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Vol 9, No 4, July/August 2001
227
Traumatic muscle contusion is a
common cause of soft-tissue injury
in virtually all contact sports. In
fact, contusion and strain injuries
make up approximately 90% of all
sports-related injuries.
1,2
Other than
strain injuries, contusion caused by
impact with a blunt, nonpenetrating
object is the most frequent muscle
injury.
3
The symptoms of a contusion
injury are often nonspecific, and
include soreness, pain with active
and passive motion, and limited
range of motion. Without a straight-
forward history of impact to the
area, the diagnosis often becomes
one of exclusion. Many contusion
injuries go unreported and un-
treated.
Healing of these injuries is a
complex phenomenon depending
on multiple factors, both within and
outside the control of the clinician.
No universally accepted treatment
modalities have been developed.

Most treatments follow the “RICE”
principle (rest, immobilization,
cold, and elevation) at least in the
short term, but clinicians differ as to
the best long-term treatment.
Common sites of contusion
injuries include the anterior, poste-
rior, and lateral aspects of the thigh
and the upper arm in the region of
the brachialis (causing “tackler’s
exostosis”). Contusions in the area
of the quadriceps and the lateral
thigh may cause excessive hema-
toma to accumulate due to the large
potential space.
4
A frequent com-
plication is ossification of the hema-
toma in response to mechanisms
that are as yet unclear. It is generally
felt that injury sufficient to cause
proliferative repair is essential to
the development of myositis ossifi-
cans.
5
At the level of the muscle
fibers, capillary bleeding and edema
can lead to hematoma formation
and can cause compartment syn-
drome in areas in which the volume

is limited by the fascial envelope.
There are a number of common
types of muscle injuries (Table 1).
Several excellent reviews of muscle
strain injuries
2,6,7
and of exercise-
induced muscle injury
8-10
have ap-
peared in the recent literature, but
there have been none that summarize
the body of literature dedicated to
muscle contusion injury. There are,
however, a large number of studies,
especially those reporting on ani-
mal research, that detail the mecha-
nisms of injury, the natural history,
and the effects of various treatment
modalities. The lessons learned in
the laboratory can now begin to be
translated to the care of the injured
patient.
Dr. Beiner is Resident, Department of Ortho-
paedics and Rehabilitation, Yale University
School of Medicine, New Haven, Conn. Dr.
Jokl is Vice Chairman and Chief, Section of
Sports Medicine, Department of Orthopaedics
and Rehabilitation, Yale University School of
Medicine.

Reprint requests: Dr. Jokl, Yale University
School of Medicine, Suite 600, 1 Long Wharf
Drive, New Haven, CT 06511.
Copyright 2001 by the American Academy of
Orthopaedic Surgeons.
Abstract
Muscle contusion is second only to strain as the leading cause of morbidity
from sports-related injuries. Severity depends on the site of impact, the activa-
tion status of the muscles involved, the age of the patient, and the presence of
fatigue. The diagnosis has traditionally been one of clinical judgment; however,
newer modalities, including ultrasonography, magnetic resonance imaging, and
spectroscopy, are becoming increasingly important in both identifying and
delineating the extent of injury. Although controlled clinical studies are scarce,
animal research into muscle contusions has allowed the description of the nat-
ural healing process, which involves a complex balance between muscle repair,
regeneration, and scar-tissue formation. Studies are being performed to evalu-
ate the effects of anti-inflammatory medications, corticosteroids, operative
repair, and exercise protocols. Prevention and treatment of complications such
as myositis ossificans have also been stressed, but recognition may improve the
outcome of these ubiquitous injuries.
J Am Acad Orthop Surg 2001;9:227-237
Muscle Contusion Injuries:
Current Treatment Options
John M. Beiner, MD, and Peter Jokl, MD
Mechanisms of Injury
The clinical entity of a muscle con-
tusion injury is most often seen after
a direct blow to an extremity. In
football, this frequently occurs in
the anterior, medial, or lateral thigh

in the area of the muscle belly of the
quadriceps femoris.
11
The greatest
number of quadriceps contusions in
one study occurred in tackle foot-
ball, although the percentage of
injuries was higher in rugby, karate,
and judo.
11
In soccer, after the
widespread adoption of the use of
shin guards, the thigh is now the
most commonly injured area as
well. However, these injuries have
been reported in virtually all contact
sports.
The injury is associated with pain
and swelling, a decreased range of
motion of joints spanned by the
injured muscles, and occasionally a
permanent palpable mass.
11
In ani-
mal studies, at a microstructural
level, contusion injury usually causes
a partial rupture of the muscle, cap-
illary rupture, and infiltrative bleed-
ing, leading to hematoma formation
within the developing gap and

around the intact muscle fibers,
edema, and inflammation.
12
De-
spite all these changes, some func-
tional capacity usually remains in
the affected muscle.
13,14
The archi-
tecture of the damaged muscle bed
is a mix of disrupted muscle cells
and collagen connective tissue. The
healing process is a delicate balance
between the formation of scar tissue
by fibroblasts and the regeneration
of normal muscle by migrating
myoblasts.
Injury Severity
Information regarding the structural,
cellular, and biochemical events in
contusion injury is essential to the
rational application of sports therapy.
Studying these injuries is difficult,
however, because of the inherent
variability in severity. In contrast, the
research setting provides a means to
control many of the confounding
variables involved in muscle contu-
sion research. Models of contusion
that have been developed use spring-

loaded hammers, crushing hemostat
forceps, reflex hammers, and a vari-
ety of other devices to cause single or
multiple contusion injuries ranging
from the mild to the severe in rodents
and nonhuman primates. Only two,
however, have been able to deliver a
standardized crush injury. Järvinen
and co-workers
15-17
developed a rat
model of muscle contusion injury
involving the use of a spring-loaded
hammer and compared the effects of
mobilization and immobilization on
the healing process. They found that
early mobilization increased the ten-
sile strength of the muscle compared
with similarly injured muscles immo-
bilized in a plaster cast.
15-17
Stratton
et al
18
used a drop-mass technique
that delivers a single blow to muscle
to study the effects of therapeutic
ultrasound on the injury.
A problem common to all of
these models, however, is the in-

ability to characterize the injury in
terms of force, displacement, energy,
and impulse of the impact actually
experienced by the target muscle.
Crisco et al
19
developed a model to
record these variables in the pro-
duction of a standard, reproducible
muscle contusion injury to the rat
gastrocnemius-soleus muscle com-
plex. Others have used this same
model to observe a standard contu-
sion injury that causes hematoma
formation, with disruption of indi-
vidual muscle fibers but preserva-
tion of others, a brisk inflammatory
reaction, and marked interstitial
edema.
20
The extrinsic factors that affect
injury severity have not been well
documented. The debate continues
in the sports arena as to whether
athletes should “tighten up” before
impact during athletic contests in
order to minimize injuries. In stud-
ies of muscle strain injury, it has
been shown that an activated or
contracted muscle will absorb more

energy and require a much higher
force to failure than passively
stretched muscle.
2,21
Crisco et al
22
showed that con-
tracted muscle was able to absorb
more energy during impact than
relaxed muscle. The peak force
recorded was less pronounced than
that in passively impacted muscle.
This is complicated, however, by
the fact that the impacted legs were
an in vivo composite of skin, mus-
cle, fascia, and bone. Contraction
simply stiffened the muscle relative
to the bone, allowing protection
from injury.
Later experiments by Beiner
23
continued the work of Crisco et al
22
and found that the relaxed muscle-
bone composite was significantly
(P<0.05) stiffer than the contracted
muscle-bone composite. This was
Muscle Contusion Injuries
Journal of the American Academy of Orthopaedic Surgeons
228

Table 1
Common Types and Causes
of Muscle Contusion
Exercise-induced injury (“delayed
onset muscle soreness”)
Strain
Laceration
Traumatic
Surgical
Vascular
Tourniquet
Traumatic vascular injury
Infectious
Bacterial
Viral
Neurologic
Denervation
Viral (central or peripheral)
Traumatic (central or peripheral)
Neuropathic
Metabolic
Viral
Genetic
Myopathies
due to the fact that on impact some
of the bulk of the relaxed muscle
parted, concentrating the force of
the impacting sphere on part of the
muscle near the bone. In contrast,
the contracted muscles were able to

absorb energy by displacing less,
distributing the force over the entire
muscle belly, and avoiding severe
damage to any one area. Energy
absorbed was 10% more than in the
relaxed muscle-bone composite
(P<0.05). These concepts are illus-
trated by Figure 1, showing that two
peaks are present for impacts to
relaxed muscle, one for initial
impact on the muscle and the sec-
ond as the impactor compresses the
remaining muscle and hits the bone.
Changing the shape of the impact-
ing surface into a bar rather than a
sphere changed the injury slightly,
but did not seem to change the over-
all force-generating capacity of the
muscles following injury.
To model the effect of constrain-
ing hard or soft padding or taping
on muscle injury, Beiner
23
analyzed
the effects of muscle contraction
with exterior constraint (by enclos-
ing the entire leg in a narrow-walled
chamber during impact), which lim-
ited the extent of the lateral defor-
mation available to the muscle as it

absorbed impact. This seemed to
cause a much more severe injury.
When the muscle was externally
constrained during impact, the
force-displacement curves of the
contracted and relaxed muscle-bone
composites were comparable. The
injury was 11% greater for con-
strained muscles in subsequent con-
tractile testing (P<0.05). Constrain-
ing the muscle also caused the
energy absorbed to increase by ap-
proximately 11%, as occurs with
contraction. It may be that the mus-
cle could not deform while con-
strained, resulting in more severe
injury.
John M. Beiner, MD, and Peter Jokl, MD
Vol 9, No 4, July/August 2001
229
Figure 1 Force-displacement behavior of rat gastrocnemius-soleus muscle complex impacted in either the contracted or relaxed state with
a drop-mass technique. The constrained muscles were held with walls on either side, limiting their lateral displacement. Constraining
and contraction caused the peak forces to be distributed over a broader area, changing the impulse to the muscles. All impact stimulation
was at 100 Hz and 70 V, with a 0.1-msec pulse duration and 1.5-sec train duration. Curves are mean ± SD (N = 27).
220
200
180
160
140
120

100
80
220
200
180
160
140
120
100
80
200
180
160
140
120
100
80
60
40
20
0
0 2 4 6 8 10 12
Displacement, mm
200
180
160
140
120
100
80

60
40
20
0
0 2 4 6 8 10 12
Displacement, mm
60
40
20
0
0 2 4 6 8 10 12
Force, N
Displacement, mm
60
40
20
0
0 2 4 6 8 10 12
Force, N
Displacement, mm
220
Force, N
220
Force, N
Nonconstrained
Constrained
Contracted
Relaxed
Beiner
23

found that both the status
of the activation of the muscle during
impact (contracted versus relaxed)
and the relative level of external con-
straint of the muscle predicted the
force the muscle could generate in
contractile testing. Contracted mus-
cle generated a 10% increased force
relative to relaxed muscle (P<0.05),
while constrained muscle was weaker
by 11%. Clinical correlates to exter-
nal constraint include design of pads;
the relative volume of muscle that is
protected by an enclosing hard plas-
tic pad may affect how the muscle
absorbs the energy of impact. More
research is needed in this area before
further recommendations can be
made in the sports arena regarding
equipment design and protective
measures for impact.
Fatigue has been shown to affect
the ability of stretched muscle to
withstand injury,
24
as has tempera-
ture
25
; no similar studies have been
performed in the setting of contusion

injury. Fatigue lessens the ability of
a muscle to fully contract, and con-
traction seems to protect the muscle
from injury, but a direct causal rela-
tionship has yet to be established.
Physiologists have long known that
muscles operate best within a certain
temperature range. Warm-up before
exertion thus has obvious benefits,
but a direct relationship between
overheating, fatigue, and injury has
not been delineated.
Muscles in young rats seem to
undergo more intense inflammation,
with more proliferation of fibro-
blasts and production of collagen,
than old muscles.
26
Young muscles
also heal more rapidly and more
completely, suggesting the greater
power of young regenerating tissue
to respond to injury.
Diagnosis
The clinical diagnosis of contusion
injury is often fairly direct (Fig. 2).
The patient experiences local swell-
ing, tenderness, pain, and impaired
athletic performance. The extent
and type of soft-tissue injury, how-

ever, are less readily established.
Many researchers have attempted
to demonstrate the usefulness of
imaging in determining the extent
and the healing of contusion injury.
Ultrasound has been used success-
fully to distinguish pervasive swell-
ing and edema from a localized, cir-
cumscribed hematoma.
27
It has also
been advocated as a noninvasive
aid in determining when to consider
surgical evacuation of the hema-
toma and when to choose the less
aggressive compression and early
mobilization.
Magnetic resonance (MR) imaging
has also been used to evaluate
patients with the clinical signs and
symptoms of contusion injury, but its
role is currently limited to selected
patients. It is most useful in the sub-
acute setting when a definite history
of trauma is lacking.
28
Although the
clinical uses of MR imaging in fol-
lowing contusion injury are less well
defined, it has been shown to be

more sensitive than computed to-
mography (CT) for the detection of
hemorrhage.
29
It may allow sequen-
tial follow-up during healing, and the
addition of contrast material may
enhance injury recognition and eval-
uation of the extent of injury.
30
Muscle Contusion Injuries
Journal of the American Academy of Orthopaedic Surgeons
230
Consider operative repair
Early mobilization with passive
range of motion, stretching
Pain-free passive
range of motion
Consider myositis
ossificans
Immobilize in neutral position
(no tension on repair)
Contusion with muscle tear
(gap, fascial tear, or avulsion detected
by physical examination or imaging)
Contusion without
muscle tear
Immobilize muscle in stretched
position for 24 hours, NSAIDs
24 to 48 hours, avoid steroids

Assess severity of muscle contusion injury:
• Physical examination (range of motion, palpable gap)
• Ultrasound, magnetic resonance imaging
Progress to concentric
active range of motion and
strengthening to tolerance
Prolonged painful
range of motion,
swelling, erythema
Functional rehabilitation
with graded increased
eccentric range of motion
Figure 2 Algorithm for the evaluation and treatment of muscle contusion injuries.
NSAIDs = nonsteroidal anti-inflammatory drugs.
Standard MR imaging provides in-
formation regarding the site and ex-
tent of injury, but MR spectroscopy,
in limited use for some years, can
also be used to estimate the ratio of
inorganic phosphate to phosphocrea-
tine, which reflects the metabolic
response to muscle injury.
31
The Healing Process
Fisher et al
32
gave a detailed account
of the ultrastructural events after
muscle contusion injury to the rat
gastrocnemius muscle. Figure 3

shows the histologic appearance of
normal healing of contused muscle.
Muscle consists primarily of tissue
derived from cells of two separate
and distinct lineages: fibroblasts
and myoblasts. After injury, the
damaged segments show gross tear-
ing and degeneration. A large num-
ber of mononuclear cells are drawn
to the injured area, with an intense
inflammatory response and intersti-
tial edema. By 24 to 48 hours, there
is an increase in the number of sar-
colemmal nuclei, with activation
and proliferation of the satellite
myogenic cells lying between the
basal lamina and the plasma mem-
brane of the muscle fibers. By day
3, regenerating muscle cells display
central nuclei and reorganizing sar-
comeres. By day 6, focal interstitial
collagen formation suggests mini-
mal to mild scar formation. After 14
to 21 days, no residual evidence of
the injury is apparent.
Lehto and Järvinen
33
described
the important role played by the
basal lamina in the regeneration of

muscle. If it is intact, it acts as a bar-
rier to fibroblast infiltration and as a
scaffold for myoblast proliferation.
With more severe injuries, when the
gap in the damaged muscle fibers is
larger, the ruptured gap can be
filled with proliferating granulation
tissue and later by a connective tis-
sue scar.
16,34
As described by Lehto
and Järvinen,
33
healing of injuries is
dependent on several factors: dam-
age to the neural input, vascular
ingrowth, oxygen supply, the rate
John M. Beiner, MD, and Peter Jokl, MD
Vol 9, No 4, July/August 2001
231
Figure 3 Histologic sections of muscle tissue after contu-
sion injury (hematoxylin-eosin; original magnification ×200).
A, At day 2, hematoma is evident, as well as a brisk inflam-
matory reaction with marked interstitial edema. B, At day
7, there is evidence of removal of the necrotic tissue, disper-
sal of the inflammatory cells, and infiltration. C, At day 14,
the tissue looks very similar to normal muscle, with clearing
of necrotic tissue, regeneration of fibers, and relatively nor-
mal tissue architecture. (Reproduced with permission from
Beiner JM, Jokl P, Cholewicki J, Panjabi MM: The effect of

anabolic steroids and corticosteroids on healing of muscle
contusion injury. Am J Sports Med 1999;27:2-9.)
C
A B
and geography of myoblast fusion
to myotubes, the collagen cross-
linking, and the overall race be-
tween regenerating myoblastic cell
infiltration and granulation and scar
formation. Some, but not total, re-
modeling occurs later.
Histologic staining with vimentin
provides qualitative and quantitative
markers for mesenchyma-derived
cells. Trichrome staining tracks colla-
gen. Crisco et al
19
used markers for
protein and collagen formation to
study the healing after contusion
injury in a rat model. At day 0 after
contusion injury, no vimentin was
noted, but inflammatory cells were
present. At day 2 of healing, an in-
tense inflammatory response with
phagocytosis of necrotic muscle fibers
and supporting tissue was noted.
The basement membranes were
intact, and spindle-shaped fibroblasts
were present in moderate numbers.

Trichrome stains demonstrated the
presence of collagenous material
beginning to form in the area. Slight
vimentin activity was noted at the
periphery, indicating differentiation
of myoblast precursor cells from satel-
lite stem cells (Fig. 4, A). At day 7 of
healing, trichrome staining of colla-
gen showed increased scarring in the
central areas where the muscle archi-
tecture was destroyed. A marked
increase in vimentin staining was
noted, localized to the center as well
as to the periphery at this time point
(Fig. 4, B). By 24 days after injury,
there was no difference between
damaged muscles and control mus-
cles with regard to the staining pat-
terns. Some scar tissue was still evi-
dent, however, in the most severely
damaged muscle.
Healing in the rat model is recog-
nized as more accelerated than in
humans, but just how much faster is
a matter of controversy. Certainly
there are phylogenetic differences
between animals and humans, and
healing in humans is usually shown
to be slower and less complete than
in an animal model.

Muscle Contusion Injuries
Journal of the American Academy of Orthopaedic Surgeons
232
Figure 4 A, Histologic sections at day 2 after injury (original magnification ×200). Top, Trichrome stain shows intense inflammatory response
with phagocytosis. Intact basement membranes are seen as thin lines stained blue. Bottom, With vimentin stain, slight activity (red) is noted at
the periphery of the injury adjacent to the intact fibers (IF). B, Histologic sections at day 7 after injury (original magnification ×200). Top, With
trichrome staining, collagenous (blue) and proteinaceous (red) ground substance can be differentiated. Bottom, Intense vimentin activity (red)
is noted at the periphery of the injury and extends centrally. (Reproduced with permission from Crisco JJ, Jokl P, Heinen GT, Connell MD,
Panjabi MM: A muscle contusion injury model: Biomechanics, physiology, and histology. Am J Sports Med 1994;22:702-710.)
A B
IF
Clinically, studies of the healing
of contusion injuries are necessarily
influenced by the type of treatment
used, whether it be immobilization,
activity ad libitum, or some other
modality. Animal studies have been
conducted in an attempt to define
the clinical course of thigh contu-
sions. In a sheep model, the injury
caused extensive scarring, with
periosteal bone formation and het-
erotopic bone formation in 17% of
the legs within 3 weeks to 3 months
after trauma and replacement of
muscle tissue by intramembranous
ossification within scar tissue.
12
Several earlier studies reported no
ossification, despite extensive ne-

crosis, regeneration, and granula-
tion tissue.
Human studies of contusion in-
juries are limited. The most impor-
tant of these are the West Point
studies of quadriceps femoris con-
tusions.
4,11
The initial study deter-
mined a rationale for treatment
and therapy with an emphasis on
achieving full extension, with im-
mobilization in extension during
rest.
4
Later, the researchers found
that normal flexion was the vari-
able that was slowest to return, and
this lack of flexion prolonged dis-
ability after pain resolved.
11
They
subsequently modified their proto-
col to immobilize the muscle in a
stretched position, with early
motion emphasizing flexion. They
classified injuries by range of
motion at 12 to 24 hours after in-
jury. Mild injuries were defined as
those after which range of motion

greater than 90 degrees was possi-
ble; moderate, 45 to 90 degrees; and
severe, less than 45 degrees. Aver-
age disability (defined as inability
to participate in full cadet activi-
ties) was 13 days for mild contu-
sions, 19 days for moderate inju-
ries, and 21 days for severe injuries.
This contrasted with the much
longer disability (up to 72 days)
with the previous treatment pro-
tocol.
Myositis Ossificans
Myositis ossificans has long been
recognized as a leading complica-
tion of muscle contusion injury.
Although certain regions are more
prone to the development of myosi-
tis, such as the quadriceps and
brachialis, the mechanisms have not
been clearly established. Similar to
the development of heterotopic ossi-
fication after surgical dissection, the
factors that make some patients
prone to this complication are un-
clear. Myositis ossificans was a
complication of 9% of the contusion
injuries in the West Point studies,
and was found to be related to the
initial grade of injury (based on

range of motion).
4,11
Several different kinds of myosi-
tis have been identified. In the stalk
type, there is a thin stalk of bone
connecting the ossified muscle to the
underlying bone. In the periosteal
type, there is a broad-based region
of ossification in contact with the
underlying bone. In the third type,
the ossified muscle is not connected
to the underlying bone at all, but
rather seems to derive entirely from
the affected muscle.
Within 3 weeks after injury, os-
teoblastic activity can be detected
with bone scanning. To minimize the
risk of recurrence, surgical removal
should be delayed until the bone has
matured (usually after 6 months to 1
year) and no longer shows increased
uptake on a bone scan.
Treatment
A general approach to the treat-
ment of muscle contusion injuries
is shown in Figure 2.
Operative Treatment
Traditionally, muscle contusion
injuries have been treated nonoper-
atively. Many surgeons have

reported their anecdotal sense that
in the presence of hematoma and a
palpable defect in the muscle belly,
it is difficult to suture the muscle
together, as there are frequently no
fascial ends to close, and muscle
fibers are poorly reapproximated.
However, recent animal studies
have provided increasing evidence
that in the setting of a contusion
injury that causes a spatial defect in
the muscle belly, suturing with
large absorbable sutures through
the thick substance of the muscle
does decrease the distance between
the lacerated edges, allowing faster
healing.
27
Following the healing of
rat gastrocnemius muscles with MR
imaging, Mellerowicz et al
30
found
that “suture of the divided muscles
resulted in more rapid healing with-
out major defects.”
In a mouse model, suturing of
the cut ends of the muscle resulted
in “better healing of the injured
muscle and prevented the develop-

ment of deep scar tissue in the lacer-
ated muscle.”
35
The authors found
that tetanic strength was 81% of that
in control muscles for sutured mus-
cles, 35% for untreated lacerated
muscles, and 18% for immobilized
muscles at 1 month after injury.
They recommended repair with a
modified Kessler stitch.
Another study stressed the need
for exercise after laceration of mus-
cle. The authors found that the
regenerating muscle-scar composite
eventually regained almost com-
plete (96%) resistance to stress, but
the surrounding area of atrophied
muscle made the muscle unit as a
whole weaker when immobilized.
They did not perform contractile
testing.
36
Human studies in this
area are lacking.
Immobilization Versus Early
Mobilization
Immobilization was long used as
part of the rehabilitation of muscle
contusion injuries. The complica-

tions of immobilization, even for
short periods of time, including
rerupture, muscle atrophy, joint stiff-
John M. Beiner, MD, and Peter Jokl, MD
Vol 9, No 4, July/August 2001
233
ness, and a high incidence of myosi-
tis ossificans, prompted studies of
early mobilization. In a study com-
paring mobilization and immobiliza-
tion after contusion injury in rats, the
immobilized legs lost 30% of their
weight, but no such atrophy was
observed in the mobilized legs. In
addition, delayed contraction and
maturation of the fibrous scar were
noted in the third week after injury.
16
These effects occurred even after
only 2 to 5 days of immobilization.
Studying load-deformation curves
when pulling injured muscle to fail-
ure after contusion injury, Järvinen
13
found that the muscles mobilized
on a treadmill failed at a significantly
greater force than the immobilized
muscles. Immediately after injury,
the muscles pulled to failure at
approximately 20% of the force

needed to cause contralateral nonin-
jured muscles to fail. After 1 week
of treatment, the decrease in tensile
stiffness for immobilized muscles
(compared with intact control mus-
cles) averaged 33%. In contrast,
mobilized muscles had healed to
within 11% of the force to failure of
control muscles. The mobilized
muscles recovered tensile strength
more quickly and more completely
than the muscles treated with “no
specific treatment” (i.e., cage activity
ad libitum). After 3 weeks of re-
training, these levels had not nor-
malized to those of muscles mobi-
lized immediately after injury. The
authors concluded that early mobi-
lization restored functional capacity
of healing muscle earlier than im-
mobilization.
Lehto et al
34
found that immobi-
lization after injury accelerated gran-
ulation tissue production. However,
they also found that if continued too
long, it can “lead to contraction of
the scar and to poor structural orga-
nization of the components of regen-

erating muscle and scar tissue.”
These conclusions were based on the
characteristics revealed by histo-
chemical staining, measurement of
tensile properties, and the gross ap-
pearance of the muscles during heal-
ing. The authors concluded that a
certain period of immobilization (5
days for rats) is beneficial to allow
subsequent mobilization without
causing further trauma to the heal-
ing tissue.
In another study, Järvinen
13
eval-
uated four exercise regimens imple-
mented after contusion injury in rats,
using the local concentrations of
leukocytes, erythrocytes, and colla-
gen fibers in the injured muscle as a
way of measuring the rate of resolu-
tion of the contusion. It was found
that running immediately after
injury is the regimen of choice,
because of more rapid disappearance
of the injury than with the delayed
or no-exercise regimens. Running
was also better than swimming.
Capillary density after injury has
been found to transiently decrease

after immobilization of muscle.
Similar trends have evolved in
the treatment of humans. Jackson
and Feagin
4
developed a treatment
strategy for West Point cadets who
suffered contusion injuries to the
quadriceps muscle. They initially
emphasized rest of the injured leg
in extension and early restoration of
full knee extension. With this treat-
ment, the trainers and therapists
noted that “normal flexion was the
slowest parameter to return,” caus-
ing prolonged disability. A later
study
11
emphasized immobilization
in muscle tension (flexion for quad-
riceps contusion) for a short period
of time (24 hours for mild injuries,
48 hours for severe injuries), fol-
lowed by well-leg and gravity-
assisted motion as soon as pain re-
lief permits. Patients are advanced
to functional rehabilitation when
120 degrees of pain-free active knee
motion is achieved. These studies
have led to the now-common clini-

cal practice of immobilization only
in the period immediately after
injury to limit hematoma formation,
followed by early mobilization.
Cryotherapy
The most common treatment of
musculoskeletal injuries is the appli-
cation of ice. One group tested the
hypothesis that cryotherapy after
contusion injury is effective because
it reduces microvascular perfusion
and subsequent edema formation.
37
The authors found that cryotherapy
caused vasoconstriction and de-
creased perfusion transiently, but
found no long-term microvascular
effects. Thus, the therapeutic win-
dow of opportunity is relatively
small for the effects of cryotherapy.
Pharmacologic Treatment
Inflammation is thought to be
beneficial in attracting reparative
cells as a part of muscle healing,
allowing clearance of nonviable tis-
sues and preventing scar formation.
However, it is also thought by some
to be the cause of continued pain
and swelling that may limit mobility
and prevent healing. Nonsteroidal

anti-inflammatory drugs (NSAIDs)
are commonly prescribed by physi-
cians dealing with musculoskeletal
injury. Once again, animal studies
provide some information. Fisher et
al
38
studied the effect of systemic
inhibition of prostaglandin synthe-
sis (by naproxen) on muscle protein
balance after contusion injury in the
rat. Their findings were similar to
those in many of the early studies of
muscle contusion injury, in that nor-
mal muscle healing for the first 3
days was characterized by a marked
catabolic response, followed by
muscle protein repletion for several
weeks. Inhibition of prostaglandin
synthesis significantly (P<0.05)
reduced the catabolic loss of muscle
protein seen locally and peripheral
to the injury site.
38
In another well-designed study,
Järvinen et al
39
used their model to
test the effects of two different
NSAIDs as well as hydrocortisone

on the healing of contusion injuries.
Histologic, enzyme, and mechani-
cal measurements were recorded.
Muscle Contusion Injuries
Journal of the American Academy of Orthopaedic Surgeons
234
They found that the drugs all sig-
nificantly (P<0.05) decreased the
acute inflammation, but also caused
a slight decrease in tensile proper-
ties in the longer term. They noted
delayed elimination of hematoma
and necrotic tissue and retardation
of muscle regeneration in the hy-
drocortisone group but not in the
NSAID groups.
Similar studies have been per-
formed with the use of other muscle
injury paradigms. In the study by
Mishra et al,
40
rabbit muscles were
subjected to a repetitive exercise
program and treated with flurbipro-
fen. The authors reported that the
treatment group showed a “more
complete functional recovery than
the untreated controls at 3 and 7
days but had a deficit in torque and
force generation at 28 days.”

Nonsteroidal anti-inflammatory
drugs have not been studied in rela-
tion to healing of muscle contusion
injuries in humans. However, the
data on NSAIDs in strain injuries
are conflicting, and there are no
definitive conclusions as to their
efficacy or long-term effects on mus-
cle regeneration.
Corticosteroids are also used by
some in the treatment of muscle
injuries. Using the contusion injury
model, Beiner et al
20
studied the
effect of systemic (depot intramus-
cular) treatment with a corticoste-
roid (methylprednisolone) versus
that with an anabolic steroid (nan-
drolone). With corticosteroid treat-
ment, there was a marked lack of
the initial inflammation at the con-
tusion site, with increased force-
generating capacity in those mus-
cles during the early phases. Later,
however, the corticosteroid-treated
muscles demonstrated a retardation
of the normal healing response,
with delayed clearing of necrotic
tissue and muscle regeneration.

Although comparable to the doses
used in other animal studies, the
doses of corticosteroid were large,
and may not simulate accepted
doses in human studies. In con-
trast, the muscles treated with the
anabolic steroid demonstrated a
robust initial inflammation but
proved to have an increased force-
generating capacity in the long run,
relative to control muscles. Thus, it
appears that corticosteroids may
have a beneficial effect in the short
term on muscle healing but may be
detrimental over the longer term,
inhibiting the normal muscle regen-
eration cascade in this animal model.
Studies in humans have had con-
flicting results. In one trial, Levine
et al
41
retrospectively reviewed a
series of hamstring injuries in Na-
tional Football League players and
found no adverse effect of injection
of corticosteroid directly into the
area of hamstring injury. However,
these injuries were strain injuries
rather than contusions, and no con-
trol group was used. Furthermore,

the outcome measures were subjec-
tive (e.g., pain control, time to re-
turn to active status) rather than ob-
jective (e.g., isometric strength, time
to fatigue). More research is neces-
sary to determine whether cortico-
steroids have a role in treatment of
contusion injuries.
Other pharmacologic agents
have also been studied in the setting
of muscle contusion injury. Using
the model of blunt contusion injury
developed by Crisco et al,
19
one
group studied eight growth factors
and their effect on healing. They
found that three growth factors—
fibroblast growth factor (FGF)-beta,
insulinlike growth factor-I, and
nerve growth factor—enhanced
myoblast proliferation and differen-
tiation in vitro and improved the
healing of the injured muscle in
vivo.
42
Injection of the growth fac-
tors also led to enhanced fast-twitch
and tetanic strength of the contused
muscles 15 days after injury. The

study suggested that gene therapy,
in the form of myoblast transplanta-
tion into injured tissue, might be
used to stimulate persistent expres-
sion of growth factors capable of
promoting the recovery of skeletal
muscle after injury.
Another group studied FGF-6
and its up-regulation after skeletal
muscle injury in mice.
43
Strains of
mice lacking the gene for FGF-6
show a severe regeneration defect
following injury, with fibrosis and
myotube degeneration. They con-
cluded that FGF-6 is a “critical com-
ponent of the muscle regeneration
machinery in mammals, possibly by
stimulating or activating satellite
cells.”
Summary
Muscle contusion injuries are com-
mon events in the athletic world.
Various diagnostic modalities are
becoming more commonly used to
establish the nature and extent of
the lesions. The factors influencing
the severity of such injuries are
becoming delineated, as are the

microstructural events following
injury.
As more and more clinical re-
search is done, several trends in
treatment are evolving. Long-term
immobilization is to be avoided in
favor of a more rapid return to mo-
tion and exercise. Nonsteroidal
anti-inflammatory drugs, similar to
corticosteroids, may have initial
beneficial effects, but their long-
term effects on muscle healing and
regeneration remain to be estab-
lished. Other medications, includ-
ing growth factors and some ste-
roids with anabolic effects, may
prove beneficial to the healing
process. Animal studies indicate
that perhaps surgeons should give
more thought to open repair of
these muscle injuries, as it appears
that, as is the case with nerve tissue,
reapproximating the damaged ends
may allow the balance between scar
formation and tissue regeneration to
shift toward a more useful repara-
tive process.
John M. Beiner, MD, and Peter Jokl, MD
Vol 9, No 4, July/August 2001
235

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237