Unloader Knee Research Articles

A Preliminary Assessment of a Novel Pneumatic Unloading Knee Brace on the Gait Mechanics of Patients With Knee Osteoarthritis

To determine whether a knee brace incorporating inflatable air bladders can alter the net peak external knee adduction moment in persons with medial compartment knee osteoarthritis. Prospective cohort study. Motion analysis laboratory. Subjects (n= 18) diagnosed with knee osteoarthritis as defined by the Diagnostic and Therapeutic Criteria Committee of the American Rheumatism Association. Instrumented gait analysis was performed while subjects walked with and without the knee brace. When subjects wore the knee brace, the air bladders were either uninflated or inflated to 7 psi. The net external knee adduction moment was obtained by subtracting the abduction moment produced by the knee brace (estimated using a finite element analysis model) from the external knee adduction moment (estimated using a camera-based motion analysis system). The net external knee adduction moment was compared across all testing conditions. A 7.6% decrease in net peak external knee adduction moment was observed when subjects wore the knee brace uninflated compared with when they did not wear the brace. Inflation of the bladders to 7 psi led to a 26.0% decrease in net peak external knee adduction moment. The results of the study suggest that the effects of an unloading knee brace may be enhanced by incorporating inflatable air bladders into the design of the brace, thus leading to an improved correction of the excessive peak external knee adduction moment observed in patients with medial compartment knee osteoarthritis.

Frontal plane corrective ability of a new unloader orthosis for medial compartment of the knee

Patients with medial compartment osteoarthritis of the knee suffer from pain and stiffness. However, current unloader braces are not being used for extended periods by knee osteoarthritis patients due to interface problems, so compliance is an issue. The aim of this study was to design a new bespoke orthosis that could be comfortable to wear while also providing the required correction to reduce medial compartment loading. A new knee orthosis design was initially tested for its frontal plane correction of knee varus using a surrogate knee model. It was then assessed by a volunteer subject with grade 2 medial compartment knee osteoarthritis using a static standing radiograph. When fitted to the surrogate knee model, the brace corrected the knee from 10° of varus to neutral alignment in the frontal plane. When worn in situ during static stance on the affected leg of the volunteer patient, it corrected the knee by 6° to a less varus position. The orthosis provided frontal plane correction of the knee during static standing. It could therefore prove to be suitable for use by knee osteoarthritis patients.

Unloader Knee Braces for Osteoarthritis: Do Patients Actually Wear Them?

Unloader braces are a nonsurgical approach for predominantly unicompartmental knee arthritis. Although noninvasive, braces are expensive and it is unclear whether clinical factors, if any, will predict regular brace use. We asked: (1) Do patients continue to use the unloader brace more than 1 year after it is prescribed? (2) Do any clinical or radiographic factors predict continued use of the unloader brace after the first year? (3) What are the most common subjective reasons that patients give for discontinuing the brace? We administered 110 surveys to all patients who were fitted for unloader knee braces for predominantly unicompartmental osteoarthritis 12 to 40 months before administration of the survey. Standardized indications and fitting protocols were used. The following parameters were tested for association with ongoing brace use: alignment, arthritis severity, compartment involved, BMI, weight, age, gender, pain and function, number of refittings, and problems with the brace. The survey response rate was 81% (89 of 110). Of the 89 responders, 28% reported regular brace use (twice per week, an hour at a time, or more); at 2 years, 25% used the brace regularly. No clinical or radiographic factors considered were associated with ongoing brace use. Patients reported lack of symptomatic relief, brace discomfort, poor fit, and skin irritation as reasons for discontinuing the brace. Surgeons and patients need to balance the benefits and absence of complications of bracing against cost and the low likelihood of ongoing use 1 year or more after the prescription of the brace.

The Effects of an Unloading Knee Brace and Insole with Subtalar Strapping for Medial Osteoarthritis of the Knee

Objectives: We evaluated whether a valgus knee brace and an insole with subtalar strapping could reduce pain and improve functional scores over 12 months in patients with medial knee osteoarthritis (OA). Methods: OA was confirmed by radiography in all patients, who were divided into three groups: exercise (n = 44), insole (n = 55), and brace (n = 19). Clinical knee functions and gait analyses were evaluated. Results: After 12 months, the clinical results for all groups had improved compared to pretreatment findings. Although the knee varus moment decreased and the gait speed increased when the insole was worn initially, the effects of the insole decreased at 6 and 12 months. In contrast, the knee varus moment decreased and the gait speed increased when the brace was initially fitted. The effects of the brace were maintained during the 12 months. Conclusions: The insole was effective for patients with Kellgren-Lawrence Grades II and III, and the knee brace was effective for patients with Grades III and IV conditions. Furthermore, the knee brace was more effective when worn for more than 6 months, while the effects of the insoles were not continuous.

Individuals with osteoarthritis after ACL reconstruction experience immediate improvements in knee pain and confidence with an unloader knee brace

Individuals with osteoarthritis after ACL reconstruction experience immediate improvements in knee pain and confidence with an unloader knee brace

In vivo open-bore MRI reveals region- and sub-arc-specific lengthening of the unloaded human posterior cruciate ligament.

Open-bore MRI scanners allow joint soft tissue to be imaged over a large, uninterrupted range of flexion. Using an open-bore scanner, 3D para-sagittal images of the posterior cruciate ligament (PCL) were collected from seven healthy subjects in unloaded, recumbent knee extension and flexion. PCL length was measured from one 2D MRI slice partition per flexion angle, per subject. The anterior surface of the PCL lengthened significantly between extension and flexion (p<0.001). Conversely, the posterior surface did not. Changes were not due to the PCL moving relative to the 2D slice partition; measurements made from 3D reconstructions, which compensated for PCL movement, did not differ significantly from measurements made from 2D slice partitions. In a second experiment, videos of knee flexion were made by imaging two subjects at several flexion angles. Videos allowed soft tissue tracking; examples are included. In a third experiment, unloaded knees of seven healthy, recumbent subjects were imaged at extension and at 40°, 70°, 90°, 100°, 110° and 120° flexion. The distance between PCL attachments increased between extension and 100°, and then decreased (p<0.001). The anterior surface of the PCL lengthened over the flexion angles measured (p<0.01). The posterior surface of the PCL lengthened between extension and 40° and then shortened (p<0.001). Both attachment separation and anterior surface length increased dramatically between extension and 40°, but varied less afterwards. Results indicate that PCL dynamics differ between terminal extension and active function sub-arcs. Also, attachment separation cannot predict the lengthening of all parts of the PCL, nor can lengthening of one part of the PCL predict the lengthening of another part. A potential connection between lengthening and loading is discussed. We conclude that low-field MRI can assess ligament lengthening during flexion, and that the dynamics of the PCL for any given region and sub-arc should be measured directly.

Comparison of the efficacy of laterally wedged insoles and bespoke unloader knee orthoses in treating medial compartment knee osteoarthritis

Patients suffering from medial compartment knee osteoarthritis (OA) may be treated with unloader knee orthoses or laterally wedged insoles. The aim of this study was to identify and compare the effects of them on the gait parameters and pain in these patients. Quasi-experimental. Volunteer subjects with medial compartment knee OA (n = 24, mean age 59.29 ± 2.23 years) were randomly assigned to two separate groups and evaluated when wearing an unloader knee orthosis or insoles incorporating a 6° lateral wedge. Testing was performed at baseline and after six weeks of each orthosis use. A visual analog scale score was used to assess pain and gait analysis was utilized to determine gait parameters. Both orthoses improved all parameters compared to the baseline condition (p = 0.000). However, no significant differences in pain (p = 0.649), adduction moment (p = 0.205), speed of walking (p = 0. 056) or step length (p = 0.687) were demonstrated between them. The knee range of motion (p = 0.000) were significantly different between the two interventions. Both orthoses reduced knee pain. Maximum knee range of motion was increased by both interventions although it was 3 degrees less when wearing the knee orthosis. Clinical relevance Both orthoses reduce pain and improve gait anomalies in medial compartment knee OA. Our results suggest a laterally wedged insole can be an alternative conservative approach to unloader knee orthosis for treating symptoms of medial compartment knee OA.

Improvement in Quality of Life with Use of an Unloader Knee Brace in Active Patients with OA: A Prospective Cohort Study

The purpose of this study was to determine if short form (SF)-12 physical component would increase with unloader brace use. Patient expectations and predictors of significant improvement were determined. Our hypothesis was that patients with unloader braces will have increases in general physical health (SF-12) and function (Western Ontario and McMaster Universities Arthritis Index [WOMAC]). Patients were enrolled in institutional review board-approved prospective cohort study. They completed a self-administered questionnaire (SF-12; WOMAC, Tegner activity scale, expectations) at enrollment, 3 weeks, 6 weeks, and 6 months. In this study, 39 patients, 23 males and 16 females (average age = 61 years [range 44 to 87]), were prescribed an unloader brace. Patients had significant improvement in quality of life (SF-12) (p < 0.05). There was significant improvement in pain, stiffness, and function (WOMAC) (p < 0.05). Patients who reported Tegner of 3 or greater at final follow-up had significantly higher SF-12 physical component (48 vs. 37; p = 0.023). Return to recreational sports was very important in 83% and somewhat important in 17%. Improving ability to walk was very important in 89%. Pain relief was very important in 69%, somewhat important in 17%. Of these, 39% expected most pain to be relieved and 57% expected all pain to be relieved. The most important expectations were to have confidence in knee (97% very important), avoid future knee degeneration (90% very important), and improve ability to maintain general health (93% very important). Patients demonstrated a significant decrease in pain and disability. Patients saw improvement in SF-12 physical component. Braces specifically designed to unload the degenerative compartment of the knee can be an effective treatment to decrease pain and maintain activity level to increase overall physical health.

Immediate effects of unloader knee brace on knee pain and confidence in individuals with osteoarthritis after anterior cruciate ligament reconstruction

Immediate effects of unloader knee brace on knee pain and confidence in individuals with osteoarthritis after anterior cruciate ligament reconstruction

The Effectiveness of Off-Loading Knee Orthoses in the Reduction of Pain in Medial Compartment Knee Osteoarthritis

In Brief The purpose of this review is to determine the effectiveness of knee orthoses in the treatment of pain in unilateral compartment osteoarthritis (OA). OA is the most common disorder affecting synovial joints, with structural changes of OA present in approximately half of the adults. The knee is the most commonly affected joint. Many treatments have been developed for OA, including the unloader knee orthosis. The principle of the unloader knee orthosis is to create a varus or valgus moment at the knee—theoretically creating additional space in the joint compartment, thus relieving pain caused by bone-on-bone contact. Several studies have been done, but none with a power or number of participants were large enough to demonstrate effective treatment of OA. Using the keywords “knee osteoarthritis” and “orthosis” or “brace,” the PubMed, CINAHL, RECAL, and ISI Web of Knowledge electronic databases were searched for randomized control trials with “orthoses” or “braces” for the knee between January 1980 and December 2010. Only studies that dealt with medial unilateral compartment knee OA and the use of a knee orthosis were selected. Of these articles, only experimental trials were selected based on the American Academy of Orthotists and Prosthetists State-of-the-Science Evidence Report Guidelines. A comparative analysis of the articles was used to determine the effectiveness of the orthoses in reducing pain. Forty-six initial articles were found. Of these, 15 articles were ultimately included and reviewed based on the inclusion guidelines. Most of these articles were either single-subject research or before-and-after studies. The majority were of moderate quality. Statistically significant pain reduction was noted by 73% of the studies reviewed, although all showed that there was pain reduction in the patients. Patient function and orthosis efficacy were also briefly examined, showing moderate increases of function. The rate of pain relief was further investigated and revealed that pain relief was almost immediate. OA knee orthoses are a cost-effective way to reduce pain in patients with medial compartment OA. The purpose of this review is to determine the effectiveness of knee orthoses in the treatment of pain in unilateral compartment osteoarthritis (OA). Only studies that dealt with medial unilateral compartment knee OA and the use of a knee orthosis were selected. Of these articles, only experimental trials were selected based on the American Academy of Orthotists and Prosthetists State-of-the-Science Evidence Report Guidelines. Statistically significant pain reduction was noted by 73% of the studies reviewed, although all showed that there was pain reduction in the patients.

In Vivo Tibiofemoral Kinematics During 4 Functional Tasks of Increasing Demand Using Biplane Fluoroscopy

Background: The anterior cruciate ligament (ACL) has been well defined as the main passive restraint to anterior tibial translation (ATT) in the knee and plays an important role in rotational stability. However, it is unknown how closely the ACL and other passive and active structures of the knee constrain translations and rotations across a set of functional activities of increasing demand on the quadriceps. Hypothesis: Anterior tibial translation and internal rotation of the tibia relative to the femur would increase as the demand on the quadriceps increased. Study Design: Controlled laboratory study. Methods: The in vivo 3-dimensional knee kinematics of 10 adult female patients (height, 167.8 ± 7.1 cm; body mass, 57 ± 4 kg; body mass index [BMI], 24.8 ± 1.7 kg/m2; age, 29.7 ± 7.9 years) was measured using biplane fluoroscopy while patients completed 4 functional tasks. The tasks included an unloaded knee extension in which the patient slowly extended the knee from 90° to 0° of flexion in 2 seconds; walking at a constant pace of 90 steps per minute; a maximum effort isometric knee extension with the knee at 70° of flexion; and landing from a height of 40 cm in which the patient stepped off a box, landed, and immediately performed a maximum effort vertical jump. Results: Landing (5.6 ± 1.9 mm) produced significantly greater peak ATT than walking (3.1 ± 2.2 mm) and unweighted full extension (2.6 ± 2.1 mm) (P < .01), but there was no difference between landing and a maximum isometric contraction (5.0 ± 1.9 mm). While there was no significant difference in peak internal rotation between landing (19.4° ± 5.7°), maximum isometric contraction (15.9° ± 6.7°), and unweighted full knee extension (14.5° ± 7.7°), each produced significantly greater internal rotation than walking (3.9° ± 4.2°) (P < .001). Knee extension torque significantly increased for each task (P < .01): unweighted knee extension (4.7 ± 1.2 N·m), walking (36.5 ± 7.9 N·m), maximum isometric knee extension (105.1 ± 8.2 N·m), and landing (140.2 ± 26.2 N·m). Conclusion: Anterior tibial translations significantly increased as demand on the quadriceps and external loading increased. Internal rotation was not significantly different between landing, isometric contraction, and unweighted knee extension. Additionally, ATT and internal rotation from each motion were within the normal range, and no excessive amounts of translation or rotation were observed. Clinical Relevance: This study demonstrated that while ATT will increase as demand on the quadriceps and external loading increases, the knee is able to effectively constrain ATT and internal rotation. This suggests that the healthy knee has a safe envelope of function that is tightly controlled even though task demand is elevated.

Clinical practice guidelines for rest orthosis, knee sleeves, and unloading knee braces in knee osteoarthritis

ObjectiveTo develop clinical practice guidelines concerning the use of bracing – rest orthosis, knee sleeves and unloading knee braces – for knee osteoarthritis. MethodsThe French Physical Medicine and Rehabilitation Society (SOFMER) methodology, associating a systematic literature review, collection of everyday clinical practice, and external review by multidisciplinary expert panel, was used. ResultsFew high-level studies of bracing for knee osteoarthritis were found. No evidence exists for the effectiveness of rest orthosis. Evidence for knee sleeves suggests that they decrease pain in knee osteoarthritis, and their use is associated with subjective improvement. These actions do not appear to depend on a local thermal effect. The effectiveness of knee sleeves for disability is not demonstrated for knee osteoarthritis. Short- and mid-term follow-up indicates that valgus knee bracing decreases pain and disability in medial knee osteoarthritis, appears to be more effective than knee sleeves, and improves quality of life, knee proprioception, quadriceps strength, and gait symmetry, and decreases compressive loads in the medial femoro-tibial compartment. However, results of response to valgus knee bracing remain inconsistent; discomfort and side effects can result. Thrombophlebitis of the lower limbs has been reported with the braces. Braces, whatever kind, are infrequently prescribed in clinical practice for osteoarthritis of the lower limbs. ConclusionModest evidence exists for the effectiveness of bracing – rest orthosis, knee sleeves and unloading knee braces – for knee osteoarthritis, with only low level recommendations for its use. Braces are prescribed infrequently in French clinical practice for osteoarthritis of the knee. Randomized clinical trials concerning bracing in knee osteoarthritis are still necessary.

The effect on patellofemoral joint stability of selective cutting of lateral retinacular and capsular structures

Patient selection for lateral retinacular release (LRR) and its efficacy are controversial. Iatrogenic medial subluxation can occur with inappropriate LRR. The aim of this study was to determine the reduction in patellofemoral stability with progressively more extensive LRR. The force required to displace the patella 10 mm medially and laterally in nine cadaveric knees was measured with and without loading of the quadriceps and iliotibial band. The knee was tested intact, then after progressive release beginning proximal to the patella (PR), the mid-level between the proximal and distal limit of the patella (MR) where the fibres are more transverse, then distally till Gerdy's tubercle (DR) and finally the joint capsule (CR). Both medial and lateral stability decreased with progressive releases, larger for the medial. The MR caused a significant reduction of lateral stability between 30° and 90° of knee flexion. There was an 8% reduction in medial stability at 0° flexion with a complete LRR (DR). A comparable reduction in medial stability in the loaded knee at 20° and 30° flexion was obtained with MR alone, with no further reduction after DR. A capsular release caused a further reduction in medial stability at 0° and 20° and this was marked in the unloaded knee. In extension, the main lateral restraint was the joint capsule. At 30° flexion, the transverse fibres were the main contributor to the lateral restraint.

Temporal Strength Changes From Resistance Exercise and Albuterol on Unloaded Muscle

To assess unloaded knee extensor temporal strength changes, healthy subjects without asthma performed 40 continuous days of unilateral limb suspension, whereby their left leg refrained from normal weight-bearing and ambulatory activity. During the 40-day period, subjects performed resistance exercise (REX) with their unloaded leg on an inertial resistance ergometer and, as part of a double-blind design, consumed the maximal oral therapeutic dosage of albuterol (i.e., 16 mg.d) or a placebo (i.e., lactose) with no crossover. Workout data were partitioned into 4 10-day periods that ran consecutively. Dependent strength variables included concentric total work, eccentric total work, concentric average power (CAP), and eccentric average power (EAP). Dependent variables were analyzed with 5 (time) x 2 (group) x 2 (gender) mixed factorial analyses of variance and the Tukey honestly significant difference test. Concentric total work, CAP, and EAP each demonstrated a time-group-gender (p < 0.05) interaction. Female REX-placebo subjects had the greatest percentage of unloaded knee extensor strength loss. However, female REX-albuterol subjects fared best throughout the 40-day period and incurred significant unloaded knee extensor strength gains. Differences in strength changes between male and female REX-albuterol subjects was likely due to the higher relative dosage administered to the latter, as body mass showed a gender (i.e., men > women) effect. Future research may elucidate the ideal dose-response relationship for REX-albuterol treatment for use aboard manned space flights and in other disuse models. Coaches and practitioners should carefully examine their sport-governing bodies' rules on albuterol administration and give the drug only if an athlete's health warrants such treatment.

Knee Injury in a Soccer Player

HISTORY: 25 y/o soccer player p/w 2-day h/o acute severe right knee pain after being slide-tackled in a game. Mechanism of injury included blunt trauma to the medial aspect of the knee, sustaining a varus & twisting-type stress - resulting in a painful "pop," immediate pain, swelling & inability to bear weight. Patient c/o right foot drop the following day. Additionally on post-injury day 10, the patient developed calf pain & swelling. PHYSICAL EXAMINATION: Post-injury day 2 exam of the right knee limited by pain, guarding & inability to bear weight. Significant effusion noted. ROM limited by guarding. Strength testing showed 4+/5 knee extension & 2/5 ankle dorsiflexion. Equivocal Lachman test. Pain & laxity to varus stress; valgus stress testing negative. Diminished sensation in deep & superficial peroneal distributions. Normal distal pulses & cap refill. Repeat exam on post-injury day 10 revealed calf TTP & 2+leg edema. Exam under anesthesia 12 days post-injury revealed a palpable soft tissue defect laterally, proximal to fibular head. Lachman test c/w grade 2 laxity w/ soft endpoint. Pivot shift & anterior drawer tests were positive, & the lateral joint opened easily (3+) w/ varus stress. Posterior drawer & valgus stress tests were normal. Posterolateral corner (PLC) tests: positive reverse pivot shift, dial & PLC drawer tests. DIFFERENTIAL DIAGNOSIS: ACL tear PCL tear LCL tear Peroneal nerve injury PLC injury Meniscal tear DVT Fracture or osteochondral lesion Dislocation or subluxation TEST AND RESULTS: Plain X-rays -No bony abn NCS & needle EMG -Severe peroneal neuropathy; no evid of transmission MRI w/o contrast -Marrow edema in medial femoral condyle; no fracture -Effusion -Complete ACL, LCL & biceps femoris tears -Thick PCL w/o abn signal -Medial meniscus tear Venous Duplex Doppler US -Peroneal vein DVT FINAL WORKING DIAGNOSIS: -ACL, PCL, LCL & medial meniscal tears -PLC injury -Peroneal nerve injury; foot drop -Peroneal vein DVT TREATMENT AND OUTCOMES: 1. IVC filter 2. ACL reconstr w/ hamstring autograft; partial medial meniscectomy 3. LCL & PLC repair; peroneal nerve dissection 4. Post-op unloader knee brace, AFO orthotic & rehabilitation 5. 6 month post-op -FROM; no laxity -Improved ankle strength -Weaned off brace & AFO 6. 12 month post-op -Doing well; jogging w/o biomechanical support

THE EFFECTIVENESS OF SELF-ADJUSTABLE CUSTOM AND OFF-THE-SHELF BRACING IN THE TREATMENT OF VARUS GONARTHROSIS

Background: A recent development in valgus-producing knee braces has been the adjustable “unloader” brace. The purpose of this study was to compare the effectiveness of off-the-shelf and custom-made patient-adjustable, valgus-producing knee unloader braces in relieving pain, reducing stiffness, and improving function and in reducing varus angulation and the peak adduction moments about the knee during gait and stair-stepping in patients with painful varus gonarthrosis of the knee. Methods: Ten adult patients served as their own controls for the measurement of baseline values and then wore each of the two braces, one after the other, for four to five weeks in a random order. Pain, stiffness, and function were assessed with the Western Ontario and McMaster Universities Osteoarthritis Index. Gait and stair-stepping were evaluated with a three-dimensional motion analysis system and multicomponent force platform. Full-length (hip, knee, and ankle) standing anteroposterior radiographs were used to determine alignment of the knee. Results: Both braces significantly reduced pain and stiffness (p < 0.05), with the custom brace reducing stiffness significantly more than the off-the-shelf brace (p = 0.030). The custom brace significantly improved function (p = 0.010) and reduced the peak knee adduction moments during gait (p = 0.033) and stair-stepping (p = 0.002) compared with baseline values and compared with the off-the-shelf brace (p = 0.029 and p = 0.027, respectively). The custom brace significantly reduced varus angulation of the knee by 1.5° compared with baseline (p = 0.001) and by 1.3° compared with the off-the-shelf brace (p = 0.009). The off-the-shelf brace did not significantly reduce the varus angle. Conclusions: We investigated only the short-term effects of custom and off-the-shelf patient-adjustable valgus-producing knee “unloader” braces and found that patients with varus gonarthrosis of the knee may benefit significantly with respect to pain relief and reduced stiffness from use of either brace. However, such patients may experience additional significant benefit in improved function and reduced stiffness, varus angulation, and medial compartment loading of the knee from use of the custom-made patient-adjustable brace. Level of Evidence: Therapeutic Level II. See Instructions to Authors for a complete description of levels of evidence.

The Effectiveness of Self-Adjustable Custom and Off-the-Shelf Bracing in the Treatment of Varus Gonarthrosis

A recent development in valgus-producing knee braces has been the adjustable "unloader" brace. The purpose of this study was to compare the effectiveness of off-the-shelf and custom-made patient-adjustable, valgus-producing knee unloader braces in relieving pain, reducing stiffness, and improving function and in reducing varus angulation and the peak adduction moments about the knee during gait and stair-stepping in patients with painful varus gonarthrosis of the knee. Ten adult patients served as their own controls for the measurement of baseline values and then wore each of the two braces, one after the other, for four to five weeks in a random order. Pain, stiffness, and function were assessed with the Western Ontario and McMaster Universities Osteoarthritis Index. Gait and stair-stepping were evaluated with a three-dimensional motion analysis system and multicomponent force platform. Full-length (hip, knee, and ankle) standing anteroposterior radiographs were used to determine alignment of the knee. Both braces significantly reduced pain and stiffness (p<0.05), with the custom brace reducing stiffness significantly more than the off-the-shelf brace (p=0.030). The custom brace significantly improved function (p=0.010) and reduced the peak knee adduction moments during gait (p=0.033) and stair-stepping (p=0.002) compared with baseline values and compared with the off-the-shelf brace (p=0.029 and p=0.027, respectively). The custom brace significantly reduced varus angulation of the knee by 1.5 degrees compared with baseline (p=0.001) and by 1.3 degrees compared with the off-the-shelf brace (p=0.009). The off-the-shelf brace did not significantly reduce the varus angle. We investigated only the short-term effects of custom and off-the-shelf patient-adjustable valgus-producing knee "unloader" braces and found that patients with varus gonarthrosis of the knee may benefit significantly with respect to pain relief and reduced stiffness from use of either brace. However, such patients may experience additional significant benefit in improved function and reduced stiffness, varus angulation, and medial compartment loading of the knee from use of the custom-made patient-adjustable brace.

Mechanics of the passive knee joint. Part 1: The role of the tibial articular surfaces in guiding the passive motion

The motion of the unloaded knee is associated with tibial internal rotation and femoral posterior translation. Although it is known that the passive motion is the result of the interaction between the articular surfaces and the ligaments, the mechanism through which the particular pattern of motion is guided is not completely understood. The goal of this study was to focus on the tibial geometry and to identify the roles that its geometric features have in guiding the passive knee motion. The method used in this study simplified the geometry of the tibial plateaux and the menisci into basic features that could be eliminated individually. The generated tibial geometry was implemented in a computer model to simulate the passive motion. Different parts of the geometry were eliminated individually and the comparison between the simulation results was used to identify the role that each part of the geometry had in guiding the passive motion. The medial meniscus was found as the feature that promoted the tibial internal rotation and restrained the femoral posterior translation. The lateral meniscus and the medial aspect of the tibial eminence, on the other hand, were found as the elements that confined the tibial internal rotation.

Elastic properties of an intact and ACL-ruptured knee joint: Measurement, mathematical modelling, and haptic rendering

An analytical, dynamic model of the human knee joint has been developed to simulate the unloaded knee joint behaviour in 6 degrees of freedom. It is based on extensive robot-based measurements of the elastic properties of a human cadaver knee joint. The measured data are compared with data from the literature to ensure that a proper database for modelling is used. The analytical modelling of the passive elastic joint properties is done with Local Linear Model Trees. The deduced knee joint model incorporates passive elastic properties of the internal knee joint structures, passive elastic muscle forces, damping forces, gravitational forces, and external forces. There are two sets of parameters, one simulating the movement of the intact knee joint, and a second simulating the knee joint with ruptured anterior cruciate ligament. The dynamic model can be easily processed in real-time. It is implemented in the haptic display of the Munich Knee Joint Simulator (MKS), which enables a person to move a plastic leg driven by a robot manipulator and feel the simulated knee joint force. Orthopaedic physicians judged the performance of the dynamic knee joint model by executing physical knee joint tests at the MKS.

Changes in the human muscle force-velocity relationship in response to resistance training and subsequent detraining

Previous studies show that cessation of resistance training, commonly known as "detraining," is associated with strength loss, decreased neural drive, and muscular atrophy. Detraining may also increase the expression of fast muscle myosin heavy chain (MHC) isoforms. The present study examined the effect of detraining subsequent to resistance training on contractile performance during slow-to-medium velocity isokinetic muscle contraction vs. performance of maximal velocity "unloaded" limb movement (i.e., no external loading of the limb). Maximal knee extensor strength was measured in an isokinetic dynamometer at 30 and 240 degrees/s, and performance of maximal velocity limb movement was measured with a goniometer during maximal unloaded knee extension. Muscle cross-sectional area was determined with MRI. Electromyographic signals were measured in the quadriceps and hamstring muscles. Twitch contractions were evoked in the passive vastus lateralis muscle. MHC isoform composition was determined with SDS-PAGE. Isokinetic muscle strength increased 18% (P < 0.01) and 10% (P < 0.05) at slow and medium velocities, respectively, along with gains in muscle cross-sectional area and increased electromyogram in response to 3 mo of resistance training. After 3 mo of detraining these gains were lost, whereas in contrast maximal unloaded knee extension velocity and power increased 14% (P < 0.05) and 44% (P < 0.05), respectively. Additionally, faster muscle twitch contractile properties along with an increased and decreased amount of MHC type II and MHC type I isoforms, respectively, were observed. In conclusion, detraining subsequent to resistance training increases maximal unloaded movement speed and power in previously untrained subjects. A phenotypic shift toward faster muscle MHC isoforms (I --> IIA --> IIX) and faster electrically evoked muscle contractile properties in response to detraining may explain the present results.