Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from Connective tissue injury in muscle tears and return to play: MRI correlation Ashutosh Prakash,1,2 Tom Entwisle,1 Michal Schneider,3 Peter Brukner,4 David Connell1

1Imaging @ Olympic Park, ABSTRACT tissues, which connect to the tendon. The integrity Melbourne, Victoria, Australia 2 Objective The aim of our study was to assess a of the connective tissue scaffold is therefore vital Diagnostic Radiology, Tan for muscle to function normally. Furthermore, Tock Seng Hospital, Singapore, group of patients with calf muscle tears and evaluate Singapore the integrity of the connective tissue boundaries and muscle fibres are vulnerable to shear forces at these 3Department of Medical interfaces. Further, we propose a novel MRI grading muscle fibre-connective tissue interfaces that can Imaging and Radiation Sciences, system based on integrity of the connective tissue occur during eccentric loading or strain.8 Faculty of Medicine, Nursing and assess any correlation between the grading score Tendon, and epimysium heal slower and Health Sciences, Monash University, Melbourne, Victoria, and time to return to play. We have also reviewed the than muscle. The status of the connective tissue Australia anatomy of the calf muscles. (epimysium, aponeurosis, intramuscular tendon 4La Trobe University, Melbourne, Materials and methods We retrospectively evaluated and free tendon) supporting the muscle fibres may Victoria, Australia 100 consecutive patients with clinical suspicion and well determine the healing time in muscle injury, MRI confirmation of calf muscle injury. We evaluated not just in the calf but in other muscles too. We Correspondence to each calf muscle tear with MRI for the particular muscle hypothesise that disruption of the muscle connec- Dr Ashutosh Prakash, Diagnostic Radiology, Tan Tock Seng injured, location of injury within the muscle and integrity tive tissue is a higher grade injury and will result in Hospital, Singapore 308433; of the connective tissue structure at the interface. The longer recovery time and time to RTP. drashutoshprakash@​ ​gmail.com​ muscle tears were graded 0–3 depending on the degree The objective of this study was to assess the integ- of muscle and connective tissue injury. The time to return rity of the calf muscle connective tissue in patients Accepted 4 October 2017 with acute calf muscle injury. We propose a grading Published Online First to play for each patient and each injury was found from 26 October 2017 the injury records and respective sports doctors. system and its correlation with time to RTP. Results In 100 patients, 114 injuries were detected. Connective tissue involvement was observed in 63 out Review of anatomy of 100 patients and failure (grade 3 injury) in 18. Mean The posterior compartment of the leg is divided by copyright. time to return to play with grade 0 injuries was 8 days, the deep transverse into superficial and deep grade 1 tears was 17 days, grade 2 tears was 25 days compartments. Collectively the superficial poste- and grade 3 tears was 48 days (p<0.001). rior compartment muscles of the leg are called the Conclusion The integrity of the connective tissue can calf muscle or triceps surae and consist of gastroc- be used to estimate and guide the time to return to play nemius, soleus and plantaris. The aponeurosis and in calf muscle tears. tendons of these muscles unite to form the Achilles 9 tendon. http://bjsm.bmj.com/ Gastrocnemius is the most superficial muscle. It possesses a higher proportion of type II fast twitch Introduction fibres than soleus, reflective of its function in rapid Calf muscle is one of the four most commonly locomotion, such as jumping and running.10 Its injured muscles in sportsmen.1 MRI muscle injury two heads arise from two proximal tendon attach- pattern in and anterior muscles ments from the femoral condyles and the subjacent have been researched and used to quantify prog- joint capsule. Both these tendons expand and on 20 August 2018 by Mr P Brukner CHESM. Protected nosis and predict the time to return to play (RTP).2–6 spread out as thin aponeuroses on the posterior However, little research has been performed for surface of the respective muscle and give origin calf injury. to muscle fibres (figure 1A). These muscle fibres MRI of the calf may not be indicated in all then attach to a broad aponeurosis on the anterior patients presenting with calf injury, and time to surface of the muscle (figure 1B–D). The anterior RTP in injured athletes is mostly guided by clinical aponeurosis then gradually condenses as it extends criteria. However, many elite athletes undergo MRI inferiorly and unites with the posterior aponeu- in suspected calf tears to confirm the diagnosis, rosis of the soleus to form the .9 11 access severity and guide rehabilitation. A previous The gastrocnemius aponeurosis is distinctly shorter MRI study has focused on size and site of tear, medially and longer laterally.11 muscle component affected, intramuscular tendon Soleus is the deeper muscle of the superficial tear and intermuscular haematoma,7 but did not posterior compartment. It is a broad flat multipen- focus on the integrity and severity of connective nate muscle, designed for power, with a predomi- tissue injury. nance of slow twitch fibres and hence contributes Dense irregular and regular connective tissues to postural control and walking.12 It arises by tendi- form a scaffold to support the muscle fibres. This nous fibres from the posterior head, proximal To cite: Prakash A, connective tissue scaffold is composed of surface one-fourth of the shaft of fibula, middle one-third Entwisle T, Schneider M, covering (epimysium and aponeuroses) and intra- of the medial border of the tibial shaft and poste- et al. Br J Sports Med muscular bands (intramuscular tendon and aponeu- rior surface of the tendinous arch between the 2018;52:929–933. roses). Muscle fibres attach to these connective and fibula.9 At the origin, there is thickening or

Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362 1 of 6 Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from

aponeuroses and tendon are subject to considerable variation in terms of number, position and dominance. The plantaris arises from the lateral supracondylar line of the distal femur and from the oblique popliteal ligament. The small muscle belly lies deep to the lateral head of the , but the long thin plantaris tendon courses obliquely and medially, lying between the soleus and the medial head of the gastrocnemius muscles (figure 2A,B). Distally, the tendon inserts on the just anteromedial to the Achilles tendon.14

Materials and methods We retrospectively searched our database backwards from March 2017 to September 2015 for patients who were referred for MRI of the leg to our clinic.

Inclusion criteria Consecutive patients in the age between 20 and 50 years, were referred for MRI of the leg with the clinical suspicion and MRI confirmation of acute calf muscle tear, and with injury occurring within the previous 2 weeks were included in the study.

Exclusion criteria MRI-negative studies, patients with delayed onset muscle sore- Figure 1 Anatomy of gastrocnemius aponeuroses: (A) PD and (B) ness or muscle overload MRI pattern, Achilles tendon tear, PD fat saturated images showing proximal posterior (arrowhead) and muscle contusion MRI pattern or history, bone stress reaction, distal anterior aponeurosis (thin arrow) of the gastrocnemius. (C,D) pre-existing non-healed muscle tear in either leg and follow-up PD fat saturated images of an athlete with grade 2 posterior soleus studies were excluded. Patients were also excluded if they were aponeurosis tear and sliver of fluid between gastrocnemius and out of play for any other reason and if we could not obtain the soleus muscles; the intermuscular fluid clearly demarcates the anterior copyright. RTP details. aponeurosis (thin arrow) of the gastrocnemius muscle.

Return to play localised aponeuroses on the anterior and posterior aspects of RTP was defined as time from the date of injury to return to full the muscle (figure 2A). Distal to the origin, there are proximal competition. intramuscular medial and lateral aponeuroses (figure 2B). These medial and lateral intramuscular aponeuroses run inferiorly, are http://bjsm.bmj.com/ directed towards the midline of the muscle belly and fade out MRI technique inferiorly. Proximal muscle fibres arise from these aponeuroses. The MRI imaging technique included placing an external marker Distally the muscle fibres insert into a long central intramuscular (vitamin E capsule) over the area of maximum symptom, as indi- tendon (figure 2B,C), which arises from the anterior aponeu- cated by the patient. All scans were carried out using 3T MRI rosis of the soleus, and also to the posterior aponeurosis of the scanners. A dedicated surface coil was used to obtain high-reso- soleus (figure 2C). The central intramuscular tendon and poste- lution image with 2.5 mm axial proton density (PD) and PD fat

rior aponeurosis merge to form the soleal contribution to the saturated axial images, as well as 2 mm sagittal and coronal PD on 20 August 2018 by Mr P Brukner CHESM. Protected Achilles tendon.13 In our experience, the soleus intramuscular fat saturated images.

Figure 2 PD fat saturated images obtained through normal (A), proximal (B), mid and (C) distal leg showing anterior (thin white arrow in A and B), posterior (curved white arrow in A, B and C), medial and lateral intramuscular (block arrows in B) aponeuroses and central intramuscular tendon (arrowhead in B and C). Plantaris tendon is shown by the thin black arrow in A and B.

2 of 6 Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362 Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from

Table 1 Grading system for evaluation of calf muscle tear on MRI Oedema or Connective tissue Connective fluid adjacent increased signal, tissue to connective Myofibril delamination or retraction or tissue detachment defect failure Grade 0 Yes No No No Grade 1 Yes Yes No No Grade 2 Yes Yes Yes No Grade 3 Yes Yes Yes Yes

MRI evaluation and grading Three experienced musculoskeletal radiologists evaluated the Figure 4 (A) Axial PD fat saturated and (B) coronal PD fat saturated MRI of 100 patients meeting the criteria by consensus. They images of a 23-year-old male athlete showing grade 1 muscle injury were blinded to the clinical history, sporting background and of the soleus. There is myofibril detachment without any change to the outcome. Each muscle tear was evaluated for muscle involved, central intramuscular tendon. His time to return to play was 14 days. location within the muscle, myofibril disruption and integrity of the connective tissue. The soleus muscle tear was designated as proximal or distal, the distal end of the lateral gastrocnemius 30.5 years. Injuries were related to various sports and included muscle belly being the landmark. In addition, each calf muscle Australian Football League (AFL), soccer, rugby, hockey and tear was graded 0–3 (table 1). Grade 0 injury was defined as running. The majority of the patients were professional or semi- oedema or fluid adjacent to an intact tendon/aponeurosis/epimy- professional footballers, or elite athletes. Right calf muscle was sium without myofibril detachment (figure 3). Grade 1 injury injured in 55 and left in 45 of the patients. A total of 114 muscle was defined as myofibril detachment without tendon/aponeu- tears were detected in 100 patients. Of the 114 muscle tears, 79 rosis/epimysium change (figure 4). Grade 2 injury was defined as (69.3%) were located in the soleus, 31 (27.2%) in the medial myofibril detachment with adjacent tendon/aponeurosis/epimy- gastrocnemius and 4 (3.5%) in the lateral gastrocnemius. Ninety sium increased signal, delamination or defect but no retraction patients had a single injury, eight had two injuries and two had (figure 5). Grade 3 injury was defined as myofibril detachment four muscle injuries in a single event. with adjacent tendon/aponeurosis/epimysium retraction indi- Of the 79 soleus tears (in 71 patients), 43 (54.4%) involved copyright. cating failure (figures 6 and 7). the proximal soleus muscle and 36 (45.6%) involved the distal soleus muscle. Twenty (25.3%) involved the anterior epimysium/ Statistical analysis aponeurosis, 16 (20.25%) the posterior epimysium/aponeurosis, The data were analysed using SPSS V.23. Frequency analyses were 15 (19%) the medial intramuscular aponeurosis, 16 (20.25 %) carried out to identify the number of injury locations according the lateral intramuscular aponeurosis and 12 (15.2%) the central to injury grades. Analysis of variance was used to compare the intramuscular tendon of the soleus. mean RTP duration periods according to injury grades. A p value Of the 35 gastrocnemius tears (in 34 patients), 1 (2.85%) http://bjsm.bmj.com/ <0.05 was used to afford significance. involved the proximal myotendinous junction, 5 (14.3%) the posterior aponeurosis/epimysium, 15 (42.85%) the anterior Results aponeurosis/epimysium and 14 (40%) the distal myotendinous Out of 260 studies during the time period, 100 patients met junction. the criteria. Of the 100 patients, 89 were men and 11 women. There were 66 patients who had injury to only soleus, 29 had The ages ranged between 20 and 49 years, with a mean age of injury to only gastrocnemius and 5 had injury to both soleus and on 20 August 2018 by Mr P Brukner CHESM. Protected

Figure 5 (A) Axial PD fat saturated and (B) coronal PD fat saturated Figure 3 (A) Axial PD fat saturated and (B) sagittal PD fat saturated images of a 24-year-old professional player showing grade 2 muscle images of a 30-year-old athlete showing grade 0 muscle injury of injury of soleus. There is myofibril detachment. The lateral intramuscular the soleus (arrow). There is oedema adjacent to a normal posterior aponeurosis shows increased intermediate signal intensity consistent aponeurosis of the soleus without myofibril detachment. He had no time with delamination (arrow in B), but no aponeurosis retraction. His time out of play. to return to play was 30 days.

Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362 3 of 6 Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from

Table 2 Time to return to play (RTP) in patients after calf muscle tear (n=100) Range of number of Mean days to Injury grade Patients (n) days to RTP RTP±SD 0 8 0–20 8.1±7.45 1 29 0–49 17.17±8.84 2 45 0–42 24.69±9.71 3 18 12–70 48±15.95

Table 3 Time to return to play (RTP) in patients after only soleus muscle tear (n=66) Range of number of Figure 6 (A) Axial PD fat saturated and (B) sagittal PD fat saturated Injury grade Patients (n) days to RTP Mean days to RTP images of a 29-year-old professional player showing grade 3 muscle 0 6 0–20 9±7.58 injury of the soleus. There is myofibril detachment. There is lateral intramuscular aponeurosis defect with retraction (arrow in B). His time 1 24 0–28 16±6.61 to return to play was 70 days. 2 29 0–40 23.2±10.66 3 7 28–70 52±15.19

gastrocnemius muscles. One patient had injury to both medial 16 and lateral gastrocnemius muscles. Cross et al found the rectus femoris central tendon injury iden- In patients with more than one injury, they were graded as tified on MRI was associated with a significantly longer rehabil- per their highest injury. Eight patients had grade 0, 29 grade 1, itation time. 45 grade 2 and 18 had a grade 3 injury. Time to RTP according Similarly, we felt that the integrity of the connective tissue to the grade of injury is shown in table 2 for all calf muscles, in supporting the calf muscles could be linked to the recovery time. table 3 for the soleus and table 4 for only the gastrocnemius. However, rather than a simple intramuscular tendon, the calf There was a statistically significant difference between the injury muscles have a complex scaffold of epimysial boundaries and flat aponeuroses which support muscle fibres. We therefore grade and time to RTP (p<0.001). Figure 8 shows the grade of copyright. injury against days to RTP in a scatter plot. proposed a grading system for calf muscle tears concentrating on the integrity of the connective tissue as well as the myofibrils. Our study has shown that involvement and failure of calf muscle Discussion connective tissue are associated with longer time to RTP. Our study has demonstrated, for the first time, the importance We believe that measuring the extent of muscle oedema or of connective tissue integrity in calf muscle tears and its correla- bleeding for grading a muscle tear is inaccurate. Blood fluid tion with time to RTP. Our proposed MRI grading system shows products travel well beyond the margins of the actual myofi- http://bjsm.bmj.com/ correlation between higher grade of calf muscle injury and bril tear and the margin is usually ill-defined. An analogy can be longer time to RTP. drawn with muscle contusions, in which the size of an intramus- Other authors have highlighted the importance of integrity cular haematoma does not always correlate with loss of muscle of the connective tissue and time to RTP. Comin et al15 focused function and the usual MRI grading systems used for indirect on the integrity of the biceps femoris intramuscular connective muscle injury cannot be applied to direct injuries.17 Likewise, tissue and showed significant longer recovery time in biceps measurements in the craniocaudal or transverse plane do not femoris tears when the intramuscular tendon was disrupted. necessary reflect the true extent of muscle injury. on 20 August 2018 by Mr P Brukner CHESM. Protected In our study, the soleus muscle was much more commonly injured than the gastrocnemius. This is in contrast to previous reports that have reported a higher incidence in medial gastroc- nemius injury.10 12 18–20 Our study cohort of patients came from a variety of sports and therefore this outcome is unlikely to be related to a particular sport or activity. It is probably related to the increased use of MRI and detection of otherwise occult soleus tears. A higher incidence of soleus tears was also noted in studies by Koulouris et al12 and Waterworth et al.7 However,

Table 4 Time to return to play (RTP) in patients after only gastrocnemius muscle tear (n=29) Range of number of Injury grade Patients (n) days to RTP Mean days to RTP 0 2 0–14 7±9.89 Figure 7 (A) Axial PD fat saturated and (B) sagittal PD fat saturated 1 1 20 20±0 images of a 25-year-old professional footballer showing grade 3 injury of the medial gastrocnemius. There is rupture and retraction of the distal 2 15 14–42 27.9±7.24 aponeurosis (arrow). His time to return to play was 56 days. 3 11 12–70 46±16.69

4 of 6 Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362 Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from

Figure 8 Scatter plot of the study with grade of injury in x-axis and time to return to play (RTP) in y-axis. our study did not show a significant difference in time to RTP between similar grades of calf injury at different locations with between soleus and gastrocnemius injuries. time to RTP. The findings in our study did not show any particular soleus Our study has a number of limitations. Majority of our aponeurosis or epimysium being significantly more commonly patients were professional and elite athletes; therefore our injured than others. However, in gastrocnemius, most tears findings may not be representative of the general population. were located in the anterior aponeurosis and distal myotendi- The number of higher grade injuries in this study group may nous junction. There were no isolated lateral gastrocnemius tears be over-represented due to bias in the patient population

in our cohort. In addition, there were no plantaris tears in our recruited, as clinically higher grade injuries were more likely copyright. cohort; in our experience this is an uncommon injury. While the to be referred for MRI. MRI evaluation was done by consensus soleus was the more commonly injured muscle, the incidence between three radiologists; the intraobserver and interobserver of grade 3 injury was higher in the gastrocnemius, particularly reliability is therefore not known. The doctors deciding the failure of the distal aponeurosis. time to RTP were not blinded to the MRI findings. We did not Our results show that the time to RTP is significantly longer in correlate between MRI and clinical findings; we therefore do patients with higher grades of connective tissue injury. An earlier not know if the MRI clinical findings add to clinical evalua- study among AFL players with calf injuries identified an asso- tion. We recognise that time to RTP in players may slightly vary http://bjsm.bmj.com/ ciation between missing at least one game and injury involving during preseason, season and postseason. Time to RTP may multiple muscles, musculotendinous junction strains, deep strain also be influenced by players’ motivation to RTP and pressure location and intramuscular tendon tears.7 Balius et al21 studied to play exerted by the clubs. We did not follow up patients in 55 cases of soleus injury by MRI and ultrasound (US), and this study for reinjury. concluded that US is not a sensitive technique for detecting and assessing soleus traumatic tears compared with MRI. 22

Pedret et al evaluated the association of different typical Conclusion on 20 August 2018 by Mr P Brukner CHESM. Protected locations of the soleus muscle tears and their recovery times, Calf muscle injuries involve muscle fibre disruption at the inter- which showed wide variation. However, soleus central intramus- face with the connective tissue structures, such as epimysium, cular tendon injuries had a significantly longer recovery time. aponeurosis and intramuscular tendon. These connective tissue They did not grade the injuries in their study. We think severity structures are likely to fail with higher grade muscle injuries. of connective tissue injury is more important than just the loca- Attention should be directed to the connective tissue integrity tion of the injury. It is a topic for future research to correlate rather than focused solely on the characteristics of the injured muscle fibre component. We propose a MRI grading system that can be used to assess the extent of injury and integrity of the connective tissue structures involved. As demonstrated in this W hat are the findings? study, higher grades of connective tissue injury have a longer time to RTP and are important in determining the duration of MRI-detected connective tissue injury in calf muscle tears is rehabilitation among athletes. associated with longer time to return to play. Competing interests None declared. Ethics approval Monash University Human Research Ethics Committee, Victoria, Australia. How might it impact on clinical practice in the future? Provenance and peer review Not commissioned; externally peer reviewed. The proposed MRI grading system for calf muscle tears can be © Article author(s) (or their employer(s) unless otherwise stated in the text of the used to guide the time to return to play in athletes. article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362 5 of 6 Original article Br J Sports Med: first published as 10.1136/bjsports-2017-098362 on 26 October 2017. Downloaded from

References 11 Blitz NM, Eliot DJ. Anatomical aspects of the gastrocnemius aponeurosis and its 1 Orchard JW, Seward H, Orchard JJ. Results of 2 decades of injury surveillance insertion: a cadaveric study. J Ankle Surg 2007;46:101–8. and public release of data in the Australian Football League. Am J Sports Med 12 Koulouris G, Ting AY, Jhamb A, et al. Magnetic resonance imaging findings of injuries 2013;41:734–41. to the calf muscle complex. Skeletal Radiol 2007;36:921–7. 2 Pomeranz SJ, Heidt RS. MR imaging of the prognostication of hamstring injury. 13 Balius R, Alomar X, Rodas G, et al. The soleus muscle: MRI. anatomic and histologic Radiology 1993;189:897–900. findings in cadavers with clinical correlation of strain injury distribution Skeletal Radiol 3 Slavotinek JP, Verrall GM, Fon GT. Hamstring injury in athletes: using MR imaging 2013;42:521–30. measurements to compare extent of muscle injury with amount of time lost from 14 Delgado GJ, Chung CB, Lektrakul N, et al. Tennis leg: clinical US study of 141 patients and anatomic investigation of four cadavers with MR imaging and US. Radiology competition. AJR Am J Roentgenol 2002;179:1621–8. 2002;224:112–9. 4 Verrall GM, Slavotinek JP, Barnes PG, et al. Diagnostic and prognostic value of clinical 15 Comin J, Malliaras P, Baquie P, et al. Return to competitive play after hamstring findings in 83 athletes with posterior thigh injury: comparison of clinical findings with injuries involving disruption of the central tendon. Am J Sports Med 2013;41:111–5. magnetic resonance imaging documentation of hamstring muscle strain. Am J Sports 16 Cross TM, Gibbs N, Houang MT, et al. Acute quadriceps muscle strains: magnetic Med 2003;31:969–73. resonance imaging features and prognosis. Am J Sports Med 2004;32:710–9. 5 Connell DA, Schneider-Kolsky ME, Hoving JL, et al. Longitudinal study comparing 17 Lee JC, Mitchell AW, Healy JC. Imaging of muscle injury in the elite athlete. Br J Radiol sonographic and MRI assessments of acute and healing hamstring injuries. AJR Am J 2012;85:1173–85. Roentgenol 2004;183:975–84. 18 Bryan Dixon J. Gastrocnemius vs. soleus strain: how to differentiate and deal with calf 6 Pollock N, James SL, Lee JC, et al. British athletics muscle injury classification: a new muscle injuries. Curr Rev Musculoskelet Med 2009;2:74–7. grading system. Br J Sports Med 2014;48:1347–51. 19 Hayashi D, Hamilton B, Guermazi A, et al. Traumatic injuries of thigh and calf muscles 7 Waterworth G, Wein S, Gorelik A, et al. MRI assessment of calf injuries in Australian in athletes: role and clinical relevance of MR imaging and ultrasound. Insights Football League players: findings that influence return to play. Skeletal Radiol Imaging 2012;3:591–601. 2017;46:343–50. 20 Armfield DR, Kim DH, Towers JD, et al. Sports-related muscle injury in the lower 8 Huijing PA. Muscle as a collagen fiber reinforced composite: a review of force extremity. Clin Sports Med 2006;25:803–42. transmission in muscle and whole limb. J Biomech 1999;32:329–45. 21 Balius R, Rodas G, Pedret C, et al. Soleus muscle injury: sensitivity of ultrasound 9 Gray H. et alMuscles of lower limb. In: Williams PL, Warwick R, Dyson M, Bannister LH, patterns. Skeletal Radiol 2014;43:805–12. . eds. Gray’s Anatomy. 37th ed. New York: Churchill Lvingston, 1989:p647–8. 22 Pedret C, Rodas G, Balius R, et al. Return to Play After Soleus Muscle Injuries. Orthop J 10 Garrett WE. Muscle strain injuries. Am J Sports Med 1996;24(6 Suppl):S2–8. Sports Med 2015;3:232596711559580. copyright. http://bjsm.bmj.com/ on 20 August 2018 by Mr P Brukner CHESM. Protected

6 of 6 Prakash A, et al. Br J Sports Med 2018;52:929–933. doi:10.1136/bjsports-2017-098362