Motor time of the rectus femoris under loading of different weights

Motor time (MT) of the rectus femoris was measured for seven normal subjects during rapid extension of the knee joint at 60 degrees flexion in the sitting position with and without external loads on the leg. MT prolonged linearly with external load from 0 to 4 kg. Tangent of this linearity, the rate of tension development (RTD), was significantly different from one another of the subjects and was not related to MT without external load. RTD is a relevant index to assess an efficiency of rapid force generation of a muscle.     

Differences in the movement pattern of a forward lunge in two types of anterior cruciate ligament deficient patients: copers and non-copers

OBJECTIVE: To determine whether differences in the knee joint movement pattern of a forward lunge could be quantified in healthy subjects and in anterior cruciate ligament deficient subjects who were able to return to the same activity level as before their injury (copers) and in those who were not (non-copers). DESIGN: The movement patterns of the injured leg of the coper and non-coper anterior cruciate ligament deficient subjects and the right leg of the control subjects were compared statistically. BACKGROUND: The forward lunge seems to be a less stressful test than the commonly used one-legged hop test, which makes it a possible tool for evaluating and comparing the functional performance of non-copers and copers. METHODS: The movement pattern of a forward lunge was analysed by using a two-dimensional inverse dynamics method. The electromyographic activity of the quadriceps and hamstring muscles were recorded. RESULTS: The non-copers moved more slowly and loaded the knee joint less than the copers and controls. The copers moved more slowly during the knee flexion phase but as fast as the controls during the knee extension. The EMG results suggest that the copers stabilized their knee joint by increasing the co-contraction of the hamstrings during the extension phase. CONCLUSIONS: Differences between the three groups' movement patterns could be quantified. The forward lunge test seems appropriate to discriminate between the knee function in coper and non-coper anterior cruciate ligament deficient subjects. RELEVANCE: Information about the performance of movements, which significantly load the knee joint in coper and non-coper anterior cruciate ligament deficient patients may contribute to a better understanding of dynamic knee joint stabilization, which is relevant in relation to the development of rehabilitation strategies.     

Neuromuscular disorder in response to anterior cruciate ligament creep

OBJECTIVE: To determine the effect of creep developed in the anterior cruciate ligament and other viscoelastic knee structures on the function of the flexor and extensor muscles of males and females. DESIGN: Static load applied to the proximal tibia of young healthy male and female subjects in a laboratory setting with maximal voluntary knee flexion and extension performed before and after the load application. BACKGROUND: Static loads applied to various joints during occupational and sports activities are epidemiologically linked to higher than normal rates of disability reports. The physiological and biomechanical processes active in the development of such a neuromuscular disorder are not known. We hypothesize that creep developed in the anterior cruciate ligament due to prolonged static load will have pronounced impact on the reflexive activation of the associated musculature in a manner that may increase the risk of injury. Females are expected to be exposed to higher risk than males. METHODS: Male and female groups performed maximal voluntary knee flexion and extension before and after applying 200 and 150 N, respectively, to the proximal tibia for a 10 min period. Flexion and extension forces as well as electromyograph from agonist and antagonist muscles were measured at 35 degrees and 90 degrees knee flexion. Data was analyzed through repeated measures of analysis of variance. RESULTS: It was found that in extension, quadriceps electromyographic activity increased significantly after anterior cruciate ligament creep while hamstrings co-activation did not change. There was also a trend towards increased extension force after creep was developed, with significant effect of gender (larger increase in females). Similarly, significant increase in hamstrings electromyographic activity and a trend towards increased force during knee flexion was observed but with no effect of gender. Electromyographic spasms from the flexors and extensors were recorded in 30% of the subjects during the 10 min static loading period at 90 degrees angle and from the flexors only at 35 degrees. Creep in the ligament was marginally greater in females than in males with a significant effect of angle, being greater at 35 degrees than in 90 degrees knee flexion. CONCLUSIONS: The results suggest that ligament creep may develop a neuromuscular disorder consisting of spasms, increased electromyography and force in the agonist muscles without compensation from the antagonist. Static loading of a joint, therefore, may develop a neuromuscular disorder compounded with laxity of the ligaments and subject the individual to increased risk of injury. RELEVANCE: The data provides evidence that prolonged static loads applied to the anterior cruciate ligament and associated viscoelastic structures results in unbalanced muscular activation which puts individuals at increased exposure to injury. Work and sports activities should be scheduled while minimizing periods of static joint loading and emphasizing sufficient rest periods to allow recovery of creep and return to balanced muscular activation and co-activation.     

Effect of quadriceps femoris muscle stretch on knee extension torque

Peak and angle specific knee extension torques produced after a quadriceps femoris muscle stretch and after a 15-second rest were compared to determine the effect of stretch on knee extension torque. Twenty healthy subjects performed eight maximum voluntary knee extensions at 90 degrees/sec under each condition. Although peak torque and torques at 15, 30, 45, and 60 degrees from full extension were measured, knee extension torque was only significantly greater (p less than .02) at 60 degrees of knee flexion after quadriceps femoris muscle stretch. The absolute difference, which was only a mean 4.9 N X m (3.6 ft-lb), was not substantial. When quadriceps femoris muscle stretch is a consequence of passive knee flexion at 90 degrees/sec, knee extension torque is apparently facilitated only during the initial part of the knee extension movement. Therefore, in healthy patients, a muscle stretch, such as used in this study, is probably of little therapeutic value.     

Electromyographic patterns accompanying isokinetic exercise under varying speed and sequencing conditions

The purposes of this study were: a) to investigate electromyographic patterns accompanying isokinetic exercise under varying speed and sequencing conditions, and b) to investigate the role of antagonist coactivation under these same conditions. Five adult males performed maximal knee extensions and flexions on a modified Orthotron isokinetic dynamometer. Tests were done at four speeds (100-400 degrees/sec) and under two counterbalanced conditions: extension followed by flexion (E/F) and flexion followed by extension (F/E). Simultaneous recordings of torque, knee joint position and agonist/antagonist EMG changes from the quadriceps and hamstring musculature were collected and analyzed. No consistent EMG patterns emerged that inferred intermittent surges of muscular activity as the primary mechanism yielding double peaked torques that characteristically occur in isokinetic exercise. Further analyses revealed relatively small co-contractions of antagonists during the various phases of movement. The findings suggest that gravity and inertia of the limb/lever system were the major factors responsible for limb deceleration and substantive antagonist co-contraction was not required for braking. If isokinetic knee flexion and extension exercises are used for conditioning or developmental purposes of healthy subjects, any distraction of the co-contracting antagonist from the recorded force of the agonist appears to be small once the activity is learned.     

Comparison of recovery strategies on muscle performance after fatiguing exercise

OBJECTIVE: The objective of this study was to assess the influence of different relaxation modes: stretching (ST), active recovery (AR), and passive recovery (PR) on muscle relaxation after dynamic exercise of the quadriceps femoris. DESIGN: Ten healthy male volunteers between 24 and 38 yrs of age participated in this study. After the warm-up, subjects performed three sets of dynamic leg extension and flexion (at an angle of 20-110 degrees) at 50% of previously determined maximal voluntary contraction (MVC), with 30 secs. of rest between sets. Immediately after completing the leg exercise, one of the relaxation methods was applied, in a randomized order (AR, PR, ST). Then, subjects performed isometric knee extension at 50% of MVC to the point of fatigue, and surface electromyogram (EMG) of the vastus lateralis muscle was measured. RESULTS: After AR, the mean MVC was significantly (P < 0.05) higher than after PR and ST. Moreover, there was no difference in MVC between AR and baseline (P > 0.05). Total time of the effort during EMG measurement was significantly lower for all three recovery modes than at baseline. During the effort after both PR and ST, there was no significant increase in motor unit activation, but a significant increase was noted after AR (P < 0.05). There was no difference in frequency between any of the recovery modes and baseline (P > 0.05). CONCLUSION: The results of this study suggest that the most appropriate and effective recovery mode after dynamic muscle fatigue involves light, active exercises, such as cycling with minimal resistance.     

Radiographic verification of knee goniometry

The accuracy of knee goniometry was examined by comparing goniometric measurements with radiographic bone angle measurements of six positions of the knee, namely, 0 degree, 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 90 degrees. Within the first 15 degrees of knee flexion joint excursion measured by goniometry differed significantly from bone angle measurement (p less than 0.01). With 30 degrees of knee flexion or more, no significant difference was found between goniometric measurements and bone angle measurements of knee motion. These findings suggest that within the first 15 degrees of knee flexion, goniometric measurement of joint excursion may be remarkably wrong. On account of this, it was suggested that when range of motion is limited at the knee joint, caution should be exercised in determining movement gains or losses within the initial 15 degrees of knee flexion.     

A videofluoroscopy method for optical distortion correction and measurement of knee-joint kinematics

Image distortion in video and image intensifier X-ray systems requires appropriate distortion correction methods to obtain accurate biomechanical quantitative measurements for joint kinematics applications. This paper presents an algorithm for coordinate reconstruction and distortion correction using a modified polynomial method. This algorithm was used for the measurement of patellar tendon moment arm, tibial plateau-tibial axis angle and patellar tendon-tibial axis angle during knee extension using videofluoroscopy in vivo. These parameters allow the determination of a two-dimensional biomechanical model of the knee for the measurement of muscle and joint forces during dynamic activities. Five males without knee joint injury history participated in the study. The mean measurement error obtained using an image intensifier-video system was 0.246 +/- 0.111 mm over a 180-mm x 180-mm field of view. The mean maximum patellar tendon moment arm was 39.87 mm at 44.9 degrees of knee flexion. The patellar tendon-tibial plateau angle was 112.9 degrees at full extension and decreased linearly to 87.6 degrees at 90 degrees of knee flexion. The mean angle between the tibial plateau and the tibial long axis was 84.8 degrees. Applications of the method include motion analysis using video and X-ray fluoroscopy systems with non-linear distortion problems. RELEVANCE: Accurate measurement of anatomical parameters from videofluoroscopy systems is important for the determination of joint biomechanical models and measurement of muscular and joint forces.     

Effect of tibial tubercle elevation on biomechanics of the entire knee joint under muscle loads

BACKGROUND: Anterior elevation of the tibial tubercle, known as Maquet procedure, is performed to reduce excessive patellofemoral contact stresses in knee joints with patellofemoral osteoarthritis and anterior pain. Previous investigations, however, have entirely focused on the likely effect of tibial tubercle elevation procedure on biomechanics of contact at the patellofemoral joint with no attention what-so-ever to associated alterations in biomechanics of the tibiofemoral joint. METHODS: Using a validated 3D nonlinear finite element model of the entire knee joint, the effect of 1.25 cm and 2.5 cm tubercle elevations on the entire knee joint biomechanics was investigated under constant quadriceps load of 411 N alone or combined with hamstrings co-activation of 205.5 N under joint angles of 0-90 degrees. FINDINGS: Results confirm the effectiveness of this procedure in reducing patellofemoral contact forces, especially at smaller flexion angles. Maximum contact stress substantially decreased at full extension but increased at 90 degrees. Substantial effects of tuberosity elevation on tibial kinematics, cruciate ligament forces, tibiofemoral contact forces and extensor lever arm were found. The posterior cruciate ligament and tibiofemoral contact forces at larger flexion angles considerably increased whereas the anterior cruciate ligament and tibiofemoral contact forces at near full extension angles decreased. Overall, the extent of changes depended on the magnitude of anterior elevation, joint flexion angle and loading considered. INTERPRETATION: Biomechanics of the tibiofemoral joint were significantly influenced by tibial tubercle elevation. Current results advocate the need for an integral view of the entire knee joint in management of various joint disorders rather than a view in which each component is considered and treated in isolation with no due attention to perturbations caused and associated consequences.     

Patellofemoral compressive force and stress during the forward and side lunges with and without a stride

BACKGROUND: Although weight bearing lunge exercises are frequently employed during patellofemoral rehabilitation, patellofemoral compressive force and stress are currently unknown for these exercises. METHODS: Eighteen subjects used their 12 repetition maximum weight while performing forward and side lunges with and without a stride. EMG, force platform, and kinematic variables were input into a biomechanical model, and patellofemoral compressive force and stress were calculated as a function of knee angle. FINDINGS: Patellofemoral force and stress progressively decreased as knee flexion increased and progressively increased as knee flexion decreased. Patellofemoral force and stress were greater in the side lunge compared to the forward lunge between 80 degrees and 90 degrees knee angles, and greater with a stride compared to without a stride between 10 degrees and 50 degrees knee angles. There were no significant interactions between lunge variations and stride variations. INTERPRETATION: A more functional knee flexion range between 0 degrees and 50 degrees may be appropriate during the early phases of patellofemoral rehabilitation due to lower patellofemoral compressive force and stress during this range compared to higher knee angles between 60 degrees and 90 degrees . Moreover, when the goal is to minimize patellofemoral compressive force and stress, it may be prudent to employ forward and side lunges without a stride compared to with a stride, especially at lower knee angles between 0 degrees and 50 degrees . Understanding differences in patellofemoral compressive force and stress among lunge variations may help clinicians prescribe safer and more effective exercise interventions.     

Hip Muscle Activity during Isometric Contraction of Hip Abduction

[Purpose] This study aimed to determine the effect of varying hip flexion angle on hip muscle activity during isometric contraction in abduction. [Subjects] Twenty-seven healthy men (mean age=21.5 years, SD=1.2) participated in this study. [Methods] Surface electromyography (EMG) was recorded of the upper portion of the gluteus maximus (UGM), lower portion of the gluteus maximus (LGM), tensor fasciae latae (TFL), and gluteus medius (GMed) during isometric contraction under two measurement conditions: hip flexion angle (0, 20, 40, 60, and 80 degrees) and abduction of the hip joint at 20, 40, 60, and 80% maximum strength. Integrated EMG (IEMG) were calculated and normalized to the value of maximum voluntary contraction (MVC). [Results] Results indicated that the IEMG of both the UGM and LGM increased significantly with increases in hip flexion angle, whereas the IEMG of the TFL decreased significantly. The maximum activities of the UGM and the LGM were 85.7 ± 80.8%MVC and 38.2 ± 32.9%MVC at 80 degrees of hip flexion, respectively, and that of the TFL was 71.0 ± 39.0%MVC at 40 degrees of hip flexion. [Conclusion] The IEMG of the GMed did not change with increases in hip flexion angle. Hip flexion angle affected the activity of the GM and TFL during isometric contraction in abduction.Key words: Hip abductor, Electromyography, Muscle activity     

Tibiofemoral joint forces during maximal isokinetic eccentric and concentric efforts of the knee flexors

OBJECTIVE: The examination of muscular and tibiofemoral joint forces during maximal efforts of the knee flexors. DESIGN: The muscular and tibiofemoral joint knee forces during eccentric and concentric isokinetic efforts of the knee flexors were determined using a two-dimensional mathematical model. BACKGROUND: The examination of joint and muscle loading during isokinetic movements is important for the determination of safety of this exercise. METHODS: Ten healthy males performed three maximal isokinetic concentric and eccentric efforts of the knee flexors at angular velocities of 30 degrees s(-1), 90 degrees s(-1), 120 degrees s(-1) and 150 degrees s(-1). The muscular, tibiofemoral shear and compressive joint forces were determined using a two-dimensional model. RESULTS: The maximum muscular force ranged from 3.44 (Standard deviation, 1.32) times body weight to 6.19 (1.78) times body weight. The tibiofemoral compressive force ranged from 2.62 (1.17) times body weight to 5.89 (1.99) times body weight occurring at angles ranging from 0 degrees to 40 degrees of knee flexion. The posterior shear force ranged from 2.61 (1.33) times body weight to 3.89 (1.62) times body weight and was observed at angles ranging from 50 degrees to 80 degrees of knee flexion. Two-way analysis of variance designs indicated significant effects of type of muscle action and angular velocity on muscle and compressive forces (P<0.05). In contrast, the shear force was not affected by the type of muscle action or the angular velocity (P>0.05). CONCLUSIONS: Isokinetic efforts of the knee flexors induce high tibiofemoral joint forces, especially during high-speed eccentric tests.     

Isometric and isokinetic measurement of hamstring and quadriceps strength.

This study evaluates quadriceps strength at varying movement velocities in a group of healthy subjects. Specific objectives included (1) investigating the effect of angular velocity on peak torque (PT) (2) investigating the effect of angular velocity on joint angle at peak torque (JAPT) and (3) evaluating whether the use of a relatively new isokinetic testing device yields new insights to previously accepted relationships between angular velocity and PT or JAPT. Twenty healthy subjects were tested for isometric and isokinetic knee extension and flexion strength on a LIDO Active Isokinetic Rehabilitation System at velocities of 0 degrees, 60 degrees, 120 degrees, and 180 degrees/sec. Isometric PT (0 degrees/sec) was found to be highly correlated with isokinetic PT for both extensors and flexors at all velocities (r = .88-.93, p less than .01). PT declined significantly as angular velocity increased for both extension (p less than .01) and flexion (p less than .05). A relationship between isometric and isokinetic JAPT was significant for extension only at 60 degrees and 180 degrees/sec (r = .48-.52, p less than .05). These results indicate that knee isometric and isokinetic PT as measured on the LIDO Active system are highly related for both extension and flexion. PT declined as isokinetic angular velocity increased. Isometric and isokinetic JAPT are significantly related only for extension.     

Co-contraction during passive movements of the knee joint in children with cerebral palsy

BACKGROUND: Co-contraction is an impairment commonly reported in children with cerebral palsy. However, co-contraction has not been investigated during passive movements which may be used to assess spasticity in children with cerebral palsy. The purpose of this study was to examine the frequency of co-contraction and the relationship between reflex activity and co-contraction during passive movements of the knee joint in children with cerebral palsy. METHODS: Twenty children with cerebral palsy participated in this study. One set of ten continuous passive movements from 90 degrees of knee flexion to 25 degrees of knee flexion and from 25 degrees of knee flexion to 90 degrees of knee flexion was completed at 15 degrees /s, 90 degrees /s, and 180 degrees /s. The mean percentage of the range of motion of each movement and mean percentage of the number of movements which exhibited electromyographic activity of the vastus lateralis, medial hamstrings, and co-contraction were calculated for each set of movements. FINDINGS: The number of the movement repetitions and the percentage of the range of motion which exhibited co-contraction were considerable regardless of the direction and speed of motion. Significant positive correlations were found between the percentage of the passive range of motion with medial hamstrings activation, vastus lateralis activation, and co-contraction during passive movements into both knee flexion and knee extension at a velocity of 15 degrees /s, 90 degrees /s, and 180 degrees /s (P<0.001). INTERPRETATION: Co-contraction commonly occurs during passive movements of the knee in children with cerebral palsy. The presence of co-contraction may influence measurements of spasticity which use passive movements to assess spasticity.     

Novel biomechanics demonstrate gait dysfunction due to hamstring tightness

BACKGROUND: Children with cerebral palsy and hamstring tightness often demonstrate limited terminal swing knee extension. The conventional clinical measure of popliteal angle describes static hamstring tightness, but is not consistent with dynamic limitation. We hypothesize hamstring tightness, determined via modification of the conventional popliteal angle measure, is directly related to decreased terminal swing knee extension in children with cerebral palsy and normal magnitude knee flexion moments. METHODS: Six patients with cerebral palsy and six normal subjects were evaluated via physical examination and instrumented gait analysis. Physical examination included popliteal angle measures at first hamstring resistance to passive extension (R(1)), and end-range extension (R(2)) with the hip in varying degrees of flexion. Passive R(1) data were used to calculate regression equations to predict R(1) during gait, resulting in a novel measure of Available Knee Extension. Hamstring EMG was also compared. FINDINGS: R(1) during physical examination was significantly correlated with Available Knee Extension at terminal swing (Pearson r = -0.7251, P < 0.0001). Patients walked with significantly decreased velocity (0.959 vs. 1.27 m/s, P = 0.0002) and decreased knee extension at terminal swing (25.6 vs. 2.05 degrees, P < 0.0001), in the presence of normal knee flexion moments (-0.289 vs. -0.306 Nm/kg, P = 0.5009), and significantly decreased power absorption (-0.821 vs. -1.43 W/kg, P < 0.0001). Eleven of 12 patient knees demonstrated negative Available Knee Extension at terminal swing, with markedly limited knee extension. Five of 12 normal knees demonstrated negative Available Knee Extension, but this was near full extension. Hamstring EMG onset times were not significantly different. INTERPRETATION: We believe Available Knee Extension, defined on the basis of clinical measures of first resistance to hamstring stretch, provides a biomechanical link between physical examination findings and dynamic limitations in terminal swing knee extension.     

The influence of tensometric evaluation of the pain threshold on the nature of resistance exercising in disorders of the knee joint

Background. We evaluated the usefulness of tensometric examination of the quadriceps as a means of assessing the pain threshold for the subcartilage layer in the patellofemoral joint and the knee joint. Material and methods. Our study, carried out from 2000 to 2003, included 131 patients, 77 men and 54 women, age 12-52. The examination results were compared with those for the unaffected leg. After each examination a new level of exercise workload was established, always just below the pain threshold. Examinations were repeated after one, three and six months. Results. The level of the pain threshold in most cases excluded workloads involving flexion of the knee at 90 degrees , 45 degrees , and 0 degrees . Training with a load adapted to the pain threshold served as endurance training, and should be regarded as a way to harden the cartilage. When the exercise load was adjusted in accordance with tensometric examination results, cartilage resistance to pressure increased. This kind of training allows the patient to achieve painlessly 80-90% strength in the quadriceps (compared to the healthy leg) in 6-12 months. Conclusions. Tensometric examination of the knee is a useful instrument in the evaluation of sensitivity to pain in the subcartilage layer, enabling the evaluation of the range of pressure that does not induce subcartilage pain when the joint is under load by working muscles. Properly selected workloads have a favorable impact on resistance to pressure and cause a virtually complete restoration of quadriceps strength after 6-12 months of rehabilitation.     

AN ELECTROMYOGRAPHIC STUDY OF THE VASTII MUSCLES DURING OPEN AND CLOSED KINETIC CHAIN SUBMAXIMAL ISOMETRIC EXERCISES

Background:

Rehabilitation programs for patients with patellofemoral dysfunction aim to recruit the vastus medialis obliquus muscle (VMO) in an attempt to reduce pain and to improve patellar tracking.

Objectives:

The aim of the present study was to use surface EMG to assess the effectiveness of two isometric submaximal contractions (10% and 60% of maximal voluntary contraction, MVC) in promoting preferential activation of VMO over vastus medialis longus (VML) and vastus lateralis (VL) in open and closed kinetic chain isometric exercises with the knee joint fixed at 30, 60 and 90 degrees of flexion.

Methods and Measures:

Surface electromyography (EMG) signals were recorded with linear adhesive arrays of four electrodes from fourteen healthy young men (age 23.5±3.2, mean±SD) during isometric knee extension contractions at 10% and 60% of the maximum voluntary contraction (MVC) for 1 min and 20 s respectively at 30, 60 and 90 degrees of knee flexion. Initial values and rate of change (slope) of mean frequency (MNF), average rectified value (ARV) and conduction velocity (CV) of the EMG signal were calculated.

Results:

Comparisons between the force levels produced at 10% and 60% MVC revealed that the initial values of ARV and CV for the VL, VML and VMO muscle were greater at 60% MVC compared to 10% MVC (3‐way ANOVA; F=536; p<0.001, F=49: p<0.01 for ARV and CV respectively). Comparisons between the different muscles demonstrated lower initial values of CV for VMO compared to VL and VLM at 10% and 60% of MVC (F=15; p<0.05). In addition, initial estimates of ARV were higher for VMO compared to VML at both force levels (F=66; p<0.05). Comparisons between open and closed kinetic chain exercises revealed higher initial estimates of ARV for open kinetic chain knee extension at both force levels (F=62; p<0.01). In addition, the absolute value of MNF slope appeared to increase at higher angles for closed kinetic chain at 60% MVC while it was minimum at 60° degrees for open kinetic chain. No significant differences were observed in the rate of change of CV and MNF among the three muscles.

Conclusions:

Based on the results of this study, both open and closed kinetic chain exercise similarly activate the three portions of the quadriceps muscle, suggesting that selective training of the vastii muscle is not achievable in these conditions.     

Functional evaluation of patello-femoral incongruence by computer tomography

Background. The purpose of this study was to specify the types of incongruence detected in the patellofemoral joint by computer tomography. The joints were examined in both internal and external rotation of the lower leg. Material and methods. We examined 16 patients with pain in the anterior compartment of the knee joint (12 women, 4 men, average age 34.2 years). CT scans of the patellofemoral joint were performed in two positions: with the knee flexed 20 degrees and 30 degrees . The measurements were taken at rest and during contracture of the quadriceps, and in both internal and external rotation of the lower leg. The results were used to calculate the lateral angle of the patella, the congruence angle, and the angle of the intercondylar sulcus. Results. Contracture of the quadriceps causes an increase in the lateral angle of the patella, both in the patient group and in the controls. In 12 cases, internal rotation of the lower leg caused increased values for the lateral angle of the patella, while external rotation reduced this angle. In the control group, in 20 degrees and 30 degrees flexion of the knee, tension in the quadriceps increased the lateral angle of the patella. Rotation in either direction did not affect the congruence angle. In 12 patients we diagnosed incongruence of the lateralization type and deviation of the patella. In 4 cases we observed reduction of the congruence angle. External rotation diminished this angle. In these patients we diagnosed incongruence of the medialization type. Conclusions. Our research confirms the suitability of computer tomography in examining the patello-femoral joint in flexion from 0 to 30 degrees. The functional examination method described here using rotation of the lower leg dives now possibilities for the exact specification of the type of incongruence in the knee joint.     

Influence of knee flexion on isometric hip extensor strength

The maximum isometric extensor muscle strength was measured in 10 healthy subjects of different combinations of hip and knee angles. An ordinary exercise device was used for the measurements and the method could be useful in clinical work. The results revealed that the knee angle does not affect the hip extensor strength. The highest extensor muscular moments occurred at 90 degrees hip flexion, decreasing with decreasing hip angle. The distribution of the strength over the motion sector differed between male and female. The weight of the body segments was found to utilize 10-24% of the maximum strength at hip angles 60 degrees-0 degrees with subjects in a prone position.