Obese Adolescent With Knee Pain

December 31, 2006

Tanisha, 12 years old, comes to your office with left knee pain. Her father says she has complainedfor about 10 days, but she insists that the pain began about 3 weeks ago. When askedabout the quality of the pain, she responds by saying, “It just hurts.” She denies any injury ordiscomfort involving the hip or ankle and direct trauma to the knee. She rarely plays sportsor games that involve intense running or other physical activity. There is no recent history offever or respiratory or GI symptoms.

PATIENT PROFILE:


Tanisha, 12 years old, comes to your office with left knee pain. Her father says she has complainedfor about 10 days, but she insists that the pain began about 3 weeks ago. When askedabout the quality of the pain, she responds by saying, "It just hurts." She denies any injury ordiscomfort involving the hip or ankle and direct trauma to the knee. She rarely plays sportsor games that involve intense running or other physical activity. There is no recent history offever or respiratory or GI symptoms.You watch Tanisha as she crosses the room. She is obese and limps with a notably antalgicgait. The left foot is turned slightly outward compared with the right foot. You arestruck by the presence of genu valgum, but her father states that she has "walked like thatsince she was a toddler." As she climbs onto the examining table, Tanisha smiles at you andsays, "My dad thinks I'm faking this so that I don't have to go to school." Her father shrugsand responds, "It wouldn't be the first time!"You first inspect both knees side-by-side. There is no visual deformity, or swelling or effusionaround the patella. Palpation of the tibial tubercle elicits no response, which lowers yoursuspicion of Osgood-Schlatter disease. Milking the patella fails to produce any fluid bulge.Tanisha denies pain when you compress the patella against the femur, which decreases yoursuspicion of patellofemoral stress syndrome. Results of the anterior and posterior drawer andLachman tests are negative, and the absenceof laxity in the medial or lateral menisci diminishesyour concerns about a ligament injuryaround the knee joint.

WHAT WOULD YOU DO NOW?

A.

Obtain anteroposterior (AP) and lateralx-ray films of the knee.

B.

Offer a trial of RICE (Rest, Icing,Compression, and Elevation of the affectedjoint) and NSAIDs, and reevaluate thepatient in 1 week.

C.

Evaluate the hip joint and obtain x-ray films.

D.

None of the above.THE CONSULTANT'S CHOICE
Option

C

is the correct response. Hip injuries orpathology can often present as thigh/knee pain, becauseof the innervation pattern of the obturator nerve.In addition, the observation that the left foot is turnedslightly outward suggests that the outward rotationlikely emanates from the hip joint rather than from theknee. Given the absence of point tenderness or otherphysical findings around the knee joint, x-ray films ofthe knee would probably be of low yield. RICE andNSAIDs might be appropriate if physical findings suggesteda knee sprain, but once again, the absenceof such findings in the presence of the antalgic gaitmakes this diagnosis unlikely. (The genu valgum is ared herring in this case.)

WHAT WOULD YOU DO NOW?

A.

Request emergent consultation with anorthopedic surgeon.

B.

Continue RICE and NSAIDs to treat thepain emanating from the hip.

C.

Refer the patient for physical therapy.

D.

Reassure the parents that this is a commoncondition seen in young, obese adolescents,and encourage weight loss through a dietand exercise regimen.THE CONSULTANT'S CHOICE
Choice

A

is the only correct answer here. SCFE isan orthopedic emergency and, once diagnosed, treatmentmust be started immediately. Although weightloss (choice

D

) is an important component of long-termtherapy, the acute focus should be on saving the hipjoint in an adolescent.SLIPPED CAPITAL FEMORAL EPIPHYSIS
SCFE usually occurs during the period of peakgrowth velocity (in males, ages 13 to 15; in females,ages 11 to 13), making it the most common hip disorderin young adolescents. During this time of rapid growth,a "stress fracture" of sorts occurs through the growthplate of the femoral epiphysis, thereby displacing thehead of the femur from the femoral neck. The displacementmay occur acutely (secondary to trauma), or itmay develop over a long period. Chronic SCFE is usuallyassociated with obesity: excess weight provides an additionalshearing force through the growth plate.Patients of African descent tend to be affectedmore often than Caucasians, and males tend to be affectedtwice as often as females. The overall incidence isabout 4 to 8 per 100,000 persons. While the disorder ismost commonly unilateral, it presents bilaterally in approximately10% to 20% of patients.Clinically, an adolescent presents with knee, hip,thigh, or groin pain without a history of trauma. Thepatient may limp and may walk with the affected leg externallyrotated. On physical examination, the hip maybe held in external rotation at rest--something mostcommonly noted when compared with the contralateralhip.Chronic SCFE can manifest with mild atrophy of thequadriceps muscle. Abduction, adduction, flexion, and internalrotation of the hip joint are often limited by pain.Slip severity is typically characterized by 4 possiblepresentations

(Table).

When evaluating a young adolescent with hip orknee pain but with no physical findings, suspect a SCFEuntil the diagnosis is ruled out via hip x-ray films. In additionto the AP views, order a frog-leg lateral view ofthe hips. A positive x-ray finding shows the displacementof the femoral head from the femoral neck. Radiologistsand orthopedists refer to the Klein line (a line drawnmedially from the superior portion of the femoral neckthrough the head of the femur) whenmaking the diagnosis. If the Kleinline does

not

intersect the femoralhead on either the AP or frog-leglateral view, then SCFE is suspected(see

Figure

).Once the diagnosis of SCFE ismade, immediately request consultationwith an orthopedic surgeon.The orthopedist will typically bringthe patient to the operating roomand insert threaded screws throughthe femoral neck, growth plate, andepiphyseal head to stabilize thejoint, thus preventing further slippage.Delays in treatment can leadto worsening slippage, avascularnecrosis of the femoral head, or degenerativejoint disease--all ofwhich result in lasting morbidity forthe adolescent.Visual inspection of Tanisha's hip joints reveals nogross deformity, although the left hip is slightly abducted.Direct palpation of the left hip joint is unremarkable.With Tanisha's knee and hip extended, you attempt torotate the left hip internally and externally, but your examinationhere is limited because Tanisha cries out inpain. You then attempt to flex and abduct the hip--onceagain without success because of pain.You decide to order hip films--an AP view aswell as a frog-leg lateral view. Tanisha is wheeled tothe radiology suite. About 45 minutes later, the radiologistcalls you and reports that the examination ispositive for slipped capital femoral epiphysis (SCFE)

(Figure).