Increased Knee Flexion Angle Research Articles

Effects of a Knee Extension Constraint Brace on Lower Extremity Movements after ACL Reconstruction

Patients have high reinjury rates after ACL reconstruction. Small knee flexion angles and large peak posterior ground reaction forces in landing tasks increase ACL loading. We determined the effects of a knee extension constraint brace on knee flexion angle, peak posterior ground reaction force, and movement speed in functional activities of patients after ACL reconstruction. Six male and six female patients 3.5 to 6.5 months after ACL reconstruction participated in the study. Three-dimensional videographic and force plate data were collected while patients performed level walking, jogging, and stair descent wearing a knee extension constraint brace, wearing a nonconstraint brace, and not wearing a knee brace. Knee flexion angle at initial foot contact with the ground, peak posterior ground reaction force, and movement speed were compared across brace conditions and between genders. Wearing the knee extension constraint brace increased the knee flexion angle at initial foot contact for each activity when compared with the other two brace conditions. Wearing the knee extension constraint brace also decreased peak posterior ground reaction force during walking but not during jogging and stair descent. Although the knee extension constraint brace did not consistently reduce the peak posterior ground reaction force in all functional activities, it consistently increased knee flexion angle and should reduce ACL loading as suggested by previous studies. These results suggest the knee extension constraint brace has potential as a rehabilitation tool to alter lower extremity movement patterns of patients after ACL reconstruction to address high reinjury rates.

Effect of Knee Flexion Angle on Length and Orientation of Posterolateral Femoral Tunnel Drilled Through Anteromedial Portal During Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction

Our purpose was to evaluate the radiologic orientation and length of the posterolateral (PL) femoral tunnel when drilled through the anteromedial (AM) portal at 90 degrees, 110 degrees, and 130 degrees of flexion. In 9 fresh cadaveric knees the anterior cruciate ligament was excised and 2.4-mm guidewires were drilled through the center of the PL bundle footprint through an accessory AM portal. Pins were advanced, in a retrograde manner, until flush with the notch wall and left in place. Outcomes were measured by use of plain anteroposterior, lateral, and tunnel radiographs to determine tunnel orientation and clock position, and direct measurement was performed to determine the intraosseous length, the shortest distance to the posterior bone cortex, and the distance to the lateral collateral ligament attachment on the lateral aspect of the femoral condyle. With regard to tunnel orientation, each increase in knee flexion angle resulted in a more horizontal tunnel on both the lateral and anteroposterior views. On the tunnel view, the PL guidewire became more vertical with knee flexion. The mean clock position was 9 o'clock (standard deviation [SD], 00:12). No significant difference in the intraosseous length of the guidewires was observed. According to our hypothesis, knee flexion influenced the PL tunnel characteristics. At 90 degrees of flexion, the guidewire may blow out the posterior cortex of the lateral femoral condyle. A PL femoral tunnel drilled through the AM portal becomes more horizontal with bending of the knee during drilling. At 90 degrees, the tunnel is at risk of back wall blowout.

The Effect of Selective Muscle Fatigue on Sagittal Lower Limb Kinematics and Muscle Activity During Level Running

Controlled laboratory study. To compare the changes in lower limb sagittal kinematics in running after a knee fatigue protocol with those observed after an ankle fatigue protocol. Impaired force-generating ability of specific muscles may affect running mechanics, with negative implications for injury occurrence and performance. Identifying the strategies used to compensate for fatigue of selected muscles may assist in the design of more effective exercise programs for injury prevention and performance enhancement in running. Sagittal plane kinematic data and the electromyographic (EMG) signal of the vastus medialis (VM), gastrocnemius (GAS), and biceps femoris (BF) muscles were collected from 15 females running at 3.61 m/s on a treadmill prior to, and following, an isokinetic knee extension/flexion and, on a separate day, an ankle plantar flexion/dorsiflexion fatigue protocol performed at 120 degrees/s. Ankle muscle fatigue caused decreased ankle dorsiflexion, while knee fatigue caused increased knee flexion at initial contact (P<.05). Both protocols increased knee flexion angle at toe-off, as well as the amplitude of GAS and VM EMG signal, with the hip more extended after knee fatigue and the ankle more plantar flexed after ankle muscle fatigue. Ankle muscle fatigue caused a significant increase in hip extensionand ankle plantar flexion angular velocity, and a decline of BF EMG signal during the swing phase (P<.05). Knee muscle fatigue decreased hip and knee flexion angular velocity and increased BF EMG signal during the swing phase (P<.05). Localized muscle fatigue effects on sagittal kinematics differed between the 2 protocols. However, the strategy used to compensate for fatigue was similar for both protocols: to protect the joints at initial impact and to prevent impairments in performance during toeoff and swing phase.

Mechanisms of Noncontact Anterior Cruciate Ligament Injury

To examine and summarize previous retrospective and observational studies assessing noncontact anterior cruciate ligament (ACL) injury mechanisms and to examine such reported ACL injury mechanisms based on ACL loading patterns due to knee loadings reported in in vivo, in vitro, and computer simulation studies. We searched MEDLINE from 1950 through 2007 using the key words anterior cruciate ligament + injury + mechanisms; anterior cruciate ligament + injury + mechanisms + retrospective; and anterior cruciate ligament + injury + mechanisms + video analysis. We selected retrospective studies and observational studies that specifically examined the noncontact ACL injury mechanisms (n = 7) and assessed ACL loading patterns in vivo, in vitro, and using computer simulations (n = 33). The motion patterns reported as noncontact ACL injury mechanisms in retrospective and observational studies were assessed and critically compared with ACL loading patterns measured during applied external or internal (or both) forces or moments to the knee. Noncontact ACL injuries are likely to happen during deceleration and acceleration motions with excessive quadriceps contraction and reduced hamstrings co-contraction at or near full knee extension. Higher ACL loading during the application of a quadriceps force when combined with a knee internal rotation moment compared with an external rotation moment was noted. The ACL loading was also higher when a valgus load was combined with internal rotation as compared with external rotation. However, because the combination of knee valgus and external rotation motions may lead to ACL impingement, these combined motions cannot be excluded from the noncontact ACL injury mechanisms. Further, excessive valgus knee loads applied during weight-bearing, decelerating activities also increased ACL loading. The findings from this review lend support to ACL injury prevention programs designed to prevent unopposed excessive quadriceps force and frontal-plane or transverse-plane (or both) moments to the knee and to encourage increased knee flexion angle during sudden deceleration and acceleration tasks.

Effects of a Knee Extension Constraint Brace on Selected Lower Extremity Motion Patterns during a Stop-Jump Task

Small knee flexion angle during landing has been proposed as a potential risk factor for sustaining noncontact ACL injury. A brace that promotes increased knee flexion and decreased posterior ground reaction force during landing may prove to be advantageous for developing prevention strategies. Forty male and forty female recreational athletes were recruited. Three-dimensional videographic and ground reaction force data in a stop-jump task were collected in three conditions. Knee flexion angle at peak posterior ground reaction force, peak posterior ground reaction force, the horizontal velocity of approach run, the vertical velocity at takeoff, and the knee flexion angle at takeoff were compared among conditions: knee extension constraint brace, nonconstraint brace, and no brace. The knee extension constraint brace significantly increased knee flexion angle at peak posterior ground reaction force. Both knee extension constraint brace and nonconstraint brace significantly decreased peak posterior ground reaction force during landing. The brace and knee extension constraint did not significantly affect the horizontal velocity of approach run, the vertical velocity at takeoff, and the knee flexion angle at takeoff. A knee extension constraint brace exhibits the ability to modify the knee flexion angle at peak posterior ground reaction force and peak posterior ground reaction force during landing.

Influence of Knee Flexion Angle on Femoral Tunnel Characteristics When Drilled Through the Anteromedial Portal During Anterior Cruciate Ligament Reconstruction

The purpose of this study was to determine the influence of knee flexion angle for drilling the femoral tunnel during anterior cruciate ligament (ACL) reconstruction via the anteromedial (AM) portal on resulting tunnel orientation and length. In 8 fresh cadaveric knees, the ACL was excised and 2.4-mm guidewires were drilled through the AM bundle footprint using a 5-mm endofemoral aimer via the AM portal. We compared knee flexion angles of 90 degrees , 110 degrees , 130 degrees , and maximum flexion. Anteroposterior-, lateral-, and tunnel-view radiographs were measured to determine tunnel orientation, o'clock position, and direct measurement to determine intra-osseous tunnel length. With regard to tunnel orientation, each increase in knee flexion angle resulted in significantly more horizontal tunnel both on the anteroposterior view and on the lateral view. While on the tunnel view, the pin became more vertical with knee flexion. At 90 degrees , tunnel length was significantly less (27 +/- 9 mm) than at greater angles, and the guidewires were either resting against the posterior cortex or breaching it. The results of this study show the knee flexion angle influences the position of the femoral drilling. It appears in the current study that 110 degrees is optimum, while the 90 degrees pin leads to short tunnel and is so close to the posterior wall there are high risks of posterior wall blow out when drilling the tunnel at its final diameter. Also, 130 degrees of knee flexion is responsible for high tunnel acuity and, finally, maximum flexion being quite variable from one specimen to another cannot be recommended. Tunnels drilled through the AM portal at 90 degrees are at risk of back wall blow out.

What is the normal response to structural differentiation within the slump and straight leg raise tests?

The purpose of the study was to assess the effect of structural differentiation or sensitising manoeuvres on responses of normal subjects to standard neurodynamic tests of straight leg raise (SLR) and slump test. Eighty-eight (39 males and 49 females) asymptomatic subjects were examined (aged 18–39 mean age 21.9±4.1 years). Knee flexion angle was measured using a goniometer during the slump test in two conditions cervical flexion and extension. Hip flexion angle was measured using a goniometer during SLR test in two conditions; ankle dorsi-flexion and neutral. The change in knee flexion, following addition of the structural differentiating manoeuvre to the slump test, was a significant increase in knee flexion angle for both males (change in knee angle; 6.6±4.7°/18.7±17.5%, p<0.01) and females (change in knee angle5.4±5.8°/17.6±23.7%, p<0.01), though showed no difference between sides ( p>0.05). During the SLR test, a significant reduction in hip flexion occurred following structural differentiation for both groups (change in hip angle; males=9.5±8.3°/21.5±18.8%, p<0.01; females=15.2±9.5°/25.9±13.9%, p<0.01), though showed no difference between sides ( p>0.05). Structural differentiating manoeuvres have a significant effect on test response in terms of range of movement even in normal asymptomatic individuals. These responses should be taken into account during the assessment clinical reasoning process.

A case study of gait compensations for hip muscle weakness in idiopathic inflammatory myopathy

The purpose of this case series was to quantify different strategies used to compensate in gait for hip muscle weakness. An instrumented gait analysis was performed of three females diagnosed with idiopathic inflammatory myopathies and compared to a healthy unimpaired subject. Lower extremity joint moments obtained from the gait analysis were used to drive an induced acceleration model which determined each moment's contribution to upright support, forward progression, and hip joint acceleration. Results showed that after midstance, the ankle plantar flexors normally provide upright support and forward progression while producing hip extension acceleration. In normal gait, the hip flexors eccentrically resist hip extension, but the hip flexor muscles of the impaired subjects (S1-3) were too weak to control extension. Instead S1-3 altered joint positions and muscle function to produce forward progression while minimizing hip extension acceleration. S1 increased knee flexion angle to decrease the hip extension effect of the ankle plantar flexors. S2 and S3 used either a knee flexor moment or gravity to produce forward progression, which had the advantage of accelerating the hip into flexion rather than extension, and decreased the demand on the hip flexors. Results showed how gait compensations for hip muscle weakness can produce independent (i.e. successful) ambulation, although at a reduced speed as compared to normal gait. Knowledge of these successful strategies can assist the rehabilitation of patients with hip muscle weakness who are unable to ambulate and potentially be used to reduce their disability.

Codominance of the individual posterior cruciate ligament bundles. An analysis of bundle lengths and orientation.

It is unclear how each bundle of the posterior cruciate ligament contributes to posterior knee stability. Changes in bundle orientation and length occur such that neither bundle dominates in restraining posterior tibial motion throughout knee flexion and extension. Controlled laboratory study. Six fresh-frozen cadaveric knees were studied in a joint-testing rig with individual quadriceps and hamstring muscle loading. Kinematic data for the tibia and femur were obtained at knee flexion angles from 0 degrees to 120 degrees. The joint was then disarticulated, and the insertions of the two bundles on the tibia and femur were digitized. Length of the anterolateral bundle increased with increasing knee flexion angle from 10 degrees to 120 degrees. Length of the posteromedial bundle decreased with increasing knee flexion angle from 0 degrees to 45 degrees and increased slightly from 60 degrees to 120 degrees. Length of the anteromedial bundle was significantly less than that of the posteromedial at 0 degrees, 10 degrees, and 20 degrees of knee flexion. The anterolateral bundle was significantly more horizontal at flexion angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 45 degrees (P < 0.05). The posteromedial bundle was more horizontal at 120 degrees. Changes in orientation take place such that neither bundle dominates in restraining posterior tibial motion throughout knee flexion and extension. Double-bundle reconstructions achieve more physiologic knee function.

Removal of the lateral or medial third of patellar tendon alters the patellofemoral contact pressure and area: an in vitro experimental study in dogs

Objectives. To compare patellofemoral contact pressure and areas after immediate removal of the lateral, central, or medial third of patellar tendon. Design. In vitro experiment in 12 dogs. Background. Alteration of the vector sum of the quadriceps muscle contraction after removal of partial patellar tendon might result in changes of patellar tracking in the trochlea. Methods. Patellofemoral contact pressure and areas were recorded using Fuji pressure-sensitive film at 45°, 60°, and 90° of knee flexion under an isometric quadriceps force of 100% body weight. The patellofemoral contact imprint from the intact knees were obtained as control, and the lateral ( n=4), central ( n=4), and medial ( n=4) third of the patellar tendon were subsequently removed and the patellofemoral contact imprint was recorded. Results. The patellofemoral contact area was found to increase with increasing knee flexion angles. No change in patellofemoral contact pressure and areas was found after removal of the central third patellar tendon. However, after removal of either lateral or medial third of patellar tendon, the patellofemoral contact was rotated with increasing knee flexion angles. This was due to the altered vector sum of the quadriceps force, resulting in significantly decreased patellofemoral contact areas and simultaneously a significantly increased contact pressure, characterized with concentration of patellofemoral contact pressure on both lateral and medial facets of the patellofemoral joint. Conclusions. The results suggest that removal of the central third of patellar tendon may not alter the patellofemoral contact pressure and areas as compared with removal of either lateral or medial third of patellar tendon that may result in an altered postoperative tracking mechanism of the patellofemoral joint immediately after operation. Relevance Findings of this in vitro animal study supports the use of central third of patellar tendon as autograft for anterior cruciate ligament reconstruction. However, further experimental studies are needed to investigate how the postoperative healing of the host patellar tendon will influence the findings obtained from this in vitro study.

EMG Analysis of the Vastus Medialis/Vastus Lateralis Muscles Utilizing the Unloaded Narrow- and Wide-Stance Squats

The purpose of this study was to see if vastus medialis oblique/vastus lateralis (VMO:VL) ratios could be increased by widening the squat stance and if the VMO activity increases with deeper ranges of knee flexion. Fifteen healthy subjects performed unloaded narrow and wide stance squats through three ranges of knee flexion: 30°, 60°, and 90°. The two squat stances were compared using a 2 × 3 ANOVA to see if the wide-stance squat had any significant difference in EMG activity for VMO: VL ratios compared to the narrow-stance squat. The difference in EMG activity of the VMO between the various angles for both squat stances was also compared. The ANOVA revealed no significant differences between the squat stances for VMO:VL ratios but did show the VMO:VL ratios to be significantly higher with increasing knee flexion angles. These findings suggest that the VMO is active throughout the 90° range and that increasing knee flexion angles can elicit greater activity of the VMO relative to the VL.

Gait and electromyographic analysis of anterior cruciate ligament deficient subjects

Some anterior cruciate ligament deficient (ACLD) patients can overcome passive sagittal joint laxity and maintain dynamic stability of the knee joint. Gait analysis with electromyographic (EMG) support was used in an attempt to identify mechanisms whereby ACLD individuals achieve this functional stability. A group of 18 patients with arthroscopically proven, unilateral, chronic (>6 months) ACLD had their gait assessed using a three-dimensional VICON gait analysis system. Simultaneous quadriceps, hamstrings and gastrocnemius muscle activity was recorded using surface electromyography. Values of minimum knee flexion angle and activity duration of leg musculature were calculated for each section of stance phase and compared to a group of nine matched controls. The minimum flexion angle at heel contact and mid-stance was larger for the ACLD group than in controls. Throughout stance phase, the ACLD patients had increased hamstrings activity duration compared to the controls. Quadriceps activity duration was similar in both groups. It was found that the duration of hamstring activity correlated with the flexion angle at foot contact. The similarity in quadriceps activity between groups implies that the previously reported net increase in internal flexion moment observed in ACLD patients during stance phase may not necessarily be due to decreased activity of the quadriceps. Net increase in internal flexion moment may be achieved by the observed increase in hamstrings activity. Mechanisms and reasons why ACLD patients maintain increased knee flexion angles in stance phase are discussed.