Journal of the American Academy of Orthopaedic Surgeons
344
Stress fractures are common inju-
ries frequently seen in athletes and
military recruits. Although the re-
ported incidence of stress fractures
in the general athletic population is
less than 1%, the incidence in run-
ners may be as high as 20%. In a
review of 370 athletes with stress
fractures, the tibia was the most
commonly involved bone (49.1% of
cases), followed by the tarsals
(25.3%) and the metatarsals (8.8%).
1
Bilateral stress fractures occurred in
16.6% of cases. With the increasing
emphasis on exercise for the elderly,
stress fractures should not be over-
looked in this population.
Although stress fractures have
been described in nearly every
bone, they are more common in the
weight-bearing bones of the lower
extremities. Specific anatomic sites
for stress fractures may be associ-
ated with individual sports, such as
the humerus in throwing sports, the
ribs in golf and rowing, the spine in
gymnastics, the lower extremities in
running activities, and the foot in

transmission of excessive forces to
the underlying bone. Muscles may
also contribute to stress injuries by
concentrating forces across a local-
ized area of bone, thus causing
mechanical insults that exceed the
stress-bearing capacity of the bone.
2
Dr. Boden is Adjunct Assistant Professor,
Uniformed Services University of the Health
Sciences, The Orthopaedic Center, Rockville,
Md. Mr. Osbahr is Laboratory Researcher,
Duke University Medical Center, Durham,
NC.
Reprint requests: Dr. Boden, The Orthopaedic
Center, #201, 9711 Medical Center Drive,
Rockville, MD 20850.
Copyright 2000 by the American Academy of
Orthopaedic Surgeons.
Abstract
Stress fractures are common overuse injuries seen in athletes and military
recruits. The pathogenesis is multifactorial and usually involves repetitive sub-
maximal stresses. Intrinsic factors, such as hormonal imbalances, may also con-
tribute to the onset of stress fractures, especially in women. The classic presenta-
tion is a patient who experiences the insidious onset of pain after an abrupt
increase in the duration or intensity of exercise. The diagnosis is primarily clini-
cal, but imaging modalities such as plain radiography, scintigraphy, computed
tomography, and magnetic resonance imaging may provide confirmation. Most
stress fractures are uncomplicated and can be managed by rest and restriction
from the precipitating activity. A subset of stress fractures can present a high

participating in high-level figure
skating, gymnastics, and cross-
country running are particularly
prone to this triad. In an effort to
minimize body fat and maintain
high athletic performance, many
young women develop eating disor-
ders during puberty. Amenorrhea
and oligomenorrhea are common
findings in competitive female dis-
tance runners, with the prevalence
of menstrual irregularities as high
as 50%.
3
The resultant estrogen-
deficient state leads to decreased
bone mineral density and an in-
creased risk of stress fractures.
Male endurance athletes are also
predisposed to stress fractures due
to abnormally low sex hormone
levels.
4
Testosterone levels may
decrease by as much as 25% within
2 days of vigorous training. Testos-
terone inhibits interleukin-6, a
cytokine responsible for enhancing
osteoclast development. Therefore,
low levels of testosterone in endur-

mechanics is essential to identify
risk factors such as muscle imbal-
ance, limb-length discrepancy, and
excessive subtalar pronation.
The differential diagnosis for
stress fractures includes stress reac-
tion, which is visualized as an area
of prefracture bone remodeling.
Unlike stress fractures, in stress
reactions the bone is weakened but
not physically disrupted. Other
pathologic processes in the differen-
tial diagnosis include periostitis,
infection, avulsion injuries, muscle
strain, bursitis, neoplasm, exertional
compartment syndrome, and nerve
entrapment. In the pelvis and fe-
mur, the diagnosis is often delayed
because the lesion is mistaken for a
more benign condition, such as
muscle strain or bursitis.
Imaging
Although a stress fracture is usually
suspected on the basis of the find-
ings from a thorough history and
physical examination, specific im-
aging modalities may be helpful in
confirming the diagnosis or provid-
ing more information. Radio-
graphs are typically normal for the

(phase III) decreases over 3 to 18
months as the bone remodels, often
lagging behind clinical resolution of
symptoms. Therefore, bone scans
should not be used to monitor heal-
ing and dictate return to activity.
Technetium bone scanning is
highly sensitive for detecting stress
fractures but lacks specificity. In
the case of patients with clinically
suspected stress-related injuries
that are radiographically negative,
bone scintigraphy is more sensitive
than magnetic resonance (MR)
imaging as the initial imaging
modality, particularly in evaluating
suspected lesions in the spine or
pelvis, identifying multiple stress
fractures, and distinguishing bipar-
tite bones from stress fractures.
However, scintigraphy may be
overly sensitive; as many as 50% of
scintigraphically positive findings
can occur at asymptomatic sites.
Areas of increased uptake may rep-
resent subclinical sites of bone
remodeling or stress reactions.
High-Risk Stress Fractures
Journal of the American Academy of Orthopaedic Surgeons
346

predicting the time to recovery.
7
In
addition, MR imaging avoids radia-
tion exposure and requires less
time than three-phase bone scintig-
raphy. Although MR imaging may
be slightly more expensive than
scintigraphy, the added sensitivity
makes the test cost-effective.
A classification system for grad-
ing stress fractures with scintigraphy
and/or MR imaging has been pro-
posed (Table 1).
8
By grading stress
fractures, the approximate time to
healing can be predicted. Indications
for obtaining an MR study include a
suspicion of a femoral neck stress
fracture in an athlete.
Treatment Overview
The first step in treating stress frac-
tures is identifying and correcting
any predisposing factors. Analysis
of training techniques by an experi-
enced coach can be helpful in re-
ducing recurrences. Intrinsic fac-
tors, such as hormonal, nutritional,
and medical abnormalities, also

is appropriate. A rest period of 1 to
6 weeks of limited weight bearing
progressing to full weight bearing
may be necessary. This is followed
by a phase of low-impact activities,
such as biking and swimming.
Table 1
Radiologic Grading System for Stress Fractures
*
Grade Radiograph Bone Scan MR Imaging
†
Treatment
1 Normal Mild uptake confined Positive STIR image Rest for 3 weeks
to one cortex
2 Normal Moderate activity; Positive STIR and Rest for 3-6 weeks
larger lesion confined T2-weighted images
to unicortical area
3 Discrete line (+/-), Increased activity No definite cortical Rest for 12-16 weeks
periosteal reaction (+/-) (>50% width of bone) break; positive T1- and
T2-weighted images
4 Fracture or periosteal More intense Fracture line; positive T1- Rest for 16+ weeks
reaction bicortical uptake and T2-weighted images
*
Adapted with permission from Arendt EA, Griffiths HJ: The use of MR imaging in the assessment and clinical management of stress
reactions of bone in high-performance athletes. Clin Sports Med 1997;16:291-306.
†
STIR = short-tau inversion sequence.
Barry P. Boden, MD, and Daryl C. Osbahr
Vol 8, No 6, November/December 2000
347

An algorithm has been formulated
to help guide treatment of high-risk
stress fractures (Fig. 1). Fractures
that are scintigraphically positive yet
radiographically negative should be
treated with a period of rest. The
same treatment is appropriate for
low-risk stress fractures. If the stress
fracture becomes evident on plain
films, treatment should be individu-
alized. For most high-risk stress frac-
tures of the lower leg and foot, an
aggressive nonoperative protocol
consisting of non-weight-bearing cast
immobilization is recommended,
especially if the diagnosis is made
soon after the onset of symptoms.
The exception to this rule is the
tension-side femoral neck stress frac-
ture, which requires internal fixation
to prevent the potentially devastating
complications of fracture progres-
sion. In the high-performance athlete
whose livelihood is dependent on
early return to competition or the
athlete who demands an early return
to activity, surgical intervention is
appropriate. Displaced stress frac-
tures and stress fractures with chron-
ic radiographic findings, such as

Surgery
Surgery
Positive
radiograph
Negative radiograph
but positive bone
scan, CT, or MR study
Negative
radiograph
Suspected stress
fracture
Nonoperative
treatment
Low-demand
athlete
Trial of nonoperative
treatment
High-demand
athlete
Nondisplaced
fracture
Displaced
fracture or
chronic changes
If unsuccessful,
surgical treatment
Figure 1 Algorithm for evaluation and treatment of suspected high-risk stress fractures.
High-Risk Stress Fractures
Journal of the American Academy of Orthopaedic Surgeons
348

neck.
10
In the more common com-
pression stress fractures, the injury
begins at the inferior cortex of the
femoral neck. As complete dis-
placement is extremely rare, nonop-
erative treatment is appropriate.
The second type, the distraction
(or tension) stress fracture, starts in
the superior cortex of the femoral
neck and may advance across the
femoral neck as a fracture line per-
pendicular to the axis of the femoral
neck. Magnetic resonance imaging
is highly sensitive in identifying and
delineating the extent of stress frac-
tures in the femoral neck. Distraction
fractures have a greater propensity
to become displaced with continued
stress than compression stress frac-
tures and, therefore, require more
aggressive treatment. Complications,
such as delayed union, nonunion,
varus deformity, and osteonecrosis,
may develop after a displaced frac-
ture. In one study,
11
60% of patients
with a displaced femoral neck frac-

13
An apparent
bipartite patella that is sympto-
matic and is visualized as increased
uptake on nuclear scanning may
actually be an acute or chronic
stress fracture.
In athletes, stress fractures may
occur in either a longitudinal or a
transverse direction. It has been
postulated that transverse stress
fractures initiate on the anterior sur-
face of the patella due to repeated
tension forces from the quadriceps
and patellar tendons with the knee in
flexion.
13
During stance, the quad-
riceps force required to stabilize the
knee is greater than 200% of body
weight.
Transverse patellar stress frac-
tures have also been identified after
anterior cruciate ligament recon-
struction. The cause may be related
to stress risers created at the bone-
plug defect after harvesting of a
bone-patella-bone graft. In addi-
tion, any postoperative knee-flexion
contracture may result in increased

and nonunions, ORIF is appropriate.
A standard tension-band wiring
technique with Kirschner wires or
cannulated compression screws pro-
vides excellent fixation.
Tibia
In athletes, the tibial shaft is the
most common location of stress
fractures.
1
Depending on the pa-
tient population, the incidence may
range from 20% to 75% of all stress
fractures. Tibial stress fractures
may occur at any site along the shaft
of the bone, but are most frequently
encountered in the posteromedial
cortex (compression side). The vast
majority of tibial stress fractures are
transverse in orientation, but longi-
tudinal stress fractures have also
been reported. Longitudinal stress
fractures often have an atypical pre-
Barry P. Boden, MD, and Daryl C. Osbahr
Vol 8, No 6, November/December 2000
349
sentation, necessitating MR imaging
for definitive diagnosis. Tibial stress
fractures on the posteromedial cor-
tex respond favorably to discontinu-

graphs focusing on the middle
third may reveal an anterior tibial
stress fracture.
Both constant tension from pos-
terior muscle forces and hypovas-
cularity of the anterior aspect of the
tibia predispose this site to non-
union or delayed union. Histo-
pathologic examination of chronic
anterior-cortex tibial stress fractures
has revealed fibrotic infiltrations,
local osteonecrosis, and limited or
no bone-remodeling activity, con-
sistent with pseudarthrosis.
In contrast to compression tibial
stress fractures, which usually
occur in distance runners, tension
tibial stress injuries typically occur
in athletes performing repetitive
jumping and leaping activities.
Patients present with point tender-
ness over the anterior aspect of the
central third of the tibia. These
fractures have the potential to
progress to complete fractures.
15
Radiographs are often initially nor-
mal, but subsequently develop a
characteristic V-shaped (or wedge)
defect in the anterior cortex, with

healing has been reported after exci-
sion and bone grafting of the le-
sion.
15
In a series in which a regi-
men of rest and external electrical
stimulation was evaluated,
16
seven
of eight patients showed complete
healing after an average of 8.7
months of treatment. Other authors
have described less favorable results
with electromagnetic stimulation.
15
Chang and Harris
17
reported good
to excellent results in five patients
with recalcitrant stress fractures that
were treated with reamed unlocked
tibial nails. Intramedullary fixation
has become the favored approach
for recalcitrant anterior-cortex tibial
stress fractures.
Medial Malleolus
The medial malleolus is a rela-
tively uncommon site for stress
fractures, but they can occur in ath-
letes participating in running and

Journal of the American Academy of Orthopaedic Surgeons
350
tients are successfully treated with
cast immobilization or ankle brac-
ing and avoidance of impact activi-
ties. Athletes desiring early return
to competition may be treated with
percutaneous drilling and immobi-
lization or internal fixation.
19
Both
surgical and nonsurgical treatment
usually result in a full return to
activity; however, resolution of
symptoms may take 4 to 5 months
with nonoperative therapy.
20
Inter-
nal fixation with malleolar screws is
advocated for patients with a com-
plete fracture line on radiographs.
18
Due to the high shear forces exerted
at the fracture site, nonunion may
develop.
20
In this circumstance,
ORIF with two cancellous screws is
required. Bone grafting is indicated
when there is fracture displacement

an orthosis to correct any excess pro-
nation.
Tarsal Navicular
Tarsal navicular stress fractures
occur primarily in active athletes
involved in sprinting and jumping
sports.
22,23
The presentation typi-
cally involves an insidious onset of
nondescript pain in the medial arch
area that is aggravated by activity.
Findings on examination are usu-
ally limited to tenderness over the
navicular with occasional limitation
of subtalar motion or dorsiflexion of
the ankle. Navicular stress fractures
occur in the sagittal plane in the
central third of the bone or at the
junction of the central and lateral
thirds of the navicular.
24
This site
corresponds to the zone of maxi-
mum shear stress on the navicular
from the surrounding bones. The
lesion begins at the proximal dorsal
articular surface and propagates in
a distal and plantar direction, result-
ing in a partial or complete injury.

more sensitive than bone scanning
and provide information on the ex-
tent of the lesion.
Patients who have an early diag-
nosis of partial or complete navicular
stress fracture have a high union rate
if treated for 6 to 8 weeks with non-
weight-bearing cast immobiliza-
tion.
22
When weight bearing is per-
mitted initially, the risk of delayed
union, nonunion, or recurrence is
dramatically higher. Minimally dis-
placed navicular stress fractures may
be treated with cast immobilization
or ORIF. Displaced fractures, de-
layed unions, and nonunions are
best treated with ORIF and bone
grafting. Fixation is accomplished
by means of one or two compression
screws placed across the fracture.
24
A semirigid molded orthosis is rec-
ommended for arch support during
the rehabilitation phase and after
return to athletic activity.
Fifth Metatarsal
Stress fractures of the fifth meta-
tarsal occur at the proximal diaph-

more than 3 weeks or if radiographs
reveal a stress fracture, treatment
options include non-weight-bearing
cast immobilization for 6 weeks or
intramedullary-screw fixation. For
high-demand athletes, internal fixa-
tion with a compression screw pro-
vides good results and faster return
to activity.
27
For patients with a de-
layed union and medullary sclerosis
on radiographs, intramedullary fixa-
tion with curettage is recommended.
To avoid reinjury, a functional me-
tatarsal brace should be used for at
least 1 month after surgery.
Careful preoperative assessment
of the radiographs to determine the
width and length of the screw is
critical to avoid intraoperative
complications, such as iatrogenic
fracture of the metatarsal. In an
average-size adult, a cannulated
4.5-mm lag screw is preferred.
Drilling the intramedullary canal
before screw placement to debride
the intramedullary fibrous tissue is
recommended. The screw should
be countersunk to avoid skin irrita-

show a medial sesamoid stress fracture.
A B
High-Risk Stress Fractures
Journal of the American Academy of Orthopaedic Surgeons
352
aspect of the first metatarsopha-
langeal joint, discomfort with maxi-
mum dorsiflexion of the first toe, or
push-off disability.
Radiographs should include
weight-bearing anteroposterior and
lateral views as well as an axial
view centered on the sesamoids.
Serial images may be helpful in dis-
tinguishing a stress fracture from
an acute fracture. The reported
incidence of bipartite sesamoid in
the general population ranges from
5% to 30%, and the incidence of
bilaterality is approximately 80%.
Most bipartite sesamoids occur in
the medial sesamoid. Radiograph-
ically, the bipartite sesamoid has
smooth edges and is larger than the
undivided sesamoid. Findings
suggestive of a stress fracture
include a transverse fracture line
with jagged margins. Nuclear
scanning can help differentiate an
acute fracture or a stress fracture

activities.
Summary
Stress fractures are caused by repet-
itive submaximal forces that exceed
the adaptive ability of the bone.
Training errors are the most com-
mon precipitating factors; however,
intrinsic systemic factors should not
be overlooked. Stress fractures are
classified as low-risk or high-risk
injuries. Low-risk stress fractures
infrequently require expensive
imaging modalities for diagnosis
and generally respond to activity
modification. High-risk stress frac-
tures have a propensity to develop
into chronic injuries; therefore,
more aggressive treatment is neces-
sary. Sophisticated imaging studies
are often necessary when the diag-
nosis is in doubt or when the extent
of the injury is difficult to establish.
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