Knee osteoarthritis (KOA) is the most common knee joint disease. Although KOA belongs to a disease of degeneration of knee joint cartilage, its pathology involves cartilage, subchondral bone, meniscus, synovial membrane, articular capsule and other joint tissue. The infrapatellar fat pad (IPFP), an intracapsular but extrasynovial structure, has some special characteristics of endocrine metabolism, then it has double roles in the development of KOA, but its protective effect is much more than harmful effect. Considering protective roles of IPFP in KOA and some serious complications after IPFP resection, the surgeon shall protect IPFP as far as possible if total knee arthroplasty surgical field is good. If it is necessary to improve the surgical field, its fibrotic tissue even all part can be removed.
Adipose Tissue ; physiology ; Arthroplasty, Replacement, Knee ; Humans ; Knee Joint ; physiopathology ; surgery ; Osteoarthritis, Knee ; surgery

AIMTo observe the difference of EMG features between junior athletes and general students of knee flexor and extensor in performing various jumps.

METHODS30 junior athletes and 30 middle school students took part in the test. EMG signal from knee flexor and extensor were measured, when subjects performed squatting jump, counter-movement jump and drop jump.

RESULTSThe results indicated that the agonists EMG activity related to sex. With the load of leg increasing, there were no significant changes in iEMG and Fmean for male. There was some increasing in iEMG but no change in Fmean for female. The antagonists EMG activity maybe related to training. With the load of leg increasing, the EMG activity of antagonists changed slightly for the junior athletes, however, increased obviously for the common students.

CONCLUSIONTo improve the performance of jump, male athletes should mostly improve efficiency, however female athletes can increase the recruiting of muscle fiber. Moreover the ability of antagonists coordinating for athlete in the course of jumping is higher than that of general students.

Adolescent ; Athletes ; Electromyography ; Female ; Humans ; Knee Joint ; physiology ; Male ; Movement ; physiology ; Muscle, Skeletal ; physiology ; Posture ; physiology

This study was designed to determine the effect of backpack loading on the gait pattern and corresponding compensatory strategy, which is important to the balance control of biped robot and military training. Five healthy subjects were instructed to walk at their preferred speed on level pathway taking three different loads i.e. 6 kg, 12 kg and 25 kg, on their backs. The results showed that the gait pattern was apparently influenced, and the dominant effects were found to be the flexion of hip, knee joints and pitch angle of torso. The stride speed decreased apparently with loading on their backs, but the stride length showed less changes. Besides, the responses to taking loads might be influenced by the strength of body. An apparent multi-joints coordination motor mode was employed to compensate the influences of loading, however, their contributions are different; hip, knee joints and torso pitch made dominant contributions to the compensation while ankle joints made minor. The anterior pitch of upper torso could be employed to adjust the overall center of mass while loading on their backs, the larger the magnitude of loading on their backs, the larger the anterior pitch angle of torso. After the heel touched the ground, the flexion of hip and knee joints were effective for the shock absorption, which means that the stiffness of hip and knee joints can be used to absorb the shock and avoid the trauma of each joints.
Adult ; Ankle Joint ; physiology ; Back ; physiology ; Gait ; physiology ; Hip Joint ; physiology ; Humans ; Knee Joint ; physiology ; Male ; Weight-Bearing ; physiology

A sagittal plane model of knee joint based on crossed-four-bar-linkage-based tibiofemoral joint model has been developed using geometric and force equilibrium constraints. The model predicts and explains the movement of contact point on the patella and femur, variation of patellar and patellar tendon angle, variation of patellar mechanism angle and variation of patellofemoral contact force and patellar tendon force. The computed results agree well with the published experimental results.
Biomechanical Phenomena ; Humans ; Knee Joint ; anatomy & histology ; physiology ; Models, Biological ; Movement ; physiology ; Patella ; anatomy & histology ; physiology

OBJECTIVETo create a 3-dimensional finite element model of knee ligaments and to analyse the stress changes of lateral collateral ligament (LCL) with or without displaced movements at different knee flexion conditions.

METHODSA four-major-ligament contained knee specimen from an adult died of skull injury was prepared for CT scanning with the detectable ligament insertion footprints, locations and orientations precisely marked in advance. The CT scanning images were converted to a 3-dimensional model of the knee with the 3-dimensional reconstruction technique and transformed into finite element model by the software of ANSYS. The model was validated using experimental and numerical results obtained by other scientists. The natural stress changes of LCL at five different knee flexion angles (0 degree, 30 degree, 60 degree, 90 degree, 120 degree) and under various motions of anterior-posterior tibial translation, tibial varus rotation and internal-external tibial rotation were measured.

RESULTSThe maximum stress reached to 87%-113% versus natural stress in varus motion at early 30 degree of knee flexions. The stress values were smaller than the peak value of natural stress at 0 degree (knee full extension) when knee bending was over 60 degree of flexion in anterior-posterior tibial translation and internal-external rotation.

CONCLUSIONLCL is vulnerable to varus motion in almost all knee bending positions and susceptible to anterior-posterior tibial translation or internal-external rotation at early 30 degree of knee flexions.

Anterior Cruciate Ligament ; physiology ; Collateral Ligaments ; physiology ; Finite Element Analysis ; Humans ; Knee Joint ; physiology ; Stress, Mechanical

Kinematics has been successfully used to describe body motion without reference to the kinetics (or forces causing the motion). In this article, both the theory and applications of the matrix method are provided to describe complex human motion. After the definition of a Cartesian coordinate frame is introduced, the description of transformations between multiple coordinate frames is given; the decomposition of a transformation matrix into anatomical joint motion parameters (e.g. Euler angles) is then explained. The advantages of the matrix method are illustrated by three examples related to biomechanical studies. The first describes a reaching and grasping task in which matrix transformations are applied to position the hand with respect to an object during grasping. The second example demonstrates the utility of the matrix method in revealing the coupling motion of the wrist between flexion-extension and radial-ulnar deviation. The last example highlights the indispensable use of the matrix method for the study of knee biomechanics, including the description of knee joint kinematics during functional activities and determination of in-situ ligament forces using robotic technology, which has advanced our understanding of the functions of the cruciate ligaments to knee joint kinematics. It is hoped that the theoretical development and biomechanical application examples will help the readers apply the matrix method to research problems related to human motion.
Biomechanical Phenomena ; methods ; Humans ; Knee ; physiology ; Motion ; Movement ; physiology ; Wrist ; physiology

Objective To explore the feasibility and clinical value of ultrasonography in evaluating the morphology and function of medial collateral ligaments (MCL) after total knee arthroplasty (TKA). Methods Totally 38 patients undergoing routine KTA (group A) and 22 patients undergoing constrained condylar knee arthroplasty KTA with MCL injury (group B) were included. Long axis views of MCL were taken and the MCL thickness was measured on femur side and tibial side 1 cm away from the joint line, respectively. The thicknesses were compared between the two groups. Subsequently, the gap between the metal part of the femoral prosthesis and the spacer after dynamic valgus stress was measured. The distribution and composition of the gap between the two groups were compared. Results High-frequency ultrasound clearly showed the prosthesis and MCL after TKA. MCL fiber structures of both groups were intact. The MCL thickness on the tibial side in group B was (0.25±0.06)cm, which was significantly thinner than group A [(0.32±0.14)cm] (t=2.12, P=0.040).For the femur side, there was no significant difference (t=1.65, P=0.110) between these two groups [(0.37±0.09) cm in group B versus (0.42±0.12)cm in group A]. Under the condition of valgus stress, the gaps between the metal part of the femoral prosthesis and the spacer could be found in 11 cases in group B but only in 1 case in group A. The proportion of gaps in group B was significantly higher than that in group A (Fisher's exact test, P=0.000). Conclusions High-frequency ultrasound can clearly show the prosthesis and MCL after TKA. The injured MCL can be well joined but the thickness is thinner. Under the condition of valgus stress of the knee, the stability of the TKA can be evaluated according to the gap between the prosthesis and the spacer.
Arthroplasty, Replacement, Knee ; Femur ; Humans ; Knee Joint ; Medial Collateral Ligament, Knee ; anatomy & histology ; diagnostic imaging ; physiology ; Tibia ; Ultrasonography

Posterior-stabilized total knee prostheses have been widely used in orthopedic clinical treatment of knee osteoarthritis, but the patients and surgeons are still troubled by the complications, for example severe wear and fracture of the post, as well as prosthetic loosening. Understanding the in vivo biomechanics of knee prostheses will aid in the decrease of postoperative prosthetic revision and patient dissatisfaction. Therefore, six different designs of posterior-stabilized total knee prostheses were used to establish the musculoskeletal multibody dynamics models of total knee arthroplasty respectively, and the biomechanical differences of six posterior-stabilized total knee prostheses were investigated under three simulated physiological activities: walking, right turn and squatting. The results showed that the post contact forces of PFC Sigma and Scorpio NGR prostheses were larger during walking, turning right, and squatting, which may increase the risk of the fracture and wear as well as the early loosening. The post design of Gemini SL prosthesis was more conductive to the knee internal-external rotation and avoided the edge contact and wear. The lower conformity design in sagittal plane and the later post-cam engagement resulted in the larger anterior-posterior translation. This study provides a theoretical support for guiding surgeon selection, improving posterior-stabilized prosthetic design and reducing the prosthetic failure.
Arthroplasty, Replacement, Knee/methods* ; Biomechanical Phenomena ; Humans ; Knee Joint/surgery* ; Knee Prosthesis ; Prosthesis Design ; Range of Motion, Articular/physiology* ; Tibia/surgery*

OBJECTIVE: To study the influence of different positions in the isokinetic muscle test of knees by CON-TREX Biomechanical Test and Training System, so as to select the suitable conditions for forensic identification of muscle strength test. METHODS: Fifty-two healthy volunteers joined the isokinetic muscle strength test in unfixed and fixed position, respectively and in two kinds of angular speed (60 degrees/s and 30 degrees/s). The differences of peak torque (PT) and peak torque angle (PTA) between bilateral knee flexor and extensor were statistically analyzed. RESULTS: In the unfixed position, under the two speed, there was statistically significant difference in PT between bilateral knee flexor and extensor (P < 0.05); while in the fixed position, under the two speed, there was no statistically significant difference (P > 0.05). In any kind of conditions, the PTA of bilateral knee flexor and extensor did not have statistically significant difference (P > 0.05). CONCLUSION The position of the subject influences the results of PT. So the position of subject in knees isokinetic muscle test should be regulated.
Humans ; Knee ; Knee Joint ; Muscle Strength ; Muscle, Skeletal/physiology* ; Muscles ; Posture ; Torque

With an un-calibrated camera a new method is proposed in this paper to measure dynamically the bending angle of knee-joint based on cross ratio invariability. Firstly, by video image processing technique, we detected 25 circular objectives distributed in the aided measurement tool and determined their geometric centers in the video frame respectively. Then we further computed the extending direction of thigh and shank by detecting position of two rectangular targets tied on them. Finally, using of the principle of cross ratio invariability in Projection Geometry, we could realize real-time dynamic measurement of the bending angle of knee-joint based on the method. Experiments have proved that the measurement precision of the introduced approach could satisfy basic requirements of clinical applications.
Algorithms ; Biomechanical Phenomena ; Humans ; Knee Joint ; anatomy & histology ; physiology ; Movement ; physiology ; Posture ; physiology ; Range of Motion, Articular ; physiology ; Video Recording