Discussion
We have described a case of symptomatic encapsulated fat necrosis lesion caused by an ML lesion in a professional hockey player. The ML lesion had resolved with nonoperative treatment (compression), but a subcutaneous pocket remained at the lesion site. Given the patient’s lesion site and occupation as a hockey player, pain with direct pressure on this lesion was a concern.
Long-standing ML lesions have 3 common patterns on MRI.14 A central region, encapsulated partially or completely by a peripheral ring of fibrous tissue or hemosiderin, shows signal properties consistent with a seroma, a homogeneous hemorrhagic collection, or a heterogeneous hemorrhagic collection. In our patient’s case, MRI was used to characterize the mobile mass for operative planning. Although thin strands or lobules of fat have been found within ML lesions, this case was the first to demonstrate a sequestered mass of necrotic fat.
Most football players who develop ML lesions on their knees do not wear kneepads.7-9 Of the 24 NFL players in the study by Tejwani and colleagues,9 52% were successfully treated with compression wrap, cryotherapy, and motion exercises. The rest, however, were treated with aspiration, and 11% underwent doxycycline sclerodesis for recurrent fluid collection. After treatment, all of their players were able to return to football. Their outcomes are consistent with that of our patient, who was treated with compression wrap and returned to hockey without any other intervention.
After our patient’s ML lesion resolved, he developed an encapsulated fat necrosis lesion from the disruption of the blood supply in the subcutaneous pocket. Encapsulated fat necrosis lesions are rare; only 65 have been reported.13,15 Clinically, these lesions are single or multiple pale-yellow encapsulated nodes.13 Most are small and asymptomatic; however, in some cases, athletes can develop symptoms from frequent impacts to the region where the lesions are located.
The literature includes 1 report of an adolescent football player who developed multiple encapsulated fat necrosis lesions 4 months after landing on another player’s cleats.15 The patient, who was having pain with direct pressure during squatting and kneeling, elected to have the lesions surgically removed. These lesions are rare and usually asymptomatic,11 but our patient had his lesion surgically removed to address the pain induced by the direct impacts that came with playing professional hockey. Surgical removal is the treatment for symptomatic encapsulated fat necrosis lesions. Other than 1 case of recurrence after excision,16 these lesions have an excellent prognosis.
Conclusion
Our patient, a professional hockey player, underwent successful surgical removal of a symptomatic encapsulated fat necrosis lesion that had developed from an ML lesion.
Am J Orthop. 2017;46(3):E144-E147. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.