Cortical desmoid
Cortical desmoid (also called tug lesion or periosteal desmoid) is an irregularity of the distal femoral cortex caused by repetitive stress at the attachment of the adductor magnus aponeurosis. It is most commonly seen in adolescents and is usually asymptomatic. It is a benign and self-limiting lesion.

References
Gould CF, Ly JQ, Lattin GE, Beall DP, Sutcliffe JB (2007). "Bone tumor mimics: avoiding misdiagnosis". Curr Probl Diagn Radiol. 36 (3): 124–41. doi:10.1067/j.cpradiol.2007.01.001. PMID 17484955.