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Abstract

Purpose

The rectus femoris has three myotendinous or myoaponeurosis junctions and causes three types of muscle strain anatomically. We aimed to investigate the anatomical injury site of the rectus femoris muscle strain in professional soccer players as well as the characteristic findings on magnetic resonance imaging (MRI) and to evaluate its relationship with the time taken to return to play at competition levels.

Methods

Thirteen Japanese professional soccer players who sustained injuries to the rectus femoris were included in this study. The mechanism of injury, anatomical injury site, severity, absence of hematomas, and time taken to return to competition were evaluated.

Results

Ten patients were injured while kicking and three while sprinting. The anatomical injury site was the origin aponeurosis in two cases, intramuscular tendon in eight cases, and distal aponeurosis in three cases. The severity was one-degree in three cases and two-degree in 10 cases. Hematomas were observed in five cases. Cases with injuries caused by sprinting, two-degree injuries, or clear hematomas were associated with significantly longer periods of return to play than the other cases. Additionally, patients with distal aponeurosis-type injuries tended to take a long time to return to the competition.

Conclusions

In rectus femoris muscle strain, it is important to evaluate the anatomical injury site, severity, and absence of hematomas on MRI. Not only the injury mechanism, a clear hematoma, and high severity but also distal aponeurosis injuries may be associated with long periods of return to play at competition levels.

Keywords

rectus femoris muscle strain myotendinous junction myoaponeurosis junction return to play

Introduction

Quadriceps muscle strain is common in football and other sports that require efferent contraction of the rectus femoris through repetitive kicking and sprinting.^1,2 The rectus femoris is the most commonly injured muscle among the quadriceps,³ and being the most superficial and the sole biarticular muscle in the quadriceps, it is prone to strain.

The rectus femoris has two main anatomical origins: the direct head, which originates from the anterior inferior iliac spine, and the indirect head or reflected head, which originates from the superior acetabular ridge and posterior coxofemoral capsule.^4,5 The direct head develops into a superficial aponeurosis (origin aponeurosis) that extends to the proximal one-third of the rectus femoris muscle and forms the myoaponeurosis junction by exposing the unipennate muscle. In contrast, the indirect head develops into an intramuscular tendon, penetrating the proximal two-thirds of the rectus femoris muscle, forming a myotendinous junction by exposing the pennate muscle.⁶ In addition, there is a distal aponeurosis that ends at the patella on the deep posterior surface of the rectus femoris muscle. This aponeurosis also constitutes the myoaponeurosis junction by exposing the unipennate muscle.⁷ Muscle strains frequently occur in the myotendinous or myoaponeurosis junction with the pennate muscle.^8,9 The rectus femoris has three myotendinous or myoaponeurosis junctions (Figure 1), each of which could be anatomical injury sites. Therefore, rectus femoris muscle strain can be anatomically divided into three types (Figure 2): origin aponeurosis, intramuscular tendon, and distal aponeurosis.¹⁰ Magnetic resonance imaging (MRI) is useful for the diagnosis of muscle strain.¹¹ Magnetic resonance imaging also affords the possibility to determine the treatment strategy and predict the time of return to competition¹² by evaluating the anatomical injury site and severity of the injury.^13–15

Figure 1.

Three muscle-tendon (aponeurosis) junctions of the rectus femoris.

Figure 2.

Rectus femoris muscle strain types. The rectus femoris muscle strain was divided into three types based on the anatomical injury sites: origin aponeurosis, intramuscular tendon, and distal aponeurosis.

However, there are few studies in which the rectus femoris muscle strain in Japanese soccer players was divided based on the anatomical injury site, and its relationship with the time to return to competition remains unknown. The purpose of this study was to investigate the anatomical injury site of the rectus femoris muscle strain in professional soccer players as well as the characteristic findings on MRI and to evaluate its relationship with the return to play.

Materials and methods

This study was approved by the ethics committee of our institution (approval number: 1842-1). Informed consent was obtained from all the patients included in this study.

Between 2016 and 2021, we investigated the rectus femoris muscle strains in a professional soccer team in Japan. This study included 13 cases of rectus femoris muscle strain that occurred during practice and games in professional soccer players from the second division professional soccer league. All patients were male, and the average age was 24.1 ± 3.9 years. Tenderness, stretch pain in the injured site, and MRI performed within 2 days of the injury aided in the diagnosis of rectus femoris muscle strain. MRI T2 STIR-weighted images revealed a high signal suggestive of bleeding inside the rectus femoris muscle or at the junction between the rectus femoris muscle and aponeurosis.¹⁶ The criteria for returning to the competition were that the rectus femoris muscle allowed a full range of motion in the knee and hip joints, that there was no tenderness and stretch pain in the affected area, and that there was maximum output.¹⁷

The mechanism of injury and the time taken to return to play at the competition level were evaluated from data available in the team’s medical records. MRI was used to assess the anatomical injury site (original aponeurosis, intramuscular tendon, or distal aponeurosis), severity of the injury (severity classification: grade I, minor injury; grade II, partial tear; and grade III, complete tear¹³), and the presence or absence of a hematoma.

Statistical analysis

Data were analyzed using the Statistical Package for the Social Sciences for Windows (version 23.0; SPSS Inc., Chicago, IL, USA). The relationship between all evaluation items and the time taken to return to play at the competition level were statistically examined using the Student’s t-test and analysis of variance (ANOVA). All statistical analyses were performed at a significance level of α = 0.05.

Results

The cause of rectus femoris muscle strain was kicking in 10 cases and sprinting in 3 cases. Based on the anatomical injury sites, there were two cases of origin aponeurosis injury, eight cases of intramuscular tendon injury, and three cases of distal aponeurosis injury, all of which had myotendinous or myoaponeurosis junction injury. MRI revealed a 1-degree injury (minor muscle injury) in three cases and two-degree injury (partial injury of the tendon or aponeurosis) in 10 cases. Furthermore, a clear hematoma separating the myotendinous or myoaponeurosis junction was observed in five cases, and the average time taken to return to play at the competition level was 14.5 ± 8.9 days in all 13 cases (Table 1).

Table 1.

Characteristics of rectus femoris muscle strain in the 13 cases.

Case	Age (years)	Mechanism of injury	Anatomical injury site	Degree of severity	Hematoma	Time taken to return to play (days)
1	25	Sprinting	Distal aponeurosis	2	+	23
2	21	Kicking	Origin aponeurosis	2	+	16
3	29	Sprinting	Origin aponeurosis	2	+	18
4	26	Kicking	Intramuscular tendon	2	−	9
5	25	Kicking	Intramuscular tendon	2	+	31
6	25	Kicking	Distal aponeurosis	2	+	17
7	26	Sprinting	Distal aponeurosis	2	−	28
8	20	Kicking	Intramuscular tendon	1	−	9
9	32	Kicking	Intramuscular tendon	2	−	6
10	19	Kicking	Intramuscular tendon	2	−	11
11	19	Kicking	Intramuscular tendon	1	−	0
12	22	Kicking	Intramuscular tendon	1	−	7
13	19	Kicking	Intramuscular tendon	2	−	13

The injury mechanism revealed a significant difference between the time taken by patients to return to competition after an injury caused by kicking (11.9 ± 7.9 days) and sprinting (23.0 ± 4.1 days) (p = 0.03). Regarding the anatomical injury site, the time taken to return to play after an injury to the origin aponeurosis, intramuscular tendon, and distal aponeurosis was 17.0 ± 1.0 days, 10.4 ± 8.4 days, and 22.7 ± 4.5 days, respectively. Although there was no statistically significant difference in the ANOVA (p = 0.15), the treatment period tended to be longer with distal aponeurosis-type injuries. Based on the severity, patients with 1-degree injuries took 5.3 ± 3.9 days to return to competition, and those with 2-degree injuries took 16.9 ± 7.9 days (p = 0.02). In addition, it took 21.0 ± 5.5 days for five patients with a clear hematoma, which separated the muscle-tendon or muscle-aponeurosis, to return to competition and 10.4 ± 7.6 days for seven patients without hematomas. The treatment period was significantly longer in patients with hematomas (p = 0.02).

Representative cases

Case 4: A 26-year-old defender injured his left rectus femoris muscle while kicking during practice. In the axial plane of the MRI T2 STIR-weighted image, an intramuscular tendon injury with bleeding surrounding the intramuscular tendon, called a “Bull’s eye,”¹⁸ was observed (Figure 3(a)). In the coronal plane, continuity of the intramuscular tendon was confirmed and bleeding was localized to the distal part of the intramuscular tendon. Furthermore, there was no apparent hematoma (Figure 3(b)), and the patient returned to competition 9 days after the injury.

Case 7: A 26-year-old defender injured his right rectus femoris muscle while sprinting. In the axial plane of the MRI T2 STIR-weighted image, bleeding with a clear hematoma along the distal aponeurosis was observed (Figure 4(a)). In the sagittal plane, a widespread injury to the distal aponeurosis was noted (Figure 4(b)), and the patient took 28 days to return to competition.

Figure 3.

Case4. (a): In the axial plane of the MRI T2 STIR-weighted image, hyperintensity (⇨) suggestive of bleeding around the intramuscular tendon (Bull’s eye) is seen. (b): In the coronal plane of the T2 STIR-weighted image, a hyperintensity localized to the distal periphery of the intramuscular tendon is seen, and the continuity of the intramuscular tendon can be confirmed (△).

Figure 4.

Case7. (a): In the axial plane of the MRI T2 STIR-weighted image, a clear hematoma is seen along the distal aponeurosis (⇨). (b): In the sagittal plane of the MRI T2 STIR-weighted image, hyperintensity suggestive of bleeding is seen extending from the proximal to the distal end of the distal aponeurosis (△).

Discussion

In our study, the characteristics of rectus femoris muscle strain in professional soccer players indicated that cases with a high grade of severity, the presence of a clear hematoma on MRI, and injuries caused by sprinting took a significant amount of time to return to competition, particularly in those with distal aponeurosis-type injuries.

Kassarjiana et al.¹⁰ reported that the most common cause of rectus femoris muscle strain in soccer players was kicking, which causes a proximal rectus femoris injury. Distal aponeurosis-type injuries, which are distal injuries, account for approximately 15% of all injuries. Most injuries are caused by the proximal rectus femoris muscle being pulled during the swing phase of the kicking motion in soccer.^1,19,20 Proximal rectus femoris injuries, especially the origin aponeurosis-type, have been reported to recover faster than distal injuries.^10,21 This is because the patients experience no pain except when kicking, in the case of superficial aponeurosis-type injuries, which are proximal injuries, and intramuscular tendon-type injuries that are localized to the proximal part, allowing for a relatively early return to training. In this study, although there were 10 injuries caused by kicking, most of these injuries occurred in the proximal part of the rectus femoris, such as the origin aponeurosis-type and intramuscular tendon-type injuries, and an early return to competition was achieved. In contrast, the three sprinting injury cases included two cases with a distal aponeurosis-type injury and two cases with a clear hematoma, all of which tended to take a long time to recover.

Evaluation based on the anatomical injury site is often divided into proximal and distal injuries [10]. Additionally, it has been reported that it takes a long time to return to competition due to bleeding surrounding the intramuscular tendons (“Bull’s eye”) or distal injuries.^18,21 Recently, some ultrasonography-based studies have reported that the length of muscle strain also affects the time taken to return to play.^22,23 In this study, those with distal aponeurosis-type injuries took a longer time to return to competition. In contrast, in the intramuscular tendon-type, even if the injury was classified as having a 2-degree severity with a “Bull’s eye,” those with a shorter length of injury returned to the competition early. Therefore, in addition to the anatomical injury site, the length of the injury is also considered to be associated with the recovery time, and it is important to carefully observe these points during MRI and ultrasonographic evaluations.

Similar to the anatomical injury site, the presence of a clear hematoma at the injury site is an important finding in MRI evaluation. Previous studies have reported that a clear hematoma in the injured area induces pain, and it takes a long time for the patient to return to competition due to the time required for the resorption of the hematoma.^1,10 In this study, cases with a clear hematoma took a significant amount of time to return to the competition, an important finding in predicting the recovery time at the time of injury. In addition, due to the dramatic improvement in ultrasonographic resolution, clear hematomas, intramuscular tendons, or aponeuroses can be diagnosed by ultrasonography.^24,25 Furthermore, we can easily perform a hematoma puncture under ultrasonographic guidance concurrently with muscle strain diagnosis, which may accelerate the patients’ return to competition.²² Ultrasound can also be used to classify the severity of the injury and predict the return to competition; hence, it may be an indispensable tool for muscle strain evaluation, diagnosis, and treatment in the near future.^26,27 Unfortunately, in this study, ultrasonographic evaluation could not be performed in all cases, and no case underwent a hematoma puncture under ultrasonographic guidance; hence, it was not included in the evaluation items. However, we will continue our study by combining ultrasonographic evaluations in the future.

Regarding the severity determined by the MRI evaluation, it has been reported that the higher the severity grade, the longer it takes to return to competition.^28–30 In a study on hamstring muscle strain in professional football players, Ekstrand et al.³¹ reported that the time taken to return to competition, based on the severity grade, was as follows: grade 1, 17 ± 10 days; grade 2, 22 ± 11 days; and grade 3, 73 ± 60 days. In our study, the target muscle was the rectus femoris, which is smaller than the hamstrings, and all subjects were professional soccer players who received conditioning support, thereby reducing the time to return to competition.

One of the strengths of our study is that we focused on rectus femoris muscle strain in Japanese professional soccer players, which has rarely been reported to date. In addition, the anatomical injury site was divided into three parts, and its relationship with recovery time was determined.

However, this study has some limitations. First, although all patients were professional soccer players and the criteria for returning to the competition were unified, their positions, ages, and status in the team may have affected the period of return to competition. Second, no MRI examination was performed at the time of return to competition, and recovery of the myotendinous or myoaponeurosis junction was not confirmed. Therefore, the time of recovery of the myotendinous or myoaponeurosis junction on MRI remains unknown. In the future, it will be necessary to perform an image recovery evaluation using MRI at the time of return to competition. Finally, the sample size of this study was small. Therefore, although this study showed the characteristics of rectus femoris muscle strain and the time taken to return to competition, statistical analysis between each evaluation item was insufficient, and further research involving a large number of cases is needed.

Conclusions

We evaluated 13 cases of rectus femoris muscle strain in professional soccer players. There were three anatomical injury sites, and it was important to evaluate the anatomical injury site, severity, and the presence or absence of a hematoma using MRI. In addition to the injury mechanism, the high grade of severity, and a clear hematoma on MRI, it should be noted that cases with a distal aponeurosis-type injury took a long time to return to competition.

Footnotes

Acknowledgements

We thank the staff of the professional soccer team who contributed to the data collection and care of the players.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical approval and consent to participate

This study was approved by the ethics committee of Kanazawa University (approval number: 1842–1), and all procedures performed in this study were in accordance with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The authors certify that they have obtained appropriate patient consent forms, on which the patients consented to the use of their images and other clinical information in the article. The patients understand that their names and initials will not be published and that every effort will be made to conceal their identity; however, anonymity cannot be guaranteed.

ORCID iD

Junsuke Nakase

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Relationship between anatomical injury site of rectus femoris muscle strain and time taken to return to play in Japanese professional soccer players

Abstract

Purpose

Methods

Results

Conclusions

Keywords

Introduction

Materials and methods

Statistical analysis

Results

Representative cases

Discussion

Conclusions

Footnotes

Acknowledgements

Declaration of Conflicting Interests

Funding

Ethical approval and consent to participate

ORCID iD

References