These findings explained the delayed course in resolution of symptoms. Over the next 48 hours, continued conservative management, as outlined above, led to the resolution of symptoms, and the athlete returned to play. At a 2-month follow-up, the athlete described normal function in his knee without any residual symptoms. He returned to play without any symptoms. At 6 months, the athlete underwent MRI of the same knee for an unrelated reason. MRI revealed a healed fat fracture with resolution of the fluid defect in the subcutaneous fat (Figures 4A, 4B).
DISCUSSION
A fat fracture was first described in 1972 in 12 cases of buttock fat fractures after blunt trauma.3 The authors explained that fat lobules are typically arranged in layers and supported by horizontal and vertical fibrous septa. Typical loads flatten the lobules and disperse the forces throughout the layer. However, abnormal loads to a local area disrupt the fat lobules and shear the septa, resulting in decreased integrity of the interface between the epidermis and the fascia.
However, the extremities typically have less adipose tissue than in the buttocks, and the anterior knee is prone to blunt trauma. A previous description of a fat fracture in the knee noted a palpable defect in the quadriceps tendon and an inability to perform a straight leg raise. Our case initially presented with swelling, which concealed any soft-tissue defect. Furthermore, a straight leg raise was always intact despite the fat fracture defect surfacing after anterior swelling subsided. However, the disparity in these 2 cases highlights the spectrum of injury that is possible, as well as the difficulty in diagnosing a fat fracture. The previous report used ultrasound to confirm the diagnosis and assess the integrity of adjacent musculotendinous structures. An ultrasound may be readily available in athletic training rooms.1 Of note, to the best of our knowledge, this is the first case in the literature to report a fat fracture in a professional athlete and in baseball players. Furthermore, this case report describes an athlete who presented with anterior and medial knee pain. The edema from the fat fracture dispersed into the medial prepatellar bursa, which could be confused with edema from an injury to the medial-sided soft tissues.
Although these injuries do not require operative management, conservative measures may not be as effective as those in a patellar contusion or ligamentous sprain, and prolonged treatment may be necessary. Additionally, healthcare providers should be aware of this possible source of injury and counsel on an appropriate recovery time. Ideally, further recognition of such injuries can facilitate improved management and a faster return to activity.