Quadriceps Angle Measurement in Adolescents With Short Stature: Exploring the Relationship Between Postural Alignment and Lower Limb Mechanics

Background The quadriceps angle (Q angle) is measured as an angle formed by two lines that extend from the anterior superior iliac spine to the midpoint of the patella and from the midpoint of the patella to the tibial tuberosity. The average Q angle value for children aged between seven to 12 years was 13.1˚±3.5˚in boys and 13.7˚±4.9˚ in girls, whereas 8˚-15˚ in men and 12˚-19˚ in women. Abnormal variation in Q angle is associated with patellofemoral pain syndrome, lateral patellar malposition, dislocation, chondromalacia patella, patella alta, genu varum, etc. Methodology The present study explores the status of Q angle values among adolescents with short stature and their comparison with age and gender-matched children between 10 and 15 years of age. Results We found a statistically significant difference between the Q angle value in the control group and the male with short stature group aged 14-15 years, with a mean difference of 3.7˚. However, among females, there was a significant difference between the control group and the short-stature group aged 12-13 and 14-15 years, with a mean difference of 2.8˚ and 2.5˚, respectively. Implications Early detection and timely remedial measures, e.g., quadriceps strengthening exercises, before skeleton maturity can prevent Q angle-related misalignments and abnormalities in the limb.


Introduction
Based on obtainable articles, the quadriceps angle (Q angle) was defined for the first time by Brattstroem in 1964, who determined it as an angle between the ligamentum patella and the extension of the line depicting the net resultant force of quadriceps femoris muscles acting on the patella [1].Therefore, the Q angle of the knee is principally a measurement of the angle between the quadriceps muscles and the patella tendon.However, at present, the anterior superior iliac spine (ASIS) is used as a convenient and easily discernible proximal landmark for the measurement [2].The Q angle provides useful information about the position of the knee joint and is hence an essential indicator of the biomechanical function of the lower extremity.Values on either side of the normal range are seen to be associated with pathological conditions (e.g., chondromalacia and recurrent dislocation of the patella), gait abnormalities, and increased susceptibility to injuries [3].
The average Q angle value for children aged between seven to 12 years was 13.1±3.5˚ in boys and 13.7±4.9in girls.The Q angle is marginally greater in females than in males because of the wider pelvis [4].The average Q angle value for adults, when measured in standing, was 8˚-15˚ in men and 12˚-19˚ in women [5].
Studies show that any abnormal variation from the normal value of the Q angle is associated with various pathologies of the lower extremities.An increase in Q angle to 15˚-20˚ may cause lateral patellofemoral contact pressures that may lead to patellofemoral pain syndrome (PFPS) with lateral patellar malposition (responsible for early degeneration of adjacent joint capsule) or dislocations; dysfunction of the knee extensor mechanism with femoral ante-version, external tibial torsion, laterally displaced tibial tubercle, or genu valgum [5][6][7][8].Although a decreased Q angle may not cause a medial shift to the patella, it may increase the medial tibiofemoral contact pressure between the medial femoral and tibial condyles by increasing the varus orientation.Abnormally low values of Q angle are also likely to develop chondromalacia patella, patella alta, and genu varum [9].These variations in Q angle likely occur because of the relative mobility caused by the pull of the patellar tendon over the knee joint.Any disturbance in the net lateral force on the patella due to the contraction of the quadriceps muscle results in knee extensor mechanism malalignment, causing hypermobility and patellar instability at the knee joint.With an increase in regional stresses, they ultimately cause unicompartmental osteoarthritis earlier compared with the normal population [10].
Despite the crucial role of the Q angle on lower extremity alignment and functionality, we could not find such studies performed on subjects with short stature.Short stature is defined as a condition in which an individual's height is inside the third percentile for the mean height of a given age, sex, and population group [11].The present study was designed in Rishikesh, Uttarakhand, India, to find out the Q angle value in adolescent children with short stature and its variation among boys and girls with short stature compared to those who fall in the normal spectrum.

Materials And Methods
Subsequent to receiving the required approval from the Institutional Ethics Committee of the All India Institute of Medical Sciences, Rishikesh (Uttarakhand), reference IEC/21/302 dated May 15, 2021, and after explaining the study briefly to the school principals and obtaining written consent and approval, 90 (45 of each gender) children with short-stature were selected for the study.
Children with a history of knee surgery, neurological deficit, open wound, cancer or tumor, any orthopedic or metabolic disease involving the lower extremities, and any systemic or localized infection were excluded.
Following preliminary considerations, children between 10-15 years of age whose height was equal to or less than given in the third percentile category in the Data Table of Stature-for-age Charts for males and females aged two-20 years issued by the National Center for Health Statistics and retrieved from the website of the Centers for Disease Control and Prevention, U.S. Department of Health & Human Services, were included in the study given (Appendices A-B) [12].A control group consisting of 90 children of matched age and gender with normal height was also selected to measure the bilateral Q angle.Written informed consent was also obtained by the principals of the schools and the students after thoroughly explaining the procedure for measuring the Q angle.
It has been established that goniometry for measuring Q angle can be used as an inexpensive and radiationfree alternative to radiographic measurement [13].In order to get information on the alignment of the knee in the frontal plane, taking into account typical weight-bearing loads, the measurements were done with the subject in a standing position.
Therefore, for measuring the Q angle, the participants were asked to stand in the anatomical position (standing erect, shoulders held back with fully extended elbows, and forearms fully supinated).The reference points, viz., anterior superior iliac spine (ASIS, point A), mid-point of the patella (point B), and tibial tuberosity (point C), were palpated and marked by using a black marker pen.Two straight lines were drawn from points A to B and point B to C; the angle formed between these two lines was measured as a Q angle, as shown in Figure 1.The angle formed (Figure 2) was measured using a standard goniometer (Figure 3) in both limbs, and the results were tabulated for both control and short stature groups for mean values.The data collected were statistically analyzed using IBM SPSS software version 22 (IBM Corp., Armonk, NY, USA) with a 0.05 (5%) significance level.

Results
Children with short and normal statures were included in the study (Tables 1-2).Measurements of the Q angle and range for children with short stature aged between 10 and 15 years were obtained by calculating the mean and standard deviation for each gender group.The mean Q angle in shortstatured boys was 9.5˚±1.4˚while in short-statured girls it was 10˚±1.6˚.The mean Q angle for all 180 legs in 90 children was 9.7˚±1.5˚(Table 3).

ABLE 3: Measurement of the Q angle for boys and girls with short stature
There was no statistically significant difference between the Q angles measured in both genders (p-value = 0.468).
There was no statistically significant difference in the Q angles of the right and left knees in both groups (Table 4).A three-way analysis of variance (ANOVA) was used between the age groups to evaluate the correlation between the Q angle values and age in both male and female children with short stature.The test values show there was a significant correlation between the two, i.e., as age increased, there was an increase in Q angle in both the girl's and boys' short-stature groups.
The Q angle measure in boys with short stature, aged 10-11 years, was 8.9˚±1.1˚;for ages 12-13 years, the values were 9.6˚±1˚; and for ages 14-15 years, the values of the Q angle were 10.2˚±1.4˚(   A comparison of male Q angle values between the control group and the short stature group showed a significant difference in the age groups of 10-11 years, 12-13 years, and 14-15 years, with a mean difference of 3˚, 3.3˚, and 3.7˚, respectively (Table 7).

Discussion
The present study was conducted to measure the quadriceps angle in adolescent girls and boys with short stature.Results show that the mean Q angle value for all 180 legs in children with short stature aged between seven to 14 years was 9.7˚±1.5˚.The mean Q angles for males and females with short statures were 9.5˚±1.4˚and 10˚±1.6˚,respectively.
Cankaya et al. conducted a study in which they assessed the quadriceps angle in children aged two to eight years and gave an average Q angle in standing position of 13.27˚±1.22°forthe right leg in boys and 13.30˚±1.16°forgirls.The mean Q angle for the left leg in boys was 13.25˚±1.23°and for girls, it was 13.29˚±1.18°.The average Q angle in the supine position for the right leg in boys was 13.30˚± 1.21° and 13.32˚± 1.17˚ for girls; the mean Q angle for the left leg in boys was 13.25˚±1.22°,and for girls, it was 13.29˚±1.14°[5].The Q angle for children between the ages of two to four years in the standing position, measured in the right leg, was 14.10˚±0.67°andfor the left leg, it was 14.07˚±0.69°.For children aged four to six years, the Q angle for the right leg was 13.08˚±1.41°and for the left leg, it was 13.06˚±1.43°and lastly, the Q angle for children aged six to eight years, for the right leg, was 12.71˚±0.87°and for the left leg, it was 12.69˚±0.90°and found that in all age groups, no significant differences were found between the right and left Q angle values in all age groups in both sex groups, which means girls' mean Q angle values and the boys' mean Q angle values were similar.This study result is in accordance with our study, as we found no significant difference between right and left Q angle values in both sexes in children with short stature.
We found no significant difference in the Q angle value between boys and girls with short stature.This is consistent with that of Bhalara et al., who measured the Q angle in children aged between seven to 12 years and found that the Q angle in the normal population was 15.7˚±4˚ in boys and 15.8˚±3.4˚ in girls [1].They also found no comparative disparity in the Q angle value among both genders.Using a three-way ANOVA between subgroups, they concluded that as age increases, there is a significant increase in Q angle among children.The average Q angle value in boys for ages seven to eight years was 10.1˚±0.9˚and 12.5˚±2.6˚ingirls, and for ages nine to 10, it was 15.6˚±4.5˚ in boys and 15.7˚±3.4˚ in girls, whereas, for ages 11-12, the Q angle value in the boys was 18.3˚±3.3˚and 16.8˚±3˚ in girls.This is in accordance with our study, as we also found a positive correlation between age and Q angle.
The mean Q angle value for all 180 legs in children with short stature aged 10-15 years was 9.7˚±1.5˚.Whereas, the mean Q angles for boys and girls with short stature were 9.5˚±1.4˚and 10˚±1.6˚,respectively.The average Q angle value in boys for ages 10-11 years was 8.9˚±1.1˚and 9.1˚± 1˚in girls, and for ages 12-13, it was 9.6˚±1˚ in boys and 9.8˚±1.5˚ in girls, whereas, for ages 14-15, the Q angle value in the boys was 10.2˚±1.4˚and 10.7˚±1.8˚ in girls.These values for normal subjects are different from those mentioned in the study performed by Khasawneh et al. on 500 volunteers, a young Arab population [14].They found that the average mean Q angle in the females was 17.35˚±0.225˚and that in the males was 14.1˚± 0.21˚.The Q angle values in both genders of the Arab population were relatively higher than in other countries and ethnicities.Compared to our study, it may be attributed to racial, ethnic, and probably socio-economic differences among Indian and Arab populations.
The quadriceps angle is an important tool to determine knee health.However, the value of the Q angle for children with normal height has varied, as reported by different researchers in the literature [15].
However, comparing the Q angle values of children with short stature with age and gender-matched control groups showed statistically significant differences among the age groups of 10-11 years, 12-13 years, and 14-15 years in both genders (p-value > 0.05).
However, there were some limitations to our study; it was conducted during the COVID-19 pandemic, and many of the classes were suspended in the schools in Rishikesh where the study was conducted.The area of our study was limited to Rishikesh.The population with short stature comprises 1/3 of the population with normal stature; that's why the sample size is too small, and further studies should be conducted over a larger area with a larger sample size.

Conclusions
The quadriceps angle is an important tool to determine knee health.However, the value of the Q angle for children with normal height has varied, as reported by different researchers in the literature.But there is very little or no literature that evaluates quadriceps angles in children with short stature or has been accepted by clinicians.In our study done among children with short stature, results showed that the mean Q angle value for all 180 legs in children with short stature aged seven to 14 years was 9.7˚±1.5˚.The mean Q angles for boys and girls with short statures were 9.5˚±1.4˚and 10˚±1.6˚,respectively.Therefore, by knowing the normal range and values of the Q angle, clinicians can properly define and identify the abnormal range and value of the quadriceps angle in the population of children with short stature.
Early detection of Q angle variation in younger populations and resting Q angle value may enhance the clinician's ability to predict which individuals are at significant risk of developing patellar tracking and patellofemoral disease that worsens with older age.
Different remedial measures, e.g., quadriceps strengthening exercises, can be instituted by clinicians to correct the abnormality at an early age before reaching skeleton maturity.

FIGURE 1 :
FIGURE 1: Reference points to measure the Q angle: A) anterior superior iliac spine (ASIS); B) midpoint of the patella; C) tibial tuberosity

FIGURE 2 :
FIGURE 2: Markings on the subject's knee

FIGURE 3 :
FIGURE 3: Measuring the Q angle using a standard goniometer (ISICO goniometer)

of children with short stature Average height of males with short stature (cm) Average height of females with short stature (cm)
2023 Sharma et al.Cureus 15(8): e43953.DOI 10.7759/cureus.439535 of 21 Years Total no.

TABLE 2 : The average height of male and female children with normal stature
cm: centimeters

TABLE 5 : Comparison of the Q angle among each age group of boys with short stature
The Q angle measure in girls with short stature, for those aged between 10-11 years, was 9.1˚±1˚; for ages 12-13 years, the values were 9.8˚±1.5˚degrees;andfor ages 14-15 years, the values of Q angle were 10.7˚±1.8˚(Table6).