Nonspecific Chronic Anteromedial Knee Pain Neuroma as a Cause of Infrapatellar Pain Syndrome: Case Study and Literature Review

The infrapatellar branch of the saphenous nerve (IBSN) is purely sensory and innervates both the anteromedial aspect of the knee and the anterior-inferior portion of the knee capsule. The IBSN arises from the saphenous nerve in the adductor hiatus before piercing the fascia lata to become subcutaneous. Infrapatellar pain syndrome (IPS), also known as an infrapatellar nerve injury, is not a widely known syndrome. The IBSN in the literature is also known as prepatellar nerve. It is not a novel phenomenon. As early as 1945, surgeons were cautioned regarding potential surgical trauma to the IBSN. IPS can be caused by trauma, such as a fall on the knee or a direct blow to the knee joint, as well as by surgical procedures, such as arthroscopy, total knee replacement, bone–patellar tendon–bone or hamstring tendon harvest for anterior cruciate ligament (ACL) procedures, tibial nailing, and open procedures of the knee. The paramount problem with IPS is the potentially long time for a proper diagnosis of anterior knee pain syndrome. IPS is not often reported and can be overlooked or misdiagnosed as it develops. In the literature, we have found patients with a history of IPS lasting 7 and even 13 years. Gordon described IPS pain as being similar to a “toothache.” Figueroa et al reported 4 types of disturbance of the IBSN, including hypoesthesia, dysesthesia, painful neuroma, and reflex sympathetic dystrophy.