Patellofemoral contact forces and knee gait mechanics 3 months after ACL reconstruction are associated with cartilage degradation 24 months after surgery.

OBJECTIVE: Evaluate patellofemoral cartilage health, as assessed by quantitative magnetic resonance imaging (qMRI) T2 relaxation times, 24-months after ACL reconstruction (ACLR) and determine if they were associated with patellofemoral contact forces and knee mechanics during gait 3 months after surgery. DESIGN: Thirty individuals completed motion analysis during overground walking at a self-selected speed 3 months after ACLR. An EMG-driven neuromusculoskeletal model was used to determine muscle forces, which were then used in a previously described model to estimate patellofemoral contact forces. Biomechanical variables of interest included peak patellofemoral contact force, peak knee flexion angle and moment, and walking speed. These same participants underwent a sagittal bilateral T2 mapping qMRI scan 24-months after surgery. T2 relaxation times were estimated for both patellar and trochlear cartilage. Paired t-tests were used to compare T2 relaxation times between limbs while Pearson correlations and linear regressions were utilized to assess the association between the biomechanical variables of interest and T2 relaxation times. RESULTS: Prolonged involved limb trochlear T2 relaxation times (vs uninvolved) were present 24-months after surgery, indicating worse cartilage health. No differences were detected in patellar cartilage. Significant negative associations were present within the involved limb for all the biomechanical variables of interest 3 months after ACLR and trochlear T2 relaxation times at 24-months. No associations were found in patellar cartilage or within the uninvolved limb. CONCLUSIONS: Altered involved limb trochlear cartilage health is present 24-months after ACLR and may be related to patellofemoral loading and other walking gait mechanics 3 months after surgery.

OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis

To update and expand upon prior Osteoarthritis Research Society International (OARSI) guidelines by developing patient-focused treatment recommendations for individuals with Knee, Hip, and Polyarticular osteoarthritis (OA) that are derived from expert consensus and based on objective review of high-quality meta-analytic data. We sought evidence for 60 unique interventions. A systematic search of all relevant databases was conducted from inception through July 2018. After abstract and full-text screening by two independent reviewers, eligible studies were matched to PICO questions. Data were extracted and meta-analyses were conducted using RevMan software. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Evidence Profiles were compiled using the GRADEpro web application. Voting for Core Treatments took place first. Four subsequent voting sessions took place via anonymous online survey, during which Panel members were tasked with voting to produce recommendations for all joint locations and comorbidity classes. We designated non-Core treatments to Level 1A, 1B, 2, 3, 4A, 4B, or 5, based on the percentage of votes in favor, in addition to the strength of the recommendation. Core Treatments for Knee OA included arthritis education and structured land-based exercise programs with or without dietary weight management. Core Treatments for Hip and Polyarticular OA included arthritis education and structured land-based exercise programs. Topical non-steroidal anti-inflammatory drugs (NSAIDs) were strongly recommended for individuals with Knee OA (Level 1A). For individuals with gastrointestinal comorbidities, COX-2 inhibitors were Level 1B and NSAIDs with proton pump inhibitors Level 2. For individuals with cardiovascular comorbidities or frailty, use of any oral NSAID was not recommended. Intra-articular (IA) corticosteroids, IA hyaluronic acid, and aquatic exercise were Level 1B/Level 2 treatments for Knee OA, dependent upon comorbidity status, but were not recommended for individuals with Hip or Polyarticular OA. The use of Acetaminophen/Paracetamol (APAP) was conditionally not recommended (Level 4A and 4B), and the use of oral and transdermal opioids was strongly not recommended (Level 5). A treatment algorithm was constructed in order to guide clinical decision-making for a variety of patient profiles, using recommended treatments as input for each decision node. These guidelines offer comprehensive and patient-centered treatment profiles for individuals with Knee, Hip, and Polyarticular OA. The treatment algorithm will facilitate individualized treatment decisions regarding the management of OA.

OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis.

OBJECTIVE: To update and expand upon prior Osteoarthritis Research Society International (OARSI) guidelines by developing patient-focused treatment recommendations for individuals with Knee, Hip, and Polyarticular osteoarthritis (OA) that are derived from expert consensus and based on objective review of high-quality meta-analytic data. METHODS: We sought evidence for 60 unique interventions. A systematic search of all relevant databases was conducted from inception through July 2018. After abstract and full-text screening by two independent reviewers, eligible studies were matched to PICO questions. Data were extracted and meta-analyses were conducted using RevMan software. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Evidence Profiles were compiled using the GRADEpro web application. Voting for Core Treatments took place first. Four subsequent voting sessions took place via anonymous online survey, during which Panel members were tasked with voting to produce recommendations for all joint locations and comorbidity classes. We designated non-Core treatments to Level 1A, 1B, 2, 3, 4A, 4B, or 5, based on the percentage of votes in favor, in addition to the strength of the recommendation. RESULTS: Core Treatments for Knee OA included arthritis education and structured land-based exercise programs with or without dietary weight management. Core Treatments for Hip and Polyarticular OA included arthritis education and structured land-based exercise programs. Topical non-steroidal anti-inflammatory drugs (NSAIDs) were strongly recommended for individuals with Knee OA (Level 1A). For individuals with gastrointestinal comorbidities, COX-2 inhibitors were Level 1B and NSAIDs with proton pump inhibitors Level 2. For individuals with cardiovascular comorbidities or frailty, use of any oral NSAID was not recommended. Intra-articular (IA) corticosteroids, IA hyaluronic acid, and aquatic exercise were Level 1B/Level 2 treatments for Knee OA, dependent upon comorbidity status, but were not recommended for individuals with Hip or Polyarticular OA. The use of Acetaminophen/Paracetamol (APAP) was conditionally not recommended (Level 4A and 4B), and the use of oral and transdermal opioids was strongly not recommended (Level 5). A treatment algorithm was constructed in order to guide clinical decision-making for a variety of patient profiles, using recommended treatments as input for each decision node. CONCLUSION: These guidelines offer comprehensive and patient-centered treatment profiles for individuals with Knee, Hip, and Polyarticular OA. The treatment algorithm will facilitate individualized treatment decisions regarding the management of OA.

Hip joint biomechanics in those with and without post-traumatic knee osteoarthritis after anterior cruciate ligament injury.

BACKGROUND: Anterior cruciate ligament injury results in altered kinematics and kinetics in the knee and hip joints that persist despite surgical reconstruction and rehabilitation. Abnormal movement patterns and a history of osteoarthritis are risk factors for articular cartilage degeneration in additional joints. The purpose of this study was to determine if hip joint biomechanics early after anterior cruciate ligament injury and reconstruction differ between patients with and without post-traumatic knee osteoarthritis 5years after reconstruction. The study's rationale was that individuals who develop knee osteoarthritis after anterior cruciate ligament injury may also demonstrate large alterations in hip joint biomechanics. METHODS: Nineteen athletes with anterior cruciate ligament injury completed standard gait analysis before (baseline) and after (post-training) extended pre-operative rehabilitation and at 6months, 1year, and 2years after reconstruction. Weightbearing knee radiographs were completed 5years after reconstruction to identify medial compartment osteoarthritis. FINDINGS: Five of 19 patients had knee osteoarthritis at 5years after anterior cruciate ligament reconstruction. Patients with knee osteoarthritis at 5years walked with smaller sagittal plane hip angles (P: 0.043) and lower sagittal (P: 0.021) and frontal plane (P: 0.042) external hip moments in the injured limb before and after reconstruction compared to those without knee osteoarthritis. INTERPRETATION: The current findings suggest hip joint biomechanics may be altered in patients who develop post-traumatic knee osteoarthritis. Further study is needed to confirm whether the risk of non-traumatic hip pathology is increased after anterior cruciate ligament injury and if hip joint biomechanics influence its development.

OARSI Clinical Trials Recommendations: Design and conduct of clinical trials of rehabilitation interventions for osteoarthritis.

A Task Force of the Osteoarthritis Research Society International (OARSI) has previously published a set of guidelines for the conduct of clinical trials in osteoarthritis (OA) of the hip and knee. Limited material available on clinical trials of rehabilitation in people with OA has prompted OARSI to establish a separate Task Force to elaborate guidelines encompassing special issues relating to rehabilitation of OA. The Task Force identified three main categories of rehabilitation clinical trials. The categories included non-operative rehabilitation trials, post-operative rehabilitation trials, and trials examining the effectiveness of devices (e.g., assistive devices, bracing, physical agents, electrical stimulation, etc.) that are used in rehabilitation of people with OA. In addition, the Task Force identified two main categories of outcomes in rehabilitation clinical trials, which include outcomes related to symptoms and function, and outcomes related to disease modification. The guidelines for rehabilitation clinical trials provided in this report encompass these main categories. The report provides guidelines for conducting and reporting on randomized clinical trials. The topics include considerations for entering patients into trials, issues related to conducting trials, considerations for selecting outcome measures, and recommendations for statistical analyses and reporting of results. The focus of the report is on rehabilitation trials for hip, knee and hand OA, however, we believe the content is broad enough that it could be applied to rehabilitation trials for other regions as well.

A more informed evaluation of medial compartment loading: the combined use of the knee adduction and flexor moments.

OBJECTIVE: To evaluate if the peak knee flexor moment (pKFM) provides unique and meaningful information about peak medial compartment loading above and beyond what is obtained from the peak knee adduction moment. METHODS: Standard video-based motion capture and EMG recordings were collected for 10 anterior cruciate ligament (ACL) reconstructed subjects walking at a self-selected speed. Knee joint moments were obtained using inverse dynamics and medial contact force was computed using an EMG-driven musculoskeletal model. Linear regression with the peak adductor moment entered first was implemented to isolate the unique contribution of the peak flexor moment to peak medial loading. RESULTS: Peak moments and medial contact force occurred during weight acceptance at approximately 23% of stance. The peak knee adduction moment (pKAM) was a significant predictor of peak medial loading (P = 0.004) accounting for approximately 63% of the variance. The pKFM was also a significant predictor (P = 0.009) accounting for an additional 22% of the variance. When entered together pKAM and pKFM accounted for more than 85% of the variance in peak medial compartment loading. CONCLUSION: The combined use of the peak knee flexor and adductor moments provides a significantly more accurate estimate of peak medial joint loading than the peak adduction moment alone. More accurate inferences of joint contact force will assist clinicians and researchers investigating relationships between joint loading and the onset and progression of knee osteoarthritis (OA).

How does a combined preoperative and postoperative rehabilitation programme influence the outcome of ACL reconstruction 2 years after surgery? A comparison between patients in the Delaware-Oslo ACL Cohort and the Norwegian National Knee Ligament Registry.

BACKGROUND: Preoperative knee function is associated with successful postoperative outcome after anterior cruciate ligament reconstruction (ACLR). However, there are few longer term studies of patients who underwent progressive preoperative and postoperative rehabilitation compared to usual care. OBJECTIVES: To compare preoperative and 2 year postoperative patient-reported outcomes (PROs) in patients undergoing progressive preoperative and postoperative rehabilitation at a sports medicine clinic compared with usual care. METHODS: We included patients aged 16-40 years undergoing primary unilateral ACLR. The preoperative and 2 year postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) of 84 patients undergoing progressive preoperative and postoperative rehabilitation at a sports medicine clinic (Norwegian Research Center for Active Rehabilitation (NAR) cohort) were compared with the scores of 2690 patients from the Norwegian National Knee Ligament Registry (NKLR). The analyses were adjusted for sex, age, months from injury to surgery and cartilage/meniscus injury at ACLR. RESULTS: The NAR cohort had significantly better preoperative KOOS in all subscales, with clinically relevant differences (>10 points) observed in KOOS Pain, activities of daily living (ADL), Sports and Quality of Life. At 2 years, the NAR cohort still had significantly better KOOS with clinically relevant differences in KOOS Symptoms, Sports and Quality of Life. At 2 years, 85.7-94% of the patients in the NAR cohort scored within the normative range of the different KOOS subscales, compared to 51.4-75.8% of the patients in the NKLR. CONCLUSIONS: Patients in a prospective cohort who underwent progressive preoperative and postoperative rehabilitation at a sports medicine clinic showed superior patient-reported outcomes both preoperatively and 2 years postoperatively compared to patients in the NKLR who received usual care.

Physical exercise after knee arthroplasty: a systematic review of controlled trials.

Total knee arthroplasty (TKA) is the gold standard treatment for end-stage knee osteoarthritis. Most patients report successful long-term outcomes and reduced pain after TKA, but recovery is variable and the majority of patients continue to demonstrate lower extremity muscle weakness and functional deficits compared to age-matched control subjects. Given the potential positive influence of postoperative rehabilitation and the lack of established standards for prescribing exercise paradigms after TKA, the purpose of this study was to systematically review randomized, controlled studies to determine the effectiveness of postoperative outpatient care on short- and long-term functional recovery. Nineteen studies were identified as highly relevant for the review and four categories of postoperative intervention were discussed: 1) strengthening exercises; 2) aquatic therapy; 3) balance training; and 4) clinical environment. Optimal outpatient physical therapy protocols should include: strengthening and intensive functional exercises given through land-based or aquatic programs, the intensity of which is increased based on patient progress. Due to the highly individualized characteristics of these types of exercises, outpatient physical therapy performed in a clinic under the supervision of a trained physical therapist may provide the best long-term outcomes after the surgery. Supervised or remotely supervised therapy may be effective at reducing some of the impairments following TKA, but several studies without direct oversight produced poor results. Most studies did not accurately describe the "usual care" or control groups and information about the dose, frequency, intensity and duration of the rehabilitation protocols were lacking from several studies.

OARSI recommended performance-based tests to assess physical function in people diagnosed with hip or knee osteoarthritis.

OBJECTIVES: To recommend a consensus-derived set of performance-based tests of physical function for use in people diagnosed with hip or knee osteoarthritis (OA) or following joint replacement. METHODS: An international, multidisciplinary expert advisory group was established to guide the study. Potential tests for consideration in the recommended set were identified via a survey of selected experts and through a systematic review of the measurement properties for performance-based tests. A multi-phase, consensus-based approach was used to prioritize and select performance-based tests by applying decision analysis methodology (1000Minds software) via online decision surveys. The recommended tests were chosen based on available measurement-property evidence, feasibility of the tests, scoring methods and expert consensus. RESULTS: Consensus incorporated the opinions of 138 experienced clinicians and researchers from 16 countries. The five tests recommended by the advisory group and endorsed by Osteoarthritis Research Society International (OARSI) were the 30-s chair-stand test, 40 m fast-paced walk test, a stair-climb test, timed up-and-go test and 6-min walk test. The first three were recommended as the minimal core set of performance-based tests for hip or knee OA. CONCLUSION: The OARSI recommended set of performance-based tests of physical function represents the tests of typical activities relevant to individuals diagnosed with hip or knee OA and following joint replacements. These tests are complementary to patient-reported measures and are recommended as prospective outcome measures in future OA research and to assist decision-making in clinical practice. Further research should be directed to expanding the measurement-property evidence of the recommended tests.

Most patients gain weight in the 2 years after total knee arthroplasty: comparison to a healthy control group.

OBJECTIVE: While joint arthroplasty improves the functional ability of persons with severe knee osteoarthritis (OA), the long-term effects of surgical intervention on body mass have not been evaluated. The objective of this study was to determine if a reduction in body mass index (BMI) was present following unilateral total knee arthroplasty (TKA) compared to an age-matched healthy control group who did not have surgery. METHOD: One hundred and six adults with unilateral, end-stage knee OA and thirty-one persons without knee pain participated in the prospective longitudinal study. Subjects with OA underwent primary unilateral TKA and received post-operative out-patient physical therapy. Height, weight, quadriceps strength and self-perceived functional ability were measured at baseline and at a 2-year follow-up. RESULTS: There was a significant interaction effect between body mass over time and subject group (P=0.017). BMI showed a significant increase over 2 years for the surgical group (P<0.001), but not for the control group (P=0.842). Sixty-six percent of the persons in the surgical group gained weight over the 2 years with an average weight gain of 6.4 kg, or 14 pounds, 2 years after their initial physical therapy visit. Educational level, marital status, income level and activity level prior to surgery were not related to post-surgical weight gain. CONCLUSION: The majority of subjects gain weight after surgery and this cannot be attributed to the effects of aging. Weight gain after TKA should be treated as an independent concern and management of orthopedic impairments will not result in weight loss. Post-operative care should include access to nutrition or weight management professionals in addition to medical and physical therapy services.

Rehabilitation after anterior cruciate ligament injury influences joint loading during walking but not hopping.

OBJECTIVE: The purpose of this study was to identify changes in clinical outcome and lower extremity biomechanics during walking and hopping in ACL-injured subjects before and after a 20-session neuromuscular and strength training programme. STUDY DESIGN: Pre and post experimental design. SETTING: Outpatient clinic, primary care. PATIENTS: 32 subjects with unilateral ACL injury, mean 60 (SD 35) days after injury, with a mean age of 26.2 (5.4) years. INTERVENTION: The rehabilitation programme consisted of neuromuscular and strength exercises. MAIN OUTCOME MEASUREMENTS: Outcome measurements assessed before and after a 20-session rehabilitation programme were: self-assessment questionnaires (KOS-ADL, IKDC2000, Global function), four single-leg hop tests, and isokinetic muscle strength tests. Lower extremity kinematics and kinetics were captured during the stance phase of gait and landing after a single leg hop, synchronised with three force plates. RESULTS: These ACL-injured individuals significantly improved their clinical outcome after rehabilitation. Gait analysis disclosed a significantly improved knee extension moment after rehabilitation, but no change in hip or knee excursions. During landing after hop no change in knee excursion or knee moment was recorded. CONCLUSION: After rehabilitation the ACL-injured subjects showed a significantly improved clinical outcome, but lower extremity biomechanics were still significantly impaired during both walking and hopping. The rehabilitation programme influenced knee joint loading during walking, but not during hopping. Longer rehabilitation should be considered before ACL-injured individuals return to jumping activities.

Disease-specific gender differences among total knee arthroplasty candidates.

BACKGROUND: Women with knee osteoarthritis are less likely to undergo joint replacement despite greater self-reported disability. The primary aim of the present study was to assess gender differences in the type and magnitude of osteoarthritis-related impairment prior to knee arthroplasty. METHODS: Two hundred and twenty-one knee arthroplasty candidates (ninety-five men and 126 women) and forty-four healthy gender, age, and body mass index-matched individuals were tested. Individuals with contralateral limb injury or abnormality, cardiovascular disease, neurological impairment, and medical conditions limiting activity were excluded. Collected data included Medical Outcomes Study Short Form-36 mental and physical component scores, the Knee Outcome Survey Activities of Daily Living Scale score, knee range of motion, timed up-and-go test time, stair-climb test time, six-minute walk distance, normalized quadriceps strength, and volitional muscle activation. RESULTS: Women in the arthroplasty group had lower Short Form-36 and Knee Outcome Survey scores, longer timed up-and-go test and stair-climb test times, shorter six-minute walk distances, and lower normalized quadriceps strength compared with men. Healthy women had longer stair-climb test times and shorter six-minute walk distances in comparison with healthy men. Between-group comparisons revealed that women in both the control group and the arthroplasty group had reduced normalized quadriceps strength in comparison with men, that healthy women had higher voluntary muscle activation in comparison with healthy men, and that female arthroplasty candidates had lower activation levels in comparison with male candidates. CONCLUSIONS: Observed gender differences in strength and function appear to be inherent but are magnified in arthroplasty candidates. Strength and functional decline should be closely monitored in women with knee osteoarthritis to serve as an indicator of worsening condition, and preoperative interventions should reflect these gender-specific impairments.

Elucidation of a potentially destabilizing control strategy in ACL deficient non-copers.

PURPOSE: The purpose was to differentiate the dynamic knee stabilization strategies of potential copers (individuals who have the potential to compensate for the absence of an ACL without episodes of giving way after return to pre-injury activities) and non-copers (those who have knee instability following ACL rupture with return to pre-injury activities). METHODS: Twenty subjects with ACL rupture were assigned to potential coper (n=10) and non-coper (n=10) groups via a screening examination. Ten active people without lower extremity injury were also tested. Knee angle, tibial position and muscle activity data were collected while subjects stood in unilateral stance on a platform that moved horizontally in an anterior direction. Analysis included the preparation for platform movement; and monosynaptic, intermediate reflex and voluntary response intervals after platform movement. RESULTS: Non-copers showed greater knee flexion than uninjured subjects, and had a posterior tibial position and altered hamstring recruitment compared to the other groups. Potential copers demonstrated greater medial quadriceps activity while maintaining knee kinematics similar to uninjured subjects. Both potential copers and non-copers had greater co-contraction between medial hamstrings and quadriceps than uninjured subjects. All excitatory muscle activation occurred in the intermediate reflex interval. DISCUSSION AND CONCLUSIONS: Non-copers displayed aberrant muscle recruitment that may contribute to knee instability. Potential copers maintained normal tibial position using a strategy that permits quadriceps activation without excessive anterior tibial translation. Muscle recruitment in the intermediate reflex interval suggests neuromuscular training may influence the strategies.

Evidence for differential control of tibial position in perturbed unilateral stance after acute ACL rupture.

Functional outcomes in anterior cruciate ligament-deficient "potential copers" and "non-copers" may be related to their knee stabilization strategies. Therefore, the purpose of this study was to differentiate dynamic knee stabilization strategies of potential copers and non-copers through analysis of sagittal plane knee angle and tibia position during disturbed and undisturbed unilateral standing. Ten uninjured potential coper and non-coper subjects stood in unilateral stance on a platform that translated anteriorly, posteriorly and laterally. Knee angle and tibia position with reference to the femur were calculated before and after platform movement. During perturbation trials, potential copers maintained kinematics that were similar to uninjured subjects across conditions. Conversely, non-copers stood with greater knee flexion than uninjured subjects and a tibia position that was more posterior than the other groups. Both non-copers and potential copers demonstrated small changes in tibia position following platform movement, but direction of movement was not similar. The similarities between the knee kinematics of potential copers and uninjured subjects suggest that potential copers compensated well from their injury by utilizing analogous dynamic knee stabilization strategies. In comparison to the other groups, by keeping the knee in greater flexion and the tibia in a more posterior position, non-copers appear to constrain the tibia in response to a challenging task, which is consistent with a "stiffening strategy". Based on the poor functional outcomes of non-copers, a stiffening strategy does not lead to dynamic knee stability, and the strategy may increase compressive forces which could contribute to or exacerbate articular cartilage degeneration.

The use of electrical stimulation to increase quadriceps femoris muscle force in an elderly patient following a total knee arthroplasty.

BACKGROUND AND PURPOSE: Persistent residual quadriceps femoris muscle force deficits after total knee arthroplasty (TKA) are commonly reported and can prevent patients from returning quickly and fully to functional activities. Neuromuscular electrical stimulation offers a potentially more effective means of increasing muscle force than current rehabilitation protocols. CASE DESCRIPTION: The patient was a 66-year-old man. Neuromuscular electrical stimulation for increasing quadriceps femoris muscle force was initiated 3 weeks after TKA for 11 sessions to supplement stretching exercises and a high-intensity volitional strengthening program. OUTCOME: The patient's isometric quadriceps femoris muscle force increased from 50% (involved/uninvolved) at 3 weeks after surgery to 86% at 8 weeks after surgery. A concurrent increase in his uninvolved quadriceps femoris muscle force concealed the patient's true increase in his involved quadriceps femoris muscle force in a side-to-side comparison. The patient's final involved quadriceps femoris muscle force (10 weeks after surgery) was 93% of the initial uninvolved quadriceps femoris muscle force. DISCUSSION: Our patient was able to return to independent activities of daily living and recreational activities, with force gains that surpassed those reported in the literature.

Dynamic knee stability: current theory and implications for clinicians and scientists.

We will discuss the mechanisms by which dynamic knee stability may be achieved and relate this to issues that interest clinicians and scientists concerned with dynamic knee stability. Emphasis is placed on the neurophysiologic evidence and theory related to neuromuscular control. Specific topics discussed include the ensemble firing of peripheral mechanoreceptors, the potential for muscle stiffness modulation via force and length feedback, postural control synergies, motor programs, and the neural control of gait. Factors related to answering the difficult question of whether or not knee ligament injuries can be prevented during athletic activities are discussed. Prevention programs that train athletes to perform their sport skills in a safe fashion are put forth as the most promising prospect for injury prevention. Methods of assessing neuromuscular function are reviewed critically and the need for future research in this area is emphasized. We conclude with a brief review of the literature regarding neuromuscular training programs.

Biomechanical evidence supporting a differential response to acute ACL injury.

OBJECTIVE: To describe movement patterns in people with complete anterior cruciate ligament rupture objectively identified as good candidates for non-operative management of the injury. DESIGN: Involved side kinematics and kinetics were compared to the uninvolved side and to uninjured subjects. BACKGROUND: High-level athletes with anterior cruciate ligament rupture and poor dynamic stability (non-copers) have movement alterations, including less knee flexion and a decreased internal knee extensor moment during loading response, that are not seen in those with excellent knee stability (copers). Our screening exam can identify people with good rehabilitation potential for non-operative management of anterior cruciate ligament injury (potential copers), but the movement strategies of these individuals are unknown. METHODS: Sagittal plane kinematics and kinetics during the stance phase of walking and jogging were collected from 11 subjects who had an acute anterior cruciate ligament rupture and met the criteria of the screening exam, and were compared to 10 uninjured subjects, who we studied previously. Variables were those in which non-copers differed from uninjured subjects. RESULTS: The potential copers flexed their involved knee less than uninjured subjects and their uninvolved side during walking. Potential copers, compared to uninjured subjects, also had a lower vertical ground reaction force during loading response, a lower knee support moment, and an increased ankle support moment during walking. In jogging, the involved knee angle at initial contact was more extended compared to uninjured subjects, and the amount of knee flexion was less than the uninvolved side. No differences in kinetics were present during jogging. CONCLUSIONS: This study provides evidence that the potential copers identified by the screening examination have movement patterns that are consistent with people who have more knee stability than non-copers. RELEVANCE: Although potential copers have developed some characteristics of a successful stabilization strategy, the presence of kinematic alterations indicates that they may benefit from training programs designed to enhance dynamic knee stability.

Characterization of the human quadriceps muscle in active elders.

OBJECTIVE: To compare muscle activation deficits and muscle physiology in older versus younger adults. DESIGN: A maximal volitional isometric contraction of the quadriceps muscle with burst-superimposition was used to assess strength and activation. In addition, force-frequency testing during fresh, fatigue, and recovery conditions and electrically elicited fatigue testing were performed. SETTING: Muscle performance laboratory. PATIENTS: Healthy, active young (age range, 20-28 yr) and older (age range, 66-83 yr) subjects. MAIN OUTCOME MEASURES: Torque production, activation of the quadriceps, F50 values from the force-frequency relationships (frequency at which 50% of the maximum normalized force is produced), and the average amount of fatigue. RESULTS: Older subjects were weaker (574.4 +/- 156 N) than younger subjects (900.9 +/- 295 N) and had significantly greater deficits in central activation in the quadriceps muscles (elderly = 95.5% activation; younger = 98.1% activation). The force-frequency curves for the elderly were to the left of the younger subjects for all 3 testing conditions. Aged muscles fatigued to the same extent as younger muscle (young = 49.8% +/- 2.6%, elderly = 51.1% +/- 2.8%). CONCLUSIONS: These results can be used to modify high-intensity strength training protocols designed to optimize sustainable strength gains in the elderly during rehabilitation.

Dynamic stability in the anterior cruciate ligament deficient knee.

Some individuals can stabilize their knees following anterior cruciate ligament rupture even during activities involving cutting and pivoting (copers), others have instability with daily activities (non-copers). Movement and muscle activation patterns of 11 copers, ten non-copers and ten uninjured subjects were studied during walking and jogging. Results indicate that distinct gait adaptations appeared primarily in the non-copers. Copers used joint ranges of motion, moments and muscle activation patterns similar to uninjured subjects. Non-copers reduced their knee motion, and external knee flexion moments that correlated well with quadriceps strength. Non-copers also achieved peak hamstring activity later in the weight acceptance phase and used a strategy involving more generalized co-contraction. Both copers and non-copers had high levels of quadriceps femoris muscle activity. The reduced knee moment in the involved limbs of the non-copers did not represent "quadriceps avoidance" but rather represented a strategy of general co-contraction with a greater relative contribution from the hamstring muscles.