Pediatric emergency medicine trisk 213

traumatizing the tendon’s insertion on the tibial tubercle during the child’s growth
spurt. The patients have localized tenderness and occasional swelling over the
tibial tubercle. The patient will refuse to extend the knee against force (e.g.,
perform a deep knee bend) and have difficulty going up or down stairs, although
they may have a normal gait on a level surface. To eliminate the possibility of a
neoplasm or a secondary avulsion if there is an acute change, the physician
should obtain radiographs. In Osgood–Schlatter disease, the radiographs will be
normal or show irregularity of the tubercle.
Patellofemoral dysfunction (PFD) or patellofemoral pain syndrome may be
caused by misalignment of the extensor mechanism of the knee. The vastus
lateralis, vastus intermedius, and rectus femoris pull the patella slightly laterally
and need to be balanced perfectly by the vastus medialis to keep the patella
tracking across the articular cartilage correctly. The patient with PFD may have
patellar pain with running and especially while going down inclines or stairs. The
patient may also have the sensation of the knee giving out when descending,
although an actual fall does not usually occur. The patient may describe pain
when sitting for a prolonged time with the knee flexed at 90 degrees (e.g., in
class). The pain disappears once the patient is ambulatory. On examination, the
patient may have a medially displaced patella, tenderness of the articular surface
of the patella, and a positive patellar stress test. This test is performed with the
patient in the supine position with the knee fully extended. The patient is asked to
relax the quadriceps so that the physician can move the patella. With the patella
pulled inferiorly, the physician should gently press down on it and ask the patient
to tighten the quadriceps. The patient should be asked to “push the knee into the
examination table.” This will move the patella superiorly as the physician
continues to press down. A patient with PFD will have acute pain with this
maneuver. Radiographs are normal.
Patellar tendonitis, or “jumper’s knee,” occurs in patients during their growth
spurt, especially those involved in jumping (knee extension) sports. The knee is
tender on the inferior pole of the patella and the adjacent patellar tendon, but not
on the tibial tubercle; radiographs are generally normal.

Prepatellar bursitis occurs after acute or chronic trauma to this bursa, which
overlies the patella. The patient will have swelling over the anterior aspect of the
knee, especially over the patella. A septic bursitis may need to be ruled out by
needle aspiration.
Osteochondritis dissecans (OCD) is the separation of a small portion of the
femoral condyle with the overlying cartilage. The patient is usually an adolescent
with a 1- to 4-week history of nonspecific knee pain. The physical examination


may be normal, or the femoral condyle may be tender with the knee flexed.
Because AP and lateral radiographs may not show the lesion, a tunnel or
intercondylar view should be obtained.
Iliotibial (IT) band syndrome usually occurs in older runners who complain of
pain over the lateral femoral condyle. The repetitive movement of the IT band
across the lateral femoral condyle as the knee flexes and extends causes this pain.
When examined, the patient is tender over the lateral femoral epicondyle,
palpable 2 cm above the joint line. Radiographs are normal.
The Baker cyst is a herniation of the synovium of the knee joint or a separate
synovial cyst located in the popliteal fossa. The patient complains of popliteal
pain and swelling only if the cyst enlarges. The sac may be palpated in the
posterior medial aspect of the popliteal space. For the most part, radiographs will
be normal or show soft tissue swelling. Ultrasound may be needed to diagnosis
Baker cyst.
In any patient with knee pain, with or without a history of trauma, the
following must be considered: benign (e.g., osteochondroma and nonossifying
fibroma) and malignant tumors (e.g., osteosarcoma or Ewing sarcoma), the
various causes of monoarticular arthritis (see Chapter 60 Pain: Joints ) and hip
disease that may present with knee pain (e.g., slipped capital femoral epiphysis or
Legg–Calvé–Perthes disease, an idiopathic avascular necrosis of the proximal
femoral epiphysis).

EVALUATION AND DECISION
Four points are critical in the patient’s history: (i) the activity and forces that led
to the injury (e.g., direction of the force, whether the foot was fixed); (ii) the
initial location of the pain; (iii) any sensations or noises (e.g., “locking,” “pops,”
or “tears”); and (iv) the timing of any swelling.
Most severe injuries (e.g., ACL, collateral ligament, or meniscal injuries) occur
with high-velocity weight-bearing activities, especially running and pivoting, or
direct valgus or varus stress. Direct trauma to the front of the knee may cause
posterior cruciate ligament injuries or patellar fractures, whereas lateral or medial
forces may cause collateral or cruciate ligament damage or fractures.
Although the knee may “hurt all over” when seen in the ED, the patient may be
able to localize the initial pain. Meniscal or collateral ligament injuries cause pain
on the lateral or medial aspect of the knee, whereas ACL injuries hurt just inferior
to the patella, and Osgood–Schlatter disease is painful over the tibial tubercle.
Distinct popping noises or tearing sensations are reported in ACL injuries and
patellar dislocation. Locking of the knee may be reported in meniscal injuries but


usually not immediately after the injury. The sensation of the knee “giving out”
may occur with meniscal injuries or PFD.
Swelling after acute injury should raise concern for significant pathology.
Swelling within 2 hours strongly suggests hemarthrosis from an ACL injury,
meniscal injury, or osteochondral fracture, while swelling with other knee
fractures is commonly seen later.
The possibility of abuse in young children must always be considered,
especially if the injury is unexplained, the history is implausible, or the delay in
seeking medical care was unreasonable.
In subacute injuries, ask about hip or groin pain because the hip and knee share
sensory nerves. Legg–Calvé–Perthes disease or a slipped capital femoral

epiphysis may cause anterior thigh or knee pain. Patellar pain and the sensation of
the knee giving way without actually falling when going down stairs or inclines
suggest PFD.
Examination of the patient should include walking and standing, if possible, to
check for medially deviated “squinting” patellae. Inspect and palpate the knee in
two positions, sitting relaxed with the knees at 90 degrees and supine. When
sitting, inspect the knees for swelling and tenderness (e.g., swelling and
tenderness over the tibial tubercle in Osgood–Schlatter disease, or joint line
tenderness in meniscal injuries). With the patient supine, repeat inspection and
palpation over the joint line, collateral ligaments, patella, proximal fibula, tibial
tuberosity, and popliteal space. If the knee appears swollen, check for an effusion
by milking any joint fluid centrally toward the patella. Normally, synovial fluid
coats the patellar surface but does not separate the patella and femur. When fluid
separates the two bones, a sharp pat on the patella results in the sensation of a tap
as the two bones meet. If the joint contains a large amount of fluid, the patella
will not touch the femur but will feel as if it is sitting on a cushion. Assess both
active and passive ROM of the knee.
The physician should test for collateral and cruciate ligament damage, meniscal
injuries, patellar subluxation, and PFD, using the appropriate maneuvers ( Table
42.2 ) although most maneuvers have poor diagnostic accuracy when used in
isolation after an acute injury.


TABLE 42.2
SUMMARY OF DIAGNOSTIC MANEUVERS FOR THE INJURED
KNEE
Maneuver

Diagnosis

Collateral laxity test
(Fig. 42.4 )
Lachman test (Fig.
42.3 )
Posterior drawer test
(Fig. 42.5 )
McMurray test (Fig.
42.6 )
Apley compression
test (Fig. 42.7 )
Patellar apprehension
test
Patellar stress test

Collateral ligament injury
Anterior cruciate ligament injury
Posterior cruciate ligament injury
Meniscal injury
Meniscal injury
Patellar subluxation
Patellofemoral pain syndrome

A neurovascular examination should include palpation of the posterior tibial
and dorsalis pedis pulses and testing of the peroneal nerve function. The deep
peroneal nerve innervates the ankle dorsiflexors and the extensor hallucis longus,
which can be tested by opposing dorsiflexion of the great toe. It also supplies
sensation to the web space between the great and second toes.
Patients with knee symptoms should have a careful hip examination because
patients with avascular necrosis of the femoral head or a slipped capital femoral
epiphysis may present with anterior thigh or knee pain.

All patients with acute knee injuries should have AP and lateral radiographs,
and if indicated, a patellar (or skyline view) radiograph. The Ottawa Knee Rules
have demonstrated 100% sensitivity for knee fractures in large, prospective,
multicentered adult trials. Studies in children are limited but they also
demonstrated a sensitivity of 100% (95% confidence interval = 95% to 100%) in
a study involving 750 children of whom 70 had fractures. According to these
rules, radiographs are required of children only if the patient has any of the
following findings: (i) isolated tenderness of the patella, (ii) tenderness of the