This 24-year-old female football player presented with a long history of activity-related anterior knee pain. The pain was vague and poorly localised. It was typically aggravated by running, sitting for prolonged periods and by going down stairs. She had not noted any swelling, mechanical symptoms or instability. On examination she had poor single-leg stability, pain with patellofemoral joint compression and an otherwise normal examination.
X-ray image of the knee show a sessile osteochondroma involving the anterior and medial aspect of the distal femoral shaft. This extends over a length of approximately 50 mm and has a depth of approximately 10 mm. There is no overlying calcification or other abnormality identified involving the distal femur. The MRI further demonstrates what is a small distal femoral exostosis arising from the antero-medial cortex. There is continuity of cortical and medullary bone between the exostosis and the femur and there is only a very thin/almost imperceptible cartilage cap. The osteochondroma is distorting the muscle belly of the vastus medialis but there is no fluid collection over the superficial surface of the osteochondroma to indicate adventitial bursa formation.
Based on the characteristic signs and symptoms this patient was diagnosed with patellofemoral pain. MRI imaging was obtained to further evaluate the lesion given that it was in the general region of the patient’s pain. Based on the characteristics of the patient’s pain and the x-ray findings the osteochondroma was not felt to be symptomatic. A physiotherapy programme was implemented. She was able to continue to play football and her symptoms progressively improved with a cycle-based programme, work on the kinetic chain and with some taping of the patellofemoral joint.
Osteochondromas are an overgrowth of cartilage and bone that happens at the end of bones near the physis. They generally affect the long bones in the leg, the pelvis, or the scapula. They may be pedunculated (on a stalk) or sessile (like this one). They generally occur/present between ages 10 and 30, affect males and females equally and are the most common noncancerous bone growth. As this case illustrates most patients do not have any associated symptoms. The most common problems that can be caused by osteochonromas are pressure or irritation with exercise, soreness of the nearby muscles or a sense of locking or catching in the region of then osteochondroma. In most cases no treatment (other than reassurance) is needed. When there is associated pain or mechanical symptoms surgical excision can be contemplated.
There is a very small chance of malignant transformation. It is important to explain this to patients and to encourage them to return should they develop additional symptoms.
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