Lipoma arborescence of knee and torn anterior cruciate ligament and meniscal RAMP lesion: a case report of rare association

Lipoma arborescence (LA) is an extremely rare condition that commonly involves the knee joint; however, it can be noted in the other appendicular joints. It has been associated with trauma as well, without any predilection for any specific ligamentous injuries. We are presenting a case of a young male patient who presented with recurrent knee joint swelling and was clinically suspected to have pigmented villonodular synovitis. However, he was diagnosed with lipoma arborescence with a completely torn anterior cruciate ligament (ACL) and RAMP lesion of the meniscus on magnetic resonance imaging (MRI) which were subsequently confirmed on arthroscopy at our center. We strongly underscore to consider this condition as a possible differential in patients presenting with atraumatic pain and recurrent swelling of the joint to ensure timely diagnosis to avoid early onset degenerative changes. We also strongly emphasize the need to do additional studies in the future to find out if this condition may occur as a complication or sequelae to any specific ligamentous injury.