Patellar kinematics, part I: the influence of vastus muscle activity in subjects with and without patellofemoral pain

BACKGROUND AND PURPOSE: Reduced motor unit activity of the vastus medialis muscle relative to the vastus lateralis muscle has been implicated as a cause of lateral patellar subluxation. The purpose of this study was to assess the influence of vastus muscle motor unit activity on patellar kinematics. SUBJECTS: Twenty-three women (mean age=26.8 years, SD=8.5, range=14-46) with a diagnosis of patellofemoral pain and 12 women (mean age=29.1 years, SD=5.0, range=24-38) without patellofemoral pain participated. Only female subjects were studied because of potential biomechanical differences between sexes. METHODS: Patellar kinematics (kinematic magnetic resonance imaging) and vastus muscle electromyographic (EMG) activity using indwelling electrodes were measured during resisted knee extension. Measurements of medial and lateral patellar displacement and tilt obtained from magnetic resonance images were correlated with normalized vastus lateralis:vastus medialis oblique muscle and vastus lateralis:vastus medialis longus muscle EMG ratios at 45, 36, 27, 18, 9, and 0 degrees of knee flexion using a stepwise regression procedure. RESULTS: The vastus lateralis:vastus medialis longus muscle EMG ratio contributed to the prediction of lateral patellar glide at 27 degrees of knee flexion (r=-.48), with increased vastus medialis longus muscle activity being associated with greater lateral patellar displacement. A similar inverse relationship was evident with lateral patellar tilt at 36, 27, 18, and 9 degrees of knee flexion. CONCLUSION AND DISCUSSION: These results suggest that increased motor unit activity of the vastus medialis muscle appears to be associated with abnormal patellar kinematics in women, but it is not necessarily a cause of abnormal patellar kinematics.     

A Study on the Differences of Quadriceps Femoris Activities by Knee Alignment during Isometric Contraction

[Purpose] This study attempted to identify how genu varum or valgum affects the electromyographic activities of the vastus medialis, vastus lateralis, and rectus femoris during knee isometric contraction. [Subjects] Fifty-two healthy young adults were enrolled in this study. They were enrolled and classified into three groups by knee alignment conditions: the genu varum, genu valgum, and control groups. [Methods] The electromyographic activity ratio of the vastus medialis to the vastus lateralis and rectus femoris were calculated using the percentage of maximum voluntary contraction. The participants contracted their quadriceps during isometric contraction at 30 and 60° of knee flexion. [Results] The genu varum group had more activity in the vastus medialis than in the vastus lateralis and rectus femoris, whereas the genu valgum group had more activity in the vastus lateralis and rectus femoris than in the vastus medialis. There was a significant difference in the muscle activity ratio between the vastus medialis and vastus lateralis by angle of knee flexion degree only in the genu valgum. There were no significant differences in any of the three groups in terms of the muscle activity ratio of the vastus medialis to the rectus femoris by angle of knee flexion. [Conclusion] The quadriceps femoris was used for different strategies according to knee alignment during isometric contraction at 30 and 60°. This study suggests that rehabilitation training programs used to strengthen the quadriceps should consider the knee alignment conditions of the target subjects.Key words: Electromyography, Quadriceps muscle, Isometric contraction     

运动疗法对膝关节骨关节炎患者肌发电量的影响

目的：研究肌发电量在膝关节骨关节炎患者股四头肌肌力训练中的变化情况及股四头肌的详细变化情况。方法：采用股四头肌的等长收缩运动训练方法和其他疗法进行比较,用肌电图进行股直肌、股内侧肌、股外侧肌的肌发电量测定,同时用“膝关节功能评定表”进行功能的辅助评定。结果：两种方法治疗后,股直肌、股内侧肌的肌发电量都有显著的变化,尤其以股内侧肌的变化极显著,股外侧的肌发电量无显著变化。两种方法中肌力训练较其他治疗方法在提高肌发电量方面更为有效。结论：股内侧肌在膝关节肌力锻炼中的变化最大,说明股内侧肌比股直肌和股外侧肌在稳定膝关节方面更重要。股外侧肌在训练中的变化最小,在维护膝关节的稳定性方面起的作用比股内侧肌和股直肌小;肌力训练比其他方法在增加肌发电量方面更有效,更能提高膝关节的稳定性。     

EMG activity of the vastus medialis oblique and the vastus lateralis in their role in patellar alignment

Using intramuscular electrodes the integrated electromyographic activity of the vastus medialis oblique and the vastus lateralis was examined in twenty normal females. The activity was recorded during the last thirty degrees of distal segment stabilized knee extension, when patellar subluxation commonly occurs. The electromyographic activity was normalized and expressed as a percentage of a maximal isometric contraction. Both muscles exhibited low levels of activity with no significant differences between the two. This study provides a quantitative method to assess whether muscular imbalance is present in patients with patellar subluxation.     

Changes in muscle activity during fast, alternating flexion-extension movements of the knee

The effects of high frequency alternating knee flexion-extension on muscle activity of the quadriceps and hamstring muscle groups has been investigated. Standard loads were used for each subject. The muscle activity in vastus medialis, vastus lateralis, rectus femoris and the lateral hamstrings were recorded by electromyography during increasing velocities. Rectus femoris and hamstrings were found to increase their activities significantly with increasing speed while vastus medialis and vastus lateralis showed no such change. The individual thigh muscles thus differ in function in relation to the velocity of movement.     

Relationship between the EMG ratio of muscle activation and bony structure in osteoarthritic knee patients with and without patellar malalignment.

OBJECTIVE: The aim of this study was to compare muscle activation patterns and patellofemoral joint morphologies between patients with knee osteoarthritis with and without patellar malalignment. SUBJECTS: The subjects were divided into 3 groups. Group A comprised 11 patients with symptomatic knee osteoarthritis without patellar malalignment. Group B comprised 14 patients with symptomatic knee osteoarthritis with patellar malalignment. Group C comprised 10 age-matched subjects with non-knee osteoarthritis as controls. METHODS: Isokinetic dynamometry with surface electromyography was used to measure maximal muscle activity in terms of vastus medialis oblique/vastus lateralis ratios. Merchant's view was taken to analyse the bony anatomy of the patellofemoral joint. Recordings were made at angular velocities of 80, 120 and 240 masculine/sec. RESULTS: The electromyographic ratios of group B were lower than groups A and C for all testing velocities (p<0.05). Group B also had larger sulcus angles, lateral patellar tilt and displacement. The electromyographic ratios correlated negatively with sulcus angles. CONCLUSION: Subjects with knee osteoarthritis with patellar malalignment exhibited an imbalance in quadriceps contraction, as confirmed by altered vastus medialis oblique/vastus lateralis ratios associated with larger sulcus angles of the patellofemoral joints. The sulcus angle may be an important contributing factor in causing abnormal patellar tracking in knee osteoarthritis.     

Alterations in patellofemoral kinematics following vastus medialis transection in the anterior cruciate ligament deficient rabbit knee

Background

Anterior cruciate ligament deficiency and quadriceps muscle weakness are considered to be important risk factors for aberrant patellar tracking and subsequent patellofemoral osteoarthritis. However, data from in vivo experiments looking at dynamic patellar joint kinematics and muscle force are scarce. Therefore, the purpose of this study was to evaluate the effects of anterior cruciate ligament transection and loss of vastus medialis force on patellar tracking in the rabbit knee in vivo.

Methods

Eight skeletally mature New Zealand White Rabbits, weighing 6.0 kg (0.6 kg standard deviation) were used. The experimental trials consisted of active, concentric and eccentric movements of the knee joint. Measurements were performed with the intact, the anterior cruciate ligament deficient, and the vastus medialis transected knee. Patellofemoral kinematics (shift, rotation) were quantified from high speed video.

Findings

Following anterior cruciate ligament transection, patellar tracking occurred more laterally, and caused a significant lateral rotation of the patella. The addition of vastus medialis transection did not alter patellar tracking or rotation significantly for any of the force-matched experimental conditions.

Interpretation

The loss of the anterior cruciate ligament results in lateral patellar shift and rotation while the loss of vastus medialis muscle force does not affect patellar tracking or rotation in the anterior cruciate ligament deficient knee. We suggest that the current results should be considered carefully in future interpretations of knee extensor imbalance. More research is needed to describe the contribution of vastus medialis muscle strength to medial patellofemoral stability and confirm these results in the human knee.     

Quantity and Quality of the Lower Extremity Muscles in Women with Knee Osteoarthritis

The objective of the study described here was to compare lower extremity muscle quantity and quality between individuals with and those without knee osteoarthritis (OA). Twenty-one women with knee OA (mild, n = 8; severe, n = 13) and 23 healthy patients participated. Ultrasonography was used to measure muscle thickness (MT) and echo intensity (EI) of the rectus femoris, vastus intermedius, vastus lateralis, vastus medialis, biceps femoris, gluteus maximus, gluteus medius, gastrocnemius, soleus and tibialis anterior. MTs of the vastus medialis and vastus intermedius were smaller, and EIs of the vastus medialis, vastus intermedius, gluteus medius and tibialis anterior were larger, in the severe OA group compared than in the healthy group. Compared with the healthy group, the mild OA group had decreased MT and enhanced EI. Changes in quality and quantity occurring with knee OA progression differed among muscles. In the vastus medialis, change was observed from an earlier stage.     

Changes in patellofemoral joint contact pressures caused by vastus medialis muscle weakness

Background

Patellofemoral joint pain is a common knee disorder, but its underlying causes remain unknown. One proposed mechanism is an imbalance in force in the knee extensor muscles. Specifically, the vastus medialis and vastus lateralis are thought to play a crucial role in proper patellar tracking, and weakness in vastus medialis is thought to lead to a lateral shift in the patella causing increased contact pressures and pain. The purpose of this study was to create an animal model of vastus medialis weakness and to test the effect of this weakness on patellofemoral contact pressures.

Methods

Experiments were performed using New Zealand white rabbits (mass 4.9–7.7 kg, n = 12). Loading of the patellofemoral joint was produced by femoral nerve stimulation of the knee extensor muscles. Knee extensor imbalance was produced by vastus medialis ablation. Fuji pressure sensitive film was used to record contact area, shape and pressures for maximal and sub-maximal, matched-force contractions at knee angles of 30°, 60°, and 90°.

Findings

Patellofemoral peak pressures, average pressures, contact areas and contact shapes were the same across all loading conditions for matched-force contractions before and after elimination of vastus medialis.

Interpretation

We conclude that vastus medialis weakness does not cause changes in patellofemoral contact pressures. Since the muscular and knee joint geometry in rabbits and humans is similar, we question the idea of vastus medialis weakness as a cause of patellar mal-tracking and patellofemoral joint pain.     

Patellar taping does not affect the onset of activities of vastus medialis obliquus and vastus lateralis before and after muscle fatigue

OBJECTIVE: This study examined the immediate effect of patellar taping with a standard force on the onset of vastus medialis obliquus and vastus lateralis activities before and after muscle fatigue in able-bodied subjects. DESIGN: This study tested 29 mature able-bodied subjects. The surface electromyographic onset time of their vastus medialis obliquus and vastus lateralis was measured after a posteroanterior perturbation at the knee in a single-legged standing position. The measurements were taken under three conditions in random order of true patellar taping, sham patellar taping, and no patellar taping. Afterward, subjects performed a knee-extension exercise until their quadriceps fatigued, and the above tests were repeated to test the effect of fatigue on the outcome. RESULTS: There was no statistically significant difference with patellar taping on the electromyographic onset time of the vastus medialis obliquus and vastus lateralis compared with the placebo-taping and no-taping conditions (P = 0.455). There was no statistically significant difference in onset of vastus medialis obliquus and vastus lateralis muscles before and after muscle fatigue (P = 0.304). CONCLUSIONS: The present study suggests that patellar taping does not enhance the temporal activation of vastus medialis obliquus in both fatigue and nonfatigue conditions on able-bodied subjects.     

Neuromuscular and architectural alterations of the vastus lateralis muscle in elderly patients with unilateral knee osteoarthritis]

AIM: The aim of this study was to determine the mechanisms involved in muscle weakness in elderly patients with unilateral knee osteoarthritis. SUBJECTS: We investigated 7 patients with unilateral knee osteoarthritis. METHOD: We measured knee position sense and isometric maximal voluntary contraction (MVC) of the knee extensors. Electromyographic (EMG) measurement of biceps femoris (BF), rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) involved different levels of contraction (25, 50, 75 and 100% MVC). Neuromuscular efficiency of quadriceps was also calculated (MVC/EMG). Ultrasonography was used to investigate the VL architectural parameters at the median part of the VL for different levels of contraction (25, 50, and 75% MVC). All tests were performed on the osteoarthritic and healthy knees. RESULTS: The quadriceps MVC of the affected knee was reduced by 30%. The VL thickness of the affected knee was 10% smaller than that of the unaffected knee. VL activity seen on EMG did not differ between knees, but RF, VM and BF activity was greater in the unaffected than affected knee. Neuromuscular efficiency was higher (26%) in the unaffected knee. Knee position sense was reduced by 33% in the affected knee. CONCLUSION: Quadriceps weakness associated with knee osteoarthritis seems to be related to changes in muscle rather than pennation angle and changes in fascicule length.     

Electromyographic activity of the quadriceps components during the final degrees of knee extension

An imbalance in the recruitment patterns of the quadriceps muscle has been implicated in patellofemoral knee pain; however ambiguity remains in the normal recruitment patterns of this muscle. We investigated the activity of the quadriceps muscle during the final degrees of knee extension, specifically in the medial and lateral components. Sixteen healthy subjects (age; 22.5 (± 3.4) years, body mass; 67.5 (± 12.1) kg and height; 173.9 (± 10.4) cm) participated.Torque and electromyographic (EMG) activity of the quadriceps muscle were measured during isokinetic and isometric knee extensions. Torque and EMG activity reduced in all component muscles during the final degrees of isokinetic extension, but this did not occur during isometric contractions at similar angles. Normalised activity of rectus femoris (RF) was greater than that of vastus lateralis (VL) and vastus medialis obliquus (VMO) during the final degrees of isokinetic knee extension at 30°/sec; there were no differences between any component muscles at the higher velocities. VMO:VL and vastus medialis longus (VML):VL ratios were unchanged during knee extensions, except that VML:VL ratio increased significantly during the final degrees of extension at 30°/sec. Future work should compare these results with people with anterior knee pain, and explore this further during activities of daily living.     

Effects of squats accompanied by hip joint adduction on the selective activity of the vastus medialis oblique

[Purpose] This study evaluated the effective selective activation method of the vastus medialis oblique for knee joint stabilization in patients with patellofemoral pain syndrome. [Subjects and Methods] Fifteen healthy college students (9 males, 6 females); mean age, height, and weight: 22.2 years, 167.8 cm, and 61.4 kg, respectively) participated. The knee angle was held at 60°. Muscle activities were measured once each during an ordinary squat and a squat accompanied by hip joint adduction. The muscle activities of the vastus medialis oblique and vastus lateralis were measured by electromyography for five seconds while maintaining 60° knee flexion. Electromyography signals were obtained at a sampling rate of 1,000 Hz and band pass filtering at 20–50 Hz. The obtained raw root mean square was divided by the maximal voluntary isometric contraction and expressed as a percentage. The selective activity of the vastus medialis oblique was assessed according to the muscle activity ratio of the vastus medialis oblique to the vastus lateralis. [Results] The activity ratio of the vastus medialis oblique was higher during a squat with hip joint adduction than without. [Conclusion] A squat accompanied by hip joint adduction is effective for the selective activation of the vastus medialis oblique.Key words: Patellofemoral pain syndrome, Vastus medialis oblique, Squat     

膝骨关节炎患者股内侧肌、股直肌和股外侧肌间的协调性

目的应用表面肌电图和等速肌力测定方法比较膝骨关节炎患者与正常人股内侧肌、股直肌和股外侧肌间的协调性改变。方法34例膝骨关节炎患者和34名膝关节健康者在膝关节屈曲10°、60°、100°等长伸膝和等速60°/s、180°/s伸膝运动测试模式下,进行股内侧肌(VM)、股直肌(RF)和股外侧肌(VL)的表面肌电图和股四头肌肌力的评测,包括肌肉激活启动顺序和VM/VL神经肌电比值。结果与正常人对比,膝骨关节炎患者在等速180°/s伸膝运动时VM相对于VL启动延迟（P＜0.05）;在膝屈10°等长伸膝运动时,VM/VL神经肌电比值降低（P＜0.05）。结论膝骨关节炎患者患侧股四头肌的协调性减退。     

Effects of neuromuscular training on knee joint stability after anterior cruciate ligament reconstruction

[Purpose] This study examined the effects of neuromuscular training on knee joint stability after anterior cruciate ligament reconstruction. [Subjects and Methods] The subjects were 16 adults who underwent arthroscopic anterior cruciate reconstruction and neuromuscular training. The Lysholm scale was used to assess functional disorders on the affected knee joint. A KT-2000 arthrometer was used to measure anterior displacement of the tibia against the femur. Surface electromyography was used to detect the muscle activation of the vastus medialis oblique, vastus lateralis, biceps femoris, and semitendinosus before and after neuromuscular training. [Results] There was significant relaxation in tibial anterior displacement of the affected and sound sides in the supine position before neuromuscular training. Furthermore, the difference in the tibial anterior displacement of the affected knee joints in the standing position was reduced after neuromuscular training. Moreover, the variation of the muscle activation evoked higher muscle activation of the vastus medialis oblique, vastus lateralis, biceps femoris, and semitendinosus. [Conclusion] Neuromuscular training may improve functional joint stability in patients with orthopedic musculoskeletal injuries in the postoperative period.Key words: Arthrometer, Anterior cruciate ligament reconstruction, Neuromuscular training     

Activities of the Vastus Lateralis and Vastus Medialis Oblique Muscles during Squats on Different Surfaces

[Purpose] The purpose of the present study was to examine the effects of squat exercises performed on different surfaces on the activity of the quadriceps femoris muscle in order to provide information on support surfaces for effective squat exercises. [Subjects and Method] Fourteen healthy subjects performed squat exercises for five seconds each on three different support surfaces: hard plates, foam, and rubber air discs. Their performance was measured using electromyography. As the subjects performed the squat exercises on each surface, data on the activity of the vastus medialis oblique and the vastus lateralis, and the vastus medials oblique/vastus lateralis ratio, were collected. [Results] The activity of the vastus medialis oblique and the vastus medialis oblique/vastus lateralis ratio were found to be statistically significantly higher on rubber air discs than when the squats were performed on hard plates or foam. [Conclusion] To activate the vastus medialis obilique, and to enhance the vastus medialis oblique/vastus lateralis ratio, unstable surfaces that are highly unstable should be selected.Key words: Support surfaces, Vastus medialis obilique, Vastus lateralis     

Assessment of skeletal muscle fatigue in men with coronary artery disease using surface electromyography during isometric contraction of quadriceps muscles

OBJECTIVE: To evaluate whether using surface electromyography to assess skeletal muscle fatigue during an isometric exercise has the potential to be clinically useful in patients with coronary artery disease (CAD). DESIGN: Double sample comparative study. SETTING: Cardiac rehabilitation service in France. PARTICIPANTS: Sixteen men with documented CAD and 9 age-matched healthy men. INTERVENTIONS: Assessment of quadriceps skeletal muscle fatigue on an isokinetic apparatus with surface electromyography measurements and a symptom-limited exercise test in a laboratory. MAIN OUTCOME MEASURES: The maximal voluntary isometric force (MVIF) of the quadriceps was quantified as a measure of muscle strength and isometric endurance was defined as the time required to sustain a contraction at 50% of MVIF until exhaustion. Surface electromyography signals were recorded from the vastus lateralis, rectus femoris, and vastus medialis during isometric endurance. The root mean square (RMS) and the median frequency (MF) were directly calculated on a computer and then normalized (as a percentage of the initial value). RESULTS: Muscle strength did not differ significantly between the patients with CAD and the healthy subjects (229+/-21N/m vs 228+/-52N/m), but isometric endurance was reduced (64+/-17s vs 90+/-7s, P <.01). The RMS values showed a significantly higher increase in the healthy subjects versus the patients with CAD for the vastus lateralis and vastus medialis ( P <.001). The MF values were significantly lower for the vastus lateralis, rectus femoris ( P <.01), and vastus medialis ( P <.05) in patients with CAD compared with the healthy subjects. CONCLUSIONS: Skeletal muscle fatigue occurs sooner in men with CAD relative to matched healthy men, despite similar muscle strength. This finding may be the result of an abnormality of skeletal muscle function and may play an important role in measuring functional capacity. In addition, it may be a useful tool to assess the efficacy of cardiac rehabilitation interventions.     

Activation of the vastus medialis oblique and vastus lateralis muscles in asymptomatic subjects during the sit-to-stand procedure

[Purpose] The purpose of this study was to examine the vastus medialis oblique to vastus lateralis ratio in two pelvic tilt positions while performing the sit-to-stand task. [Subjects and Methods] Activation of the vastus medialis oblique and the vastus lateralis muscles of 46 healthy subjects (25 males, 21 females) were recorded by surface electromyography during the STS task with anterior pelvic tilt (sit with thoracolumbar spine extended and pelvis in an anterior tilt) and neutral pelvic tilt (sit with thoracolumbar spine relaxed and pelvis in the neutral tilt position) positions. Changes in vastus medialis oblique, vastus lateralis activation and the vastus medialis oblique/vastus lateralis ratio were analyzed. [Results] Vastus medialis oblique and vastus lateralis muscle activation significantly increased in neutral pelvic tilt position, but the vastus medialis oblique/vastus lateralis ratio was not statistically different. [Conclusion] The sit-to-stand procedure with neutral pelvic tilt position increased activation of the vastus medialis oblique and vastus lateralis, usefully strengthening the quadriceps, but did not selectively activate the vastus medialis oblique muscle.Key words: Anterior pelvic tilt, Neutral pelvic tilt, Sit-to-stand task     

Activation of the quadriceps muscle during semisquatting with different hip and knee positions in patients with anterior knee pain.

OBJECTIVE: We measured the surface electromyographic activities of vastus medialis obliquus and vastus lateralis in 16 subjects with patellofemoral joint pain syndrome. DESIGN: Each subject performed bilateral static knee extension exercises at 60% of his or her maximal voluntary effort under different combinations of hip rotation (30 degrees of medial rotation, neutral, 45 degrees of lateral rotation) and knee flexion (20 and 40 degrees) in a standing position. The ratio of surface-integrated electromyographic signals of vastus medialis obliquus over vastus lateralis was calculated for each of the six conditions. Because of significant interaction of hip rotation and knee flexion in the two-way analysis of variance, data were analyzed separately with paired t tests for the effect of knee positions and one-way repeated measures analysis of variance for hip positions. RESULTS: At 20 degrees of knee flexion, there was no significant difference among the three hip positions, whereas at 40 degrees of knee flexion, medial rotation of the hip resulted in significantly higher vastus medialis obliquus over vastus lateralis activity ratio than lateral rotation (P < 0.05). CONCLUSIONS: There was relatively more activation of vastus medialis obliquus than vastus lateralis at 40 degrees of semisquat with the hip medially rotated by 30 degrees. This finding has clinical implications for training the vastus medialis obliquus in patients with patellofemoral joint pain syndrome.     

Electromyographic analysis of knee exercises in healthy subjects and in patients with knee pathologies

Little information exists about the intensity of contraction required from knee and hip musculature during common therapeutic exercises used for patient populations. This study, therefore, was designed to compare electromyographic data obtained from the vastus medialis, rectus femoris, gluteus medius, and biceps femoris muscles during maximally resisted straight-leg-raising (SLR) exercises with EMG data obtained from the same muscles during quadriceps femoris muscle setting (QS) exercises in healthy subjects and in patients with knee pathologies. Of the 30 participants in the study, 16 had a history of knee injury or surgery. All participants performed randomly ordered trials of the SLR and QS exercises while the EMG data were recorded from surface electrodes and normalized to values derived from maximal effort isometric contraction trials. An analysis of variance demonstrated significantly greater activity (p less than .05) of the vastus medialis, biceps femoris, and gluteus medius muscles during QS exercises than during SLR exercises. The rectus femoris muscle was significantly more active (p less than .05) during SLR exercises than during QS exercises. The study demonstrated remarkably different degrees of muscle activation between the SLR and QS exercises, indicating that the exercise selected will affect the therapeutic intention.