A 72-year-old man presented with complaints of pain on the anteromedial infrapatellar side of the right knee with sensory disturbance that began 2 years earlier.
The patient previously underwent right knee arthroscopy at another hospital for a meniscus injury in May 2020, which gave him relief from knee pain, but pain and discomfort near the incision of the medial portal persisted. Given this situation, various physical treatments, such as ice compress, were administered postoperatively. However, the symptom was only partially relieved before discharge. Subsequently, the patient visited two other hospitals and began taking oral pregabalin and duloxetine for treatment of the pain based on a diagnosis of right common peroneal nerve injury. Pain in the same dermatomal distribution was slightly relieved, but a withdrawal reaction was observed. The patient still felt migratory pain at the inner foretibia.
The patient had high blood pressure for 5 years and had no other history of chronic disease or surgery.
The patient's parents were deceased, cause of death unknown; he had one brother in good health. The patient denied (1) any similar disease in the family; (2) tuberculosis, hepatitis, or other infectious diseases in the family; and (3) hereditary or familial diseases, such as diabetes or hemophilia, in the family.
Physical examination of the right knee detected atrophy of the quadriceps femoris muscle, decreased muscle strength (M4), obvious tenderness in the medial side, radiating pain along the anterior tibia, sensory disturbance (S3+), and positive Tinel's sign. The results of a drawer test, McMurray test, pivot shift test, and lateral stress test were negative.
Color ultrasound and magnetic resonance imaging (MRI) examination of the patient's right knee were performed. Color ultrasound showed a hypoechoic area suggesting inflammatory changes in the right medial quadriceps femoris tendon. MRI showed level II injury in the posterior horn of the medial meniscus of the right knee joint and edema of the infrapatellar fat pad.
The final diagnosis was injury to the infrapatellar branch of the saphenous nerve.
The patient underwent neurolysis for the infrapatellar branch of the saphenous nerve under epidural anesthesia in July 2022. An enlarged incision was made along the original medial approach. Scar hyperplasia was observed after careful separation of the subcutaneous tissue. During neurolysis, branches were found wrapped in the scar; their continuity and integrity were confirmed after relief. We translocated the nerve and embedded it under the fat (Figure 1). After surgery, the patient took 0.5 mg mecobalamin orally three times per day for 4 weeks.
The patient's pain was clearly relieved, and numbness disappeared on the first postoperative day. One month after surgery, the pain had disappeared completely and the patient was satisfied with the outcome.