Biomechanic studies can provide a powerful theoretical and scientific basis for studies on knee osteoarthritis (OA), which is of great significance for clinical management as it provides new concepts and methods in clinical and research settings. This study aimed to discuss and summarize biomechanical research on lower extremities in individuals with knee OA in the past ten years. The methodology of this review followed the framework outlined in the Joanna Briggs Institute (JBI) guidelines and strictly followed the checklist for drafting the findings. A literature search was conducted using PubMed, Scopus, Cochrane Library, Embase, Web of Science, Grey literature search in Open Library, and Google Academic databases. Relevant literature was searched from 2011 to 2023. Sixteen studies were included in this scoping review. Biomechanical research on knee OA in the last decade demonstrates that the biomechanics of the hip, knee, and ankle have a profound influence on the pathogenesis and treatment of knee OA. Individuals with knee OA have biomechanical changes in hip, knee, and ankle joints such as a significant defect in the strength of ankle varus muscles, weakness of hip abductor muscle, walking with toes outwards, increased knee adduction moment and angle, and decreased knee extensor moment. As the severity of knee OA increases, the tendency of hip abduction positions also increases. Further research with a longitudinal study design should focus on the determination of the relative importance of different biomechanical and neuromuscular factors in the development and progression of the disease.

BACKGROUND: Impaired knee stability is observed in patients with medial compartment knee osteoarthritis (OA) and varus malalignment. Although high tibial osteotomy (HTO) is widely used to treat OA-related knee varus deformity, its long-term influence on balance control in OA patients is poorly reported. This study aimed to evaluate the impact of HTO on balance control and assess its biological and functional significance.
METHODS: Thirty-two patients with medial compartment knee OA as well as varus deformity who were scheduled for HTO underwent static posturographic tests one month pre- and three months as well as one year postoperatively, respectively, along with forty matched control subjects. Radiographic and clinical evaluations were synchronously carried out on patients pre- and postoperatively.
RESULTS: Decreased postural sway was observed in patients one year after HTO. When compared to the control subjects, more postural sway was found in patients one month pre- and three months postoperatively. No difference was observed between the patients and control subjects one year postoperatively. The alignment and joint function of the affected knees significantly improved after HTO.
CONCLUSIONS: This study revealed that HTO improves balance control in patients with knee OA and varus deformity. Correct alignment and improved joint function enhance the likelihood of normal postural stability. Hence, this intervention allows the knee joint to recover its corrective compensatory role in postural regulation and should be taken into account for managing knee OA patients.

OBJECTIVE: To explore application value and efficacy of personalized osteotomy in primary total knee arthroplasty (TKA) for severe varus knee osteoarthritis.
METHODS: From June 2018 to January 2020, 36 patients (49 knees) with severe varus knee osteoarthritis were treated, including 15 males (21 knees) and 21 females (28 knees), aged from 59 to 82 years old with an average of (67.6 ± 6.5) years old;the course of disease ranged from 9.5 to 20.5 years with an average of (15.0 ± 5.0) years;11 patients (15 knees) with Kellgren-Lawrence grade Ⅲ and 25 patients (34 knees) with grade Ⅳ according to Kellgren-Lawrence grading. According to AORI clsssification of tibial bone defects, 8 patients (15 knees) were typeⅠTa and 16 patients (18 knees) were typeⅡ T2a. All patients\' femor-tibial angle (FTA) was above 15°, and received primary TKA with personalized osteotomy. Thirty-three patients (45 knees) were treated with posterior-stabilized (PS) prostheses, 13 patients (15 knees) with PS prostheses combined with a metal pad and extension rod on the tibial side, and 3 patients (4 knees) with legacy constrained condylar knee (LCCK) prostheses. FTA, posterior condylar angle (PCA), medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) before and after operation at 1 month were measured and compared by using picture archiving and communication systems (PACS). Recovery of lower limbs before and after operation at 12 months was evaluated by American Knee Society Score(KSS), and complications were observed and recorded.
RESULTS: All 36 patients (49 knees) were followed up from 15 to 40 months with an average of (23.46±7.65) months. FTA, MPTA were corrected from preoperative (18.65±4.28)° and (83.75±3.65)° to postoperative (2.35±1.46)° and (88.85±2.25)° at 1 month, respectively (P<0.001). PCA was decreased from (2.42±2.16)° before operation to (1.65±1.35)° at 1 month after operation, LDFA improved from (89.56 ± 3.55)° before operation to (91.63±3.38)° at 1 month after operation (P<0.05). KSS increased from (67.58±24.16) before opertion to(171.31±15.24) at 12 months after operation, 14 patients (19 knees) got excellent result, 19 (26 knees) good, and 3 (4 knees) fair.
CONCLUSIONS: Personalized osteotomy is helpful for recovery of axial alignment of lower limbs and correct placement of prosthesis, could effectively relieve pain of knee joint, recover knee joint function.

BACKGROUND: Post-operative misalignment of the lower limb mechanical axis following total knee arthroplasty (TKA) is thought to be associated with clinical failure. In a balanced knee, a neutral global mechanical axis following the use of intra-medullary (IM) guidance does not necessarily imply a horizontal TKA joint line. Using femoral and tibial axes separately would be more accurate in evaluating TKA alignment. Thus, the aim of the study is to define a pre-operative mechanical tibial and/or femoral angle threshold value for post-operative optimal alignment correction using IM guides.
METHODS: This single-center prospective continuous pilot study included 50 patients treated with a TKA for primitive osteoarthritis. Femoral and tibial cuts were performed using intramedullary (IM) guide. Three angles were calculated and analyzed pre and post-operatively on standing antero-posterior views using long-leg radiographs: femorotibial angle (FTA), mechanical femoral angle (MFA), and mechanical tibial angle (MTA). Statistical analysis was performed for the whole sample and for the three following FTA subgroups; normo-axial, varus and valgus.
RESULTS: The pre-operative MTA is the only parameter for which a threshold value was observed; when pre-operative MTA exceeded the value of 94°, an optimal correction might not be obtained post-operatively.
CONCLUSIONS: Our results suggest that the bony correction obtained via IM guiding depends exclusively on the primary deformation of the tibia. In cases of a varus of more than 94°, the IM guide was found to yield sub-optimal corrections. Thus, other solutions need to be investigated.

OBJECTIVE: To investigate the influence of soccer-specific fatigue on concurrent changes in knee joint kinematics and hamstring strength, given the increased risk of injury during the latter stages of match-play and the prevalence of knee joint and hamstring muscular injury.
METHODS: Repeated measures, randomized order trials.
METHODS: Laboratory.
METHODS: Ten male professional soccer players.
METHODS: Reactive inversion, eversion and neutral hop tasks were completed at 15 min intervals during a soccer-specific protocol, with touchdown knee joint kinematics in the frontal and sagittal planes calculated at 200 Hz. In a separate trial, players completed maximal eccentric knee flexions at 160°·s-1 (reflecting average knee angular velocity in the functional task) at 15 min intervals, quantifying peak torque.
RESULTS: All trials were characterized by knee varus at touchdown, with ∼4° greater mal-alignment elicited over the final 15 min of the protocol (P ≤ 0.05). Peak eccentric hamstring strength was significantly (P = 0.045) reduced throughout the 2nd half.
CONCLUSIONS: The coincident impairment of eccentric hamstring strength and increased knee varus at touchdown predisposes the player to injury, supporting epidemiological observations. Knee varus in these elite male players is in marked contrast to the valgus associated with ACL injury risk in female players.

BACKGROUND: Biomechanical deviations long (approx. 5years) after anterior cruciate ligament reconstruction have not been quantified in males, despite their distinct risk profile as compared to females. These deviations can indicate altered joint loading during chronic, repetitive motions.
METHODS: Cross-sectional study, comparing kinematic and kinetic variables between 15 male anterior cruciate ligament reconstructed patients and 15 healthy controls. During walking and running gait, measurements were taken of impact dynamics, knee and hip sagittal plane angles and moments, and knee varus angles and adduction moments.
RESULTS: Comparing affected limbs to control limbs, significantly lower maximum (P=0.001) and initial (P=0.003) loading rates were found during running, but not in walking. Hip angles were lower for affected limbs of patients compared to the control group (P=0.039) in walking, but not during running. Between-limb comparisons showed important differences in symmetry of the affected patients. Maximum force during running was higher in the unaffected limb (P=0.015), which was linked with a higher loading rate (P=0.008). Knee flexion angle was reduced by 2° on average for the affected limb during running (P=0.010), and both walking and running knee and hip moments showed differences. Knee varus angle showed a 1° difference during walking (P<0.001), but not during running. Knee adduction moment was significantly lower (more valgus) during both walking and running.
CONCLUSIONS: Male anterior cruciate ligament reconstructed patients demonstrate persistent, clinically important gait asymmetries and differences from healthy controls long after surgery in kinematics, kinetics, and impact biomechanics.

BACKGROUND: Ankle-dorsiflexion (DF) range of motion (ROM) may influence movement variables that are known to affect anterior cruciate ligament loading, such as knee valgus and knee flexion. To our knowledge, researchers have not studied individuals with limited or normal ankle DF-ROM to investigate the relationship between those factors and the lower extremity movement patterns associated with anterior cruciate ligament injury.
OBJECTIVE: To determine, using 2 different measurement techniques, whether knee- and ankle-joint kinematics differ between participants with limited and normal ankle DF-ROM.
METHODS: Cross-sectional study.
METHODS: Sports medicine research laboratory.
METHODS: Forty physically active adults (20 with limited ankle DF-ROM, 20 with normal ankle DF-ROM).
METHODS: Ankle DF-ROM was assessed using 2 techniques: (1) nonweight-bearing ankle DF-ROM with the knee straight, and (2) weight-bearing lunge (WBL). Knee flexion, knee valgus-varus, knee internal-external rotation, and ankle DF displacements were assessed during the overhead-squat, single-legged squat, and jump-landing tasks. Separate 1-way analyses of variance were performed to determine whether differences in knee- and ankle-joint kinematics existed between the normal and limited groups for each assessment.
RESULTS: We observed no differences between the normal and limited groups when classifying groups based on nonweight-bearing passive-ankle DF-ROM. However, individuals with greater ankle DF-ROM during the WBL displayed greater knee-flexion and ankle-DF displacement and peak knee flexion during the overhead-squat and single-legged squat tasks. In addition, those individuals also demonstrated greater knee-varus displacement during the single-legged squat.
CONCLUSIONS: Greater ankle DF-ROM assessed during the WBL was associated with greater knee-flexion and ankle-DF displacement during both squatting tasks as well as greater knee-varus displacement during the single-legged squat. Assessment of ankle DF-ROM using the WBL provided important insight into compensatory movement patterns during squatting, whereas nonweight-bearing passive ankle DF-ROM did not. Improving ankle DF-ROM during the WBL may be an important intervention for altering high-risk movement patterns commonly associated with noncontact anterior cruciate ligament injury.