INTRODUCTION
Postural control is defined as the ability to maintain body equilibrium and regulate the spatial orientation of body segments (Ambhore et al., 2021). This ability depends on the integrated function of the neuromuscular and musculoskeletal systems and is strongly influenced by sensory input and motor coordination, particularly within the lower extremities (Kimijanová et al., 2024). Supination and pronation moments generated at the foot and ankle joints play a critical role in maintaining postural stability and are influenced by knee malalignment conditions such as genu varum and genu valgum (Kim, 2024; Mitamura et al., 2025). Consequently, lower limb alignment has been identified as a key determinant of postural control and balance performance (Lee, 2017; Wu et al., 2021).
Genu varum is a coronal-plane knee deformity characterized by medial deviation of the tibia relative to the femur, resulting in a bow-shaped appearance of the lower extremities (Coppa et al., 2022; Soheilipour et al., 2020). In normal standing posture, the lower limb weight-bearing line passes through the center of the knee joint, allowing symmetrical load distribution; however, in individuals with genu varum, this line shifts medially, leading to increased compressive loading in the medial knee compartment and asymmetric joint loading (Samaei et al., 2012; Shohat et al., 2018). This abnormal load distribution not only compromises frontal-plane knee stability but also increases varus motion during gait, further exacerbating medial compartment loading, accelerating joint degeneration, and inducing pain during weight-bearing activities (Skou et al., 2014). In addition, genu varum is closely associated with the development and progression of tibiofemoral osteoarthritis and represents a major risk factor for compensatory alignment changes in the foot and ankle joints, as well as tibial fractures (Chang et al., 2005). These structural and biomechanical alterations impair neuromuscular control, resulting in reduced static and dynamic balance performance, particularly in middle-aged women who experience age-related declines in muscle strength, proprioception, bone mineral density, and the presence of sarcopenia (Ibeneme et al., 2018; Kudo et al., 2020). Consequently, functional stability is compromised, leading to decreased performance in activities of daily living and an increased risk of falls.
Given the neuromuscular deficits and impaired dynamic joint stabilization associated with genu varum, conventional strength-focused exercise alone may be insufficient to address the functional impairments related to this condition (Samaei et al., 2012). In contrast, neuromuscular exercise integrates sensorimotor control, proprioceptive stimulation, postural alignment, and coordinated muscle activation to enhance central motor control strategies (Zaidi et al., 2025), thereby improving lower limb alignment and dynamic stability. Furthermore, neuromuscular exercise has been shown to reduce abnormal joint loading, alleviate pain, and enhance functional stability during movement, contributing to improved balance performance (Huang et al., 2025). Previous studies have reported that balance- and sensorimotor-based exercise programs improve muscle activation around the knee joint, enhance proprioception, and positively influence dynamic stability, pain reduction, and balance performance (Kakati and Borthakur, 2025; Şirin Ahısha and Paker, 2025).
However, most previous studies have focused on pain or structural alignment alone, whereas the rehabilitation relevance of genu varum lies in the interaction among frontal-plane malalignment, pain-related sensorimotor impairment, and balance control during weight-bearing tasks. Therefore, examining alignment, pain, and plantar-pressure-based balance outcomes together may provide clinically meaningful information regarding how neuromuscular exercise influences alignment-related functional control rather than structural correction alone.
MATERIALS AND METHODS
Participants
A total of 40 female patients who visited the Department of Rehabilitation Medicine at Shinwoo Hospital in Bundang-gu, Gyeonggi Province, South Korea, were enrolled in this study. The sample size was calculated using G*Power software based on the group-by-time interaction effect reported in a previous randomized controlled trial investigating exercise intervention in patients with genu varum. The effect size was estimated from the reported eta-squared value and converted to Cohen f. Using an effect size f of 0.716, an alpha error probability of 0.05, a statistical power of 0.80, a numerator degree of freedom of 1, two groups, and no covariates, the minimum required sample size was estimated to be 18 participants. Considering potential dropout and to ensure more stable estimates, 40 participants who met the eligibility criteria for genu varum were recruited and, following baseline assessment, randomly allocated in a 1:1 ratio to either the exercise group (EG, n=20) or the control group (CG, n=20) using a computer-generated randomization sequence. Allocation concealment was maintained using sequentially numbered, opaque, sealed envelopes prepared by an independent researcher who was not involved in participant recruitment, assessment, or intervention delivery. Inclusion criteria were: (a) age between 40 and 60 years, (b) radiographically confirmed genu varum, and (c) a Short-Form McGill Pain Questionnaire (SF-MPQ) score of ≥18.0. Exclusion criteria were: (a) history of trauma or fracture within the previous 3 months; (b) clinically diagnosed neuromusculoskeletal disorders affecting lower extremity function; (c) radiographic evidence of knee osteoarthritis (Kellgren-Lawrence grade ≥2); and (d) prior experience with knee-related therapeutic exercise. All participants provided written informed consent, and this study was conducted at Shinwoo Hospital and was reviewed and approved by the institutional review board (IRB) of Dongguk University (approval No. DGU IRB 2022007-01) because the principal investigator was affiliated with Dongguk University at the time of study approval.
Clinical assessment
Whole-leg radiographic imaging was performed using the INNOVISION ver. 2.0 software (DK Medical Systems Co., Ltd., Korea). During the examination, participants were instructed to stand in an upright position while facing forward, with the medial malleoli of both ankles in contact.
Knee-to-knee length
The knee-to-knee length (KTKL) was defined as the linear distance between the medial epicondyles of both knee joints in the standing position, as shown in Fig. 1A, and measurements were recorded to the nearest 0.1 cm (Navali et al., 2012). This variable is a distance-based measure used to assess lower limb alignment in the frontal plane and serves as a clinically applicable alignment indicator.
Hip inclination angle and medial proximal tibial angle
In this study, the hip inclination angle (HIA) and medial proximal tibial angle (MPTA) were measured to provide a more systematic assessment of lower limb alignment. The HIA reflects the alignment status of the hip joint and was used as an indicator to evaluate proximal alignment characteristics and the contribution of the hip within the lower extremity kinetic chain (Cooke et al., 2007). In contrast, the MPTA reflects changes in tibia-knee alignment associated with increased varus moment during weight-bearing and was used to assess distal alignment characteristics (Palmer et al., 2020). The HIA was defined as the angle between a line connecting a point 10 cm inferior to the superior aspect of the femoral neck and a point 10 cm superior to the distal femoral shaft, and a second line connecting the narrowest portion of the femoral neck to the terminal point of the femoral head, as shown in Fig. 1B. If the HIA was less than 125°, it was considered genu varum based on the previous study (Moon et al., 2022). The MPTA was calculated as the intersection angle between the longitudinal axis of the tibia and the proximal tibial joint line, as shown in Fig. 1C. A value of less than 90° was considered indicative of varus knee alignment (Moon et al., 2022).
Short-Form McGill Pain Questionnaire
The SF-MPQ is a multidimensional pain assessment tool consisting of 15 pain descriptors, including 11 sensory and four affective descriptors, each rated on a 4-point intensity scale from 0 (none) to 3 (severe). The sensory, affective, and total pain scores are calculated by summing the intensity rank values of the selected descriptors (Melzack, 1987).
Static and dynamic plantar pressure
The Gaitview AFA-50 system (alFOOTs, Korea) was used to examine static plantar foot pressure. First, participants were asked to stand in a comfortable position on Gaitview with both hands placed on the navel area and hold the same posture for 15 sec. The static plantar foot pressure was analyzed by dividing the sole into the front and rear sections, and left and right sections according to the pressure distribution of the sole, and the average value was used. For dynamic plantar pressure measurement, the process of taking one step at a time during gait was examined. The measured value was obtained using the sum of the pressure ratio of the forefoot and the total pressure ratio. The same method was used for the measurements of the rear foot. Intraclass correlation coefficients ranged from 0.69 to 0.97 (Kim and Lee, 2012).
Neuromuscular exercise program
The neuromuscular exercise program was designed to improve the relative alignment of the trunk and lower extremity joints and to enhance movement quality while dynamically strengthening the lower limb musculature (Bennell et al., 2011). Because individuals with genu varum have difficulty selectively activating muscle groups that correct varus deformity (e.g., hip musculature, lateral hamstrings, hip adductors, tensor fasciae latae, lateral gastrocnemius, and quadriceps femoris) in isolation, a pragmatic training approach was adopted (Ageberg et al., 2010). Participants were instructed to focus on maintaining neutral hip-knee alignment during structured exercises and functional tasks. This training strategy was implemented to facilitate neuromuscular control of the hip and knee joints. The program was conducted 3 times per week for 12 weeks, and each session lasted 60 min. Exercise intensity was prescribed using the Borg rating of perceived exertion (RPE, 6–20) scale. Warm-up and cool-down exercises were performed at an intensity of RPE 11–13, whereas the main exercises were performed at an intensity of RPE 14–16, with progressive increases throughout the intervention period. Rest intervals were set at 60 sec between exercises and 30 sec between sets. Detailed components of the neuromuscular exercise program are presented in Table 1. To ensure effective implementation of the intervention, participant adherence was systematically monitored throughout the study period. At each visit, the supervising therapist recorded attendance using a structured attendance log. All 20 participants in the EG completed all 36 scheduled sessions during the 12-week intervention period, resulting in a 100% adherence rate with no missed sessions. Exercise intensity was individually progressed based on RPE feedback obtained during each session. When a participant’s RPE was below 14, resistance or exercise load was increased during the subsequent session according to the demands of the specific exercise (e.g., elastic band resistance, number of repetitions, dumbbell weight, and duration of position holding). Adherence was additionally monitored through weekly therapist-led sessions, during which exercise form, duration, intensity, and ratings of RPE were assessed and recorded.
Statistical analysis
Continuous variables were presented as mean±standard deviation for normally distributed data and as median (interquartile range) for nonnormally distributed data. Categorical variables were expressed as frequencies and percentages. The normality of the distribution was evaluated using the Shapiro–Wilk test. Between-group comparisons were performed using the independent t-test or Mann–Whitney U-test, as appropriate. Associations between categorical variables were analyzed using the chi-square test. A two-way mixed analysis of variance was conducted with group and time as factors to examine the main and interaction effects on structural changes of the knee joint, pain, and static and dynamic balance ability. When significant interaction was observed, post hoc analyses were performed with Bonferroni correction. Because the EG was significantly older than the CG at baseline, age-adjusted analysis of covariance (ANCOVA) was additionally conducted for the main outcomes. The age-adjusted group-by-time interaction was examined to determine whether the intervention effects remained significant after controlling for baseline age differences. A P-value <0.05 was considered statistically significant. All statistical analyses were performed using IBM SPSS Statistics ver. 29.0 (IBM Co., USA).
RESULTS
Baseline characteristics
Baseline characteristics of the participants are presented in Table 2. This study included 40 female participants, with 20 assigned to the EG and 20 to the CG. The EG was significantly older than the CG (51.35±4.15 years vs. 45.85±5.46 years, P=0.002). No significant between-group differences were observed for height, body weight, or body mass index (P>0.05). All participants were female, indicating comparable sex distribution between groups.
Changes in structural alignment and pain
Changes in lower limb alignment and pain outcomes are summarized in Table 3. Significant group-by-time interactions were observed for KTKL (F=30.634, P<0.001, η2=0.446), bilateral HIA (right: F=222.573, P<0.001, η2=0.373; left: F=33.608, P<0.001, η2=0.469), bilateral MPTA (right: F=51.244, P<0.001, η2=0.574; left: F=17.571, P<0.001, η2=0.316), and SF-MPQ score (F=77.905, P<0.001, η2=0.672). Compared with the CG, the EG showed greater improvements in KTKL, bilateral HIA, bilateral MPTA, and pain scores following the intervention. Bonferroni-corrected post hoc analyses revealed significant pre- to postintervention improvements in KTKL, bilateral HIA, left MPTA, and SF-MPQ score in the EG, whereas the change in right MPTA did not remain statistically significant after correction. No significant pre- to postintervention changes were observed in the CG for these variables (Table 3). Because age differed significantly between the groups at baseline, an additional age-adjusted ANCOVA was performed. After adjustment for age, significant group-by-time interactions remained for KTKL (F=18.831, P<0.001, partial η2=0.337), right HIA (F=16.849, P<0.001, partial η2=0.313), left HIA (F=29.480, P<0.001, partial η2=0.443), right MPTA (F=32.136, P<0.001, partial η2=0.465), left MPTA (F=16.200, P<0.001, partial η2=0.305), and SF-MPQ score (F=67.544, P<0.001, partial η2=0.646). These findings indicate that the intervention effects on structural alignment and pain-related outcomes were maintained after controlling for baseline age differences.
Changes in balance performance
Balance outcomes are presented in Table 4. Significant group-by-time interactions were observed for static anterior balance (F=5.624, P=0.023, η2=0.129), static right balance (F=11.989, P=0.001, η2=0.240), static left balance (F=14.983, P<0.001, partial η2=0.283), dynamic right balance (F=6.607, P=0.014, η2=0.148), and dynamic left balance (F=5.072, P=0.030, η2= 0.118). No significant interaction effects were observed for static posterior, dynamic anterior, or dynamic posterior balance measures. Bonferroni-corrected post hoc analyses showed significant improvements only in static right and dynamic right balance in the EG, whereas static anterior and dynamic left balance did not remain significant after correction. No significant pre- to postintervention changes in balance variables were detected in the CG. Additional age-adjusted ANCOVA was performed for balance variables that showed significant group-by-time interactions in the unadjusted analysis. After adjustment for age, significant group-by-time interactions remained for static right balance (F=10.789, P=0.002, partial η2=0.226), static left balance (F=13.154, P<0.001, partial η2=0.262), and dynamic right balance (F=4.838, P=0.034, partial η2=0.116). However, static anterior balance (F=3.831, P= 0.058, partial η2=0.094) and dynamic left balance (F=3.617, P=0.065, partial η2=0.089) were no longer statistically significant after age adjustment. These findings suggest that the intervention-related improvements in balance performance were limited to selected variables after controlling for baseline age differences.
DISCUSSION
The main finding of this study was that neuromuscular exercise produced improvements in alignment-related measures and pain, with selective changes in balance performance. These findings should not be interpreted as evidence of marked structural correction of genu varum. Rather, they suggest that repeated neuromuscular exercise may improve functional control of the lower extremity kinetic chain by enhancing sensorimotor regulation, coordinated hip-knee-ankle alignment, and pain-related proprioceptive function during weight-bearing activities.
The reduction in KTKL, along with improvements in HIA and MPTA, suggests that the neuromuscular exercise program contributed to enhanced regulation of lower limb alignment in the frontal plane. Genu varum increases compressive loading in the medial compartment of the knee during weight-bearing, thereby compromising joint stability and inducing compensatory alignment changes throughout the lower extremity kinetic chain, including the hip and ankle joints (Van Oevelen et al., 2023). From a clinical perspective, even small changes in alignment may be meaningful because they can reduce excessive loading in the medial compartment of the knee and promote a more efficient load distribution (Van Rossom et al., 2019). In this context, neuromuscular exercise may improve joint position control during weight-bearing through enhanced sensorimotor integration and coordinated muscle activation, leading to functional improvements in lower limb alignment. In particular, the changes in HIA and MPTA may reflect improved neuromuscular stability across the hip-knee-ankle kinetic chain (Ford et al., 2015). Although statistically significant changes were observed in some radiographic alignment variables, the magnitude of change in HIA and MPTA was relatively small, approximately 1°. Therefore, these findings should not be interpreted as definitive anatomical realignment or structural correction. The findings may be interpreted as reflecting improvements in functional neuromuscular adaptation rather than definitive structural alignment correction.
The significant reduction in pain observed in this study suggests that neuromuscular exercise contributed to meaningful modulation of knee pain. Given that knee pain is known to compromise proprioceptive acuity, muscle activation, and dynamic joint stability—thereby interfering with neuromuscular control—pain reduction in the present study may have facilitated the restoration of effective neuromuscular regulation rather than representing mere symptomatic relief (Seeley et al., 2022). Furthermore, neuromuscular exercise-induced strengthening of the lower extremity musculature may have enhanced dynamic stabilization around the knee joint and redistributed excessive loading concentrated in the medial compartment during weight-bearing activities through coordinated muscle activation, thereby improving joint stability and reducing mechanical stress on the knee (Kaya et al., 2019). From a mechanistic perspective, the combined effects of pain attenuation and alignment-related load redistribution likely created a more favorable neuromuscular environment for coordinated movement control. Collectively, these findings underscore the clinical relevance of neuromuscular exercise as an intervention that addresses both sensory-motor dysfunction associated with pain and biomechanical contributors to knee joint loading in individuals with genu varum (Bennell et al., 2014).
Individuals with genu varum are known to exhibit increased mediolateral postural sway and impaired balance compared with those with normal alignment, a characteristic associated with an elevated risk of falls (Samaei et al., 2012). Balance deficits in this population are multifactorial, reflecting interactions among frontal-plane malalignment, pain-related proprioceptive impairment, and reduced neuromuscular control (Ha et al., 2018; Seeley et al., 2022). Neuromuscular exercise has been shown to selectively enhance postural control and dynamic stability by improving sensorimotor integration and coordinated muscle activation, particularly during weight-bearing tasks requiring frontal-plane control (Ageberg et al., 2010; Rashid et al., 2019). The findings of the present study suggest that the neuromuscular exercise program contributed to improvements in balance ability through enhanced proprioceptive input, optimized postural alignment, and coordinated muscle activation. These results are in line with previous evidence demonstrating that comprehensive exercise interventions incorporating strength, sensorimotor, and functional training effectively improve balance performance in individuals with knee osteoarthritis (Wang et al., 2025). Moreover, neuromuscular exercise has been shown to reduce knee pain and stiffness while enhancing physical function and sensorimotor components, including joint position sense (Lee and Choi, 2019; Wang et al., 2021). Consistent with these observations, prior studies have further reported that sensorimotor-based exercise programs lead to significant improvements in functional performance and balance ability in patients with knee osteoarthritis (Ahmed et al., 2011).
The present study has several limitations that should be acknowledged. First, there was a statistically significant difference in baseline age between the groups. Although the EG was older than the CG, it demonstrated more favorable outcomes; therefore, the age imbalance should be considered when interpreting the findings and may have biased the results toward underestimating, rather than overestimating, the intervention effect. Second, the present study employed the KTKL as a parameter of coronal lower extremity alignment in patients with genu varum, while the HIA was used as an indicator of proximal alignment within the lower extremity kinetic chain, and the MPTA was used to reflect distal tibiofemoral alignment characteristics. These variables were used to evaluate hip joint and tibiofemoral alignment within the lower extremity kinetic chain, respectively. However, the present study did not incorporate standardized full-length coronal radiographic measurements, such as the hip-knee-ankle angle, which is considered the gold standard for quantifying structural varus alignment. This represents a methodological limitation, as it precludes definitive determination of whether the observed improvements reflect true structural correction of the entire lower extremity or are attributable to soft tissue or neuromuscular adaptations. Third, significant improvements were not observed across all balance-related variables. This finding may be attributable to task specificity and to potential constraints related to the duration and intensity of the intervention. Balance ability is a multidimensional construct in which sensorimotor strategies are differentially engaged depending on task characteristics, including static versus dynamic conditions, movement direction, and support surface stability (Giboin et al., 2015). Accordingly, exercise-induced adaptations may manifest selectively rather than uniformly across all balance measures, a pattern consistent with previous studies reporting nonuniform balance improvements following exercise interventions (Kümmel et al., 2016). Future research should therefore consider incorporating balance training components that more specifically target mediolateral stability and dynamic postural control, as well as extending intervention duration and individualizing exercise intensity to promote broader balance adaptations. Fourth, because all participants in this study were female, the generalizability of the findings to male populations is limited. Future studies should include participants of both sexes and a wider age range to enhance external validity. Finally, the absence of follow-up assessments precludes conclusions regarding the long-term sustainability of the observed effects. Longitudinal studies incorporating postintervention follow-up are warranted to determine the persistence of neuromuscular exercise-induced adaptations.
In conclusion, the 12-week neuromuscular exercise program improved alignment-related variables and reduced knee pain in women with genu varum, although improvements in balance ability were observed only in selected variables. These findings suggest that neuromuscular exercise may be beneficial for reducing pain and improving functional control of the lower extremity kinetic chain in women with genu varum. However, the present results should be interpreted with caution and should not be regarded as evidence of definitive structural correction. Further studies with larger sample sizes, standardized assessments of the mechanical axis, and mechanistic outcomes are needed to clarify the clinical and biomechanical effects of neuromuscular exercise in this population.
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