This is a  6-year old male who presents with a chief 
complaint of a limp which began 6 months ago.  There 
is no history of trauma, fever, swelling or pain.  
Recently, he began complaining of right hip pain and 
the limping became more noticeable.  He was seen by 
his physician on two occasions in the last six months for 
this complaint.  Mother was advised to administer 
ibuprofen on both visits.  He was diagnosed as having 
toxic synovitis of the hip joint on the first encounter and 
a non-specific soft tissue injury at the second visit.
     His past history is not contributory.  His family 
history is negative for arthritis or skeletal disorders.  His 
growth and development are normal.
     Exam:  VS T36.9 C, P 108, R 24, BP 110/68.  Wt. 
24.3 kg.  Alert, active, well developed, in no acute 
distress.  He is not toxic.  HEENT exam negative.  Neck 
without lymphadenopathy or thyromegaly.  Heart 
regular without murmurs.  Lungs clear bilaterally.  
Abdomen soft, no organomegaly, no masses.  Normal 
male genitalia.  Extremities:  There is a  2 cm leg length 
discrepancy.  His right thigh is smaller than his left.  
There is pain with hip extension and external rotation.  
Trendelenburg test:  no hip abductor weakness.  Gait:  
shortened stance phase on the right.  The right knee is 
flexed indicative of a leg length discrepancy.
     Lab studies:  CBC WBC 7,000, Hgb 12.0, Hct 36%, 
ESR 13 mm/hr.  UA normal.  Radiographs of his hips 
are obtained.

View hip radiographs.

     The right hip (left on the image) shows widening of 
the joint space.  The femoral epiphysis is fragmented 
and flattened.  The physis appears narrow.  The 
femoral neck is short and wide (Coxa magna). There is 
flattening of the femoral capitellum (Coxa plana).  Not 
seen here but common in patients with this disease is 
lateral displacement of the femur relative to the 
acetabulum (Coxa varus).

Discussion
     Avascular necrosis (AVN) of the femoral head may 
be idiopathic (Legg-Calve-Perthe's Disease) or due to 
some insult to the vascular supply of the femur.  For 
example, septic arthritis of the hip, trauma to the hip, 
especially with dislocation, or steroid use may result in 
avascular necrosis.  In our patient, there is no recall of 
trauma, steroid use or known congenital hip disease to 
explain his AVN, leaving Legg-Calve-Perthe's Disease 
to be the best explanation of his radiographic findings 
and limp.
     Pathophysiology.  The blood supply of the femoral 
head changes with time and growth.  Initially the main 
source of nutrition is supplied directly by nutrient 
vessels within the femoral head.  A small amount of 
blood passes to the head via the ligamentum teres.  By 
the time the child reaches 1.5 years of age the blood 
supply has changed.  Now most of the blood is being 
supplied by the femoral circumflex arteries, which enter 
the femoral epiphysis after traversing the hip capsule.  
Any injury to the hip can result in avascular necrosis 
since the blood supply is so tenuous.
     Limping is a dysfunction in gait which can be divided 
into two phases, the stance and the swing phase.  The 
stance phase begins with the heel strike and ends with 
the toe off.  The swing phase begins with the push off 
and ends with the heel strike.  Both feet are on the 
ground for about 20% of the cycle.  Any aberration of 
the cycle will be noticed as a limp.  The gait may 
appear choppy or labored and may be due to pain, 
weakness or deformity.  Determining the cause of the 
limp may be easier if one can determine what type of 
limp is present.  Historically, limps have been divided 
into three types:  antalgic, Trendelenburg, and short 
leg.
     Antalgic gait is caused by pain and is also called  
the quick step gait.  Patients with this will have a shorter 
stance phase on the affected leg.  This quick step 
minimizes the time stress is placed on the painful  
extremity.  A compensatory acceleration is seen in the 
contralateral swing phase.
     Trendelenburg gait, also called the abductor lurch 
gait, is seen in children with chronic hip disease.  In this 
type of gait the hip drops down (pelvic tilt) during the 
swing phase due to weakness of the contralateral 
gluteus medius muscle.  With bilateral involvement, the 
trunk will sway from side to side with walking.  
Trendelenburg gaits do not affect the amount of time 
standing on either foot.  You can detect gluteus medius 
paresis by performing the Trendelenburg test.  In this 
test, the patient is asked to stand with one foot off the 
ground and is observed for dropping or tilting of the 
pelvis on that side.  A slight rise in the pelvis is to be 
expected.  In the case of our patient, the Trendelenburg 
test was negative for pelvic tilt on either side, indicating 
that the cause of his limp was not due to muscle 
weakness, nor was the condition present long enough 
to result in atrophic weakness of the gluteus medius 
muscles.
     The so called short leg gait is the result of true or 
pseudo leg length discrepancies.  In this gait, the longer 
leg will have persistent knee flexion on standing.  The 
child might also walk on the toes of the shorter leg to 
compensate.  An up and down motion of the pelvis may 
be seen in this gait, but the Trendelenburg test will be 
normal.  True leg length  abnormality can be 
determined by measuring the anterior iliac spine to 
medial malleolus distance.  Apparent or pseudo-leg 
length mismatches may be due to joint contractures of 
either hip or knee flexors.  In this case, measuring the 
umbilical to medial malleolus distance will quantify the 
differences more accurately.
     Our patient had a 2 cm discrepancy and, when 
standing, it appeared that the right leg was longer as he 
kept the right knee flexed.  His gait was consistent with 
both an antalgic gait and a short leg gait.
     The differential diagnosis of limping may be divided 
into categories by disease class and also sub-divided 
by age at presentation.  For the purposes of this 
discussion, I have divided the etiologies of limp into 
pathophysiologic groups as follows:  vascular (vasculitic 
and inflammatory), infectious, congenital, trauma, 
toxic/metabolic, neoplastic, degenerative, 
neuromuscular, and other.

    Vascular causes include juvenile rheumatoid arthritis, 
ankylosing spondylitis, systemic lupus erythematosis, 
scleroderma, Henoch Schonlein purpura, psoriasis, 
insect venoms, Stevens-Johnson syndrome, and deep 
venous thrombosis.  Rheumatologic conditions such as 
juvenile rheumatoid arthritis (JRA) can  present in a 
single joint and are easily mistaken for a septic joint.  
An associated rash or iridocyclitis may help in making 
the diagnosis.  Limping may also be a presenting 
problem in Henoch Schonlein purpura (HSP) as arthritis 
may occur in association with HSP.
     Rheumatic Fever, Lyme Disease and Kawasaki's 
Disease should be kept in mind (see infectious causes).  
Other inflammatory conditions associated with limping 
include serum sickness, Stevens-Johnson syndrome, 
reactions to insect venom and overuse syndromes.  
Deep Vein Thrombosis (DVT) is rare in children but 
may present in patients with hypercoagulable states, 
poor blood flow, or after trauma to the lower extremities.  
The diagnosis of DVT may be made via Doppler flow 
studies, impedance plethysmography or venograms.  
Treatment will vary depending on the age of the 
thrombus, location and co-existing disease.  Psoriasis 
may have an arthritis associated with its dermatologic 
manifestations and, ironically, the arthritis can precede 
the skin changes.  The collagen vascular disorders and 
rheumatoid diseases constitute a wide assortment of 
diseases that may present with limping.  Often, 
radiographic findings will be absent until degenerative 
changes occur.
     Infectious causes include osteomyelitis, septic 
arthritis, toxic synovitis, diskitis, Lyme arthritis, 
tuberculous arthritis, etc.  Bone and joint infections can 
be easily missed and can result in permanent sequelae 
if the diagnosis is delayed.  Usually there is fever with 
swelling, erythema and tenderness near the area of 
infection, but often the only help in detecting 
osteomyelitis or pyogenic arthritis is the limp.  Major 
etiologic agents include Staphylococcus aureus and 
Streptococcus pyogenes (group A beta-hemolytic 
strep).  In neonates, group B streptococcus may be 
causative.  Adolescents need to be screened for 
Neisseria gonorrhea and, in patients with sickle cell 
anemia, Salmonella species may be the cause.  
Evaluation should include the spine and pelvis in 
addition to the extremity to avoid missing diskitis or 
sacroiliac disease.
     Not to be confused with infectious arthritis, toxic 
synovitis presents as joint pain with low grade fever 
usually associated with or shortly after a viral illness.  It 
is self-limited and can be treated with analgesics and 
observation.  Rubella vaccine can also cause an 
arthritis. 
     Lyme arthritis is a sequelae to Lyme disease, a 
tick-borne infection due to Borrelia burgdorferi.  
Characteristically the disease starts with erythema 
migrans.  It may involve all major body systems, 
including the brain, peripheral nerves (Bell's Palsy is 
seen, often bilaterally) and joints.  Five types of  arthritis 
can occur:  1) episodic, involving 1-4 joints for < 1 week 
recurring at least 2 weeks later,  2) acute pauciarticular, 
1-4 joints for < 4 weeks,  3) chronic pauciarticular, 1-4 
joints > 4 weeks,  4) > 3 joints in sequence, and 5) > 5 
joints.  Treatment may include amoxicillin, doxycycline 
(if older than 9) or ceftriaxone.
     Tuberculous disease of the bones was once a major 
concern and may be showing a resurgence in today's 
medical environment because of multiple drug 
resistance, AIDS and other immune suppressed 
patients in our communities. There are some infectious 
diseases that will have an arthritic component to them.  
Yersenia enterocolitica, hepatitis A & B, infectious 
mononucleosis, rubella, rubeola, coxsackie virus and 
human parvovirus B-19 all cause arthritis/arthralgias 
and should be considered as possible etiologies in the 
evaluation of the limping patient.
     One particularly common infectious source of 
limping is Hallux incarnatus or ingrown toenail. This 
usually affects teenagers, especially those active in 
sports.  The mechanism in this disorder involves the 
way the nail is clipped or manually pared.  Treatment 
consists of soaking and local treatment.  If infection 
recurs, surgical removal of the nail or part of the nail is 
effective. 
     Congenital causes of limp include coxa vara, 
congenital hip dysplasia, congenital short femur, spinal 
dysraphism, and other congenital limb deficiencies.  
Congenital hip dislocation (CHD) usually presents in the 
nursery but may not be detected until the child is older.  
This topic was  presented in Pediatrics in Review, vol. 
16, no. 8, 1995.  Please refer to that issue for more 
details.  Another radiographic case of congenital hip 
dislocation and a discussion are presented in Case 13 
of Volume 2, Vomiting Following Reduction of 
Intussusception.
     As some children may not have dislocated hips at 
birth, the term congenital hip dislocation is a misnomer.  
For those whose dislocation occurs later in the first year 
of life, the term "acquired hip dislocation" is more 
appropriate.  Meyers dysplasia, which can look similar 
to Legg-Calve-Perthes disease, involves the growth 
plates of both femoral capital epiphyses only.  Also, 
multiple epiphyseal dysplasia and hypothyroidism can 
mimic LCP.  Multiple epiphyseal dysplasia is inherited 
as an autosomal-dominant trait.  It presents in two 
ways:  hip abnormalities and short stature.  Hip pain 
occurs by age 5 and certainly by age 10.  The epiphysis 
will appear flattened but otherwise normal.
     Examples of trauma include toddler's fracture, stress 
fracture, patellofemoral pain, spondylolisthesis, ruptured 
plantaris tendon, knee strain, meniscal injuries, 
herniated nucleous pulposis.  When trauma  is the 
cause of the limp, the older child or adolescent will 
provide an accurate description of the forces invoked.  
Toddlers (age 1-3 years), however, can present without 
a history for injury, or the witness may have felt the 
trauma was too insignificant to cause a fracture.  Such 
a scenario is often found in children who have a 
non-displaced fracture of the tibia, known as the 
toddler's fracture.
     The toddler's fracture usually is a spiral fracture of 
the distal tibia without displacement.  Refer to Case 17 
in Volume 4, The Toddler's Fracture:  Accident or Child 
Abuse.  Sometimes the fracture is only picked up on 
follow-up radiographs or by bone scan.  In addition to 
the toddler's fracture, two other injuries noted in the 
limping toddler include fibula fractures caused by 
recurrent infant walker trauma and occult cuboid 
fractures.  Always consider the possibility of inflicted 
injuries when assessing infants and children with 
limping, and look for bucket handle fractures or corner 
fractures that are suggestive of child abuse.
     Also remember that contusions, muscle injuries, 
splinters, foreign bodies and shoe abnormalities can 
result in limping.  Teenagers and school age children 
may have sprains of the ankle, knee or hip resulting in 
limping.  Other traumatic causes of limping would 
include an avulsion fracture of the base of the fifth 
metatarsal, ankle sprains, and stress fractures of the 
metatarsals.  Salter Harris Type 1 fractures of the distal 
fibula may appear as simple ankle sprains.  Refer to 
Case 3 of Volume 3,  Ankle Injuries:  A Sprained 
Ankle?
     Also the limping patient may have torn his plantaris 
tendon.  This structure is an aponeurosis found in the 
lower leg posterior compartment and may rupture 
during exercise.  Patients report a snapping noise, then 
onset of pain.  Pain is increased with dorsiflexion.  
Treatment involves resting the lower leg (splinting and 
non-weight bearing) and analgesics.
     Patellofemoral disorders include patellar subluxation, 
recurrent patellar dislocation and chondromalacia 
patella.  This is more commonly seen in females and is 
easily aggravated by repetitive bending.  Permanent 
injury to the cartilage is rare.  Typically pain is elicited 
by squeezing the patella or is exacerbated by stair 
climbing.  Treatment includes anti-inflammatory 
medications, rest and ice applications.  Rarely, a 
surgeon may need to debride the underside of the 
patella.
     Ruptured vertebral disc is more a disease of adults 
but has been seen in teenagers, especially those 
involved in heavy weight training or arduous labor.  
Symptoms are similar to those found in adults with 
paresthesias, foot drop, or intractable pain.  Treatment 
depends on the extent of nerve impingement and may 
involve physical therapy, exercises, chemonucleolysis 
or surgery.
     Toxic/metabolic causes include drugs, rickets, 
scurvy, hyperparathyroidism.  Surprisingly, some drugs 
can cause limb pains and present as limping.  Vitamin A 
intoxication and carbamazepine have been implicated.  
Corticosteroids, ergotamine, phenothiazines and 
thiazides may cause muscle cramps.  Also, recall that 
some drugs can cause a lupus-like syndrome.  
Hypercalcemia can cause bone pains.  Rickets may be 
associated with fractures and pain.  The most common 
form of rickets seen in the U.S. is vitamin D-resistant.  It 
is inherited in an X-linked dominant manner.  The defect 
is in the proximal absorption of phosphate which leads 
to hyperphosphaturia.  Skeletal changes occur as the 
child ages.  Other metabolic diseases that affect the 
skeletal system include the mucopolysaccharidoses.  
All of these disorders usually involve some type of 
spinal deformity, with kyphosis being the most common.
     Neoplastic causes include benign bone tumors 
(unicameral and aneurysmal bone cysts), malignant 
bone tumors, metastatic bone disease, and leukemia.  
Sarcoma may involve the hip, femur or proximal tibia.  
Growing children are affected most often, with the peak 
incidence occurring in the teen years.  The two most 
often seen are Ewing's sarcoma and osteogenic 
sarcoma.
     Leukemia may present with limb pain or a limp.  
Metastatic disease from other primary sites such as 
neuroblastoma and lymphoma may also cause bone 
pain and limping.  Another cause of lower extremity 
weakness, and  hence limping, is a sacrococcygeal 
teratoma.  Benign bone lesions such as 
osteochondromas and osteoid osteoma may be found 
in the limping child.
     Degenerative causes include avascular necrosis of 
the femoral head (Legg-Calve-Perthe's Disease).  Legg 
described a non-tuberculous degeneration of the hip 
among American children in 1909 at the same time 
Perthes of Germany and Calve of France did.  
Originally thought to be due to some infectious process, 
Legg-Calve-Perthes (LCP) is currently believed to be 
caused by avascular necrosis of the femoral head 
ossification center.  It is seen in about 1 out of 750 
children who usually present between ages 4 and 10.  
Most likely LCP is due to repeated trauma to the hip in 
active boys which may impair the blood supply to this 
area.  Typical patients will complain of pain with hip 
motion and limp.  The pain may radiate down the thigh 
towards the knee.  Swelling and tenderness on exam 
are rare.  Other findings might include limited internal 
rotation, decreased hip abduction, and mild hip flexion 
contractures.  Occasionally, the thigh is atrophic.  
Laboratory examinations are all normal, and the 
diagnosis is made by plain radiographs of the hips once 
significant necrosis has occurred.  Radiographs may be 
negative early on.  Management of patients with LCP 
depends on when they present.  Young children who 
still have substantial femoral head cartilage have a 
good prognosis.  Goals of therapy include resolving the 
hip joint inflammation and positioning the femoral head 
in such a way as to promote healing.  If 50% or more of 
the femoral head can be seen, therapy is aimed at 
maintaining the range of motion until healing occurs.  
When more than 50% of the head is involved, 
orthopedists will place the hip in an abduction brace, or 
hip spica cast, or perform an osteotomy of the proximal 
femur to position the femoral head well into the 
acetabulum.  Usually the brace is used for children 
under 7, and osteotomy reserved for the older patient.  
Ultimately, the outcome for those who present with less 
than 50% of their femoral head involved is good.  
Children under 6 do very well, but those over 10 or 
those with flattening of the femoral head do not.
     Avascular necrosis of the tarsal navicular (Kohler's 
disease) can be difficult to diagnose.  Irregular 
ossification of tarsal bones is common and, when they 
occur in the absence of pain or swelling, the diagnosis 
should be that of a normal variant.  However when 
there is pain or swelling, Kohler's disease is present.  
This disorder typically is seen in boys between 4 and 7 
years.  Pain is aggravated by running.  Radiographs 
show a flattened navicular, which is radiodense and 
may appear fragmented. Bilateral changes occur 
commonly.  For severe symptoms, a short walking cast 
(3-6 weeks) may be helpful.  If asymptomatic, no 
treatment is needed.
     Sever's disease results in a painful heel and limping.  
It is most common in active children between 9 and 12 
years.  The calcaneal apophysis joins with the 
secondary ossification center to form the posterior 
portion of the calcaneus.  The Achilles tendon inserts 
onto the secondary ossification center.  Stress on this 
insertion results in microfractures, which lead to 
inflammation and pain.  Although it was previously held 
that the fragmentation and sclerotic changes seen on 
lateral radiographs of the calcaneal apophysis were 
diagnostic of this condition, it is now thought these 
changes represent one of several normal patterns for 
ossification.  The diagnosis is now made on clinical 
grounds with a typical history and tenderness at the 
insertion of the Achilles tendon.  Treatment may include 
heel pads or Achilles stretching prior to participation in 
sports.  Ice may also be of benefit following exercise.  
Refer to Case 20 in Volume 1, Sever's Disease.
     Osgood Schlatter's disease is characterized by pain 
just below the knee in the vicinity of the tibial tuberosity.  
This disease is felt to be due to repeated microtrauma 
to the insertion of the patella tendon, similar to Sever's 
disease.  It occurs most often in adolescent boys during 
accelerated growth.  The diagnosis is made based on 
the presence of tenderness to palpation over the tibial 
tuberosity.  The tuberosity may be more prominent.  No 
effusions should be found and the pain should be 
exacerbated by forced extension against resistance or 
jumping repetitively.  Resolution occurs when the 
secondary ossification center fuses to the proximal 
tibia, which occurs with maturation. Treatment is limiting 
activity and also may involve immobilization and 
anti-inflammatory medications.
     Slipped capital femoral epiphysis (SCFE) is a medial 
or posterior slipping of the femoral capital epiphysis.  It 
often presents with a limp.  This diagnosis is difficult to 
make and is often delayed.  SCFE patients are usually 
overweight or have had a significant shear stress 
applied to the femoral head.  SCFE will often present 
with knee pain, thigh pain, groin pain, or hip pain.  
SCFE should be considered when pain in one of these 
areas is present.  Physical exam finds the hip externally 
rotated with painful range of motion, especially to 
internal rotation, abduction and flexion.  Early 
symptoms may be subtle.  Delaying the diagnosis 
results in worsening of the condition and a poorer 
outcome.  Refer to Case 10 in Volume 2, Thigh and 
Knee Pain in an Obese 10-Year Old.
     Osteochondritis dessicans is a disease in which a 
small island of bone dies and is then sloughed.  
Typically, the child complains of poorly localized knee 
pain.  Osteochondritis dessicans commonly presents in 
the preteen or early adolescent.  Pain with full flexion is 
usually found.  If there is a piece of sloughed bone, one 
may find an effusion.  Locking of the knee can occur 
while in flexion.  Typically involving the distal femur, 
osteochondritis dessicans can be easily identified on 
plain AP radiographs of the femur.  Treatment starts 
with immobilization.  Isometric exercises may help 
retain quadriceps tone.  Arthroscopic surgery is 
indicated for continued pain.
     Freiberg's disease is another example of avascular 
necrosis.  This time the second metatarsal is involved.  
Treatment for this one is use of a shoe insert to ease 
weight bearing.  Other osteochondroses such as 
Scheurmann's (involving the spine) or Ashman's 
(involving the 5th metatarsal) can present as limping.
     Neuromuscular conditions include any disease 
causing weakness in the hip girdle or lower spine or 
extremities which can present as limping.  The reader is 
referred to standard neurology texts for more 
discussion on the myopathic or neuropathic entities.
     Miscellaneous causes include sickle cell disease, 
hemophilia, tarsal coalition, Blount's disease, 
conversion reactions/hysteria, and growing pains.  
Blount's Disease is a major cause of angular 
deformation in children.  It is also called infantile tibia 
vara and results from some problem with the growth of 
the posteriomedial aspect of the tibial physis.  
Physiologic bowing usually has resolved by age 3, but 
Blount's disease advances to more severe angulation.  
Bracing is needed for those children between 14 and 30 
months if the metaphyseal-diaphyseal angle is 9 to 16 
degrees and the knee is unstable when walking.  Tarsal 
coalition is a congenital disorder that results in a vertical 
talus with a fixed foot deformity.  Patients usually 
present with foot pain and limping.
     Conclusion:  Limping is a common symptom found 
in pediatric patients.  The evaluation of these patients 
requires a careful history and detailed examination.  
There are many other sources which discuss limping.

References
     Lee RW, Demos TC.  Limp and Altered Gait.  In:  
Rosen P, Doris PE, Barkin RM, et al (eds).  Diagnostic 
Radiology in Emergency Medicine, 1992, St. Louis, 
Mosby YearBook, pp. 509-540.
     Dabney KW, Lipton G.  Evaluation of limp in 
children.  Curr Opin in Pediatr 1995;7:88-94.
     Tolo VT, Wood B.  Hip and Thigh.  In:  Tolo VT, 
Wood B.  Pediatric Orthopedics in Primary Care.  
Baltimore, Williams and Wilkins, 1993, pp. 135-168.
     Sheenan KM,Gordon S, Tanz R.  Bilateral fibula 
fractures from infant walker use.  Pediatric Emerg Care 
1995;11(1):27-29.
     Simonian PT, et al.  Fracture of the cuboid in 
children.  J Bone Surg 1995;77: B104-106.
     Illingworth RS.  Limp, Limb and Bone Pains.  In:  
Illingworth RS.  Common Symptoms of Disease in 
Children.  Oxford, Blackwell Scientific Publications, 
1979, pp. 239-243.
     Swischuk LE, John SD.  Bones and Soft TIssue.  In:  
Swischuk LE, John SD.  Differential Diagnosis in 
Pediatric Radiology.  Baltimore, Williams and Wilkins, 
1995, pp. 187-263.
     Causey AL, et al.  Missed Slipped Capital Femoral 
Epiphysis:  Illustrative Cases and a Review.  J Emerg 
Med 1995;13(2):175-189.