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IMAGING

A 15-Year-Old Male With Persistent Knee Pain

Shea, Sheila Sanning MSN, RN, ANP, CEN

Editor(s): Ramirez, Elda G. PhD, RN, FNP-BC, FAANP; Column Editor

Author Information
Advanced Emergency Nursing Journal: July/September 2011 - Volume 33 - Issue 3 - p 205-211
doi: 10.1097/TME.0b013e31822611d0
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Abstract

THE EMERGENCY DEPARTMENT (ED) often serves as a portal for access to primary care for many nonurgent patients. Difficulty or delay in being seen by a primary care provider has resulted in an increase in ED visits for seemingly minor problems such as medication refills. However, care should be taken to avoid overlooking occult or potentially serious presenting problems. It is essential that every patient encounter includes a thorough reason for visit, history, medical screening examination, and evaluation.

CASE STUDY

Chief Complaint

A 15-year-old Hispanic boy presented to the ED with his father who requested a medication refill for ibuprofen.

History of Present Illness

The patient reported a history of chronic right-knee pain for about 1 month. He denied direct trauma or overuse injury, and he was not involved in any sports. There had been no previous episodes of similar pain. He described the pain as a mild-to-moderate dull ache that was nonradiating and localized to the inner upper-knee area. His pain had recently increased, especially with exercise and occasionally at night. He could now feel a painful lump in the area. The patient had been ambulatory and obtained only partial relief with the use of nonsteroidal anti-inflammatory drugs. No fever, sweats, rash, back pain, hip, groin, or thigh pain were observed. There were no other musculoskeletal complaints. He had been seen twice by his pediatrician for the problem; he could not get an appointment for over a week and the father had run out of ibuprofen.

Medical History

There were no past medical problems and no previous surgery or hospitalizations.

Current Medications

Ibuprofen and multivitamins are the current medications.

Allergies

No medication, food, or environmental allergies are found.

Immunizations

Routine childhood immunizations are up-to-date.

Social History

The patient lives with both parents and two younger siblings. He is not involved in any sports or athletic activities. The patient denies illicit drug or alcohol use. He is not sexually active.

Family History

The patient's 45-year-old father is well without any known medical problems. His mother is 43 years old, and she is also well. Medical history for out-of-country grandparents is largely unknown, although the maternal grandmother may have diabetes. There is no known family history of malignancy.

Physical Examination

The patient was awake, alert, and oriented in no acute distress. He was able to ambulate to the treatment area without difficulty or antalgic gait. His general appearance was that of a thin, short-stature adolescent teenager.

Vital Signs

Temperature 98.8 °F (37 °C); blood pressure 118/68 mmHg; and heart rate normal at 76 beats per minute are noted. Respirations are 16 unlabored with oxygen saturation within normal limits at 98% on room air. Pertinent physical examination findings are shown in Table 1.

Table 1
Table 1:
Patient physical examination

DIFFERENTIAL DIAGNOSES

Adolescent knee pain is a common problem and is often related to sports or minor injuries. Common differential diagnoses include patellar subluxation or patellar tendonitis, Osgood-Schlatter lesion, sprains of medial/lateral collateral ligaments, osteomyelitis, or osteochondritis dissecans. Internal derangement may be due to meniscal tears or anterior or posterior cruciate damage. Referred pain may be related to a slipped capital femoral epiphysis. Still other causes include rheumatoid arthritis, inflammatory arthopathy, septic arthritis, or malignancy (Table 2). Other potential problems to consider in any pediatric patient with limp or trouble bearing weight are listed in Table 3.

Table 2-a
Table 2-a:
Common differential diagnoses of adolescents with knee pain
Table 2-b
Table 2-b:
Common differential diagnoses of adolescents with knee pain
Table 3
Table 3:
Other potential causes of pediatric limp

PATIENT MANAGEMENT AND FINDINGS

An oral narcotic analgesic was administered, with good reduction in the patient's discomfort. A discussion was held with the father regarding the potential causes of persistent knee pain and options for investigation. On the basis of the length of time since onset of symptoms and recent increase in pain, initial assessment would begin with radiographic evaluation.

Radiological Studies

Any suspected bony lesion should be evaluated in at least two views, and plain radiographs of the right knee were ordered, including anteroposterior and lateral views (Figure 1). Interpretation of the films revealed no fracture, no obvious soft tissue mass, and patent epiphysis. However, in the region of the metaphysis to diaphysis of distal femur, there was a mottled lucent lesion with localized periosteal reaction. A femur radiograph was then ordered, which showed a lesion of the mid to distal femur approximately 12 cm in length with periosteal thickening, although not “onion skin.”

Figure 1
Figure 1:
(a) Anterior–posterior right femur radiograph; (b) anterior–posterior right knee radiograph; (c) lateral knee radiograph; (d) oblique knee radiograph. Reproduced with permission from Long Beach Emergency Medical Group, CA.

As the tumor grows, the periosteum cannot create new bone as fast as the lesion; there may be several layers of new calcified bone as the mass expands. This appears as rings of bone over the tumor. The periosteal growth has the appearance of layers of onion skin. The osteosarcoma tumor is an irregular solid mass that can appear “moth eaten,” “fir-tree,” or “sun-burst” on radiologic examination (Mehlman & Cripe, 1). Tumors may be osteolytic (loss of bone density), osteoblastic (bone forming), or a combination of both processes. Tiny spike-like points are visible because of the formation of a new subperiosteal lesion as the periosteum is raised by the tumor. This area of new bone growth is known as “Codman's triangle” (Mehlman & Cripe, 2010). Although films can be suggestive of osteosarcoma, a bone biopsy is required for definitive diagnosis. Immediate concern about the possibility of malignancy prompted an order for a scout chest radiograph that was negative for the evidence of unexplained nodes, masses, or bony changes. Later, comprehensive workup would likely include both computed tomographic scan and magnetic resonance imaging to assess for pulmonary metastasis and extent of the primary lesion.

Lateral plain radiograph of the knee revealed an osteosarcoma of the distal femur. The lesion was mainly posterior, with disruption and elevation of the periosteum (Codman triangle), and extended beyond the bone into the soft tissue.

Laboratory Studies

Baseline diagnostic laboratory studies were performed. Complete blood cell count with differential was unremarkable with a normal white blood cell (WBC) count of 10.2. A basic metabolic panel was also within normal limits. Lactate dehydrogenase was normal at 64 U/L and alkaline phosphatase normal at 70 U/L. Erythrocyte sedimentation rate was elevated at 106 mm/hr. Routine urinalysis was also unremarkable. Simultaneous consultation with the local tertiary pediatric medical center was made, and the patient prepared for urgent transfer for pediatric oncology and orthopedic management with a provisional diagnosis of osteosarcoma.

Although many children who present to the ED with inability to bear weight have minor problems, laboratory testing may be indicated if an exact etiology is not immediately apparent. Complaints of persistent extremity bone pain or limp require a diligent search for the cause. A detailed history and physical examination and access to follow-up care will help to determine the diagnostics to be ordered. A complete blood cell is important to detect the possibility of infection or malignancy. An abnormal (WBC), hematocrit level, or platelet count may indicate early evidence of serious illnesses such as leukemia or osteosarcoma. The presence of fever and an elevated WBC (>12,000 cells/mm) in conjunction with an elevated erythrocyte sedimentation rate (>40 mm/hr) or C-reactive protein level suggest a septic arthritis condition. Blood cultures are usually obtained in the evaluation of a child with fever and limp. A basic metabolic panel and urinalysis are done to establish a baseline and evaluate renal function. Aspartate aminotransferase, alanine aminotransferase, bilirubin, and albumin levels may be obtained to assess liver function. Rare in children, a diagnosis of gout may be identified by an elevated serum uric acid level. Of note, in patients with osteosarcoma, measurement of lactate dehydrogenase and alkaline phosphatase levels provide the only reliable prognostic indicator of disease and patient outcome (Mialou, 2005).

DISCUSSION

Extremity pain and swelling are among the most common presenting complaints of children with osteosarcoma (also known as osteogenic sarcoma). Osteosarcoma is the most common primary malignant bone cancer in children (Cripe, 2010). The metaphyseal areas of fast-growing tubular long bones are most often affected with the distal femur, the most common site affected (Cripe, 2010; Mehlman & Cripe, 2010). Other areas include the proximal humerus or tibia and, less frequently, the ribs, spine, pelvis, or mandible. Unfortunately, metastasis is common, especially to the lungs, and is the usual cause of death.

This aggressive cancer is most often found in adolescents and young adults, and there is a slight increase in incidence in males. Current data show the incidence in the United States to be about 400 cases per year or 4.8 cases per million persons less than 20 years of age (Cripe, 2010).

Implications for Advanced Practice Nurses

Nurses are usually the first point of contact for most patients presenting to the ED either during a traditional triage interaction or during a medical screening examination by an advanced practice nurse. The majority of patients seen in the ED have minor problems or primary care issues, but there are instances when a minor complaint is a subtle indicator of a more-serious medical condition. This case of bone tumor causing unilateral bony extremity pain is one such instance. Other scenarios are patients with persistent low back pain, thought to be musculoskeletal in nature, masking unrecognized malignancy, or areas of unexplained lymphadenopathy. A seemingly innocuous request for a medication refill should prompt the nurse to question why the patient is having continued or increasing pain.

CONCLUSION

Most children and adolescents who present to the ED with extremity pain have minor injuries or musculoskeletal problems that are easily diagnosed and managed. Patients with undiagnosed bone tumors often have symptoms that are insidious and subtle and easily dismissed as insignificant findings. A history of a child or teenager with persistent extremity pain lasting more than a few weeks or pain that wakes the child at night is of clinical concern and requires investigation. It is essential to take the time during the initial screening examination to determine the real reason for each patient's ED visit and review previous medical care. In the case of this teenager with persistent extremity pain, a simple radiograph may have saved his life.

REFERENCES

Cripe T. (2010). Pediatric osteosarcoma. Retrieved March 25, 2011, from http://emedicine.medscape.com/article/988516-overview
Mehlman C., Cripe T. (2010). Osteosarcoma. Retrieved March 25, 2011, from http://emedicine.medscape.com/article/1256857-overview
Mialou V. (2005). Metastatic osteosarcoma at diagnosis. Cancer, 104 (5), 1100–1109. Retrieved March 2, 2011, from http://onlinelibrary.wiley.com/doi/10.1002/cncr.21263/abstract
Rabinovich C. E. (2010). Juvenile rheumatoid arthritis. Retrieved March 26, 2011, from http://emedicine.medscape.com/article/1007276-overview
    Keywords:

    child with limp; pediatric orthopedics; pediatric osteosarcoma; pediatric persistent; knee pain

    © 2011 Lippincott Williams & Wilkins, Inc.