Unbraced Condition Research Articles

The Effect of Knee Braces on Tibial Rotation in Anterior Cruciate Ligament–Deficient Knees During High-Demand Athletic Activities

To examine if bracing can restrict tibial rotation in anterior cruciate ligament (ACL)-deficient patients during high loading activities. Repeated measures. Kinematic data were collected with an 8-camera Vicon system while each patient performed 2 tasks that are known to cause increased rotational and translational loads on the knee: (1) descending from a stair and subsequent pivoting, and (2) landing from a platform and subsequent pivoting. The tasks were repeated under 3 brace conditions for the ACL-deficient knee: (1) wearing a prophylactic brace (braced condition), (2) wearing a patellofemoral brace (sleeved condition), and (3) without brace (unbraced condition). Biomechanical laboratory study. Twenty-one male subjects with a confirmed unilateral ACL rupture were assessed in vivo. Tibial internal rotation. Two repeated measures ANOVAs tested for differences in tibial internal rotation among the 3 conditions of the ACL-deficient knee and the unbraced condition of the intact knee. In both tasks, tibial rotation was significantly lower in the intact knee compared with all 3 conditions of the ACL-deficient knee (P ≤ 0.031). Bracing the ACL-deficient knee resulted in lower rotation than the unbraced (P ≤ 0.001) and sleeved (P ≤ 0.033) conditions. The sleeved condition resulted in lower tibial rotation in the drop landing and pivoting task compared with the unbraced condition (P = 0.019) but not in the stair descending and pivoting task (P = 0.256). Bracing decreased the excessive tibial rotation in ACL-deficient patients during high-demand activities but failed to fully restore normative values. If knee braces can enhance rotational knee stability in ACL-deficient patients, then they could possibly play an important role in preventing further knee pathology in such patients.

Effects of knee bracing on postural control after anterior cruciate ligament rupture

Study designRandomized clinical trial. ObjectivesTo investigate the effects of functional knee braces on postural control in patients with anterior cruciate ligament (ACL) rupture. BackgroundACL rupture leads to both mechanical knee instability and deficits in proprioception. Although elastic knee braces do not increase mechanical stability, patients report improved stability when wearing a brace. Elastic braces were found to reduce the loss of proprioception. It is, however, still unclear whether they also improve postural control, which involves the processing of proprioceptive input at a higher level. MethodsWe studied 58 patients with isolated unilateral ACL rupture using computerized dynamic posturography and compared overall stability index (OSI) scores for injured and uninjured legs with and without a knee brace. In addition, patients were classified as copers and non-copers depending on knee function. ResultsWithin subjects, OSI scores were 3.0±1.1° for uninjured legs when unbraced, 2.8±1.3° for uninjured legs when braced (p=0.17), 3.7±1.5° for unbraced injured legs, and 2.9±1.3° for braced injured legs (p<0.001). For the injured legs of copers and non-copers, OSI scores were 3.4°±1.2° for copers and 4.0°±1.6° for non-copers in the unbraced condition (p=0.11) and 2.7±1.0° for copers and 3.1±1.4° for non-copers in the braced condition (p=0.26). ConclusionElastic knee braces increase postural stability by approximately 22% in patients with ACL rupture. There was no difference in postural stability between uninjured and injured legs in the braced condition. One possible explanation is that bracing improves both proprioception and postural control. Level of evidenceControlled clinical trial, level 2a.

Knee braces can decrease tibial rotation during pivoting that occurs in high demanding activities

The purpose of this study was to investigate whether knee braces could effectively decrease tibial rotation during high demanding activities. Using an in vivo three-dimensional kinematic analysis, 21 physically active, healthy, male subjects were evaluated. Each subject performed two tasks that were used extensively in the literature because they combine increased rotational and translational loads on the knee, (1) descending from a stair and subsequent pivoting and (2) landing from a platform and subsequent pivoting under three conditions: (A) wearing a prophylactic brace (braced), (B) wearing a patellofemoral brace (sleeved), and (C) unbraced condition. In the first task, tibial rotation during the pivoting phase was significantly decreased in the braced condition as compared to the sleeved condition (P = 0.019) and the non-braced condition (P = 0.002). In the second task, the same variable was significantly decreased in the braced condition as compared to the sleeved (P = 0.001) and the unbraced condition (P < 0.001). The sleeved condition also produced significantly decreased tibial rotation with respect to the unbraced condition (P = 0.021). Bracing decreased tibial rotation in activities where increased translational and rotational forces were applied. Because knee braces decreased tibial rotation, they can possibly be used with ACL-reconstructed and ACL-deficient patients to prevent such problems. Case-control study, Level III.

Effects of unloading bracing on knee and hip joints for patients with medial compartment knee osteoarthritis

BackgroundOsteoarthritis affects the whole body, thus biomechanical effects on other joints should be considered. Unloading knee braces could be effective for knee osteoarthritis, but their effects on the contralateral knee and bilateral hip joints remain unknown. This study investigated the effects of bracing on the kinematics and kinetics of involved and contralateral joints during gait. MethodsNineteen patients with medial compartment knee osteoarthritis were analysed. Kinematics and kinetics of the knee and hip joints in frontal and sagittal planes were measured during walking without and with bracing on the more symptomatic knee. FindingsThe ipsilateral hip in the braced condition showed a lower adduction angle by an average of 2.58° (range, 1.05°–4.16°) during 1%–49% of the stance phase, and a lower abduction moment at the second peak during the stance phase than the hip in the unbraced condition (P<0.05 and P<0.005, respectively). With bracing, the contralateral hip showed a more marked peak extension moment and lower abduction moment at the first peak (P<0.05), and the contralateral knee adduction angle increased by an average of 0.32° (range, 0.21°–0.45°) during 46%–55% of the stance phase (P<0.05), compared to no bracing. InterpretationUnloading bracing modified the contralateral knee adduction angle pattern at a specific time point during gait. It also affected the frontal plane on the ipsilateral hip and the frontal and sagittal planes on the contralateral hip joint. Consideration should be provided to other joints when treating knee osteoarthritis.

Effect of an anterior-sloped brace joint on anterior tibial translation and axial tibial rotation: A motion analysis study

Background Anterior tibial translation and axial tibial rotation are major biomechanical factors involved in anterior cruciate ligament injuries. This study sought to evaluate a brace prototype designed with an anterior-sloped joint, in terms of its efficacy in attenuating anterior tibial translation and axial tibial rotation during landing, using a motion analysis approach. Methods Ten healthy male subjects performed single-leg landing tasks from a 0.6-m height with and without the brace prototype. Ground reaction force and kinematics data were obtained using a motion-capture system and force-plates. Anterior tibial translation and axial tibial rotation were determined based on tibial and femoral marker reference frames. Vertical and anterior–posterior ground reaction forces, hip, knee and ankle joint range-of-motions and angular velocities, anterior tibial translation and axial tibial rotation were compared between unbraced and braced conditions using Wilcoxon signed-rank test. Findings We found no significant difference in peak vertical and anterior–posterior ground reaction forces ( p = 0.770 and p = 0.332 respectively) between unbraced and braced conditions. Knee joint range-of-motion and angular velocity were lower ( p = 0.037 and p = 0.038 respectively) for braced condition than unbraced condition. Anterior tibial translation and axial tibial rotation were reduced ( p = 0.027 and p = 0.006 respectively) in braced condition, compared to unbraced condition. Interpretation The anterior-sloped brace joint helps to attenuate anterior tibial translation and axial tibial rotation present in the knee joint during landing. It is necessary to test the brace prototype in a sporting population with realistic sports landing situations in order to assess its effectiveness in lowering anterior cruciate ligament injury risk.

Quantifying complexity and variability in phase portraits of gait

Background Injuries to the lower extremity often cause limitations to joint motion and alter movement patterns of limb segments during gait. We hypothesized that complexity and variability of limb segment motion during gait would increase in both limbs due to unilateral injury. Using simulated injury to generate asymmetric gait, we developed new methods to quantify changes in the complexity and variability of limb segment angular phase portraits. Methods To simulate reduced range of motion associated with knee injury, the right knee was constrained to full extension by an external brace. Thigh, shank and foot segment angular phase portraits were generated from 20 healthy male subjects walking for 3-minute trials with and without the brace. Using Fourier-based methods, complexity was quantified by the number of harmonic frequencies suitable for fitting the phase-portrait shape — with a larger number of harmonics indicating greater complexity. Variability was characterized by the drift and confidence area generated by the inter-cycle excursion of the phase-portrait centroid. Findings Significant differences were found in complexity and variability measures due to bracing. Phase-portrait shape complexity and variability increased in the right (braced) limb, compared to the unbraced condition; while only variability increased for the left (contralateral) limb during bracing. Interpretation These new methods proved successful at quantifying changes in the complexity and variability that have been visually observed in phase portraits during asymmetric gait. This work provides a method that can be incorporated into clinical assessments to provide quantifiable measures of more precise differences in gait dynamics.

Study on three-dimensional kinematics and electromyography of ACL deficient knee participants wearing a functional knee brace during running

This investigation examined the muscular activity and 3D knee joint kinematic changes of anterior cruciate ligament-deficient (ACLD) participants in the involved leg under bracing condition during running. Different adaptation strategies have been found between patients who can cope with the injury and patients who cannot. One of the expected changes can be the muscle activation characteristic of the injured knee during strenuous activity with and without a functional knee brace. Three-dimensional kinematic and electromyographical (EMG) data were collected from 11 participants for 10 consecutive gait cycles during running on a treadmill under both braced and unbraced conditions. Participants were administered the "Knee Outcome Survey Activities of Daily Living Scale" to distinguish functional and non-functional candidates. No significant differences on 3D kinematics and EMG data were noted between functional and non-functional participants, thus data analysis focused on comparisons of bracing conditions for one combined group. Bracing significantly reduced total range of motion in the frontal and transverse planes (P<0.05). Muscle activity at heel-strike showed a consistent trend to increase for the hamstrings and decrease for the quadriceps under the braced condition when compared to the unbraced condition. Our findings indicate that bracing the ACLD knee alters the kinematics of the injured leg while running. Tendencies toward reductions in quadriceps and increases in hamstrings activity at heel-strike indicate that bracing might have resulted in added stability of the injured knee. The adaptations to bracing found in this preliminary study further support the potential mechanical and proprioceptive contributions of the functional knee brace to protect the ACLD knee.

Increased reflex activation of the peroneus longus following application of an ankle brace declines over time

Two experiments were performed to document the time-dependent characteristics of the peroneus longus short latency stretch reflex amplitude following application of an ankle brace. In Experiment 1, stretch reflexes were induced in 15 weightbearing subjects during an unbraced condition and braced condition. In Experiment 2, stretch reflexes were induced in 15 weightbearing subjects before and after 3 h of wearing the brace. In Experiment 1, the amplitude of the stretch reflex increased in the braced condition by about 25% relative to the non-braced condition ( p=0.006). In Experiment 2 the amplitude of the stretch reflex increased about 18% immediately after application of the brace relative to the non-braced condition ( p=0.037). After 3 h, the stretch reflex amplitude was not different from that of initial non-braced condition. Given the importance of the peroneus longus muscle in ankle complex stability, further attention should be directed to whether the increased stretch reflex gain can be exploited during rehabilitation from ankle complex injuries. The findings provide a framework by which the effect of ankle braces on ankle joint proprioception, muscle activation profiles and balance may be physiologically interpreted.

Knee Stability Controlled by Hamstrings and Functional Knee Brace

The purpose of this study was to determine the effectiveness of an off-the-shelf functional knee brace on preventing anterior tibial translation in anterior cruciate ligament-deficient knees (ACL-d) with greater than 6 mm of side-to-side difference, and the effect of a 50% maximal voluntary hamstring contraction on knee joint laxity. A therapist experienced in using the Knee Signature System (KSS) screened 14 patients who had been diagnosed arthroscopically with ACL deficiency. Nine patients (8 men, 1 woman; mean age, 32.9 years; mean mass, 75 kg; mean height, 177 cm) met the inclusion criteria. All participants were 240 ± 42 days post injury. Participants in the study were tested with no brace, with brace, and 50% maximal voluntary contraction (MVC) of the hamstrings. The uninjured limb was tested only in the unbraced condition. Repeated measures ANOVA (p ≤ .05) and a Bonferroni post hoc analysis was used to detect specific differences between conditions. Results indicate that a 50% hamstring contraction provided better control of anterior tibial displacement than a functional knee brace under the same loading conditions, but a brace may contribute significantly to reducing anterior displacement when the hamstring force is not sufficient.

A Parametric Design Evaluation of Lateral Prophylactic Knee Braces

Six major mechanical design variables characterizing single-upright lateral prophylactic knee braces were studied experimentally, using a generic modular brace (GMB). Impulsive valgus loading tests were conducted with the GMB applied to a surrogate leg model. The surrogate involved anatomically realistic aluminum-reinforced acrylic components to model bone, and expendable polymeric blanks to mimic the major knee ligaments. Behavior of the surrogate system reasonably reproduced that of human cadaveric knees under similar loading conditions. Load at failure of the medial collateral ligament (MCL) analog, gross knee stiffness, and MCL relative strain relief were measured for each of twelve parametric brace design permutations. Compared to the unbraced condition, bracing provided statistically significant increases in valgus load uptake at failure and in MCL strain relief. Increasing the dimensions of individual brace components (hinge length and offset; upright length, breadth, and thickness; cuff area), relative to those of a GMB baseline configuration deemed representative of current commercial products, failed to achieve statistically significant improvements in brace performance. However, most below-baseline dimensioning of individual components did significantly compromise GMB performance. These surrogate test data indicate that geometric modifications of current single-upright lateral brace designs are unlikely to substantially improve upon the fairly modest valgus load protection afforded by this class of devices.

A mechanical and electromyographical analysis of the effects of various joint counterforce braces on the tennis player.

Biomechanical data on most bracing and protective equipment systems is lacking. To better understand the clinical success of counterforce bracing, a biomechanical analysis of braced and unbraced tennis players (serve and backhand strokes) was undertaken. Three-dimensional cinematography and electromyographic techniques were used. Three commonly used counterforce braces (lateral elbow, medial elbow, and radial-ulnar wrist) were compared with the unbraced condition. The overall results basically reveal positive biomechanical alterations in forearm muscle activity and angular joint acceleration dependent upon the brace and joint area analyzed.