A girl, age 13 years, 4 months, presented to her primary care provider’s office for a well visit. Among her concerns, she mentioned a “bump” she had had on her right leg “for the past six months, maybe longer.” The area felt irritated when touched or when the patient “ran too much.” She had seen no change in the bump since she first noticed it. The patient knew of no trauma or other preceding factors. She denied any fever or warmth, redness, or ecchymosis to the area.
Medical history was unremarkable except for familial short stature and myopia. The patient was the fifth of eight children born to nonconsanguinous parents. She denied any surgical history or hospitalizations and was premenarcheal. She was up to date on all age-appropriate vaccines, with her meningococcal vaccine administered at that visit.
The patient’s blood pressure was 99/58 mm Hg with an apical pulse rate of 82 beats/min. Her growth parameters were following her curve. Her height was 55” (0.3 percentile); weight, 81 lb (7.5 percentile); and BMI, 18.8 (48.6 percentile).
The physical exam was normal with the exception of the musculoskeletal exam. Examination of the lower extremities revealed a palpable, 4 cm x 5 cm lesion at the right distal medial thigh just proximal to the knee. The lesion could not be visualized but on palpation was tender and firm. There was some question as to whether the lesion itself or inflamed soft tissue overlying the lesion was mobile. No overlying warmth, induration, erythema, or ecchymosis was noted.
Passive and active range of motion was intact at the hip and knee. No lesions to the upper extremities were evident, and no scoliosis was seen.
Blood work was done to rule out certain diagnoses. Results from a complete blood count with differential, lactate dehydrogenase (LDH), parathyroid hormone, lipid profiles, thyroid function, and a comprehensive metabolic profile were unremarkable. A low level of vitamin D 25-OH was detected: 21.7 ng/mL (normal range, 32 to 100 ng/mL).
Distal femur x-rays with posteroanterior, lateral, and oblique views were ordered. The imaging revealed a 3 cm x 3 cm lesion projecting from the “distal, somewhat medial” femur, which was diagnosed as a benign femoral osteochondroma. Significant inflammation to the surrounding soft-tissue structures was observed. A questionable old fracture of the osteochondroma was noted. The remaining bony structures and joints appeared normal.
An ultrasound of the lesion was also ordered to investigate soft-tissue swelling. This revealed a hypoechoic collar around the distal end of the osteochondroma, which could represent a fluid collection, hematoma from trauma, or bursitis. The soft tissues were deemed normal.
Because of the extent of inflammation, the radiologist recommended MRI without contrast to rule out bursitis or trauma to the osteochondroma.