Posttraumatic fat necrosis and lipoatrophy can occur in the subcutaneous fat following falls, blunt injury, surgery, and minor procedures or injections. While these processes have no inherent serious medical consequences, they occasionally require treatment due to severe or concerning symptoms. Three patients (all women; average age, 47 years) who sustained blunt trauma to the pelvis and were diagnosed with posttraumatic fat necrosis or lipoatrophy were retrospectively identified from our orthopedic oncology records. All patients recalled blunt trauma to the posterior pelvis just prior to symptom onset; 2 patients fell down stairs and 1 fell from a bed. Chief symptoms were a painful mass, a painless mass, and chronic pain in the injured area. Magnetic resonance imaging (MRI) revealed atrophy of the subcutaneous fat in all cases and a small mass in 1 patient. A bright linear signal was seen on T2-weighted, fat-saturated images in 2 cases, likely representing scar tissue. One patient with chronic pain underwent surgery to provide better soft tissue coverage in the area of atrophic fat. The other 2 patients did not undergo surgical treatment: 1 was treated at a pain center for reflex sympathetic dystropy-type pain, and 1 remained pain free. Blunt trauma with subsequent fat atrophy and necrosis manifests as a mass, a subcutaneous fat defect, and even as chronic pain. Characteristic MRI findings are often sufficient for diagnosis, but any indeterminate masses should be further evaluated to rule out aggressive or malignant neoplasms. Chronic unrelenting pain despite treatment may be related to posttraumatic reflex sympathetic dystropy-like symptoms. Copyright ® 2009 SLACK Incorporated. All rights reserved.