A patient, aged 16 years, presented to the office with anterior medical knee pain after being hit during a hockey game. The patient denied any prior knee pain before this injury.
On exam of the knee, a subtle laxity with valgus stress consistent with a medial ligament (MLC) sprain was found. The rest of the exam was unremarkable.
When reviewing the patient’s x-rays, a well circumscribed radiolucent lesion on the medial side of the proximal tibia was noted.
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Non-ossifying fibromas, or fibrous cortical defects, are the most common tumor in childhood and are estimated to be present in 30% of all children and adolescents.
Common locations include the metaphysis of long bones — particularly in the distal femur, proximal tibia, and distal tibia. The lesion is asymptomatic and typically found incidentally on x-ray.
X-rays will show a radiolucent, multilocular appearance that is surrounded by a sclerotic rim of bone. The lesions expand toward the diaphysis with growth of the bone during childhood. Most lesions will regress during skeletal maturity and ossify into adulthood.
Because most non-ossifying fibromas will ossify with time, conservative treatment with observation is the first line treatment. Lesions that are located in high stress areas, composed of 50% or more of the bone diameter, and have thin cortices are at high risk of pathological fracture.
Curettage and bone grafting may be indicated in large symptomatic lesions and in lesions with an increased risk of fracture. Pathological fracture resulting from non-ossifying fibromas can be treated with closed treatment in most cases.
Dagan Cloutier, MPAS, PA-C, practices in a multispeciality orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- McKean J. (2015, May 8.) Non-ossifying fibroma. Retrieved from http://www.orthobullets.com/pathology/8027/non-ossifying-fibroma
- Temple HT, Scully SP, Aboulafia AJ. (2002). AAOS Instructional Course Lectures. 2002; (51) 429-439.
All electronic resources were accessed on April 9, 2015.