Genu varum indicates a type of deformity marked by the laterally bowed knee joints and the distant side of the shinbones and splint bones that were inwardly curved. Genu varum deformity, involves a varus angulation of the tibia in which the knees are separated more than the feet during standing (Gheluwe et al., 2005). It is basically caused by instability of the joints or ligaments, abnormality of the bones, degenerative joint deformity, and pain. Joint deformity is usually caused by static factors such as inherent congenitalness or development deformity and abnormal stress (Jacquelin and Judith, 2012). The legs with genu varum may be caused by deformity either in the spine or in the lower limbs and in consequent induce secondary and tertiary problems to have effects on the physique and balance, which makes the deformity (Kwon, 2002).

Genu varum is reported to occur 15 to 20% in the whole population. While genu valgum, or inwardly-bent knees, is generally found in Western Europeans, genu varum occupies more than 90% in Korean cases (Moon et al., 1976), a phenomenon that may be caused by wearing high heels and life habit such as sedentary lifestyle. Genu varum induces gait difficulty and aesthetical problems, causing chronic fatigue, spinal deformity, aging, backache, and neuralgia (Kwon, 2002). When compared to the normal knees, the knees with genu varum may increase postural swaying and cause postural imbalance (Chang, 2010; Samaei et al., 2012).

It has also been claimed that genu varum deformity would tend to cause an increase in subtalar pronation moment during the contact and also in the propulsion phases of walking, while a genu valgum deformity may cause some increase in subtalar pronation moment during the contact phase and an increase in subtalar supination moment during the early propulsive phase (Karen et al., 2005). The specific effects of genu varum deformities on foot function. If genu varum deformities alter the nature of the ground reaction force (GRF), then this would significantly affect the mechanical function of the foot (Gheluwe et al., 2005).

Genu varum can be corrected either by non-surgical or surgical techniques. Non-surgical therapies include stretching, elastic band exercise, sling exercise, walking traction, muscle resistance exercise, chiropractic, chuna, and wearing corrective apparatus (Kang, 2008; Kim and Lee, 2010; Oh, 2011; Han, 2009). Stretching and elastic band exercise among the non-surgical treatments are interventions that are easy to be accessed.

Stretching is reported to be effective on prevention of musculoskeletal damage (Wilkinson, 1992; Smith, 1994; Kim et al., 2013), to increase the connective tissues around the joints (Jacobson and Speechley, 1990), and to be helpful in improving motor performance and in rehabilitating musculoskeletal system (Anderson and Burke, 1991; Beaulieu, 1981; Worrell et al., 1994). Anyone can easily do stretching regardless of time and space because it does not require special skills nor physical conditions (Hong, 2009). Elastic bands are rubber bands that are used as an instrument of medical rehabilitation; they are convenient to use, economical, and widely used (Ham, 2000). The bands are appropriate for strengthening muscles because they can provide wide-ranged loads, being widely used for rehabilitation treatment of sports injury or disability (Yamamoto, 2000). The elastic bands stimulate proprioceptive sensibility in the joints and the muscles, which delivers information of location and movement of the joints to the brain, contributing to maintaining proper postures and improving basic physical fitness (Petterson et al., 2011; Kim et al., 2016) According to some reports, combination of stretching, elastic band, and sling exercises reduced the distance of both knees while regular elastic band exercise decreased the distance in those who had deformed knees by genu varum (Kang et al., 2009; Han et al., 2011). However, there have been few domestic reports on relations of such exercises to physical balance in people with genu varum, a type of knee deformity common in Koreans.

In this study investigated effects of stretching and elastic band exercise on the knee space distance and plantar pressure distribution in people with genu varum.

1. Subject and Methods

This study was conducted as a single blind study. The study participants did not know about the group they joined. The subjects were randomly selected by drawing lots and divided into two groups as a stretching group and a Thera-band group.

The subjects of this study were students of a college who had genu varum. Based on the research of Moon et al. (1976), those who were at least Grade II in the distance of both knees (2.5 cm and more) and who did not have other medical, neurological, and musculoskeletal disorders were selected to be the subjects of this study (Table 1). We sufficiently explained the purpose and the methods of this study to the students, and those who voluntarily participated in the experiment were selected to be the subjects.

Table 1

Grade of Knee space width

Grade	Knee space width
Grade I	2.5 cm less than
Grade II	2.5 cm ~ 5 cm
Grade III	5 cm ~ 7.5 cm
Grade IV	7.5 cm more than

While the research of Yu and Kim (2015) performed a type of complex exercise of stretching mixed with elastic band exercise, we in this study divided the subjects into a group of stretching and a group of elastic band (Thera-band) exercise in order to identify more effective intervention. Stretching exercises were performed mainly hip adductor and extension. It was located on the thigh. The elastic band exercises were organized mainly to a hip joint motion for the strengthening of muscle.

A total of 14 subjects were randomly divided into a stretching group (n=7) and a Thera-band group (n=7). The stretching group consisted of four males and three females (20.14±2.54 years old, 167.1±9.78 cm in height, and 58.6±10.13 kg in weight), while the Thera-band group consisted of five males and two females (19.85±2.04 years old, 166.5±5.82 cm in height, and 54.2±5.59 kg in weight). The stretching and the There-band exercises were performed three times per week, for four weeks.

2. Exercise Programs

3. Measurement

We measured changes the plantar pressure distribution during walking, using a Gait Analyzer (TS-GT001010, Korea) (Fig. 1). The plantar pressure distribution was measured during walking, the change occurs in the contact surface of the foot and the ground (Kim, 2006). While a subject was gaiting barefoot as he/she saw front, we measured the changes three times-before and after the program and after 45 days of the experiment. The average of the three measured values was used in statistical analysis.

Fig. 1.

Foot plantar pressure measurement.

While measurement, at least two footprints had to be recognized; a case in which even one footprint was not recognized was excluded from the analysis.

We measured the knee space distance provided by Han (2009) to be used in this study. In this study, the measurement of knee space distance was performed by one person for reliability of measurement. When a barefoot subject stood in such a way that a board on which lines were drawn at intervals of .5 cm was behind his/her knees and his/her feet were parallel to each other anatomically, we took a picture in front of the subject to measure the distance of medial epicondyles of the knees (Fig. 2).

Fig. 2.

Knees space distance measurement (provided by Han, 2009).

4. Statistical analysis

The SPSS 20.0 was used to statistically process the data in this study. A Mann-Whitney test and a Wilcoxon signed ranks test as nonparametric tests were used. To compare the two groups Mean averages per group and standard deviation were calculated from all the data. The level of statistical significance was set at p<.05.

1. The homogeneity of subjects

The results of the Mann-Whitney test for group homogeneity showed no statistically significance differences, indicating that there was homogeneity in the stretching group and the Thera-band group. Therefore, the homogeneity of the two groups is secured (Table 4).

Table 4

Homogeneity of stretching & Thera-band exercises

	Group	Mean Rank	Mann-Whitney U	Z	p
Pre	Stretching (n=7)	7.14	22	-.32	.749
	Thera-band (n=7)	7.85
Post	Stretching	6.57	18	-.83	.406
	Thera-band	8.43

2. Changes in knee space distance

Changes in the knee space distance of the subjects with genu varum were investigated at pre- and post-intervention. According to analysis of the knee space distance intervened by the exercise program, the width showed statistically significant differences before and after the intervention (p<.05) (Table 5). Therefore, the stretching and Thera-band exercise in this study reduced the space distance between knees.

Table 5

Knees space width changed after stretching & Thera-band exercises

Group	Pre	Post	Z	p
Stretch group (n=7)	4.39±1.16Ａ	3.43±1.0Ｂ	-2.20	.028
Thera band group (n=7)	4.71±1.42	4.08±1.52	-2.37	.018

3. Changes in the plantar pressure distribution

When changes in the plantar pressure distribution was investigated, there was no statistically significant changes in both groups before and after the intervention. In most of the subjects in both groups at pre- and post-intervention, the plantar pressure distribution was on their right feet rather than their left feet, and on the front part rather than the rear part of the feet (Fig. 3). Even on the front part of the foot, the plantar pressure distribution of foot was usually on the right side of the subjects. There were slight changes after the intervention; in both groups, the plantar pressure distribution of foot was slightly moved from the front to the rear part and from the right foot to the left foot. However, statistical significance was found only when the plantar pressure was reduced from the front part of the left foot (Fig. 3D).

Fig. 3.

Plantar pressure. A) and C) Thera-band resistance exercise group. B) and D) Stretching exercise group. Left bar: pre-treatment, Right bar: post-treatment, Ant: anterior, Post: posterior, Lt: Left, Rt: Right

The purpose of this study was to identify effects of stretching and elastic band exercise for strengthening muscles on changes in the plantar pressure distribution and the knee space distance of young individuals with genu varum to investigate methods of intervention in effectively managing genu varum. We restructured exercise methods including stretching and elastic band exercise provided by some previous researches to improve knee space width, and applied the adjusted methods to the subjects for four weeks. As a result, the distance in both groups was significantly reduced.

The adductor muscles play a role of producing torque in every movement of the hip joints and generating internal rotation torque (Han, 2009). Shortening of the adductors may increase lateral rotation of the femur to exacerbate genu varum. As the hamstring muscles effectively control the locations of the hip and the trunk against the femur, shortening of the hamstring may induce imbalance in stabilizing the hip to damage physical stability. In this context, we applied exercises for extension of the adductors and the hamstring muscles to the stretching group. Meanwhile, the exercise methods using the elastic bands strengthened muscles around the hip joints such as the hip abductors, the gluteus maximus muscles, and the lateral rotators to reduce the knee space width. A stable standing posture does not require considerable muscular activities of the hip joint muscles because static balance is formed between the force of gravity and the extended connective tissues. When the body is swayed by external loads, however, the muscles are strongly contracted to provide more stability. Thus, strengthening of the muscles around the hip joints using elastic bands may increase physical stability more.

During the dynamics of walking, the effect of a genu varum condition has been estimated to cause either an increase in the subtalar joint (STJ) pronation moment or a decrease in the STJ supination moment during the heel loading and propulsion phases of gait. Who walked with genu varum over a force plate and a plantar pressure distribution mat to determine the changes in the ground reaction force vector within the frontal plane and the changes in the center-of-pressure location on the plantar foot (Gheluwe et al., 2005). Most of the subjects in this study used their right feet as the dominant foot, but after the four-week intervention, their plantar pressure was slightly moved from the right to the left feet. The plantar pressure was dispersed from the feet front to the rear, showing patterns of plantar pressure between the front and the rear as well as between the left and the right of the feet. The genu varum deformity would tend to cause a subtalar pronation moment to increase or a supination moment to decrease during the contact and propulsion phases of walking (Gheluwe et al., 2005).

Exercises of correcting genu varum might have positive effects on changes in hip joint angle, Q angle, and knee space distance, and lower limb deformity not by structural causes but by muscular imbalance might be corrected via consistent exercises (Han et al., 2011). Therefore, the genu varum patients in both of the elastic band group and the stretching group showed reduction in the knee space distance, and keeping such exercises may be helpful in correcting the knee space distance. Such results are consistent with those of the existing researches. In addition, correcting the knee space distance by exercises contributed to physical stability to enhance physical balance.

Further studies are needed to identify correlation between genu varum and balance to support the results of this study. Researches of exercise programs for genu varum may improve the quality of life of people with genu varum.

When the genu varum subjects of this study were divided into the stretching group and the elastic band (Thera-band) exercise group for intervention, there were significant changes in the knee space distance. In conclusion, the elastic band exercise and stretching may reduce the knee space distance of people with genu varum to induce physical stability, and these two exercise methods may serve as effective interventions to improve genu varum.

This study is supported by 2015 Research Grant from Kangwon National University (No. 201510108).