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Kathryn E. Keenan, Saikat Pal, Derek P. Lindsey, Thor F. Besier and Gary S. Beaupre

Cartilage material properties provide important insights into joint health, and cartilage material models are used in whole-joint finite element models. Although the biphasic model representing experimental creep indentation tests is commonly used to characterize cartilage, cartilage short-term response to loading is generally not characterized using the biphasic model. The purpose of this study was to determine the short-term and equilibrium material properties of human patella cartilage using a viscoelastic model representation of creep indentation tests. We performed 24 experimental creep indentation tests from 14 human patellar specimens ranging in age from 20 to 90 years (median age 61 years). We used a finite element model to reproduce the experimental tests and determined cartilage material properties from viscoelastic and biphasic representations of cartilage. The viscoelastic model consistently provided excellent representation of the short-term and equilibrium creep displacements. We determined initial elastic modulus, equilibrium elastic modulus, and equilibrium Poisson’s ratio using the viscoelastic model. The viscoelastic model can represent the short-term and equilibrium response of cartilage and may easily be implemented in whole-joint finite element models.

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Nicholas M. Brisson, Paul W. Stratford, Saara Totterman, José G. Tamez-Peña, Karen A. Beattie, Jonathan D. Adachi and Monica R. Maly

Investigations of joint loading in knee osteoarthritis (OA) typically normalize the knee adduction moment to global measures of body size (eg, body mass, height) to allow comparison between individuals. However, such measurements may not reflect knee size. This study used a morphometric measurement of the cartilage surface area on the medial tibial plateau, which better represents medial knee size. This study aimed to determine whether normalizing the peak knee adduction moment and knee adduction moment impulse during gait to the medial tibial bone–cartilage interface could classify radiographic knee OA severity more accurately than traditional normalization techniques. Individuals with mild (N = 22) and severe (N = 17) radiographic knee OA participated. The medial tibial bone–cartilage interface was quantified from magnetic resonance imaging scans. Gait analysis was performed, and the peak knee adduction moment and knee adduction moment impulse were calculated in nonnormalized units and normalized to body mass, body weight × height, and the medial tibial bone–cartilage interface. Receiver operating characteristic curves compared the ability of each knee adduction moment normalization technique to classify participants according to radiographic disease severity. No normalization technique was superior at distinguishing between OA severities. Knee adduction moments normalized to medial knee size were not more sensitive to OA severity.

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Caroline Lisee, Melanie L. McGrath, Christopher Kuenze, Ming Zhang, Matt Salzler, Jeffrey B. Driban and Matthew S. Harkey

Knee osteoarthritis (OA) is characterized by declining synovial joint health, especially in the articular cartilage. 1 Clinically feasible assessments of early articular cartilage changes may overcome the barriers of technically demanding or expensive biomarkers and encourage implementation of

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Jonathan S. Goodwin, Robert A. Creighton, Brian G. Pietrosimone, Jeffery T. Spang and J. Troy Blackburn

Individuals who sustain traumatic joint injuries are at an increased risk of knee osteoarthritis (OA). 1 , 2 Several surgical procedures are performed to repair cartilage following trauma (eg, microfracture, osteochondral allograft transplantation surgery), but their ability to reduce knee OA risk

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Tzu-Chieh Liao, Joyce H. Keyak and Christopher M. Powers

patellofemoral joint stress during walking and greater cartilage and bone stress during squatting when compared with pain-free individuals. 5 , 6 However, the finding of elevated stress in persons with PFP has not been consistent across studies that have examined higher-demand activities, such as stair climbing

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Rebecca L. Lambach, Jay W. Young, David C. Flanigan, Robert A. Siston and Ajit M.W. Chaudhari

Linemen are at high risk for knee cartilage injuries and osteoarthritis. High-intensity movements from squatting positions (eg, 3-point stance) may produce high joint loads, increasing the risk for cartilage damage. We hypothesized that knee moments and joint reaction forces during lineman-specific activities would be greater than during walking or jogging. Data were collected using standard motion analysis techniques. Fifteen NCAA linemen (mean ± SD: height = 1.86 ± 0.07 m, mass = 121.45 ± 12.78 kg) walked, jogged, and performed 3 unloaded lineman-specific blocking movements from a 3-point stance. External 3-dimensional knee moments and joint reaction forces were calculated using inverse dynamics equations. MANOVA with subsequent univariate ANOVA and post hoc Tukey comparisons were used to determine differences in peak kinetic variables and the flexion angles at which they occurred. All peak moments and joint reaction forces were significantly higher during jogging than during all blocking drills (all P < .001). Peak moments occurred at average knee flexion angles > 70° during blocking versus < 44° in walking or jogging. The magnitude of moments and joint reaction forces when initiating movement from a 3-point stance do not appear to increase risk for cartilage damage, but the high flexion angles at which they occur may increase risk on the posterior femoral condyles.

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Andrea Bailey, Nicola Goodstone, Sharon Roberts, Jane Hughes, Simon Roberts, Louw van Niekerk, James Richardson and Dai Rees

Objective:

To develop a postoperative rehabilitation protocol for patients receiving autologous-chondrocyte implantation (ACI) to repair articular-cartilage defects of the knee.

Data Sources:

careful review of both basic science and clinical literature, personal communication with colleagues dealing with similar cases, and the authors’ experience and expertise in rehabilitating numerous patients with knee pathologies, injuries, and trauma.

Data Synthesis:

Postoperative rehabilitation of the ACI patient plays a critical role in the outcome of the procedure. The goals are to improve function and reduce discomfort by focusing on 3 key elements: weight bearing, range of motion, and strengthening.

Conclusions:

The authors present 2 flexible postoperative protocols to rehabilitate patients after an ACI procedure to the knee.

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Andrea Kay Bailey, Claire Minshull, James Richardson and Nigel P. Gleeson

Context:

Autologous chondrocyte implantation (ACI) aims to restore hyaline cartilage. Traditionally, ACI rehabilitation is prescribed in a concurrent (CON) format. However, it is well known from studies in asymptomatic populations that CON training produces an interference effect that can attenuate strength gains. Strength is integral to joint function, so adopting a nonconcurrent (N-CON) approach to ACI rehabilitation might improve outcomes.

Objective:

To assess changes in function and neuromuscular performance during 48 wk of CON and N-CON physical rehabilitation after ACI to the knee.

Setting:

Orthopedic Hospital NHS Foundation Trust.

Design:

Randomized control, pilot study.

Participants:

11 patients (9 male, 2 female; age 32.3 ± 6.6 y; body mass 79.3 ±10.4 kg; time from injury to surgery 7.1 ± 4.9 mo [mean ± SD]) randomly allocated to N-CON:CON (2:1).

Interventions:

Standardized CON and N-CON physiotherapy that involved separation of strength and cardiovascular-endurance conditioning.

Main Outcome Measures:

Function in the single-leg-hop test, patient-reported outcomes (Knee injury and Osteoarthritis Outcome Score [KOOS], International Knee Documentation Committee subjective questionnaire [IKDC]), and neuromuscular outcomes of peak force (PF), rate of force development (RFD), electromechanical delay (EMD), and sensorimotor performance (force error [FE]) of the knee extensors and flexors of the injured and noninjured legs, measured presurgery and at 6, 12, 24, and 48 wk postsurgery.

Results:

Factorial ANOVAs with repeated measures of group by leg and by test occasion revealed significantly superior improvements for KOOS, IKDC, PF, EMD, and FE associated with N-CON vs CON rehabilitation (F 1.5, 13.4 GG = 3.7−4.7, P < .05). These results confirm increased peak effectiveness of N-CON rehabilitation (~4.5−13.3% better than CON over 48 wk of rehabilitation). N-CON and CON showed similar patterns of improvement for single-leg-hop test and RFD.

Conclusions:

Nonconcurrent strength and cardiovascular-endurance conditioning during 48 wk of rehabilitation after ACI surgery elicited significantly greater improvements to functional and neuromuscular outcomes than did contemporary concurrent rehabilitation.

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Andre Filipe Santos-Magalhaes and Karen Hambly

Context:

The assessment of physical activity and return to sport and exercise activities is an important component in the overall evaluation of outcome after autologous cartilage implantation (ACI).

Objective:

To identify the patient-report instruments that are commonly used in the evaluation of physical activity and return to sport after ACI and provide a critical analysis of these instruments from a rehabilitative perspective.

Evidence Acquisition:

A computerized search was performed in January 2013 and repeated in March 2013. Criteria for inclusion required that studies (1) be written in English and published between 1994 and 2013; (2) be clinical studies where knee ACI cartilage repair was the primary treatment, or comparison studies between ACI and other techniques or between different ACI generations; (3) report postoperative physical activity and sport participation outcomes results, and (4) have evidence level of I–III.

Evidence Synthesis:

Twenty-six studies fulfilled the inclusion criteria. Three physical activity scales were identified: the Tegner Activity Scale, Modified Baecke Questionnaire, and Activity Rating Scale. Five knee-specific instruments were identified: the Lysholm Knee Function Scale, International Knee Documentation Committee Score Subjective Form, Knee Injury and Osteoarthritis Outcome Score, Modified Cincinnati Knee Score, and Stanmore-Bentley Functional Score.

Conclusions:

Considerable heterogeneity exists in the reporting of physical activity and sports participation after ACI. Current instruments do not fulfill the rehabilitative needs in the evaluation of physical activity and sports participation. The validated instruments fail in the assessment of frequency, intensity, and duration of sports participation.

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Louise M. Thoma, David C. Flanigan, Ajit M. Chaudhari, Robert A. Siston, Thomas M. Best and Laura C. Schmitt

Context:

Few objective data are available regarding strength and movement patterns in individuals with articular cartilage defects (ACDs) of the knee.

Objectives:

To test the following hypotheses: (1) The involved limb of individuals with ACDs would demonstrate lower peak knee-flexion angle, peak internal knee-extension moment, and peak vertical ground-reaction force (vGRF) than the contralateral limb and healthy controls. (2) On the involved limb of individuals with ACDs, quadriceps femoris strength would positively correlate with peak knee-flexion angle, peak internal knee-extension moment, and peak vGRF.

Design:

Cross-sectional.

Setting:

Biomechanics research laboratory.

Participants:

11 individuals with ACDs in the knee who were eligible for surgical cartilage restoration and 10 healthy controls.

Methods:

Quadriceps femoris strength was quantified as peak isometric knee-extension torque via an isokinetic dynamometer. Sagittal-plane knee kinematics and kinetics were measured during the stance phase of stair ascent with 3-dimensional motion analysis.

Main Outcome Measures:

Quadriceps strength and knee biomechanics during stair ascent were compared between the involved and contralateral limbs of participants with ACD (paired t tests) and with a control group (independent-samples t tests). Pearson correlations evaluated relationships between strength and stair-ascent biomechanics.

Results:

Lower quadriceps strength and peak internal knee-extension moments were observed in the involved limb than in the contralateral limb (P < .01) and the control group (P < .01). For the involved limb of the ACD group, quadriceps femoris strength was strongly correlated (r = .847) with involved-limb peak internal knee-extension moment and inversely correlated (r = −.635) with contralateral peak vGRF. Conclusions: Individuals with ACDs demonstrated deficits in quadriceps femoris strength with associated alterations in movement patterns during stair ascent. The results of this study are not comprehensive; further research is needed to understand the physiological characteristics, activity performance, and movement quality in this population.