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

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*

The capacity to perform certain activities is frequently compromised after total knee arthroplasty (TKA) due to a functional decline resulting from decreased range of motion and a diminished ability to kneel. In this manuscript, the current biomechanical understanding of hyperflexion and kneeling before and after TKA will be discussed. Patellofemoral and tibiofemoral joint contact area, contact pressure, and kinematics were evaluated in cadaveric studies using a Tekscan pressure measuring system and Microscribe. Testing was performed on intact knees and following cruciate retaining and posterior stabilized TKA at knee flexion angles of 90degrees, 105degrees, 120degrees, and 135degrees. Three loading conditions were used to simulate squatting, double stance kneeling, and single stance kneeling. Following TKA with double stance kneeling, patellofemoral contact areas did not increase significantly at high knee flexion angle (135degrees). Kneeling resulted in tibial posterior translation and external rotation at all flexion angles. Moving from double to single stance kneeling tended to increase pressures in the cruciate retaining group, but decreased pressures in the posterior stabilized group. The cruciate retaining group had significantly larger contact areas than the posterior stabilized group, although no significant differences in pressures were observed comparing the two TKA designs (p < 0.05). If greater than 120degrees of postoperative knee range of motion can be achieved following TKA, then kneeling may be performed with less risk in the patellofemoral joint than was previously believed to be the case. However, kneeling may increase the likelihood of damage to cartilage and menisci in intact knees and after TKA increases in tibiofemoral contact area and pressures may lead to polyethyelene wear if performed on a chronic, repetitive basis.
*Arthroplasty, Replacement, Knee ; Biomechanical Phenomena ; Cadaver ; Humans ; Knee Joint/*physiopathology/surgery ; Osteoarthritis, Knee/*physiopathology/surgery ; Patellofemoral Joint/physiopathology/surgery ; Posture/physiology ; Range of Motion, Articular

In this paper, a three-dimensional finite element analysis (FEA) model was created for bionic artificial joint with joint capsule. Finite element method (FEM) was used to calculate and simulate mechanics distribution of the joint capsule under different thickness of the joint capsule, different loading, and different angular displacements. The results of the simulation show that the maximum stress is created in the joint area between artificial joint capsule. And the effect of the thickness of the artificial joint capsule on the stress magnitude and distribution is depend on motion model. On standing situation, the maximum stress decreases with the increase of the thickness of joint capsule. However, on walking situation, the maximum stress increases with the increase of the thickness of joint capsule. Whatever conditions simulated, the maximum stress of the artificial joint capsule is not over the limit of the material strength (9.97 megapascals). All the large stress, which gained from the simulation under different situations, locates at the interface between the capsule and the artificial joint. This is because the artificial joint and the capsule transfer loading each other at the interface. At the same time, supporting area of the capsule at the location of the interface is minimum for the whole vesicle. The stress concentration is inevitable at the interface due to the model structure. This result will offer guidance for the optimum joint structure of the capsule and the artificial joint.
Arthroplasty, Replacement, Knee ; Biomechanical Phenomena ; Computer Simulation ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional ; Joint Capsule ; physiology ; Knee Joint ; physiology ; surgery ; Knee Prosthesis ; Models, Biological ; Stress, Mechanical

BACKGROUNDThe anterior cruciate ligament (ACL) is one of the most commonly injured knee ligaments. Even following ACL reconstruction, significant articular cartilage degeneration can be observed and most patients suffer from premature osteoarthritis. Articular cartilage degeneration and osteoarthritis development after ACL injury are regarded as progressive process that are affected by cyclic loading during frequently performed low-intensity daily activities. The purpose of this study was to perform a meta analysis on studies assessing the effects of ACL reconstruction on kinematics, kinetics and proprioception of knee during level walking.

METHODSThis meta analysis was conducted according to the methodological guidelines outlined by the Cochrane Collaboration. An electronic search of the literature was performed and all trials published between January 1966 and July 2010 comparing gait and proprioception of a reconstructed-ACL group with an intact-ACL group were pooled for this review. Thirteen studies were included in the final meta analysis.

RESULTSThere was no significant difference in step length, walking speed, maximum knee flexion angle during loading response, joint position sense and threshold to detect passive motion between the reconstructed-ACL group and the intact-ACL group (P > 0.05). However, there was a significant difference in peak knee flexion angle, maximum angular knee flexion excursion during stance, peak knee flexion moment during walking and maximum external tibial rotation angle throughout the gait cycle between the reconstructed-ACL group and the intact-ACL group (P < 0.05).

CONCLUSIONSStep length, walking speed, maximum knee flexion angle during loading response, joint position sense and threshold to detect passive motion usually observed with ACL deficiency were restored after the ACL reconstruction and rehabilitation, but no significant improvements were observed for peak knee flexion angle, maximum angular knee flexion excursion during stance, peak knee flexion moment during walking and maximum external tibial rotation angle throughout the gait cycle.

Anterior Cruciate Ligament ; surgery ; Biomechanical Phenomena ; Humans ; Knee Joint ; surgery ; Reconstructive Surgical Procedures ; methods ; Walking ; physiology

A goal of total knee arthroplasty is to obtain symmetric and balanced flexion and extension gaps. Controversy exists regarding the best surgical technique to utilize to obtain gap balance. Some favor the use of a measured resection technique in which bone landmarks, such as the transepicondylar, the anterior-posterior, or the posterior condylar axes are used to determine proper femoral component rotation and subsequent gap balance. Others favor a gap balancing technique in which the femoral component is positioned parallel to the resected proximal tibia with each collateral ligament equally tensioned to obtain a rectangular flexion gap. Two scientific studies have been performed comparing the two surgical techniques. The first utilized computer navigation and demonstrated a balanced and rectangular flexion gap was obtained much more frequently with use of a gap balanced technique. The second utilized in vivo video fluoroscopy and demonstrated a much high incidence of femoral condylar lift-off (instability) when a measured resection technique was used. In summary, the authors believe gap balancing techniques provide superior gap balance and function following total knee arthroplasty.
Arthroplasty, Replacement, Knee/adverse effects/*methods ; Fluoroscopy/methods ; Humans ; Knee Joint/physiology/surgery ; Surgery, Computer-Assisted/methods ; Treatment Outcome

BACKGROUND: Despite the importance of soft tissue balancing during total knee arthroplasty (TKA), all estimating techniques are dependent on a surgeon's manual distraction force or subjective feeling based on experience. We developed a new device for dynamic gap balancing, which can offer constant load to the gap between the femur and tibia, using pneumatic pressure during range of motion. METHODS: To determine the amount of distraction force for the new device, 3 experienced surgeons' manual distraction force was measured using a conventional spreader. A new device called the consistent load pneumatic tensor was developed on the basis of the biomechanical tests. Reliability testing for the new device was performed using 5 cadaveric knees by the same surgeons. Intraclass correlation coefficients (ICCs) were calculated. RESULTS: The distraction force applied to the new pneumatic tensioning device was determined to be 150 N. The interobserver reliability was very good for the newly tested spreader device with ICCs between 0.828 and 0.881. CONCLUSIONS: The new pneumatic tensioning device can enable us to properly evaluate the soft tissue balance throughout the range of motion during TKA with acceptable reproducibility.
Arthroplasty, Replacement, Knee/*instrumentation/methods ; Biomechanics ; Equipment Design ; Femur/surgery ; Humans ; Knee Joint/physiology/*surgery ; Mechanical Processes ; Range of Motion, Articular ; Reproducibility of Results ; Tibia/surgery

Dynamic loads at knee joint of amputee are fundamental for rehabilitation of knee injury and prosthesis design. In this paper, a 3-D model for calculation of dynamic load at knee joint of trans-tibial amputee was developed. Gait analysis was done on three terrains including normal level walking, upstairs and downstairs. Dynamic loads at knee joint were calculated during one gait cycle. The results show that gait patterns and dynamic loads at knee joint were different among these three terrains. Although the general waveforms were about the same, the motion range of knee joint, ground reaction forces and loads at knee joint when walking upstairs or downstairs were larger than those in a normal level walking. The quantitative findings provide the theoretical basis of gait analysis and prosthesis design for trans-tibial amputee.
Amputation Stumps ; physiopathology ; Artificial Limbs ; Biomechanical Phenomena ; Gait ; physiology ; Humans ; Knee Joint ; physiopathology ; Leg ; physiopathology ; surgery ; Prosthesis Design ; Stress, Mechanical ; Tibia ; physiopathology ; surgery ; Walking ; physiology ; Weight-Bearing ; physiology

PURPOSE: This study investigated the correlation between isometric muscle strength, gross motor function, and gait parameters in patients with spastic cerebral palsy and to find which muscle groups play an important role for gait pattern in a flexed knee gait. MATERIALS AND METHODS: Twenty-four ambulatory patients (mean age, 10.0 years) with spastic cerebral palsy who were scheduled for single event multilevel surgery, including distal hamstring lengthening, were included. Preoperatively, peak isometric muscle strength was measured for the hip flexor, hip extensor, knee flexor, and knee extensor muscle groups using a handheld dynamometer, and three-dimensional (3D) gait analysis and gross motor function measure (GMFM) scoring were also performed. Correlations between peak isometric strength and GMFM, gait kinematics, and gait kinetics were analyzed. RESULTS: Peak isometric muscle strength of all muscle groups was not related to the GMFM score and the gross motor function classification system level. Peak isometric strength of the hip extensor and knee extensor was significantly correlated with the mean pelvic tilt (r=-0.588, p=0.003 and r=-0.436, p=0.033) and maximum pelvic obliquity (r=-0.450, p=0.031 and r=-0.419, p=0.041). There were significant correlations between peak isometric strength of the knee extensor and peak knee extensor moment in early stance (r=0.467, p=0.021) and in terminal stance (r=0.416, p=0.043). CONCLUSION: There is no correlation between muscle strength and gross motor function. However, this study showed that muscle strength, especially of the extensor muscle group of the hip and knee joints, might play a critical role in gait by stabilizing pelvic motion and decreasing energy consumption in a flexed knee gait.
Biomechanical Phenomena ; Cerebral Palsy/*physiopathology/surgery ; Female ; Gait/*physiology ; Humans ; Isometric Contraction/physiology ; Knee/physiopathology ; Knee Joint/surgery ; Male ; Muscle Spasticity/etiology/physiopathology ; Muscle Strength/*physiology ; Muscle Strength Dynamometer ; Muscle, Skeletal/*physiopathology ; Pelvis ; Postural Balance/physiology ; Tenotomy

BACKGROUND: The purpose of this study was to compare the initial stability of anatomical and non-anatomical single bundle anterior cruciate ligament (ACL) reconstruction and to determine which would better restore intact knee kinematics. Our hypothesis was that the initial stability of anatomical single bundle ACL reconstruction would be superior to that of non-anatomical single bundle ACL reconstruction. METHODS: Anterior tibial translation (ATT) and internal rotation of the tibia were measured with a computer navigation system in seven pairs of fresh-frozen cadaveric knees under two testing conditions (manual maximum anterior force, and a manual maximum anterior force combined with an internal rotational force). Tests were performed at 0, 30, 60, and 90 degrees of flexion with the ACL intact, the ACL transected, and after reconstruction of one side of a pair with either anatomical or non-anatomical single bundle ACL reconstruction. RESULTS: Under manual maximal anterior force, both reconstruction techniques showed no significant difference of ATT when compared to ACL intact knee state at 30degrees of knee flexion (p > 0.05). Under the combined anterior and internal rotatory force, non-anatomical single-bundle ACL reconstruction showed significant difference of ATT compared to those in ACL intact group (p < 0.05). In contrast, central anatomical single bundle ACL reconstruction showed no significant difference of ATT compared to those in ACL intact group (p > 0.05). Internal rotation of the tibia showed no significant difference in the ACL intact, the ACL transected, non-anatomical reconstructed and anatomical reconstructed knees. CONCLUSIONS: Anatomical single bundle ACL reconstruction restored the initial stability closer to the native ACL under combined anterior and internal rotational forces when compared to non-anatomical ACL single bundle reconstruction.
Aged ; Aged, 80 and over ; Anterior Cruciate Ligament/*anatomy & histology/physiology/*surgery ; Anterior Cruciate Ligament Reconstruction/*methods ; Biomechanics/physiology ; Cadaver ; Humans ; Knee Joint/*anatomy & histology/physiology/*surgery ; Middle Aged ; Random Allocation ; Range of Motion, Articular/physiology ; Tibia/anatomy & histology/physiology/surgery