The knee joint, as the main lower limb motor joint, is the most vulnerable and susceptible joint. The knee injuries considerably impact the normal living ability and mental health of patients. Understanding the biomechanics of a normal and diseased knee joint is in urgent need for designing knee assistive devices and optimizing a rehabilitation exercise program. In this paper, we systematically searched electronic databases (from 2000 to November 2019) including ScienceDirect, Web of Science, PubMed, Google Scholar, and IEEE/IET Electronic Library for potentially relevant articles. After duplicates were removed and inclusion criteria applied to the titles, abstracts, and full text, 138 articles remained for review. The selected articles were divided into two groups to be analyzed. Firstly, the real movement of a normal knee joint and the normal knee biomechanics of four kinds of daily motions in the sagittal and coronal planes, which include normal walking, running, stair climbing, and sit-to-stand, were discussed and analyzed. Secondly, an overview of the current knowledge on the movement biomechanical effects of common knee musculoskeletal disorders and knee neurological disorders were provided. Finally, a discussion of the existing problems in the current studies and some recommendation for future research were presented. In general, this review reveals that there is no clear assessment about the biomechanics of normal and diseased knee joints at the current state of the art. The biomechanics properties could be significantly affected by knee musculoskeletal or neurological disorders. Deeper understanding of the biomechanics of the normal and diseased knee joint will still be an urgent need in the future.
Since the number of the old and obese worldwide has been increasing yearly, the research on human motion dysfunction is getting more and more attention. The knee joint, as the main lower limb motor joint, is the most vulnerable and susceptible joint [
In the last decade, several related review papers appeared and could be divided into two aspects, normal knee biomechanics and diseased knee biomechanics. For the former, Masouros et al. [
Understanding the knee biomechanics is a prerequisite for designing knee assistive devices and optimizing rehabilitation exercises. This paper provides an overview of the current biomechanical knowledge on normal and injured knee joints. For better assessment of the function of the knee joint, the biomechanical parameters including angle, moment, power, and stiffness from various researchers in different daily motions are reviewed and compared. For better understanding the kinematics and kinetics of real knee movement, the polycentric rotation in the sagittal plane and biomechanics in the coronal plane are also discussed. Further, the common knee disorders including musculoskeletal and neurological disorders and their influences on the knee biomechanics are also reviewed and discussed. We hypothesized that the comprehensive understanding of the knee joint biomechanics in physiological and pathological conditions could significantly improve the design of knee assistive devices and rehabilitation exercise programs.
The rest of this paper is organized as follows. In Section
This review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [
Studies were considered eligible if they met the following inclusion criteria: normal knee kinematics related, normal knee dynamics related, diseased knee kinematics related, diseased knee dynamics related, English, and full-text articles. Two reviewers (LZ and ZW) independently assessed the title and abstracts of the potential studies. After an initial decision, the full text of the studies that potentially met the inclusion criteria were assessed before a final decision was made. A senior reviewer (GL) was consulted in cases involving disagreement. After exclusion of irrelevant titles and screening of abstracts, 203 articles remained. Subsequently, detailed full-text screening based on the inclusion criteria was carried out, and 65 articles were excluded. Finally, 138 full-text articles were examined for full review. The search process is demonstrated using the following diagram shown in Figure
The PRISMA flow diagram of study selection process.
We divided the 138 selected articles, which fulfilled the literature search inclusion criteria, into two groups: biomechanical properties of normal knee joint and biomechanical properties of diseased knee joint. For the former, the real movement of a normal knee joint and the normal knee biomechanics of four kinds of daily motions in the sagittal and coronal planes, which include normal walking, running, stair climbing, and sit-to-stand, were discussed and analyzed. For the latter, an overview of the current knowledge on the movement biomechanical effects of common knee musculoskeletal disorders (KOA) and knee neurological disorders (SCI, stroke, and CP) were provided.
Walking, running, stair climbing, and sit-to-stand are very frequent motions in human’s daily life. In all of the motions, the main functions of the knee joint include supporting the body weight (BW), absorbing shock of heel strikes, and assisting lower limbs swing [
As shown in Figure
A sketch map of motion and the typical curves of knee angle, moment, and power in the sagittal plane for a walking gait cycle. (a) Sketch map of walking motion [
Overview over the experimental results of knee angle for normal walking.
Study | Subjects ( |
Speed (m/s) | A (°) | B (°) | C (°) | D (°) | C-A (°) | ROM (°) |
---|---|---|---|---|---|---|---|---|
Collins et al. [ |
9 ( |
1.25 | 12 | 3 | 61 | -5 | 49 | 66 |
Zheng [ |
1 (1.78, 70) | 1.2 | 22 | 10 | 66 | 6 | 44 | 60 |
Wang [ |
1 (1.69, 63.5) | 1.5 | 7 | 3 | 53 | -2 | 46 | 55 |
Mooney and Herr [ |
6 ( |
1.4 | 28 | 5 | 78 | 4 | 50 | 74 |
Shamaei et al. [ |
3 ( |
1.25 | 26 | 15 | 69 | 6 | 43 | 63 |
Blazkiewicz [ |
1 (1.85, 80) | — | 10 | -2 | 53 | 0 | 43 | 55 |
Sridar et al. [ |
3 ( |
1.0 | 22 | 11 | 62 | 2 | 40 | 60 |
Knaepen et al. [ |
10 ( |
0.69 | 14 | 8 | 62 | 8 | 48 | 54 |
Shirota et al. [ |
4 ( |
1.24 | 13 | 5 | 65 | 1 | 52 | 64 |
Gordon et al. [ |
3 ( |
1.0 | 6 | 0 | 55 | 16 | 49 | 55 |
Ding et al. [ |
8 ( |
1.25 | 24 | 7 | 75 | 0 | 51 | 75 |
Winter [ |
1 (—, 58) | 1.3 | 16 | 5 | 67 | -2 | 51 | 69 |
Beyl et al. [ |
— | — | 22 | 8 | 64 | 1 | 42 | 63 |
Baliunas et al. [ |
15 ( |
0.98 | 17 | 3 | 60 | -2 | 43 | 62 |
Yang et al. [ |
1 (1.75, 70) | 1.0 | 14 | 3 | 56 | 6 | 42 | 53 |
A: first peak knee flexion angle; B: first peak knee extension angle; C: second peak knee flexion angle; D: second peak knee extension angle.
Overview over the experimental results of knee moment for normal walking.
Study | Subjects ( |
Speed (m/s) | E (Nm/kg) | F (Nm/kg) | G (Nm/kg) | H (Nm/kg) | E-G (Nm/kg) | F-H (Nm/kg) | Range (Nm/kg) |
---|---|---|---|---|---|---|---|---|---|
Collins et al. [ |
9 ( |
1.25 | 0.556 | -0.245 | 0.207 | -0.388 | 0.349 | 0.143 | 0.944 |
Shamaei et al. [ |
3 ( |
1.25 | 0.335 | -0.248 | 0.102 | -0.379 | 0.233 | 0.131 | 0.714 |
Zheng [ |
1 (1.78, 70) | 1.2 | 0.571 | -0.171 | 0.114 | 0.086 | 0.457 | -0.257 | 0.742 |
Mooney and Herr [ |
6 ( |
1.4 | 0.766 | -0.344 | 0.189 | -0.378 | 0.577 | 0.034 | 1.144 |
Blazkiewicz [ |
1 (1.85, 80) | — | 0.263 | -0.675 | 0.225 | -0.063 | 0.038 | -0.612 | 0.938 |
Ding et al. [ |
8 ( |
1.25 | 0.777 | -0.204 | 0.204 | -0.420 | 0.573 | 0.198 | 1.197 |
Winter [ |
1 (—, 58) | 1.3 | 0.517 | -0.155 | 0.189 | -0.224 | 0.328 | 0.069 | 0.741 |
Yang et al. [ |
1 (1.75, 70) | 1.0 | 0.129 | -0.329 | 0.101 | -0.257 | 0.028 | -0.072 | 0.458 |
Dijk et al. [ |
8 ( |
1.11 | 0.945 | 0.067 | 0.466 | -0.320 | 0.479 | -0.387 | 1.265 |
Briggs et al. [ |
20 ( |
— | 0.534 | -0.276 | 0.190 | — | 0.344 | — | — |
E: first peak knee extension moment; F: first peak knee flexion moment; G: second peak knee extension moment; H: second peak knee flexion moment.
Overview over the experimental results of knee power for normal walking.
Study | Subjects ( |
Speed (m/s) | I (W/kg) | J (W/kg) | K (W/kg) | L (W/kg) | Range (W/kg) |
---|---|---|---|---|---|---|---|
Collins et al. [ |
9 ( |
1.25 | -0.571 | 0.286 | -1.057 | -1.457 | 1.743 |
Zheng [ |
1 (1.78, 70) | 1.2 | -0.489 | 0.591 | -0.469 | -0.321 | 1.080 |
Mooney et al. [ |
6 ( |
1.4 | -0.889 | 0.834 | -1.334 | -1.639 | 2.473 |
Malcolm et al. [ |
8 ( |
1.38 | -1.736 | 0.502 | -0.763 | -2.712 | 3.214 |
Ding et al. [ |
8 ( |
1.25 | -0.968 | 0.606 | -1.290 | -1.677 | 2.283 |
Winter [ |
1 (—, 58) | 1.3 | -0.755 | 0.324 | -0.924 | -1.247 | 1.571 |
Yang et al. [ |
1 (1.75, 70) | 1.0 | -0.116 | 0.296 | -0.403 | -0.739 | 1.035 |
Dijk et al. [ |
8 ( |
1.1 | -1.242 | 0.586 | -1.509 | -1.329 | 2.095 |
Walsh et al. [ |
1 (—, 60) | 0.8 | -0.828 | 0.667 | -1.935 | -1.410 | 2.602 |
I: first peak knee absorption power; J: first peak knee generation power; K: second peak knee absorption power; L: third peak knee absorption power.
As shown in Figure
A sketch map of motion and the typical curves of knee angle, moment, and power in the sagittal plane for a running cycle. (a) Sketch map of running motion [
Overview over the experimental results of knee angle for running.
Study | Subjects (mean |
Speed (m/s) | A (°) | B (°) | C (°) | D (°) | C-A (°) | ROM (°) |
---|---|---|---|---|---|---|---|---|
Zheng [ |
1 (1.78, 70) | 2.1 | 36 | 22 | 80 | 20 | 44 | 60 |
2.8 | 49 | 20 | 90 | 17 | 41 | 73 | ||
Hamner and Delp [ |
10 ( |
2.0 | 42 | 18 | 85 | 11 | 43 | 74 |
3.0 | 44 | 16 | 103 | 12 | 59 | 91 | ||
4.0 | 46 | 15 | 119 | 13 | 73 | 106 | ||
5.0 | 47 | 15 | 129 | 14 | 82 | 115 | ||
Dollar et and Herr[ |
1 (—, 85) | 3.2 | 43 | 23 | 89 | 21 | 46 | 68 |
Elliott [ |
6 ( |
3.5 | 44 | 15 | 105 | 13 | 61 | 92 |
Sobhani et al. [ |
16 ( |
2.48 | 48 | 17 | 86 | 10 | 38 | 76 |
Miller et al. [ |
12 ( |
3.8 | 60 | 29 | 96 | 16 | 36 | 80 |
Ferber et al. [ |
20 ( |
3.65 | 46 | 13 | — | — | — | — |
A: first peak knee flexion angle; B: first peak knee extension angle; C: second peak knee flexion angle; D: second peak knee extension angle.
Overview over the experimental results of knee moment for running.
Study | Subjects ( |
Speed (m/s) | E (Nm/kg) | F (Nm/kg) | G (Nm/kg) | H (Nm/kg) | E-G (Nm/kg) | F-H (Nm/kg) | Range (Nm/kg) |
---|---|---|---|---|---|---|---|---|---|
Zheng [ |
1 (1.78, 70) | 2.1 | 1.157 | -0.030 | 0.274 | -0.277 | 0.883 | 0.247 | 1.434 |
2.8 | 1.749 | 0.320 | 0.320 | -0.351 | 1.429 | 0.671 | 2.100 | ||
Hamner and Delp [ |
10 ( |
2.0 | 1.798 | -0.205 | 0.135 | -0.697 | 1.663 | 0.492 | 2.495 |
3.0 | 2.159 | -0.226 | 0.269 | -0.925 | 1.890 | 0.699 | 3.084 | ||
4.0 | 2.402 | -0.233 | 0.405 | -1.147 | 1.997 | 0.914 | 3.549 | ||
5.0 | 2.430 | -0.259 | 0.585 | -1.474 | 1.845 | 1.215 | 3.904 | ||
Dollar and Herr [ |
1 (—, 85) | 3.2 | 1.571 | 0.175 | 0.175 | -0.591 | 1.396 | 0.766 | 2.162 |
Elliott [ |
6 ( |
3.5 | 2.196 | -0.249 | 0.248 | -0.775 | 1.948 | 0.526 | 2.971 |
Sobhani et al. [ |
16 ( |
2.48 | 2.574 | -0.221 | 0.307 | -0.649 | 2.267 | 0.428 | 3.223 |
E: first peak knee extension moment; F: first peak knee flexion moment; G: second peak knee extension moment; H: second peak knee flexion moment.
Overview over the experimental results of knee power for running.
Study | Subjects ( |
Speed (m/s) | I (W/kg) | J (W/kg) | K (W/kg) | L (W/kg) | Range (W/kg) |
---|---|---|---|---|---|---|---|
Zheng [ |
1 (1.78, 70) | 2.1 | -5.859 | 4.336 | -2.231 | -3.521 | 10.195 |
2.8 | -8.008 | 7.386 | -3.456 | -3.456 | 15.394 | ||
Dollar and Herr [ |
1 (—, 85) | 3.2 | -1.706 | 4.766 | -1.525 | -3.958 | 8.724 |
Elliott [ |
6 ( |
3.5 | -9.013 | 4.539 | -2.439 | -6.732 | 13.552 |
Sobhani et al. [ |
16 ( |
2.48 | -12.567 | 9.405 | -2.371 | -4.473 | 21.972 |
Ferber et al. [ |
20 ( |
3.65 | -5.462 | 2.739 | — | — | — |
Heiderscheit et al. [ |
45 ( |
2.9 | -6.948 | 5.422 | — | — | — |
I: first peak knee absorption power; J: first peak knee generation power; K: second peak knee absorption power; L: third peak knee absorption power.
As shown in Figure
A sketch map of motion and the typical curves of knee angle, moment, and power in sagittal plane for stair ascent and stair descent. (a) Sketch map of the stair ascent and stair descent motion. (b) Knee angle-time curve ((A) peak knee flexion angle and (B) peak knee extension angle. (c) Knee moment-time curve ((E) first peak knee extension moment, (F) first peak knee flexion moment, (G) second peak knee extension moment, and (H) second peak knee flexion moment). (d) Knee power-time curve ((I) first peak knee generation power, (J) first peak knee absorption power, (K) second peak knee generation power, and (L) second peak knee absorption power) [
Overview over the experimental results of knee angle for stair ascent and stair descent.
Study | Subjects ( |
Type | A (°) | B (°) | ROM (°) | |
---|---|---|---|---|---|---|
Riener et al. [ |
10 ( |
Ascent | 91 | 9 | 82 | |
Descent | 89 | 13 | 76 | |||
Ascent | 95 | 9 | 86 | |||
Descent | 93 | 15 | 78 | |||
Ascent | 102 | 10 | 92 | |||
Descent | 102 | 13 | 89 | |||
Mcfadyen and Winter [ |
3 (—, —) | Ascent | 99 | 11 | 88 | |
Descent | 105 | 19 | 86 | |||
Zhang et al. [ |
10 ( |
Ascent | 89 | 7 | 82 | |
Descent | 96 | 10 | 86 | |||
Musselman [ |
17 ( |
Ascent | 83 | 5 | 78 | |
Descent | 83 | 6 | 77 | |||
Protopapadaki et al. [ |
33 ( |
Ascent | 94 | 0 | 94 | |
Descent | 91 | 1 | 90 | |||
Law [ |
19 ( |
Ascent | 95 | 11 | 84 | |
Descent | 93 | 3 | 90 |
A: peak knee flexion angle; B: peak knee extension angle.
Overview over the experimental results of knee moment for stair ascent and stair descent.
Study | Subjects ( |
Type | E (Nm/kg) | F (Nm/kg) | G (Nm/kg) | H (Nm/kg) | E-G (Nm/kg) | F-H (Nm/kg) | Range (Nm/kg) | |
---|---|---|---|---|---|---|---|---|---|---|
Riener et al. [ |
10 ( |
Ascent | 1.055 | -0.179 | 0.027 | -0.183 | 1.028 | 0.004 | 1.238 | |
Descent | 0.916 | 0.587 | 1.247 | -0.096 | -0.331 | 0.683 | 1.343 | |||
Ascent | 1.093 | -0.218 | 0.042 | -0.177 | 1.051 | -0.041 | 1.311 | |||
Descent | 1.006 | 0.662 | 1.345 | -0.091 | -0.339 | 0.753 | 1.436 | |||
Ascent | 1.164 | -0.247 | 0.037 | -0.172 | 1.127 | 0.075 | 1.411 | |||
Descent | 0.991 | 0.653 | 1.470 | -0.088 | -0.479 | 0.741 | 1.558 | |||
Mcfadyen and Winter[ |
3 (—, —) | Ascent | 1.409 | -0.406 | 0.164 | -0.314 | 1.245 | -0.092 | 1.815 | |
Descent | 1.512 | 0.405 | 1.620 | -0.266 | -0.108 | 0.671 | 1.886 | |||
Zhang et al. [ |
10 ( |
Ascent | 0.588 | -0.493 | 0.144 | -0.256 | 0.444 | -0.237 | 1.081 | |
Descent | 0.338 | 0.152 | 1.106 | -0.201 | -0.768 | 0.353 | 1.307 | |||
Musselman [ |
17 ( |
Ascent | 0.921 | -0.456 | 0.043 | -0.206 | 0.878 | -0.250 | 1.377 | |
Descent | 0.448 | 0.263 | 1.012 | -0.167 | -0.564 | 0.430 | 1.179 | |||
Protopapadaki et al. [ |
33 ( |
Ascent | 0.454 | -0.556 | 0.032 | -0.121 | 0.422 | -0.435 | 1.010 | |
Descent | 0.007 | -0.070 | 0.365 | -0.040 | -0.358 | -0.030 | 0.435 | |||
Law [ |
19 ( |
Ascent | 0.899 | -0.145 | 0.046 | -0.147 | 0.085 | 0.002 | 1.036 | |
Descent | 0.603 | 0.439 | 1.006 | -0.076 | -0.403 | 0.515 | 1.082 |
E: first peak knee extension moment; F: first peak knee flexion moment; G: second peak knee extension moment; H: second peak knee flexion moment.
Overview over the experimental results of knee power for stair ascent and stair descent.
Study | Subjects ( |
Type | I (W/kg) | J (W/kg) | K (W/kg) | L (W/kg) | Range (W/kg0 | |
---|---|---|---|---|---|---|---|---|
Riener et al. [ |
10 ( |
Ascent | 2.322 | 0.071 | 0.647 | -0.309 | 2.631 | |
Descent | 0.256 | -0.678 | -0.429 | -3.788 | 4.044 | |||
Ascent | 2.538 | 0.055 | 0.696 | -0.312 | 2.850 | |||
Descent | 0.305 | -1.029 | -0.453 | -4.141 | 4.446 | |||
Ascent | 2.887 | 0.049 | 0.811 | -0.288 | 3.175 | |||
Descent | -0.212 | -1.255 | -0.472 | -4.843 | 4.631 | |||
Mcfadyen and Winter [ |
3 (—, —) | Ascent | 2.742 | -0.228 | 1.020 | -0.739 | 3.481 | |
Descent | 0.569 | -3.621 | -1.326 | -5.485 | 6.054 | |||
Musselman [ |
17 ( |
Ascent | 1.044 | -0.223 | 0.447 | -0.265 | 1.309 | |
Descent | 0.037 | -0.248 | -0.558 | -2.077 | 2.114 |
I: first peak knee generation power; J: first peak knee absorption power; K: second peak knee generation power; L: second peak knee absorption power.
As shown in Figure
A sketch map of motion and the typical curves of knee angle, moment, and power in the sagittal plane for sit-to-stand. (a) Sketch map of sit-to-stand cycle [
Overview over the experimental results of knee angle for sit-to-stand.
Study | Subjects ( |
A (°) | B (°) | ROM (°) |
---|---|---|---|---|
Wu et al. [ |
1 (—, 75) | 96 | 9 | 87 |
Hurley et al. [ |
10 ( |
90 | 12 | 78 |
Spyropoulos et al. [ |
17 ( |
86 | -1 | 87 |
Karavas et al. [ |
1 (1.85, 82.5) | 86 | 5 | 81 |
Yu et al. [ |
10 ( |
82 | 22 | 60 |
Bowser et al. [ |
12 ( |
83 | -3 | 86 |
A: peak knee flexion angle; B: peak knee extension angle.
Overview over the experimental results of knee moment for running.
Study | Subjects ( |
E (Nm/kg) | F (Nm/kg) | Range (Nm/kg) |
---|---|---|---|---|
Wu et al. [ |
1 (—, 75) | 2.187 | 0.609 | 1.578 |
Hurley et al. [ |
10 ( |
0.619 | 0 | 0.619 |
Yoshioka et al. [ |
1 (—, 73.8) | 1.087 | -0.038 | 1.125 |
Spyropoulos et al. [ |
17 ( |
1.132 | -0.157 | 1.289 |
Karavas et al. [ |
1 (1.85, 82.5) | 1.293 | 0.168 | 1.125 |
Bowser et al. [ |
12 ( |
0.901 | 0 | 0.901 |
Kamali et al. [ |
1 (1.72, 70) | 1.126 | 0.136 | 0.990 |
Schofield et al. [ |
10 ( |
0.679 | 0.038 | 0.641 |
Robert et al. [ |
7 ( |
1.136 | -0.198 | 1.334 |
E: peak knee extension moment; F: peak knee flexion moment.
Because of the complicated interaction of the underlying biological mechanisms, the knee joint demonstrates a spring-like behavior in common motions [
The moment-angle (stiffness) curves of the knee joint for normal walking, running, stair climbing, and sit-to-stand. (a) Normal walking [
Since the nonuniform shape of the knee articular surface and the complicated physical structure of the femur and tibia, the knee motion cannot be modeled as simple as a perfect hinge [
In addition to the motion in the sagittal plane, the knee joint also has internal-external rotation in the horizontal plane [
In the coronal plane, the knee adduction moment and the loads of knee medial and lateral compartments are key parameters of biomechanics. For the former, Gaasbeek et al. [
According to the pathogeny, the knee disorders can be mainly divided into musculoskeletal and neurological disorders. For the former, the pathogeny is inside the knee joint, but the neural control system of these patients is normal. Knee osteoarthritis (KOA), knee ligament injury, and meniscus injury are the most common forms of these disorders and will be mainly discussed in this section. Some evidences showed that the partial assistance from an external mechanism can alleviate the symptoms [
KOA, one of the major health problems, affects 7-17% of individuals especially for the elder, obese, and previous limb injury people [
Medical radiological assessment, kinematics analysis, kinetics analysis, and knee muscle analysis are the common biomechanical methods for KOA, as shown in Table
Overview over the biomechanical effects of KOA.
Study | Analysis | Effects |
---|---|---|
Chao et al. [ |
Medical radiology | HKAA: ~178.8 deg for normal knee; <178 deg for MKOA patients |
Paley [ |
Medical radiology | mLDFA: 85-90 deg for normal knee; >90 deg for MKOA patients |
Russell [ |
Medical radiology | HKAA: ~177.7 deg for normal knee; ~174.2 deg for MKOA patients |
Kinematics | A lower knee flexion angle for MKOA patients | |
Kinetics | A higher knee adduction moment for MKOA patients | |
Muscles | A lower quadriceps strength for MKOA patients | |
Zhu et al. [ |
Kinematics | A longer gait time, a smaller stride length and ROM, a greater knee flexion angle at heel strike, and an unobvious fluctuation of knee flexion angle in stand phase of walking for MKOA patients |
Alzahrani [ |
Kinematics | A slower walking speed, a shorter step length, a longer stance, and double support time, and smaller cadence, stride length, and knee ROM for MKOA patients |
Muscles | The medial and lateral muscle cocontraction was increased for KOA patients | |
Astephen et al. [ |
Kinetics | A greater knee adduction moment in mid-stance for MKOA patients |
Guo et al. [ |
Kinetics | A greater peak adduction moment during stair climbing for MKOA patients |
Rudolph et al. [ |
Kinetics | A smaller peak knee flexion moment during early and late stance phases for MKOA patients |
Fitzgerald [ |
Kinetics | A 4-6 deg increase in varus alignment could increase around 70-90% medial compartment load during single limb bearing |
Lim et al. [ |
Kinetics | Genu varum exceeding 5 deg was associated with greater functional deterioration over 18 months than the value of 5 deg or less |
Muscles | No significant relationship between the varus malalignment and the EMG ratio of VM and VL | |
Kemp et al. [ |
Kinetics | A 20% increase in the peak adduction moment could increase the KOA progression risk |
Slemenda et al. [ |
Muscles | A smaller quadriceps strength and muscle activation for KOA patients |
Hubley-Kozey et al. [ |
Muscles | The medial and lateral muscle cocontraction was increased for KOA patients |
The knee alignment measurement methods and the effect of KOA on flexion angle and adduction moment. (a) Sketch map of HKAA, mLDFA, MPTA, and MAD [
Knee ligament injury is a common and serious disease in sport injuries and can significantly change the biomechanics. According to where the injury hits, the knee ligament injury can be divided into the ACL, PCL, TCL, FCL, and PL injuries. Many researchers pointed out that the secondary injuries, e.g., cartilage injury, meniscus injury, and KOA, can occur if not treated in time. And the ligament reconstruction, as a recognized effective treatment, can dramatically recover the knee biomechanics [
The biomechanical effects of ACL were shown in Table
Overview over the biomechanical effects of ACL and meniscus injury.
Study | Knee disorders | Analysis | Effects |
---|---|---|---|
Zhao et al. [ |
ACL | Kinematics | A lower knee ROM during stair climbing for ACL-injured patients |
Gronstrom et al. [ |
ACL | Kinematics | A greater knee adduction angle during weight-bearing activities for ACL-injured patients |
Gao and Zheng[ |
ACL | Kinematics | A slower speed and smaller stride length during walking for ACL-injured patients |
Alexander and Schwameder[ |
ACL | Kinetics | A 430% and 475% increase in the patella-femur contact force during upslope and downslope, respectively, for ACL-injured patients. |
Goerger et al. [ |
ACL | Kinetics | A greater peak knee adduction moment during weight-bearing activities for ACL-injured patients |
Slater et al. [ |
ACL | Kinematics | A smaller peak knee flexion angle and a greater peak knee adduction angle during walking for ACL-injured patients |
Kinetics | A smaller peak E-KFM and E-KAM for ACL-injured patients | ||
Thomas et al. [ |
ACL | Kinetics | No difference in the E-KAM among individuals with ACL injury and those who are healthy |
Norcross et al. [ |
ACL | Kinetics | A greater knee energy adsorption for ACL-injured patients |
Magyar et al. [ |
Meniscus injury | Kinematics | A smaller walking speed and knee ROM and a larger cadence, step length, duration of support, and double support phase for meniscus injured patients |
Zhou [ |
Meniscus injury | Kinematics | A larger minimum flexion angle and a smaller maximum internal-external rotation angle for meniscus-injured patients |
Kinetics | A larger knee pressure and a smaller knee stressed area for meniscus-injured patients |
Meniscus injury, as a sport-induced injury, is common among athletes and general population [
To our knowledge, there are rare research that study the biomechanical effects of meniscus injury, as shown in Table
SCI, one of the main causes of mobility disorders, affects around 0.25-0.5 million people every year around the world especially the young [
Overview over the biomechanical effects of SCI, stroke, and CP.
Study | Knee disorders | Analysis | Effects |
---|---|---|---|
Barbeau et al. [ |
SCI | Kinematics | A lower knee ROM and peak knee-swing-flexion angle for SCI patients |
Kinetics | A larger peak knee moment for SCI patients | ||
Desrosiers et al. [ |
SCI | Kinetics | A lower knee power during uphill and downhill walking for SCI patients |
Pepin et al. [ |
SCI | Kinematics | A longer knee flexion at good contact and maintain the longer flexion throughout the stance phase of walking for SCI patients. |
Sridar et al. [ |
Stroke | Kinematics | A lower walking speed for stroke patients |
Muscles | A lower quadriceps muscle moment and power for stroke patients | ||
Chen et al. [ |
Stroke | Kinematics | A lower knee flexion in the swing phase of walking for poststroke patients |
Stanhope et al. [ |
Stroke | Kinematics | Post-stroke patients can compensate their poor knee flexion in walking through faster speed |
Marrocco et al. [ |
Stroke | Kinetics | A greater dynamic knee joint loading for stroke patients and no significant difference between the E-KFM/E-KAM of stroke and healthy subjects. |
Novak et al. [ |
Stroke | Kinetics | A less energy transference in mid-stance of walking and a lower energy absorption in the late stance of walking for stroke patients |
Lerner [ |
CP | Kinetics | Crouch gait (characterized by excessive knee flexion in stance phase), walking inefficiency, and consumes much more energy |
Hicks et al. [ |
CP | Kinematics | Minimum knee flexion angle during the stance phase exceeding 40 deg for CP patients |
Stroke, a common cerebrovascular disease, has a high mortality and disability rate [
CP, the most common pediatric neuromotor disorder, affects around 0.2-0.3% live births [
Knee disorders, including musculoskeletal and neurological disorders, have serious influences on knee biomechanics. A number of researches related with the biomechanics of normal and diseased knee joint have been done during the last decades. Many advances have been made to understand the kinematics and kinetics of normal and diseased knee during different common motions. In the aspect of normal knee biomechanics, there is no clear assessment at the current state-of-the-art. The difference between the results of different researches is significant. In the aspect of diseased knee biomechanics, a lower knee flexion angle, walking speed, muscles strength, and a higher knee contact pressure were always observed. Understanding how pathologies affect the knee joint biomechanics is important for designing knee assistive devices and optimizing rehabilitation exercise program. However, the current understanding still has not met the requirement of a designer and rehabilitative physician. And it is hard to find a research that can systematic study all aspects of knee biomechanics completely. Thus, deeper understanding of the biomechanics of normal and diseased knee joint will still be an urgent need in the future.
Some limitations of the current studies must be noted. First, the current understanding on the knee biomechanics is not enough. Many research about the theoretical analysis of knee biomechanics are based on the mathematical modeling. Whether a link model or a simulation model, there is a difference between the model and the reality. And some simplification should always be made, such as the mechanical property, geometry, and relative motion of the bone, muscle, cartilage, etc. Thus, the current computational knee biomechanics cannot describe the real knee biomechanics completely. Second, the kinematics and kinetics results from different research are vastly different. The results are hard to apply in the designing knee assistive devices and optimizing rehabilitation exercise program directly. Therefore, the kinematics and kinetics analyses must be redone in actual use. Third, the studies about the biomechanical influences of knee disorders are mainly concentrated in walking. Little research has been done on other daily life activities, such as running, stair climbing, and sit-to-stand. Fourth, there is an insufficient recognition of the influence of disorders on the knee biomechanics. The influence will always be obtained by patients-normal comparative experiments. And there is severe shortage of deeper rational analyses of the influence.
There are several limitations of our review. First, only articles published in English were included posing a language bias to article selection. Second, the review findings are limited to the articles identified by the set search strategy. Third, the quality of evidence for each study was very low because of the study designs and high heterogeneity.
In the future, the biomechanics of the normal and diseased knee joint will constitute a key research direction. More realistic biomechanical models and computing methods will be further developed for a deeper understanding of the kinematics and kinetics of the knee joint. And more rational analyses about the biomechanical influences of knee disorders will be further established to design better assistive mechanisms.
The authors have no conflicts of interest to declare.
The research is supported by the Fundamental Research Funds for the Central Universities (Grant No. 31020190503004) and the 111 Project (Grant No. B13044).