Saphenous Nerve Damage

Introduction

• The saphenous nerve is the largest purely sensory branch of the femoral nerve, providing cutaneous innervation to the medial knee, leg, and ankle.1 Because of its superficial course and its close relationship to the adductor canal, sartorius muscle, and great saphenous vein, it is vulnerable to iatrogenic injury during both surgical and regional anesthetic procedures.³
• The clinical significance of saphenous nerve injury lies in its ability to result in persistent neuropathic pain, dysesthesia, or sensory deficits, often affecting mobility and rehabilitation after lower-limb surgery.^3,7 As regional anesthesia continues to play a central role in improved recovery pathways, understanding the anatomy, mechanisms of injury, diagnosis, and prevention of saphenous nerve damage is essential for safe perioperative practice.⁴

Anatomy

• The saphenous nerve originates from the posterior division of the femoral nerve (L3-L4) within the femoral triangle.¹
• It travels laterally to the femoral artery, then enters the adductor canal with the femoral vessels beneath the sartorius muscle¹ (Figure 1, source).
• Distally, it gives rise to the infrapatellar branch and continues as the saphenous nerve proper, which emerges with the great saphenous vein near the medial knee.²
• Cutaneous distribution: medial knee, leg, ankle, and foot to the first metatarsophalangeal joint¹ (Figure 2, source).

Clinical Relevance

• The infrapatellar branch is commonly injured during knee arthroscopy, medial meniscal procedures, and anterior cruciate ligament (ACL) reconstruction.^2,3,7
• The main trunk is at risk during great saphenous vein stripping or ablation due to the nerve’s intimate relationship with the vein distal to the knee.^1,3
• The sensory-only nature of the nerve helps differentiate saphenous neuropathy from femoral neuropathy or L3 radiculopathy.¹

Mechanisms of Injury

Regional Anesthesia-Related Injury

Most common contexts:

• Adductor canal block
• Femoral nerve block
• Saphenous nerve-specific block at the tibial flare^2,4

Potential mechanisms:

• Intraneural injection causing mechanical fascicular injury³
• High-pressure fascial plane injection³
• Local anesthetic neurotoxicity³
• Ultrasound guidance has significantly reduced but not eliminated risk⁵

Surgical Injury

Knee surgery:

• Medial meniscal repair²
• Total knee arthroplasty⁶
• ACL reconstruction (especially hamstring graft harvest)^2,6
• Arthroscopy using anterior-medial ports^2,7
• Tourniquet application near the adductor canal⁴

Vascular surgery:

• Great saphenous vein stripping, phlebotomy, or ablation^2,3 since the saphenous nerve lies immediately adjacent to great saphenous vein below the knee^1,6

Orthopedic trauma surgery:

• Medial tibial open rotation and internal fixation³
• Total knee replacement or arthroscopy⁶
• Medial soft-tissue dissection, aggressive retraction, or placement of incision along typical course of infrapatellar branch^1,3

Trauma

• Direct laceration³
• Medial tibial contusion³
• Fracture-related nerve entrapment or traction⁷

Clinical Presentation

• Because the saphenous nerve is purely sensory, deficits are typically confined to loss of sensation without motor weakness.

Sensory Symptoms

• Numbness along the medial knee or leg^1,3
• Tingling or electric sensations^1,2
• Burning neuropathic pain
• Hypersensitivity to light touch

Physical Examination Findings

• Reduced light touch or pinprick sensation
• Preservation of quadriceps strength^1,3
• Positive Tinel sign (tapping the nerve elicits a tingling sensation) along the saphenous nerve distribution^1,6
• Pain provoked by tapping or stretching the nerve

Functional Consequences

• Pain with ambulation^3,7
• Difficulty descending stairs
• Medial knee instability sensations (proprioceptive alteration)

Diagnosis

• Saphenous neuropathy is primarily diagnosed by history and physical examination. Key features include sensory-only deficits and recent exposure to knee surgery, nerve block, trauma, or vascular intervention.^2,3

Clinical Evaluation

• Detailed sensory mapping with associated lack of motor involvement
• Differentiation from L3-L4 radiculopathy or femoral neuropathy
• Ask about history of recent nerve block, knee surgery or vein intervention^4,7

Electrodiagnostic Testing

• Nerve conduction studies may detect reduced sensory nerve action potentials but are often limited due to anatomical variability^2,3
• Electromyography helps rule out femoral neuropathy or lumbar radiculopathy^2,8

Ultrasound

• May show nerve discontinuity, neuroma, thickening, scarring, or entrapment^3,5
• Useful for guiding diagnostic nerve blocks with local anesthetic^3,5

X-ray and MRI

• Will be normal in the majority of cases, thus not a part of workup of saphenous nerve injury

Management

• Please see the OA summary on peripheral nerve injury from regional anesthesia for more details. Link

Acute Injury

• Reassurance: most neurapraxic injuries resolve over weeks to months³
• Nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesics for early postoperative pain
• Saphenous nerve block with local anesthetic or corticosteroid for confirmation and temporary relief of symptoms^3,7

Chronic Neuropathic Pain

• Physical therapy emphasizing gait mechanics⁸
• Desensitization therapy
• Neuropathic pain agents such as gabapentin, pregabalin, duloxetine, or amitriptyline for dysesthesia^3,7,8

Surgical Options

• Neurolysis for scar encasement or entrapment⁷
• Neurectomy for persistent debilitating pain⁷
• Ultrasound-guided hydrodissection⁷
• Typically reserved for rare, refractory cases

Prevention

Regional Anesthesia

• Use ultrasound to identify the saphenous nerve as well as surrounding structures such as the femoral artery, sartorius muscle, and adductor canal boundaries⁵ (Figure 3, source).
• Avoid intraneural injection by maintaining low injection pressures and frequent aspiration, pausing when resistance is encountered^2,4
• The local anesthetic should be injected incrementally^2,4

Surgical Precautions

• Respect the anatomic course of the infrapatellar branch
• For knee arthroscopy, avoid excessively medial port placement^1,6
• Avoid aggressive medial traction during hamstring graft harvesting^1,3
• Careful dissection near the great saphenous vein, particularly below the knee¹

Tourniquet Precautions

• Avoid high-pressure or prolonged thigh tourniquet inflation²
• Consider distal tourniquet placement when appropriate for surgical exposure²