Saphenous Nerve

Introduction

Peripheral nerve stimulation (PNS) is an evolving neuromodulation modality that is used to treat chronic neuropathic pain in the distribution of a specific named nerve or branch of a named nerve. PNS continues to evolve, with the addition of multiple sites of stimulation and associated evidence. The saphenous nerve plays an important role in the treatment algorithm for chronic knee and foot/ankle pain. Patients suffering from recalcitrant chronic medial knee or foot/ankle pain can benefit from PNS of the saphenous nerve targeted either above or below the knee.

Clinical Presentation

Saphenous nerve involvement can manifest as chronic pain from the groin, to the medial thigh, to the medial knee, to the great toe. The site of PNS lead implantation will be dictated by the patient’s chronic pain presentation. Chronic knee pain in the setting of total knee arthroplasty or osteoarthritis can be debilitating and have long-term detrimental effects on function.

Similarly, chronic medial foot and ankle pain secondary to trauma, instrumented fusion, or osteoarthritis can lead to biomechanically unstable gait. As an example, surfers are known to suffer from saphenous neuropathy owing to gripping the surfboard between their knees, leading to chronic medial thigh and knee pain.

Another common site of saphenous nerve entrapment is along the distribution of infrapatellar saphenous (IPS) nerve. It clinically presents as neuropathic pain along the inferomedial aspect of the knee. Patients sometimes ambulate with “stiff leg” to minimize flexion at the knee joint.