Five patients with Paget's disease involving the patella were evaluated for the following radiographic features: trabecular pattern, cortical integrity, density, and size of the affected patella. Radiographic appearances consisted of minimal trabecular coarsening in the patella of nearly normal size and progressed to considerable cortical thickening and osteoblastic remodeling in a dramatically enlarged patella. The radiologic features of Paget's disease of the patella are distinctive and should obviate biopsy.