Knee Function (knee + function)

Distribution by Scientific Domains

Selected Abstracts

Kinematics of the knee at high flexion angles: An in vitro investigation

Guoan Li
Abstract Restoration of knee function after total knee, meniscus, or cruciate ligament surgery requires an understanding of knee behavior throughout the entire range of knee motion. However, little data are available regarding knee kinematics and kinetics at flexion angles greater than 120 (high flexion). In this study, 13 cadaveric human knee specimens were tested using an in vitro robotic experimental setup. Tibial anteroposterior translation and internal,external rotation were measured along the passive path and under simulated muscle loading from full extension to 150 of flexion. Anterior tibial translation was observed in the unloaded passive path throughout, with a peak of 31.2 13.2 mm at 150. Internal tibial rotation increased with flexion to 150 on the passive path to a maximum of 11.1 6.7. The simulated muscle loads affected tibial translation and rotation between full extension and 120 of knee flexion. Interestingly, at high flexion, the application of muscle loads had little effect on tibial translation and rotation when compared to values at 120. The kinematic behavior of the knee at 150 was markedly different from that measured at other flexion angles. Muscle loads appear to play a minimal role in influencing tibial translation and rotation at maximal flexion. The results imply that the knee is highly constrained at high flexion, which could be due in part to compression of the posterior soft tissues (posterior capsule, menisci, muscle, fat, and skin) between the tibia and the femur. 2003 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

In vivo kinematics of total knee arthroplasty: Flat compared with concave tibial joint surface

J. Uvehammer
This study evaluated the influence of the geometric configuration of the tibial joint area on the kinematics of the knee. Twenty-two patients with noninflammatory arthritis and minor preoperative deformity were studied. They each received an AMK total knee replacement with retention of the posterior cruciate ligament. Eleven patients without any knee abnormalities were used as controls. The patients were stratified to either the flat (terminology of the manufacturer: standard) or concave (terminology of the manufacturer: constrained) polyethylene insert (n = 11 in each group). Knee kinematics were assessed 1 year after the operation by having the patient ascend a platform corresponding to an extension of the knee from 50 to 70 of flexion. During this motion, two film-exchangers simultaneously exposed six to 13 pairs of serial stereoradiographs. The concave geometric configuration of the tibial insert resulted paradoxically in increased anterior-posterior translations compared with the flat insect but no significant change of rotations and translations in the other directions. Compared with normal knees, the most obvious abnormality was increased anterior-posterior translations (p < 0.004). At 50 of flexion, the implants with the flat tibial polyethylene insert had displaced 2 times and the concave ones had displaced 2.5 times more posteriorly than the normal knees (p , 0.001). Less internal tibial rotation was also recorded in the flexed positions for both types of inserts compared with the normal knees (p < 0.02). Four knees in four patients, who reported symptoms of instability and abnormal knee function, showed significantly increased proximal displacement of the center of the tibial plateau in the flexed position. The findings suggest that current prosthetic designs and surgical technique do not restore normal knee kinematics and indicate that design improvements should rely on in vivo kinematic studies. [source]


Vanessa Wells
Background: This article describes the incidence of total knee and hip replacement, and compares post-surgery health status outcomes in veterans and civilians. Methods: The numbers of male veterans and civilians who had a knee and/or a hip replacement in South Australia (1994,2002) were obtained. Standardized morbidity ratios, and odds ratios for age group by veteran/civilian interactions, were calculated. Presurgery and 1-year post-surgery Medical Outcomes Short Form (36) Health Survey, Knee Society and Harris hip scores were completed. Independent samples t -tests were used to compare presurgery scores. ancova models were used to determine any differences between veterans and civilians post-surgery. Results: For veterans, standardized morbidity ratios were 0.987 and 0.715 for knee and hip replacements, respectively (P < 0.0001). Veterans' odds ratios for knee and hip replacements were significantly lower in the 65- to 74-year age group (P < 0.001), similar in the 75- to 84-year and above 85-year age groups for hip replacement, but significantly higher in the above 85-year age group for knee replacement (P < 0.001). Presurgery, veterans reported significantly lower scores (P < 0.003) for knee function. After knee replacement, veterans reported significantly lower Medical Outcomes Short Form (36) Health Survey scores for bodily pain, physical functioning, role , physical, role , emotional, social functioning and physical component summary (P < 0.033). Significantly lower physical functioning, role , physical and physical component summary scores (P < 0.02) were reported by veterans post-surgery for hip replacement. Conclusion: Veterans are delaying joint replacement. Presurgical knee function is worse in veterans. Post-surgery, the veterans are worse off in a number of health status outcomes. [source]

Calcification of articular cartilage in human osteoarthritis

M. Fuerst
Objective Hypertrophic chondrocyte differentiation is a key step in endochondral ossification that produces basic calcium phosphates (BCPs). Although chondrocyte hypertrophy has been associated with osteoarthritis (OA), chondrocalcinosis has been considered an irregular event and linked mainly to calcium pyrophosphate dihydrate (CPPD) deposition. The aim of this study was to determine the prevalence and composition of calcium crystals in human OA and analyze their relationship to disease severity and markers of chondrocyte hypertrophy. Methods One hundred twenty patients with end-stage OA undergoing total knee replacement were prospectively evaluated. Cartilage calcification was studied by conventional x-ray radiography, digital-contact radiography (DCR), field-emission scanning electron microscopy (FE-SEM), and synovial fluid analysis. Cartilage calcification findings were correlated with scores of knee function as well as histologic changes and chondrocyte hypertrophy as analyzed in vitro. Results DCR revealed mineralization in all cartilage specimens. Its extent correlated significantly with the Hospital for Special Surgery knee score but not with age. FE-SEM analysis showed that BCPs, rather than CPPD, were the prominent minerals. On histologic analysis, it was observed that mineralization correlated with the expression of type X collagen, a marker of chondrocyte hypertrophy. Moreover, there was a strong correlation between the extent of mineralization in vivo and the ability of chondrocytes to produce BCPs in vitro. The induction of hypertrophy in healthy human chondrocytes resulted in a prominent mineralization of the extracellular matrix. Conclusion These results indicate that mineralization of articular cartilage by BCP is an indissociable process of OA and does not characterize a specific subset of the disease, which has important consequences in the development of therapeutic strategies for patients with OA. [source]