CASE REPORT
Muscle Strain of the Subscapularis Muscle: A Case Report
Jun Iwamoto, Tsuyoshi Takeda, Kiyohisa Ogawa, and Hideo Matsumoto

Department of Sports Medicine, Keio University School of Medicine, Tokyo, Japan(Received for publication on January 26, 2007)(Revised for publication on April 24, 2007)(Accepted for publication on June 21, 2007)

Abstract. We report on a case of muscle strain of the subscapularis muscle in a baseballplayer. An out-fielder (throws right-handed and bats left-handed) hurt his right shoulder
while playing baseball. He complained of right-shoulder pain just after he forcefully hit hisright hand against the fence in an attempt to jump and catch a flying ball with a glove on
the left hand during a baseball game. Fat-suppressed T2-weighted magnetic resonance images (MRIs) of the right shoulder joint revealed muscle strain in the middle part of the subscapularis muscle, and the injury was surmised to have occurred on account of eccentric
contraction of the subscapularis muscle. The case was considered to have moderate muscle
strain, because he had modest muscle weakness with a negative lift-off test. Active stretching exercises were begun just after his first visit to our clinic, and throwing exercises werestarted 3 weeks later, by when the right-shoulder pain had completely disappeared. Repeat
MRIs of the right shoulder joint obtained 4 weeks after his first visit to our clinic revealed asignificant reduction of the high-intensity lesions in the subscapularis muscle. Conservative
treatment was effective for managing moderate muscle strain of the subscapularis muscle.
Muscle strain of the subscapularis muscle should be taken into consideration in the differential diagnosis of shoulder injuries in athletes. (Keio J Med 56 (3) : 92 － 95, September 2007)
Key words: muscle injury, shoulder joint, MR images, baseball, sports

Introduction

Case report

Muscle strain is a common sports-related injury, andoccurs most often in sprinters or athletes engaging in
high-speed activities. It has been defined as an indirect
injury of muscle caused by excessive stretch.1 Muscle
strains are more common in sports that require bursts ofspeed or rapid acceleration, such as track and field activities, football, basketball, rugby, and soccer, and are mostcommonly encountered in the gastrocnemius, hamstrings, quadriceps, adductor longus, and pectoralis major muscles.2 To the best of our knowledge, no case of
muscle strain of the subscapularis muscle has been reported until now. We report on a case of muscle strain of
the subscapularis muscle encountered by us in an athlete.
Informed consent was obtained from the patient for thiscase report.

A 30-year-old regular professional baseball player(throws right-handed and bats left-handed), playing as an
outfielder, hurt his right shoulder when he forcefully hit
his right hand against the fence in an attempt to jumpand catch a flying ball with a glove on the left hand during a baseball game, with the right elbow joint fully extended and the right shoulder joint flexed, abducted, andexternally rotated. He consulted our clinic 2 days after
the injury. At the first consultation, the ranges of motionsof the right shoulder joint including extension, flexion,abduction, adduction, and internal and external rotations
were not restricted at all when compared with the noninjured side, but he complained of pain in the anterior
shoulder during joint movement. Internal rotation of theright shoulder joint against resistance induced shoulderpain. Modest muscle weakness (manual muscle test: 4＋)
was found in the internal rotator muscles of the right

To whom correspondence should be addressed: Jun Iwamoto, M.D., Department of Sports Medicine, School of Medicine, Keio University, 35 Shinanomachi,Shinjuku-ku, Tokyo 160-8582, Japan, E-mail: jiwamoto@sc.itc.keio.ac.jp92Keio J Med 2007; 56 (3): 92 － 9593Fig. 1 MRIs of the right shoulder joint in the current case at the first visit to our clinic
Both the left proton density weighted MRI (TR/TE, 2500/18 msec) and the right fat-suppressed T2-weighted MRI (TR/TE,3200/106 msec) of the right shoulder joint obtained at the first visit to our clinic show high signal intensity lesions in the middle part ofthe subscapularis muscle.

shoulder joint, however, the lift-off test was negative.
The lift-off test was performed by placing the hand of
the affected arm on the back (at the position of the midlumbar spine) and asking the patient to internally rotate
the arm to lift the hand posteriorly off of the back.3 The
test was considered positive if the patient was unable tolift the arm posteriorly off of the back or if he performed
the lifting maneuver by extending the elbow or theshoulder.3 Although plain radiographs of the right shoulder joint showed no abnormal findings, proton density
weighted and fat-suppressed T2-weighted magnetic resonance images (MRIs) of the right shoulder joint revealed
high signal intensity lesions in the middle part of thesubscapularis muscle (Fig. 1). T1-weighted MRIs were
not obtained. Because no contusion was reported in hisright shoulder joint, diagnosis of muscle strain of thesubscapularis muscle was made. According to a carefully
guided physical therapy program, active stretching exercises (10 times x 5 sets per day) were started just after
his first visit to our clinic, and the volume of the exercises was increased gradually to 10 times x 10 sets per day.
Isotonic exercises with a flexible rubber tube (10 times x
5 sets per day) were started 2 weeks after his first visit toour clinic, by when the right-shoulder pain on internalrotation against resistance had disappeared, and the volume of the exercises was gradually increased to 10 times
x 10 sets per day. Throwing exercises were started 3
weeks after his first visit to our clinic, by when the rightshoulder pain had completely disappeared, and the volume of the exercises was gradually increased according
to the instruction of his coach. Repeat fat-suppressed T2-

weighted MRI of the right shoulder joint obtained 4
weeks after his first visit to our clinic revealed disappearance of high signal intensity lesions in the subscapularis muscle (Fig. 2).

Fig. 2 MRI of the right shoulder joint in the current casefour weeks after his first visit to our clinic
The fat-suppressed T2-weighted MRI (TR/TE, 3800/86 msec)of the right shoulder joint obtained 4 weeks after his first visit toour clinic revealed disappearance of high signal intensity lesions
in the subscapularis muscle.

Iwamoto J, et al: Muscle strain of the subscapularis94

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（������������������）Fig. 3 136 cases of muscle strain in our sports medicine clinic
Besides the two current cases, we have encountered 136 cases (117 males and 19 females) of muscle strain in Japanese athletes atour clinic over the past 13 years. Muscle strain occurs most commonly in people engaging in sports activities, such as track and field
activities, basketball, baseball, golf, soccer, rugby, aerobics and tennis, and most commonly involves the hamstraings, quadriceps andgastrocnemius muscles, followed in frequency by the adductor longus, abdominal oblique, and pectoralis major muscles.

Discussion
Besides the current case, we have encountered 136
cases of muscle strain in Japanese athletes at our sports
medicine clinic over the past 13 years. Fig. 3 shows thesporting activities and the injured muscles in these subjects. Muscle strain occurs most commonly in people engaging in sports activities, such as track and field activities, basketball, baseball, golf, soccer, rugby, aerobics
and tennis, and most commonly involves the hamstrings,quadriceps and gastrocnemius muscles, followed in frequency by the adductor longus, abdominal oblique, andpectoralis major muscles. These data in the Japanese
population are consistent with those reported from Caucasian populations.2 In our experience, muscle strain of
the adductor longus during pitching, and strain of the abdominal oblique muscle during pitching and batting havethe most common types of strain peculiar to professional
baseball players, and until now, no case of muscle strainof the subscapularis muscle has been reported.
Because most muscle strain injuries resolve with conservative management within 3 - 4 weeks, the pathogenesis of muscle strain has not been adequately examined. However, the recent widespread use of computed
tomography (CT) and MRIs have allowed us to clarify
the characteristics of muscle strain in detail.4, 5 Firstly,
only certain muscles are susceptible to strain injury (thatis, muscles that cross multiple joints or have a complex

architecture, i.e., multipennate architecture). Secondly,
eccentric contraction of the muscle is a frequent occurrence. Thirdly, muscle strains occur near the muscle-tendon junctions rather than within the muscle belly.
The subscapularis muscle fibers extend from the anterior surface of the scapula, with insertion of the muscle
tendon into the lesser tubercle of the humerus. The function of the subscapularis muscle is to assist in internalrotation of the shoulder joint. It certainly has a multipennate architecture (complex architecture). Basically, pennate muscles are generally powerful, because their organization allows a large number of fibers to work in unison. 4 Furthermore, because pennate muscles containshort fibers in an oblique arrangement, the maximum velocity of shortening is low and the work performed canbe considerably remarkably little.4 Consequently, pennate muscles resist elongation and have a steep lengthtension slope.4 Powerful stretch of the pennate muscles
by eccentric contraction can lead to either a muscle-tendon junction injury or a more disabling injury involving
avulsion of the tendinous origin. Because the subscapularis muscle has a multipennate architecture in terms of
multiple muscle-tendon junctions, muscle strain could
occur at any site in the muscle.
Basically, muscle strain occurs when the muscle is either stretched passively or activated during stretch. Thus,
it is speculated that in the current case, eccentric contraction of the subscapularis muscle against excessive

Keio J Med 2007; 56 (3): 92 － 95

external rotation of the right shoulder joint in an attempt
to catch a flying ball with a glove on the left hand might
have forced a powerful stretch on the muscle-tendon
junctions of the subscapularis muscle, resulting in themuscle strain. The current case was considered to correspond to acute muscle strain injury that resulted from asingle violent force applied to the muscle.6
Muscle strain of the subscapularis muscle is characterized by difficulty in diagnosis by physical examinationof the shoulder, unlike muscle strains in the hamstrings,
quadriceps and gastrocnemius muscles, probably because this muscle is located deep in the anterior shoulder, the sites of injury are not consistent due to the multipennate architecture of the muscle, and there are no distinctive features. Therefore, CT or MRIs are necessary toidentify muscle strain in the subscapularis muscle.
Muscle strain can be classified into three categories ofseverity; mild (pulled muscle), moderate (partial tear),and severe (complete tear).1, 7 According to this classification, if weakness is absent, the strain is mild, and isbelieved to represent injury in the absence of myofascial
disruption. In order to be categorized as mild strain,
pathologic findings must be restricted to mild inflammatory cell infiltration, edema, and swelling.7 In moderatestrains, weakness is associated with a variable degree ofseparation of muscle from tendon or fascia.7 In severe
strains, myofascial separation is complete and there is anassociated lack of muscle function.7 Muscle strain can berevealed by high signal intensity on conventional andfat-suppressed T2-weighted MRIs according to its pathogenesis. Muscle strain should be differentiated frommuscle bruise, because both are characterized by similarfindings on MRIs. However, it is easy clinically to differentiate between the two, because muscle bruise isusually caused by direct damage injury, such as contusion. In the current case who showed high signal intensity lesions on MRIs in the subscapularis muscle, however, no contusion was reported in the right shoulder joint.

95

Thus, diagnosis of muscle strain of the subscapularismuscle could be made. The current case was considered
to correspond to moderate injury, because of the detection of modest muscle weakness in the internal rotator
muscles including the subscapularis muscle with a negative lift-off test. The subject could start throwing exercises by 3 weeks after his first visit to our clinic, with asignificant reduction of the high signal intensity lesions
on repeat MRIs. Thus, conservative treatment was effective for the management of moderate muscle strain of
the subscapularis muscle.
In conclusion, to the best of our knowledge, this is thefirst report of muscle strain of the subscapularis muscle,encountered in the athlete. The condition was rarely diagnosed clinically, probably on account of the absenceof any distinctive clinical features, prior to the era of
MRI assessment of injuries. Thus, muscle strain of thesubscapularis muscle should be considered in the differential diagnosis of shoulder injuries in athletes.
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