Maximum Knee Flexion Angle Research Articles

Rôle de l’épaisseur du cartilage condylien postérieur dans le calcul de l’offset condylien. Influence sur la mobilité après prothèse totale du genou postéro-stabilisée

BackgroundThe association between posterior condylar offset (PCO) and maximal knee flexion remains controversial. The measured PCO in the previous studies is usually determined on the plain radiographs without taking into account the cartilage thickness. HypothesisFull-thickness cartilage-based PCO is a valid criterion to compare pre-operative and post-operative offset, and has a significant influence on post-operative knee flexion after total knee arthroplasty.Materials and methods: Ninety-five patients (107 knees) who underwent posterior-stabilized total knee arthroplasty were enrolled in a prospective study. Intra-operative measurement of cartilage thickness of the posterior femoral condyle was documented in all patients. Pre-operative and post-operative radiographic PCO was measured respectively on the true lateral view of the knee. True PCO was adjusted by adding cartilage thickness of the posterior femoral condyle. The relationship between the change in knee flexion and PCO difference was assessed using Pearson correlation analysis. ResultsThe post-operative radiographic PCO difference (2.01±2.05mm) was significantly greater than the true PCO difference (0.09±2.12mm). The mean post-operative change in maximum knee flexion angle was 5.4°±9.9°. No significant correlation was found between PCO difference and the change in knee flexion, regardless of radiographic (P=0.232) or cartilage-based measurements (P=0.693). ConclusionsFull-thickness cartilage-based PCO is an optimal criterion to estimate the change in PCO before and after total knee arthroplasty. However in this study, neither cartilage-based nor radiographic PCO appeared to have a significant influence on post-operative knee flexion after posterior-stabilized total knee arthroplasty. Level of evidenceLevel 4 cohort study.

Full-thickness cartilage-based posterior femoral condylar offset. Influence on knee flexion after posterior-stabilized total knee arthroplasty

BackgroundThe association between posterior condylar offset (PCO) and maximal knee flexion remains controversial. The measured PCO in the previous studies is usually determined on the plain radiographs without taking into account the cartilage thickness. HypothesisFull-thickness cartilage-based PCO is a valid criterion to compare preoperative and postoperative offset, and has a significant influence on postoperative knee flexion after total knee arthroplasty. Materials and methodsNinety-five patients (107 knees) who underwent posterior-stabilized total knee arthroplasty were enrolled in a prospective study. Intra-operative measurement of cartilage thickness of the posterior femoral condyle was documented in all patients. Preoperative and postoperative radiographic PCO was measured respectively on the true lateral view of the knee. True PCO was adjusted by adding cartilage thickness of the posterior femoral condyle. The relationship between the change in knee flexion and PCO difference was assessed using Pearson correlation analysis. ResultsThe postoperative radiographic PCO difference (2.01±2.05mm) was significantly greater than the true PCO difference (0.09±2.12mm). The mean postoperative change in maximum knee flexion angle was 5.4°±9.9°. No significant correlation was found between PCO difference and the change in knee flexion, regardless of radiographic (P=0.232) or cartilage-based measurements (P=0.693). ConclusionsFull-thickness cartilage-based PCO is an optimal criterion to estimate the change in PCO before and after total knee arthroplasty. However in this study, neither cartilage-based nor radiographic PCO appeared to have a significant influence on postoperative knee flexion after posterior-stabilized total knee arthroplasty. Level of evidenceLevel 4 Cohort Study.

Hyaluronic acid injections reduce knee load during stair climbing in knee osteoarthritis patients

Results: Student’s T-Test found statistically significant differences between patients with ankle fracture and control group for all parameters. Patients with ankle fracture had lower knee ROM during swing phase compared to control (average of 43 compared to 66.7 , respectively, p value< 0.001). Maximum knee flexion angle during stance was lower in patients with ankle fracture compared to control (average of 10.5 compared to 21.2 , respectively, p value< 0.001). Patients with ankle fracture had lower gait cycle thigh and calf ROM angles in comparison to control (averages of 30.8 , 52.9 in patients group compared to 42.5 ,78.9 in control group, respectively, p value< 0.001). Patients with ankle fracture had longer average stride duration than control (average of 1.4 seconds compared to 1 second, respectively, p value< 0.001). Analysis of differences between severity groups did not reveal any statistically significant findings. Conclusions: Gait kinematic characteristics vary between healthy people and patients recovering an ankle fracture injury during the short-term period post injury. The gait profile was not significantly different between fracture severity groups.

Differences and correlations in knee and hip mechanics during single-leg landing, single-leg squat, double-leg landing, and double-leg squat tasks

Landing and squat tasks have been utilized to assess lower extremity biomechanics associated with anterior cruciate ligament loading and injury risks. The purpose of this study was to identify the differences and correlations in knee and hip mechanics during a single-leg landing, a single-leg squat, a double-leg landing, and a double-leg squat. Seventeen male and 17 female recreational athletes performed landings and squats when kinematic and kinetic data were collected. ANOVAs showed significant differences (p < 0.00001) for maximum knee flexion angles, maximum hip flexion angles, maximum knee abduction angles, maximum hip adduction angles, and maximum external knee abduction moments among squats and landings. For maximum knee and hip flexion angles, significant correlations (r ≥ 0.5, p ≤ 0.003) were observed between the two landings and between the two squats. For maximum knee abduction and hip adduction angles and maximum external knee abduction moments, significant correlations were mostly found between the two landings, and between the single-leg squat and landings (r ≥ 0.54, p ≤ 0.001). Individuals are likely to demonstrate different profiles of injury risks when screened using different tasks. While a double-leg landing should be considered as a priority in screening, a single-leg squat may be used as a surrogate to assess frontal plane motion and loading.

Comparison of knee kinematics between meniscal tear and normal control during a step-down task

BackgroundDifficulty descending stairs is a common functional complaint reported by patients with meniscal tears. Abnormal knee movement patterns, such as dynamic valgus of the knee or decreased knee flexion during step down, have been reported by clinicians, but 3D knee kinematics descending stairs has never been described in this population. ObjectiveThe objective of this study is to compare 3D knee kinematics of individuals with a meniscal tear to that of control individuals during a step-down task. MethodsTen participants (6 men and 4 women) diagnosed with a meniscal tear and eleven healthy participants (3 men and 8 women) were recruited. Three-dimensional knee kinematic data were recorded during five step-down task trials with a VICON™ motion analysis system. The following parameters were extracted from the stance phase period only: maximum angle, minimum knee angle, and range of motion (maximum minus minimum) values for sagittal, frontal, and transverse planes. A group comparison was performed by ANOVA using the velocity of the step-down task as the control variable. FindingsSignificant reductions in the mean maximum knee flexion angle, knee flexion/extension range of motion, and knee abduction/adduction were observed among the participants with a meniscal tear compared to the control group (mean differences and P values were 4.7°, P=0.02; 5.4°, P=0.02 and 1.6°, P=0.03 respectively). Differences in rotation movement were not significant. InterpretationThis study is the first to describe and compare 3D knee kinematics of persons with a meniscal tear during a step-down task. These findings support that significant kinematic changes occur in the sagittal and frontal plane in individuals with a meniscal tear compared to normal controls.

Fatigue Alters Shock Attenuation during Landings of Sidestep Cutting

PURPOSE: Landings in fatigue condition are considered to be one of the factors to cause non-contact anterior cruciate ligament injury. It is known that fatigue alters lower extremity landing strategies and decreases the ability to attenuate shock during landing. However, lower extremity kinematics and shock attenuation during landings of sidestep cutting movement in fatigue condition has not been clarified. The purpose of this study is to reveal characteristic of lower extremity kinematics and shock attenuation during landings of sidestep cutting in fatigue condition. METHODS: Ten healthy female (age = 21.2±2.3 years old, height = 161.5±3.5 cm, weight = 53.9±8.5 kg) volunteered to participate in this experiment. All of them gave written informed consent before this experiment. They performed sidestep cutting movement before and after completing the fatigue protocol. The fatigue protocol was performed by using a bike ergometer. Lower kinematics and kinetics data were obtained from the three-dimensional motion analysis system with eight cameras (Vicon MX, Vicon Motion Systems, Oxford, UK) and three force plates (MSA-6, AMTI, Mass., USA). Maximum knee flexion angle, angular velocity and minimum angular acceleration were analyzed from initial contact to toe off during landings of sidestep cutting movement. Paired T test was used to identify differences of lower extremity kinematics between before and after completing fatigue protocol. RESULTS: Maximum knee flexion angle, angular velocity and times from initial contact to peak knee flexion angle had no differences between before and after completing the fatigue protocol. Minimum knee flexion acceleration increased significantly after completing the fatigue protocol (-146.9 vs. -165.7 rad/s2, P<0.05). CONCLUSIONS: Sidestep cutting movement in fatigue condition decelerated by increasing knee flexion angle in a short time. Maximum knee flexion angle and times from initial contact to peak knee flexion angle during landings of sidestep cutting movement were not altered. Our study indicates that fatigue decreased the ability to attenuate shock by decreasing minimum angular acceleration of knee flexion during landings of sidestep cutting movement.

Fatigue Reduces the Ability of Shock Attenuation during Landings of Drop Vertical Jump

PURPOSE: There are some researches focused on lower extremity kinematics during drop vertical jumps. It has been considered and recently attracted attention that fatigue decreases the ability to attenuate shock for lower extremity during landings. Fatigue on lower extremity kinematics is considered to reveal risks regarding non-contact anterior cruciate ligament injury. However, the effect of lower extremity kinematics on shock attenuation during drop vertical jump has not been clarified. The purpose of this study is to reveal characteristic of lower extremity kinematics on shock attenuation during drop vertical jump in fatigue condition. METHODS: Nine healthy college female (age = 21.1±2.5 years old, height = 161.1±3.6 cm, weight = 53.4±8.9 kg) volunteered to participate in this experiment. All of them gave written informed consent before this experiment. They performed drop vertical jumps before and after completing the fatigue protocol. The fatigue protocol was performed by using a bike ergometer. Lower kinematics and kinetics data were obtained from the three-dimensional motion analysis system with eight cameras (Vicon MX, Vicon Motion Systems, Oxford, UK) and three force plates (MSA-6, AMTI, Mass., USA). Maximum knee flexion angle, angular velocity and minimum angular acceleration were analyzed from initial contact to toe off during the first landing of drop vertical jump. Times from initial contact to peak knee flexion angle normalized to 100% of the first landing phase. Paired T test was used to identify differences of lower extremity kinematics between before and after completing fatigue protocol. RESULTS: Maximum knee flexion angle, angular velocity had no differences between before and after completing the fatigue protocol. Minimum knee flexion acceleration decreased significantly (-160.0 vs. -171.8 rad/s2, P<0.05) and times from initial contact to peak knee flexion angle shortened significantly after completing the fatigue protocol (47.4 vs. 45.5 %, P<0.05). CONCLUSIONS: Landings in fatigue condition decelerated by increasing knee flexion angle in a short time. Times from initial contact to peak knee flexion angle shortened, however, peak knee flexion angle were not altered in fatigue condition. Our study indicates that fatigue induced decreased the ability to attenuate shock by shortened times to peak knee flexion angle and decreased knee flexion acceleration during drop vertical jump.

Combined Effects of Drop Height and Fatigue on Landing Mechanics in Active Females.

Drop height and fatigue have been shown in isolation to affect landing mechanics and increase the risk of sustaining an anterior cruciate ligament injury. The purpose of this study was to identify the combined effects of drop height and fatigue on landing mechanics in recreationally active females. To assess this, 11 healthy, young adult females performed a series of drop jumps from randomized heights before and following a lower extremity fatiguing protocol. Findings for kinematic results demonstrated that hip flexion decreased at initial contact (P = .003) and maximum hip (P = .005) and knee flexion (P = .001) angles increased with increases in drop height. Kinetic results demonstrated that vertical ground reaction forces and joint moments and powers increased as height increased. Ground reaction forces and maximum knee valgus increased from pre- to postfatigue with interactive effects observed in frontal plane hip angle at impact and peak ankle moment. These results confirm the effects of drop height and fatigue and highlighted interactions between these factors. The differential effect of fatigue as a function of drop heights helps to illustrate potentially risky situations that should be addressed in training and injury prevention programs.

Assessment of Muscle Architecture of the Biceps Femoris and Vastus Lateralis by Ultrasound After a Chronic Stretching Program

To evaluate the chronic effects of a static stretching program on the muscle architecture of biceps femoris (BF) and vastus lateralis (VL) muscles in ultrasound (US) images. Randomized controlled longitudinal trial. Biomechanics Laboratory of Physical Education School of the Army, Rio de Janeiro, Brazil. The study included 24 healthy and physically active male volunteers (19.05 ± 1.40 years, 1.73 ± 0.07 m, and 73.15 ± 8.33 kg), randomly allocated to 1 of 2 groups: stretching group (SG, n = 12) and control group (n = 12). The SG was submitted to 3 sets of 30 seconds of static stretching 3 times a week during 8 weeks. Ultrasound equipment (7.5 MHz) was used for the evaluation of BF and VL muscle architecture variables (pennation angle, fiber length, muscle thickness, and fascicle displacement) before and after training. Knee range of motion (ROM) and isometric flexion and extension torque (TQ) were also measured. There were no significant changes in muscle architecture, TQ, and maximum knee flexion angle (P > 0.05). However, maximum knee extension angle (MEA) increased significantly in the SG (pretraining: 159.37 ± 7.27 degrees and posttraining: 168.9 ± 3.7 degrees; P < 0.05). Volume or intensity (or both) of the stretching protocol was insufficient to cause structural changes in the VL and BF muscles. The increase in MEA could not be explained by muscle architecture changes. To describe changes in the VL and BF muscle tendon unit using US after a long-term stretching program to identify which structures are responsible for ROM increase.

Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces.

[Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern.

A resistance band increased internal hip abduction moments and gluteus medius activation during pre-landing and early-landing

An increased knee abduction angle during jump-landing has been identified as a risk factor for anterior cruciate ligament injuries. Activation of the hip abductors may decrease the knee abduction angle during jump-landing. The purpose of this study was to examine the effects of a resistance band on the internal hip abduction moment and gluteus medius activation during the pre-landing (100ms before initial contact) and early-landing (100ms after initial contact) phases of a jump–landing–jump task. Thirteen male and 15 female recreational athletes (age: 21.1±2.4yr; mass: 73.8±14.6kg; height: 1.76±0.1m) participated in the study. Subjects performed jump–landing–jump tasks with or without a resistance band applied to their lower shanks. During the with-band condition, subjects were instructed to maintain their movement patterns as performing the jump-landing task without a resistance band. Lower extremity kinematics, kinetics, and gluteus medius electromyography (EMG) were collected. Applying the band increased the average hip abduction moment during pre-landing (p<0.001, Cohen׳s d (d)=2.8) and early-landing (p<0.001, d=1.5), and the average gluteus medius EMG during pre-landing (p<0.001, d=1.0) and early-landing (p=0.003, d=0.55). Applying the band decreased the initial hip flexion angle (p=0.028, d=0.25), initial hip abduction angle (p<0.001, d=0.91), maximum knee flexion angle (p=0.046, d=0.17), and jump height (p=0.004, d=0.16). Applying a resistance band provides a potential strategy to train the strength and muscle activation for the gluteus medius during jump-landing. Additional instructions and feedback regarding hip abduction, hip flexion, and knee flexion may be required to minimize negative changes to other kinematic variables.

A functional comparison of conventional knee–ankle–foot orthoses and a microprocessor-controlled leg orthosis system based on biomechanical parameters

The microprocessor-controlled leg orthosis C-Brace enables patients with paretic or paralysed lower limb muscles to use dampened knee flexion under weight-bearing and speed-adapted control of the swing phase. The objective of the present study was to investigate the new technical functions of the C-Brace orthosis, based on biomechanical parameters. The study enrolled six patients. The C-Brace orthosis is compared with conventional leg orthoses (four stance control orthoses, two locked knee-ankle-foot orthoses) using biomechanical parameters of level walking, descending ramps and descending stairs. Ground reaction forces, joint moments and kinematic parameters were measured for level walking as well as ascending and descending ramps and stairs. With the C-Brace, a nearly natural stance phase knee flexion was measured during level walking (mean value 11° ± 5.6°). The maximum swing phase knee flexion angle of the C-Brace approached the normal value of 65° more closely than the stance control orthoses (66° ± 8.5° vs 74° ± 6.4°). No significant differences in the joint moments were found between the C-Brace and stance control orthosis conditions. In contrast to the conventional orthoses, all patients were able to ambulate ramps and stairs using a step-over-step technique with C-Brace (flexion angle 64.6° ± 8.2° and 70.5° ± 12.4°). The results show that the functions of the C-Brace for situation-dependent knee flexion under weight bearing have been used by patients with a high level of confidence. The functional benefits of the C-Brace in comparison with the conventional orthotic mechanisms could be demonstrated most clearly for descending ramps and stairs. The C-Brace orthosis is able to combine improved orthotic function with sustained orthotic safety.

Effects of menarcheal age on the anterior cruciate ligament injury risk factors during single-legged drop landing in female artistic elite gymnasts.

Although numerous studies have demonstrated the relationship between maturation and lower extremity biomechanics during landing in team sport athletes, we are presently uninformed of any research that examined the single-legged drop landing biomechanics of gymnasts. The purpose of this study is to investigate the effects of the menarcheal age on the lower extremity biomechanics during a single-legged drop landing in female artistic elite gymnasts. Twenty-two female artistic elite gymnasts, between 9 and 36years of age, participated in this study. The participants were divided into two groups pre- (n=11) and post- (n=11) menarche and asked to perform a single-legged drop landing on top of a 30cm platform and land on a force plate. The statistical analysis consisted of the multivariate analysis with the level of significance set at p<0.05. The post-menarche group showed a decrease in their maximum knee flexion angle and increase in their maximum knee abduction angle, maximum internal tibial rotation angle, maximum knee abduction moment, and hamstring-quadriceps muscle activity ratio compared with the pre-menarche group during the single-legged drop landing. The post-menarche group showed an increased noncontact anterior cruciate ligament injury risk, due to their greater knee loads, compared with the pre-menarche group.

Partial harvesting technique in anterior cruciate ligament reconstruction with autologous semitendinosus tendon to prevent a postoperative decrease in deep knee flexion torque

BackgroundA significant decrease in deep knee flexion torque has been reported after harvesting the semitendinosus tendon for anterior cruciate ligament (ACL) reconstruction. Thus, we have developed a partial harvesting technique that leaves part of the width of the insertion of semitendinosus tendon by splitting it. Our hypothesis was that the partial harvesting technique would reduce postoperative functional deficits in deep knee flexion by achieving regeneration of harvested tendon without shortening. MethodsA total of 36 patients who underwent ACL reconstruction with an autologous semitendinosus tendon by means of either the conventional whole harvesting technique (whole-ST group, n=16) or the partial harvesting technique (partial-ST group, n=20) were included in this study. Clinical outcome, semitendinosus muscle length, and deep knee flexion torque were assessed 2years after surgery. ResultsNo significant group differences were found in terms of range of motion, Lysholm score, or anterior knee laxity. Shortening of the semitendinosus muscle was significantly less in the partial-ST group (mean 8mm) than in the whole-ST group (mean 36mm; P<0.001). The side-to-side ratio of isometric knee flexion torque in the prone position with 90° of knee flexion was statistically different between the partial-ST (87.0±20.4%) and whole-ST (55.3±13.9%; P<0.001) groups. ConclusionsThe present partial harvesting technique not only prevented shortening of the semitendinosus muscle, but also reduced the deficit in the maximum knee flexion angle in the standing position and a decrease in the deep knee flexion torque in the prone position with the partial harvesting technique compared to the nonoperated side with good clinical outcomes. Level of evidenceCase–control study, Level III.

Designs and performance of microprocessor-controlled knee joints

In this comparative study, three transfemoral amputee subjects were fitted with four different microprocessor-controlled exoprosthetic knee joints (MPK): C-Leg, Orion, Plié2.0, and Rel-K. In a motion analysis laboratory, objective gait measures were acquired during level walking at different velocities. Subsequent technical analyses, which involved X-ray computed tomography, identified the functional mechanisms of each device and enabled corroboration of the performance in the gait laboratory by the engineering design of the MPK. Gait measures showed that the mean increase of the maximum knee flexion angle at different walking velocities was closest in value to the unaffected contralateral knee (6.2°/m/s) with C-Leg (3.5°/m/s; Rel-K 17.0°/m/s, Orion 18.3°/m/s, and Plié2.0 28.1°/m/s). Technical analyses corroborated that only with Plié2.0 the flexion resistances were not regulated by microprocessor control at different walking velocities. The muscular effort for the initiation of the swing phase, measured by the minimum hip moment, was found to be lowest with C-Leg (-82.1±14.1 Nm; Rel-K -83.59±17.8 Nm, Orion -88.0±16.3 Nm, and Plié2.0 -91.6±16.5 Nm). Reaching the extension stop at the end of swing phase was reliably executed with both Plié2.0 and C-Leg. Abrupt terminal stance phase extension observed with Plié2.0 and Rel-K could be attributed to the absence of microprocessor control of extension resistance.

Can Technique Modification Training Reduce Knee Moments in a Landing Task?

Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee moments that load the ACL. This study examined whether landing technique training alters knee moments. Nineteen team sport athletes completed the study. Motion analysis and ground reaction forces were recorded before and after 6 weeks of technique modification. An inverse dynamic model was used to calculate three-dimensional knee loading. Pre- and postintervention scores were compared using paired t tests. Maximal knee flexion angle during landing was increased following training. There was no change in valgus or flexion moments, but an increase in peak internal rotation moment. This increase in internal rotation moment may increase the risk of ACL injury. However, the increased angle at which the peak internal rotation moment occurred at follow up may mitigate any increase in injury risk by reducing load transmission.

Effects of Stability by Using Different Types of Taping on Knee Joint during a Jump-stop Task

The purpose of this study was to investigate the effects of stability by using different types of taping on knee joint during a jump-stop task. Eight healthy males (aged=19.5±1.2 year, height=174.3±5.9 cm, weight=65.9±4.2 kg) were participated in this study. All the participants performed a jump-stop task under three knee taping conditions (traditional taping, Kinesio taping and non-taping). A high speed camera (Mega Speed 30 Ks), two AMTI force plates and four Biovision electromyography (EMG) systems were used synchronously to collect kinematic, kinetic and EMG data during the landing phase. The Kwon3D and DASYLab 6.0 software were used for further analyses of the data. The results indicated that smaller maximal anteroposterior force and fewer displacement of anteroposterior center of pressure were observed under the traditional and Kinesio taping conditions than the non-taping condition. A smaller average loading rate was reported with the Kinesio taping compared to the non-taping. Regarding kinematic parameters, an increased knee flexion angle at peak impact was observed under the traditional and Kinesio taping conditions than the non-taping condition. A larger maximum knee flexion angle was reported under the Kinesio taping compared to the non-taping. Furthermore, smaller mean EMG amplitudes were found in the rectus femoris and gastrocnemius muscles under the traditional and Kinesio taping conditions. The study concluded that the traditional and Kinesio taping techniques effectively increases the stability by giving a strong support and limiting the forward displacement of the anterior cruciate ligament at a jump-stop task. The Kinesio taping is also beneficial to increase the range of motion of knee joint.

Do knee concentric and eccentric strength and sagittal-plane knee joint biomechanics differ between jumpers and non-jumpers in landing?

The purpose of this study was to investigate the differences of knee concentric and eccentric strength and impact related knee biomechanics between jumpers and non-jumpers during step-off landing tasks. Ten male college swimming athletes (non-jumpers) and 10 track and volleyball athletes (jumpers) were recruited to participate in two test sessions: a muscle strength testing session of concentric and eccentric extension for dominant knee joint at 60°/s and 180°/s and a landing testing session. The participants performed five trials of step-off landing in each of four conditions: soft and stiff landing from 0.4m and 0.6m landing heights. The three-dimensional kinematics and ground reaction force were recorded simultaneously during step-off landing conditions. The results showed that the jumpers had significantly greater peak knee eccentric extension and concentric flexion torques compared to the non-jumpers. No significant group effects were found for peak vertical ground reaction force and knee range of motion during landing. The jumpers had significantly greater knee contact flexion angle, maximum knee flexion angle and initial knee extension moment compared to the non-jumpers. These results suggest that these athletes adopted a favorable impact attenuation strategy that is related to the greater knee eccentric muscle strength and training.

Anteroposterior Translation Does Not Correlate With Knee Flexion After Total Knee Arthroplasty

BackgroundStiffness after a TKA can cause patient dissatisfaction and diminished function, therefore it is important to characterize predictors of ROM after TKA. Studies of AP translation in conscious individuals disagree whether AP translation affects maximum knee flexion angle after implantation of a highly congruent sphere and trough geometry PCL-substituting prosthesis in a TKA.Questions/purposesWe investigated whether AP translation correlated with maximum knee flexion angle (1) in patients who were awake, and (2) who were under anesthesia (to minimize the effects of voluntary muscle contraction) in a TKA with implantation of a PCL-substituting mobile-bearing prosthesis.MethodsAP translation was examined under both conditions in 34 primary TKAs. Measurements under anesthesia were performed when the patients were having anesthesia for a contralateral TKA. Awake measurements were made within 4 days of that anesthetic session in patients who had no residual sedative effects. The average postoperative interval for the index TKA flexion measurements was 23 months (range, 6–114 months). AP translation was evaluated at 75° flexion using an arthrometer.ResultsThere was no correlation between postoperative maximum knee flexion and AP translation at 75° during consciousness. There was no correlation between postoperative maximum knee flexion and AP translation under anesthesia.ConclusionAP translation at 75° flexion did not correlate with postoperative maximum knee flexion in either awake or anesthetized patients during a TKA with implantation of a posterior cruciate-substituting prosthesis.Level of EvidenceLevel II, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Stiffness, intralimb coordination, and joint modulation during a continuous vertical jump test

This study analysed the modulation of jump performance, vertical stiffness as well as joint and intralimb coordination throughout a 30-s vertical jump test. Twenty male athletes performed the test on a force plate while undergoing kinematic analysis. Jump height, power output, ground contact time, vertical stiffness, maximum knee and hip flexion angles, and coordination by continuous relative phase (CRP) were analysed. Analysis of variance was used to compare variables within deciles, and t-tests were used to compare CRP data between the initial and final jumps. Results showed reduction in jump height, power output, and vertical stiffness, with an increase in contact time found during the test. Maximum knee and hip flexion angles declined, but hip angle decreased earlier (10–20% of the test) than knee angle (90–100%). No changes were observed in CRP for thigh–leg coupling when comparing initial and final jumps, but the trunk–thigh coupling was more in-phase near the end of the test. We conclude that fatigue causes reduction in jump performance, as well as changes in stiffness and joint angles. Furthermore, changes in intralimb coordination appear at the last 10% of the test, suggesting a neuromotor mechanism to counterbalance the loss of muscle strength.