Influence of quadriceps angle on static and dynamic balance in young adults

Abstract

BACKGROUND:

Changes in postural stability may be a reason for injuries in individuals who have altered musculoskeletal alignment. Q angle (QA) has shown to be a predictor for lower extremity injuries. However, the relationship between balance and QA has not been investigated in young adults.

OBJECTIVE:

The aim of the study was to investigate the relationship between QA and balance in young adults.

METHODS:

Ninety participants performed the single leg stance test (SLST) and Star Excursion Balance Test (SEBT) to assess static and dynamic balance, respectively. QA was measured using a manual goniometer. Participants were divided into low, normal and high QA groups.

RESULTS:

The relationship between SLST and QA was not statistically significant in both eyes opened and closed condition ( $r=$ $-$ 0.030, $p=$ 0.782; $r=$ 0.031, $p=$ 0.774; respectively). SLST scores did not differ among the three groups in both eyes opened and closed condition ( $p=$ 0.781, $p=$ 0.790; respectively). QA significantly correlated with lateral, posterolateral directions and sum score of SEBT ( $r=$ 0.240, $p=$ 0.023; $r=$ 0.269, $p=$ 0.010; $r=$ 0.210, $p=$ 0.047). The comparisons among the low, normal and high Q angle groups’ SEBT scores showed that balance performance in lateral direction was poorer in low QA group ( $p=$ 0.027).

CONCLUSIONS:

The results of the study showed that QA and dynamic balance have a significant relationship. To reduce musculoskeletal injury risk, the dynamic balance should be assessed in young adults who have lower QA.

Keywords

Q angle lower extremity star excursion balance test single leg stance test

1. Introduction

Postural control is the ability to maintain balance and adjustment reactions in a gravitational environment [1]. The effect of differences in biomechanical parameters on postural control or performance has been investigated, and it is assumed that differences in lower extremity morphology may influence postural control strategies because of changes in the proprioceptive feedback [2, 3, 4].

Participants with supinated and pronated feet present insufficient postural control during single leg stance [5]. For dynamic postural control, maximum distance reached in any of the directions in Star Excursion Balance Test (SEBT) is affected by pronated or supinated feet types [2]. It has also been claimed that pronated and supinated feet posture may have an interactive effect on the Quadriceps angle (QA) [6, 7].

QA gives a general impression of lower extremity biomechanics. Alterations of QA affect knee kinematics in both static and dynamic conditions [8]. A study showed that a high QA ( $>$ 15 ${}^{\circ}$ ) delays the reaching maximum tibial internal rotation during running [9]. Furthermore, participants with high QA ( $>$ 17 ${}^{\circ}$ ) had 10 to 12 milliseconds slower internal rotation perturbations than those with normal QA [10]. A study revealed that basketball players with lower QA showed abnormal knee strategies during knee bending phase of countermovement jump [11]. Differences in QA alter both biomechanical and neuromuscular responses during activities. Regarding postural control, it is shown that high QA ( $>$ 14 ${}^{\circ}$ ; genu valgus) is correlated with increased body sway in elderly women [4]. Another study reported that genu varus deformity increases the postural sway in mediolateral direction and falling risk, which could be explained by the medial shift of line of gravity in those subjects [3].

The poor balance is associated with an increased risk of injury in various populations [12]. Injuries generally occur in cutting, jumping and single-leg landing maneuvers [13]. Because of these reasons, measurement of balance performance on single leg may be an important predictor for musculoskeletal injuries [14]. The single leg stance test (SLST) is a simple test for measuring static characteristics of balance that requires minimal equipment in clinics [15]. On the other hand, as a dynamic balance test, SEBT is a series of unilateral mini squats performed in different directions which are used as a measure of performance and injury risk among healthy active populations [12].

To our best knowledge, none of the studies investigated the relationship between QA and static and dynamic balance in young adults on single leg stance position, which is the common position for lower extremity injuries. Since the alterations in QA may affect the balance performance in young adults, the aim of the study was to determine the effects of QA on static and dynamic balance in young adults.

Table 1
QA values and balance scores of participants

QA ( ${}^{\circ}$ )		12.0 $\pm$ 4.2
		X $\pm$ SD
QA groups	Low QA ( $<$ 10 ${}^{\circ}$ ) ( $n=$ 30)	7.7 $\pm$ 2.0
	Normal QA (10 ${}^{\circ}$ –14 ${}^{\circ}$ ) ( $n=$ 35)	12.0 $\pm$ 1.5
	High QA ( $>$ 14 ${}^{\circ}$ ) ( $n=$ 25)	17.3 $\pm$ 1.9
SLST (s)	Opened eyes	175.5 (2.0–210.0)
	Closed eyes	21.7 (2.0–105.0)
SEBT directions	Anteromedial	70.9 $\pm$ 5.9
(% of leg length)	Anterior	70.1 $\pm$ 6.4
	Anterolateral	64.7 $\pm$ 7.0
	Lateral	55.0 $\pm$ 7.3
	Posterolateral	54.3 $\pm$ 9.4
	Posterior	61.4 $\pm$ 8.9
	Posteromedial	67.6 $\pm$ 78
	Medial	69.3 $\pm$ 6.8
	Sum SEBT	513.2 $\pm$ 48.4

QA: Q angle, SLST: single leg stance test, SEBT: star excursion balance test, s: second, M: mean, SD: standard deviation.

2. Methods

Ninety right dominant subjects (45 females and 45 males) between the ages of 18–25 volunteered for this study. Leg dominance was determined by the ball kicking test. Patients were included if they did not have any musculoskeletal, neurological and cardiovascular problems. Participants were excluded if they had an injury or operation in the past year, previous history of immobilization in the last three years, persistent pain or pathology or laxity, disorders of the circulatory system in lower extremities or visual and vestibular problems. All participants provided informed consent prior to enrolling in this study. The study protocol was approved by the human ethics committee of Abant Izzet Baysal University.

QA was measured with a standard goniometer (MSD evaluation products goniometer 30 cm; MSD, Oss, The Netherlands) between the intersection of a line from the anterior superior iliac spina to a sign on the center of the patella and a line from the center of the patella to the center of the tibial tubercle. Participants were positioned standing with their feet a comfortable width apart, knees straight and feet in a natural position without shoes [16]. All measurements were performed three times for right leg by the same investigator. The average value of measurements was accepted as QA. Participants were also divided into three QA groups: physiological valgus or normal QA (QA from 10 ${}^{\circ}$ to 14 ${}^{\circ}$ ), varus or low QA (QA $<$ 10 ${}^{\circ}$ ), valgus or high QA (QA $>$ 14 ${}^{\circ}$ ) [4].

Static balance was assessed with SLST in eyes open and eyes closed condition. Participants who placed their hands on their hips were asked to stay as long as possible on their right foot which stands barefoot on a smooth and hard surface while the left leg was raised without touching the ankle of their stance leg [15]. The timer was ended if the participant either moved the weight-bearing foot on the ground, opened their eyes on eyes closed trials or maximum of 210 seconds for eyes open, or when the maximum of 150 seconds for eyes closed had elapsed. At least 2 minutes of rest was allowed between trials to avoid fatigue.

Dynamic balance was tested by using SEBT in eight directions for the right leg. Before SEBT, participants practiced six trials to prevent learning effect. Participants whose hands were on their hips, stood in the middle of the testing grid with strips of tape placed at 45 ${}^{\circ}$ angles, and reached with their left foot as far as possible along the different grid lines which represent for anteromedial (AM), anterior (A), anterolateral (AL), lateral (L), posterolateral (PL), posterior (P), posteromedial (PM) and medial (M) directions and then returned to starting position [17]. The trial was considered invalid and repeated if the participant could not maintain single leg stance, moved the stance foot from the grid, touched down with the reach foot or did not return the reach foot to the apex of the grid. The average of 3 trials for each direction was recorded for maximum reach distance.

SEBT scores were normalized with the length of the stance leg which was measured from anterior superior iliac spine to the most distal point of the medial malleolus, using a standard tape measure in the supine position (SEBT score (cm)/leg length (cm) $\times$ 100) [18]. Also, the reach distances from each direction were summed to provide a composite reach distance for analysis of the general performance of the test [19].

3. Statistical analysis

All statistical analysis was completed using SPSS version 21.0 for Windows. Normality of distribution was assessed through the use of the Kolmogorov-Smirnov test. Pearson correlation analysis was used to evaluate the relationship between QA and balance scores. The strength of correlations were categorized as strong ( $>$ 0.5), moderate (0.3–0.5), weak (0.1–0.3), or very weak ( $<$ 0.1) according to $r$ value $p<$ 0.05 was accepted as the significance level. One-way ANOVA followed by Tukey HSD test was performed on the balance test scores to determine differences between groups. The power analysis showed that to have 80% power to detect a correlation coefficient of at least 0.3 as being statistically different from 0 (with $\alpha=$ 0.05, two-sided test), a minimum of 84 subjects would be needed.

Table 2
The balance performance differences among low, normal and high Q angle groups, and correlation of balance tests with QA

	Low QA $X\pm SD$	Normal QA $X\pm SD$	High QA $X\pm SD$	$F$	$p$	Correlation with QA
	( $n=$ 30)	( $n=$ 35)	( $n=$ 25)			$r$	$p$
SLST (s)
Opened eyes	154.1 $\pm$ 68.2	142.2 $\pm$ 72.9	150.3 $\pm$ 65.8	0.247	0.781	$-$ 0.030	0.782
Closed eyes	19.3 $\pm$ 19.7	22.3 $\pm$ 28.1	23.6 $\pm$ 24.1	0.236	0.790	0.031	0.774
SEBT directions (% of leg length)
Anteromedial	69.9 $\pm$ 5.9	71.2 $\pm$ 6.4	72.1 $\pm$ 5.1	0.973	0.382	0.137	0.197
Anterior	68.9 $\pm$ 6.8	70.1 $\pm$ 6.6	71.3 $\pm$ 5.6	0.968	0.384	0.163	0.125
Anterolateral	63.9 $\pm$ 7.1	63.9 $\pm$ 6.9	66.6 $\pm$ 6.8	1.298	0.278	0.178	0.094
Lateral	52.1 $\pm$ 6.2	56.1 $\pm$ 7.7	56.9 $\pm$ 7.3	3.774	0.027 ${}^{{\dagger}}$	0.240	0.023 ${}^{*}$
Posterolateral	51.5 $\pm$ 7.5	55.1 $\pm$ 11.4	56.4 $\pm$ 7.5	2.083	0.131	0.269	0.010 ${}^{*}$
Posterior	60.7 $\pm$ 7.7	60.7 $\pm$ 11.5	63.3 $\pm$ 5.8	0.759	0.471	0.154	0.148
Posteromedial	67.2 $\pm$ 7.9	67.5 $\pm$ 8.6	68.3 $\pm$ 6.4	0.159	0.853	0.106	0.321
Medial	68.8 $\pm$ 7.5	69.2 $\pm$ 7.1	69.9 $\pm$ 5.4	0.187	0.829	0.090	0.398
Sum SEBT	503.0 $\pm$ 42.6	513.8 $\pm$ 58.9	524.8 $\pm$ 35.9	1.394	0.253	0.210	0.047 ${}^{*}$

${}^{{\dagger}}$ Differences among groups by using one way ANOVA. Tukey’s HSD test was performed if the results showed statistically significant differences, and showed as $p<$ 0.05. ${}^{\ast}$ Pearson Correlation between Q angle and L,PL and sum SEBT. $p<$ 0.05 is statistically significant. QA: Q angle, SLST: single leg stance test, SEBT: star excursion balance test, M: mean, SD: standard deviation.

4. Results

The mean body weight and height of subjects were 64.7 kg (SD 11.5 kg) and 170.2 cm (SD 9.2 cm), respectively. Table 1 presents mean QA value, SLST and SEBT scores of all participants and mean QA value of each QA groups. The relationship between QA and SLST were not significant ( $p>$ 0.05) (Table 2). QA had a significant and positive weak relationship at in L and PL directions ( $r=$ 0.240, $p=$ 0.023; $r=$ 0.269, $p=$ 0.010, respectively) and sum of SEBT scores ( $r=$ 0.210, $p=$ 0.047) (Table 2). The mean L direction SEBT score had statistically significant difference among the low, normal, high QA groups ( $p=$ 0.027) (Table 2). Post-hoc tests revealed that low QA group’s score was significantly worse than normal and high QA’s score in L direction. There were no differences in SLST scores among QA groups ( $p>$ 0.05) (Table 2).

5. Discussion

In this study, a weak relationship was found between QA and dynamic balance in young adults. Regarding dynamic balance; QA was related to L, PL directions and sum of SEBT score. The comparisons of SEBT scores among low, normal and high QA groups showed that subjects with low QA had poorer balance performance in L direction. QA had no relationship with static balance. Low, normal and high QA did not affect static balance.

Assessment of lower extremity alignment may help clinicians reducing the risk of lower extremity injury and improving performance. For this purpose, QA measurement which represents frontal plane alignment and provides information about whole lower extremity, especially extensor mechanism, is frequently used as a reference value [20]. A study showed that a low QA was predictive of an Anterior Cruciate Ligament (ACL) injury together with other factors such as knee laxity, posterior knee stiffness, and navicular drop [21]. In the present study, low QA group mostly presented decreased balance performance compared to high and normal QA groups, but the difference was only in L direction. The worst balance performance was determined in low QA group that supports the assumption of a low QA is being predictive for non-contact ACL injuries.

The quadriceps femoris muscle is the primary muscle worked during knee extension. QA may affect the resultant force of the quadriceps femoris muscle on the patella [22]. These biomechanical changes can result in deficits in postural control components. Mainenti et al. [4] showed that a high QA is correlated with increased body sway in elderly women. Participants with genu valgus showed higher stabilometric variable values than those with genu varus such as lateral standard deviation, anteroposterior standard deviation, lateral range, anteroposterior range. In contrast, Ferreira et al. [23] presented that varus knee had lower center of foot pressure mean velocity than neutral and valgus knee based on the reduction of the support area. Similarly, Samaei et al. [3] showed that genu varum deformity might increase postural sway in the mediolateral direction in both static and dynamic conditions and also the falling risk in a young group. QA is a frontal plane angle where the mediolateral movements occur. The medial shifting of the line of gravity which occurs in subjects who have knee deformity in the frontal plane may alter the normal weight distribution on the knee [24] and ankle joints [25]. This may increase postural sway in the medial-lateral direction. Changes in frontal plane angle (such as tibiofemoral angle, QA) may influence the movements of lower extremity joints and also the strategies for balance control. Considering these findings, it seems that a low QA may affect frontal plane balance control via the base of support or ankle and knee alignment.

Tibiofemoral angle is also a frontal plane angle parameter which is strongly associated with QA; the greater tibiofemoral angle results in higher QA [20]. Nyland et al. [26] used the tibiofemoral angle to determine the knee joint alignment and revealed that the participants with genu valgus or genu varus use different dynamic postural control strategy during single leg stance at 20 ${}^{\circ}$ knee flexion. The plantar flexor muscle group has a peak pressure and displays a subtalar and midtarsal joint inversion-eversion modulator on a more mobile foot lever to maintain postural control during single leg stance in genu varus or genu valgus [26]. Similarly, a study showed that a low QA leads to higher mean peak plantar pressure values in the lateral aspects of the foot [27]. The study by Eltoukhy et al. [28] which only assessed A, PM and PL directions demonstrated that greater calcaneal marker tortuosity was related to poor PL performance. As a result, subtalar joint movements are mainly on the frontal and transverse planes, compensation of structural deformities in subtalar joint also occur in the frontal plane [29, 30]. A low QA may eliminate compensation strategy of foot and result in worse score in L direction on SEBT which includes repetitive unilaterally mini squats. Furthermore, a greater knee inside displacement was reported in basketball players with low QA during knee flexion phase of countermovement jump [11]. Medial displacement of the knee in low QA may also be one of the explanations for L direction. In the same study, low QA was found to be a patellar instability factor during knee bending due to the softer patellar tendon. No relationship between QA and static balance was detected in the present study. The SLST test was completed at knee extension position, but the dynamic test was performed as consecutive knee flexions. Because the patella is not entirely engaged in the patellar groove during these flexion movements, the sumSEBT score may be increasing with higher QA.

There are some limitations in the study. In the literature weak inter-observer and intra-observer reliability of QA measurement and poor correlation between clinically and radiographically derived QA was reported. The patella may be centralised in the femoral trochlear groove to accurate the QA measurement [31]. Furthermore, QA was assessed in the double-leg stance position, but the balance assessments were performed on single-leg. Since the QA varies at different positions, we recommend that future studies should evaluate the Q angle in a single leg position [32]. Although we did not use computer-based assessment tools such as pedobarography or balance-systems, these clinical balance tests were confirmed to be valid and reliable in the literature. Furthermore, measuring the muscle strength of lower extremity may help to explain the interaction between QA and performance on SEBT.

In conclusion, low QA should be considered during evaluations to reduce the risk of injury, particularly in individuals who interested in sports activities. Further studies are required to develop specific training programmes to prevent injuries because of low QA.

Footnotes

Conflict of interest

All authors declare that there is no conflict of interest.

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Influence of quadriceps angle on static and dynamic balance in young adults

Abstract

BACKGROUND:

OBJECTIVE:

METHODS:

RESULTS:

CONCLUSIONS:

Keywords

1. Introduction

Table 1 QA values and balance scores of participants

3. Statistical analysis

Table 2 The balance performance differences among low, normal and high Q angle groups, and correlation of balance tests with QA

5. Discussion

Footnotes

Conflict of interest

References

Table 1
QA values and balance scores of participants

Table 2
The balance performance differences among low, normal and high Q angle groups, and correlation of balance tests with QA