Knee disorders
Maneesh Bhatia, Tim Jennings in An Orthopaedics Guide for Today's GP, 2017
The knee joints are covered only by a thin layer of soft tissue and bear the weight of the whole body above them. Although it is a hinge joint with primarily flexion–extension movement, it also allows rotatory movements. The joint stability is provided mainly by soft tissues rather than significant bony structures. The primary stabilisers are the ligaments: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), lateral collateral ligament (LCL), medial collateral ligament (MCL) and posterolateral corner (PLC), providing support in translations, angulations and rotations. The crescent- and wedge-shaped medial and lateral menisci increase the depth and contact surface area for the femoral condyles and allow rotatory movement on top of the tibia plateau. A congruent and healthy cartilage allows painless and functional range of movements. The joint capsule provides the remaining stability. An injury to any of these structures may disturb the homeostasis of the knee.2
Biomechanical simulation models of sports activities
Youlian Hong, Roger Bartlett in Routledge Handbook of Biomechanics and Human Movement Science, 2008
Typically, the rigid links in the simulation model are joined together by frictionless joints, whereby adjacent segments share a common line or a common point. For example, Neptune and Kautz (2000) used a hinge joint to allow for flexion-extension at the knee while Hatze (1981) used a universal joint at the hip with three degrees of freedom to allow for flexion-extension, abduction-adduction and internal-external rotation. The assumption that adjacent segments share a common point or line is a simplification of reality and, although reasonable for most joints, it is questionable at the shoulder where motion occurs at four different joints. Models of the shoulder joint have ranged in complexity from a one degree of freedom pin joint (Yeadon and King, 2002) to relatively simple viscoelastic representations (Hiley and Yeadon, 2003) and complex finite element models (van der Helm, 1994). The complexity to be used depends on the requirements of the study. Simple viscoelastic representations have been used successfully in whole body models, where the overall movement is of interest, whereas complex models have been used to address issues such as the contribution of individual muscles to movement at the shoulder joint.
Orthopaedics
Kelvin Yan in Surgical and Anaesthetic Instruments for OSCEs, 2021
This is a knee prosthetic implant which is used for a total knee arthroplasty (TKA) (Figure 8.2). It can be made of metal alloys plus ceramic or plastic parts. It has 3 components: the femoral part, the patella part and the tibial component with a plastic spacer. The rationale is to recreate the surfaces of the hinge joint of the knee by first removing damaged bones and/or cartilages and replacing them with metal prostheses and a plastic spacer to ensure better movement and reduce wear and tear. The femoral component has various forms including the posterior-stabilised design, the cruciate-retaining design and the bicruciate-retaining design. The posterior-stabilised design involves removing the cruciate ligaments and replacing it with a centre post-cam design in the prosthesis that substitutes the function of the posterior cruciate ligament. The Cruciate-retaining design requires the retention of the posterior cruciate ligament as it does not offer a substitution. The Bicruciate-retaining design, on the other hand, is a relatively new design that requires the retention of both the anterior and posterior cruciate ligaments with the aim to mimic the human knee as closely as possible.
Non-rigid deformation to include subject-specific detail in musculoskeletal models of CP children with proximal femoral deformity and its effect on muscle and contact forces during gait
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Mariska Wesseling, Lode Bosmans, Christophe Van Dijck, Jos Vander Sloten, Roel Wirix-Speetjens, Ilse Jonkers
MRI models were defined for all subjects based on the acquired MR images using a dedicated workflow (Figure 1) (Scheys et al. 2006). Bone structures of the pelvis, femora, patellae and tibiae were segmented from the images (Mimics Innovation Suite, Materialise N.V., Leuven, Belgium). The hip joint center was determined by fitting a sphere to the femoral head using an iterative closest point algorithm (Besl and McKay 1992). The knee joint was modelled as a sliding hinge joint (Yamaguchi and Zajac 1989), where the knee axis was based on the geometry of the distal femur, by connecting the centers of two spheres fitted to the lateral and medial posterior condyles. Segmental coordinate frames were defined for the bone meshes (Wu et al. 2002) and marker coordinates, based on the radio opaque markers in the MR images, were expressed in the respective segmental coordinate frames. Next, the muscle points of all hip and knee actuating muscles were identified in the MR images (Scheys et al. 2006). The number of muscle points were defined similar to the generic model. The muscle points of all distal tibia and foot muscles as well as the ankle joint center were the same in the scaled generic and MRI models.
A multi-body model for comparative study of cervical traction simulation – development, improvement and validation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Lawrence K. F. Wong, Zhiwei Luo, Nobuyuki Kurusu, Keiji Fujino
In both positions, the vertex of the traction angle is set at a fixed point at the chair, near the back of the first thoracic vertebra (T1) of the subject. In the simulation model, T1 connects the base of the cervical spine to the rest of the upper body. The upper limbs and forearm are modeled as rigid bodies and are connected to the shoulder with hinge joints. The hip joint is a hinge joint that connects to the thighs. Since the subject is heavy enough that the friction at the seat prevents the subject from sliding along the seat, the thighs and the rest of the lower body are modeled as fixed structure attached to the traction devices. This design allows the subject to remain stable during traction. It also matches the observed behavior of the human subjects in our radiographic experiment.
A multi-body model for comparative study of cervical traction simulation – comparison between inclined and sitting traction
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Lawrence K. F. Wong, Zhiwei Luo, Nobuyuki Kurusu, Keiji Fujino
Figure 1 shows the rendering of the multi-body cervical traction model in inclined and sitting positions. In the inclined position (Tractizer 2018a), the subject sits on a motorized chair. By changing the angle of the seat, desired traction angles between 10° and 40° is achieved. In the sitting position (Tractizer 2018b), the subject sits up-right on a fixed chair. By adjusting the cable to different positions at a metal bar located at the top of the device, desired traction angles can be realized. In both positions, the head halter is connected to a motor and cable system to control the amount of traction force. In the skeleton, the upper limbs and forearm are modeled as rigid bodies and are connected to the shoulder with hinge joints. The hip joint is a hinge joint that connects to the lower body, which is modeled as fixed structure attached to the traction devices. This design allows the subject to remain stable during traction. It also matches the observed behavior of the human subjects in the radiographic experiment.
Related Knowledge Centers
- Ankle
- Bone
- Ligament
- Joint
- Ulna
- Humerus
- Interphalangeal Joints of The Hand
- Interphalangeal Joints of The Foot
- Knee
- Limb