post-stroke after a 12-weeks FastFES gait retraining program. RESULTS: An median increase of 0.07 (Range [-0.01,0.22]) was seen in simulated activation averaged across all plantar flexors during the double support phase of gait from pre- to post-intervention. A concurrent increase in walking speed and plantar flexor induced forward center of mass acceleration by the plantar flexors was seen post-intervention for seven of the eight subject simulations. Additionally, post-training, the plantar flexors had an simulated increase in contribution to knee flexion acceleration during double support. CONCLUSIONS: For the first time, muscle-actuated musculoskeletal models were used to simulate the effect of a gait retraining intervention on post-stroke muscle model predicted activation and function. The simulations showed a new pattern of simulated activation for the plantar flexor muscles after training, suggesting that the subjects activated these muscles with more appropriate timing following the intervention. Functionally, simulations calculated that the plantar flexors provided greater contribution to knee flexion acceleration after training, which is important for increasing swing phase knee flexion and foot clearance.

Concepts: Knee, Sartorius muscle, Flexion, Extension, Semitendinosus muscle, Semimembranosus muscle, Popliteus muscle, Musculoskeletal system


INTRODUCTION: Many studies regarding spinal sagittal alignment were focused mainly on above-hip structures, not considering the knee joint. Knee-spine syndrome was proposed earlier, but the mechanism of this phenomenon has not been revealed. The aim of the study was to demonstrate how spinopelvic alignment and sagittal balance change in response to simulated knee flexion in normal non-diseased population. METHODS: Thirty young male were enrolled in the study cohort. Two motion-controlled knee braces were used to simulate knee flexion of 0°, 15°, and 30° settings. Whole spine and lower extremity lateral radiographs were taken at each knee setting of 0°, 15°, and 30° flexion. Spinal and pelvic parameters were measured, including two angular parameters, femoropelvic angle (FPA) and femoral tilt angle (FTA). RESULTS: The following equation can be made; PT (pelvic tilt) = FPA + FTA. The mean values of FPA and lumbar lordosis decreased significantly at 15° and 30° knee settings compared to the parameters at the 0° knee setting, while the mean values of pelvic tilt and sacral slope rarely changed. Results also showed FTA was not correlated with PT, but strongly correlated with FPA (R = -0.83, p < 0.01). CONCLUSIONS: The knee flexion resulted in decrease of lumbar lordosis without a significant change of pelvic posture in non-diseased population group.

Concepts: Vertebral column, Knee, Joint, Sartorius muscle, Flexion, Extension, Semimembranosus muscle, Popliteus muscle


Recent scientific advances in the treatment of hip and knee osteoarthritis (OA) relating to education, exercise, weight control and passive non-pharmacological and non-surgical treatments such as manual therapy, orthoses/orthotics and other aids are described.

Concepts: Obesity, Sartorius muscle


BACKGROUND: The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. METHODS: In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. FINDINGS: The knee experienced mean peak loadings of 2.4-4.6×body weight at the patellofemoral joint, 6.9-9.0×body weight at the tibiofemoral joint, 0.3-1.4×body weight anterior tibial shear and 1.0-3.1×body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4×body weight and the ankle 8.9-10.0×body weight. INTERPRETATION: The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations.

Concepts: Knee, Joint, Sartorius muscle, Knowledge, Synovial joint, Joints, Human leg, Popliteal artery


Objective: To evaluate the effects of a 20-min gait training session using the Lokomat® combined with a negative kinematic constraint on the non-paretic limb and a positive kinematic constraint on the paretic limb, on peak knee flexion and other biomechanical parameters in chronic hemiparetic subjects. Design: Preliminary study, before-after design. Subjects: Fifteen hemiparetic subjects. Methods: Subjects were evaluated using 3-dimensional gait analysis before, immediately after the end of the training, and after a 20-min rest period. The positive constraint increased the range of motion of the paretic limb (hip and knee), while the negative constraint reduced the range of motion of the non-paretic limb (hip and knee). Results: Peak knee flexion and other, kinematic, kinetic and spatiotemporal, parameters were significantly improved following the training session. These positive effects occurred predominantly in the paretic limb. Moreover, there was no worsening of biomechanical parameters of the non-paretic limb despite the use of negative constraint on this limb. These effects persisted for at least 20 min following the end of the gait training session. Conclusion: This type of training may be effective to improve gait in hemiparetic patients. A larger investigation of the training programme is justified.

Concepts: Stroke, Knee, Sartorius muscle, Classical mechanics, Kinematics, Flexion, Extension, Semimembranosus muscle


Slipped capital femoral epiphysis (SCFE) is a common hip condition in adolescents, most commonly treated with in-situ cannulated screw fixation. We report two cases of cannulated screw failure within the femoral neck following SCFE fixation. To our knowledge, this is the first reported case in the literature of cannulated screw failure within the femoral neck following in-situ screw fixation for unstable SCFE. Level of evidence: Level IV.

Concepts: Report, Sartorius muscle, Case, Slipped capital femoral epiphysis


BACKGROUND: Damage to the hip can occur due to impingement or instability caused by anatomic factors such as femoral and acetabular version, neck-shaft angle, alpha angle, and lateral center-edge angle (CEA). The associations between these anatomic factors and how often they occur in a painful hip are unclear but if unaddressed might explain failed hip preservation surgery. QUESTIONS/PURPOSES: We determined (1) the influence of sex on the expression of impingement-related or instability-related factors, (2) the associations among these factors, and (3) how often both impingement and/or instability factors occur in the same hip. METHODS: We retrospectively reviewed a cohort of 170 hips (145 patients) undergoing MR arthrography of the hip for any reason. We excluded 58 hips with high-grade dysplasia, Perthes' sequelae, previous surgery, or incomplete radiographic information, leaving 112 hips (96 patients). We measured femoral version and alpha angles on MR arthrograms. Acetabular anteversion, lateral CEA, and neck-shaft angle were measured on pelvic radiographs. RESULTS: We observed a correlation between sex and alpha angle. Weak or no correlations were observed between the other five parameters. In 66% of hips, two or more (of five) impingement parameters, and in 51% of hips, two or more (of five) instability parameters were found. CONCLUSIONS: Patients with hip pain frequently have several anatomic factors potentially contributing to chondrolabral damage. To address pathologic hip loading due to impingement and/or instability, all of the anatomic influences should be known. As we found no associations between anatomic factors, we recommend an individualized assessment of each painful hip. LEVEL OF EVIDENCE: Level III, prognostic study. See Instructions for Authors for a complete description of levels of evidence.

Concepts: Physician, Pain, Hip, Pelvis, Sartorius muscle, Human anatomy, Iliopsoas, Obturator internus muscle


The purpose of this study was to investigate the relationship between femoral neck version and pre- and intraoperative findings in hips with femoroacetabular impingement (FAI). The authors retrospectively reviewed prospectively collected data on 188 patients (204 hips) who underwent hip arthroscopy for FAI and labral pathology. Femoral version was measured on magnetic resonance imaging by a fellowship-trained musculoskeletal radiologist. The study group comprised 100 men and 88 women with a mean age of 35 years (range, 18 to 62 years). Mean femoral version was 9° (range, -10° to 27°). No relationship was found between femoral version and patient demographics (ie, age, sex, weight, height, and body mass index). A significant correlation was found between version and degrees of external rotation (r=-0.208; P=.027) and internal rotation (r=0.231; P=.002) on physical examination. Patients with femoral version less than 5° had significantly increased external rotation (P=.027). Intraoperative findings demonstrated that femoral version greater than 15° was related to larger labral tears that averaged approximately 38 mm in size, whereas patients with anteversion less than 5° had tear sizes measuring 30 mm and patients with angles between 5° and 15° had tear sizes averaging 34 mm (P=.008). Hips with femoral version greater than 15° were 2.2 times more likely (95% confidence interval, 1.2 to 4.1) to have labral tears that extended beyond the 3 o'clock position, denoting more anterior tears. Hips in which a psoas release was performed had higher version angles (8° vs 11°; P=.023).

Concepts: Measurement, Medical imaging, Nuclear magnetic resonance, Magnetic resonance imaging, Body mass index, Radiology, Sartorius muscle, Nontotient


This investigation examined the characteristics of a failed back squat. Subjects were instructed to perform 3 repetitions of a barbell squat with a 3 repetition maximum load while instrumented for biomechanical analyses and standing atop force platforms. Inverse dynamics calculations were used to determine the net joint moment (NJM) power, work, and energy of the hip, knee, and ankle. Five subjects failed to complete all 3 repetitions, allowing for comparisons between a successful and the failed repetition. While the NJM power and work were lower at all 3 joints during the failed attempt, the only statistically significant differences were at the hip. These findings suggest that the energy generated by the hip joint NJM limited performance of the task. However, examination of the NJM energy generation over time on an individual basis uncovered some features that were masked by the aggregated group mean data. For some subjects, the knee NJM limited the movement. Additionally, negligible to modest compensations occurred between the hip and knee NJM: a decreased energy generated by one NJM was often accompanied by an increase in energy generated at the other. A limiting joint, or “weak link,” may explain failure to complete a lift. Interventions should address the limiting joint on an individual-specific basis, and incorporate assistive exercises that target these deficiencies.

Concepts: Statistics, Statistical significance, Knee, Joint, Force, Sartorius muscle, Synovial joint, Joints


The purpose of this study was to investigate changes in muscle oxygenation of knee extensor and plantar flexor muscles during repeated muscle contractions under the same condition. In addition, we compared changes in muscle oxygenation between superficial and deep regions of both muscles.

Concepts: Knee, Muscle contraction, Sartorius muscle, Flexion, Extension, Semitendinosus muscle, Semimembranosus muscle, Popliteus muscle