Saphenous Nerve Block, Ultrasound, NYSORA Technique, Anatomy, Distribution, Knee & Ankle Applications, Coverage, and Procedure Guide
- What is Saphenous Nerve Block?
- Saphenous Nerve Block — Ultrasound
- Saphenous Nerve Block — NYSORA Technique
- Saphenous Nerve Block — Anatomy
- Saphenous Nerve Block — Distribution
- Saphenous Nerve Block — Knee & Ankle Applications
- Saphenous Nerve Block — Coverage
- Saphenous Nerve Block — Procedure Guide
What is Saphenous Nerve Block?
A saphenous nerve block is a regional anesthetic technique that targets the saphenous nerve — the largest purely sensory branch of the femoral nerve — to provide analgesia to the medial aspect of the lower leg, ankle, and foot. Unlike motor blocks that affect muscle strength, the saphenous block is fundamentally sensory and is used to control pain after procedures such as knee arthroscopy, medial meniscal repairs, saphenous vein surgeries, or ankle and foot procedures where medial innervation is important. In ambulatory and inpatient settings it is valued for its targeted pain relief with minimal effect on quadriceps strength when performed distal to the femoral triangle. This property allows early mobilization and reduces fall risk compared with proximal femoral nerve blocks. The block can be delivered using different approaches — adductor canal (subsartorial) approach, at the level of the knee, or at the ankle — and can be performed as a single-shot injection or via catheter for continuous analgesia depending on the clinical need and expected duration of pain.
Clinicians use the saphenous nerve block to reduce opioid consumption, improve patient comfort, and facilitate physiotherapy in the immediate postoperative period. It is particularly useful when analgesia is required on the medial side of the leg and foot without compromising limb function. Patient selection, informed consent, and clear documentation of the target area and expected effects are essential. Contraindications are similar to other peripheral nerve blocks and include local infection at the insertion site, allergy to local anesthetic, or a patient who cannot cooperate. When combined appropriately with multimodal analgesia, a saphenous nerve block is an effective and safe component of perioperative pain management plans for lower limb procedures.
Saphenous Nerve Block — Ultrasound
Ultrasound guidance has transformed the practice of peripheral nerve blocks and is now the standard of care for saphenous nerve blockade in many centers. With ultrasound, the practitioner can visualize local anatomy in real time — including the femoral vessels, sartorius and vastus medialis muscles, the adductor canal, and the descending genicular branches — to precisely deposit local anesthetic around the saphenous nerve or its sensory branches. The adductor canal (subsartorial) approach is commonly used because the saphenous nerve lies adjacent to the femoral artery inside this canal; the nerve is usually visible as a small hyperechoic or hypoechoic structure adjacent to the pulsatile artery. Ultrasound reduces the required local anesthetic volume, lowers the risk of vascular puncture, and allows dynamic needle visualization, which increases safety and success rates. Doppler mode also helps avoid inadvertent intravascular injection by identifying vessels and their flow.
Performing the block under ultrasound guidance typically involves scanning the mid-thigh region to locate the femoral artery within the adductor canal, then using an in-plane or out-of-plane needle trajectory to place the tip adjacent to the nerve. Hydrodissection with small aliquots of saline or local anesthetic confirms proper spread and displaces tissue planes safely. Ultrasound guidance also facilitates distal approaches at the level of the knee or ankle where the nerve courses superficially. For teaching and quality assurance, ultrasound images can be saved in the electronic record. Overall, ultrasound guidance improves patient comfort, speeds block onset, and reduces complications compared with landmark-only techniques, making it the preferred approach for modern saphenous nerve blockade.
Saphenous Nerve Block — NYSORA Technique
NYSORA (The New York School of Regional Anesthesia) provides widely used, pragmatic techniques and educational resources for peripheral blocks, including the saphenous nerve block. The NYSORA approach emphasizes ultrasound-based adductor canal blockade as a reliable method to achieve saphenous nerve analgesia while preserving quadriceps strength. Their recommended technique typically includes positioning the patient supine with the leg slightly externally rotated, identifying the mid-thigh adductor canal under ultrasound, and using an in-plane needle approach for controlled deposition of local anesthetic around the saphenous nerve and around the femoral artery within the canal. NYSORA highlights small-volume, targeted injections (for example 5–10 mL for single-shot blocks) to obtain effective sensory block while minimizing proximal spread that could affect motor branches.
NYSORA’s guidance also outlines variations for continuous catheter placement when prolonged analgesia is desired. This includes tunneling the catheter superficially for fixation and using infusion rates of dilute local anesthetics (e.g., 0.1–0.2% ropivacaine at 3–6 mL/hr) depending on institutional protocols. Education from NYSORA stresses safety steps: use of sterile technique, incremental aspiration and test dosing to avoid intravascular injection, and careful ultrasound identification of anatomy. Their resources include step-by-step images, needle trajectory tips, and troubleshooting advice for difficult anatomy — all presented in an accessible manner for learners and experienced providers alike. Following NYSORA principles helps standardize practice and improves reproducibility across clinicians.
Saphenous Nerve Block — Anatomy
Understanding the anatomy of the saphenous nerve is critical for successful blockade. The saphenous nerve originates as the terminal sensory branch of the femoral nerve, exiting the femoral triangle and traveling into the adductor canal beneath the sartorius muscle. It courses alongside the femoral artery and vein within the canal, then becomes more superficial as it passes between the tendons of the sartorius and gracilis near the knee. Distally, the nerve supplies the medial aspect of the leg, medial malleolus, and arch of the foot via infrapatellar and inframalleolar branches. Anatomical variations exist: the site where the nerve separates from the femoral nerve and its relationship to the descending genicular artery can vary, so real-time imaging is helpful to account for individual differences.
Anatomical knowledge also informs choice of approach. The adductor canal approach targets the nerve while it is adjacent to the femoral artery and relatively protected from motor branches. More distal approaches near the knee or at the level of the tibial insertion of sartorius can be used when ankle or foot coverage is needed. Awareness of nearby structures — particularly the femoral vessels, the saphenous branch communications, and the pes anserinus tendons — reduces the risk of vascular puncture and incomplete block. Anatomical studies show that the saphenous nerve remains a sensory-only nerve; therefore, blocks performed in the adductor canal region typically spare quadriceps motor function, which is a key advantage for early mobilization and fall prevention in postoperative patients.
Saphenous Nerve Block — Distribution
The sensory distribution of the saphenous nerve includes the medial knee, the medial lower leg down to the medial malleolus, and part of the medial foot. Specifically, its infrapatellar branch supplies the skin over the patella and the medial knee; distal branches run with the great saphenous vein to provide sensation over the medial shin and ankle. This pattern makes the saphenous nerve block especially useful in procedures localized to the medial aspect of the leg and foot, such as saphenous vein harvesting, medial ankle procedures, or skin graft donor site analgesia. It does not cover the lateral leg, dorsum of the foot, or plantar surfaces—areas innervated by other peripheral nerves.
Because the saphenous nerve is purely sensory, the block does not relieve pain originating from deep joint structures supplied by other nerves (for example, the femoral nerve’s articular branches or the sciatic nerve). For comprehensive analgesia for knee surgery, a saphenous block is often combined with other modalities such as local infiltration analgesia, periarticular blocks, or sciatic nerve/sciatic component blocks for posterior knee pain. When planning anesthesia, clinicians must map expected surgical incisions to the saphenous distribution and decide if supplemental blocks are required. Properly informing patients about the exact area of numbness helps set expectations and improves postoperative care, particularly for wound surveillance and protected weight-bearing.
Saphenous Nerve Block — Knee & Ankle Applications
In knee surgery, saphenous nerve blocks provide targeted analgesia for medial incisions, arthroscopic portals, and skin graft donor sites. They are particularly useful for outpatient knee arthroscopy, medial meniscus repair, and procedures addressing the pes anserinus. For total knee arthroplasty or more extensive procedures where anterior and lateral pain is significant, clinicians often combine a saphenous block with adductor canal block variants, periarticular infiltration, or even low-volume femoral nerve blocks depending on the balance between analgesia and motor preservation needed. For ankle and foot surgery, distal saphenous nerve blocks or combined superficial peroneal/sural blocks may be used to provide complete medial ankle coverage for procedures such as bunion correction, medial malleolus fixation, or soft-tissue repairs.
Saphenous blockade can also be used for analgesia in vascular surgery involving the great saphenous vein, for pain control after saphenous vein stripping, and for chronic pain interventions in certain neuropathic conditions. The choice between single-shot and continuous catheter techniques depends on expected pain duration: single-shot provides 8–18 hours of analgesia with long-acting agents, while catheters give multi-day control with adjustable infusion rates. Clinical outcomes often show reduced opioid consumption, improved patient satisfaction, and earlier participation in physiotherapy when saphenous blocks are integrated into multimodal pain protocols. Patient education on limb protection while numb and instructions on catheter care are essential for outpatient management.
Saphenous Nerve Block — Coverage
The coverage achieved by a saphenous nerve block depends on the approach and local anesthetic volume. With an adductor canal approach using ultrasound and 5–10 mL of a long-acting local anesthetic (e.g., 0.5% ropivacaine or 0.25–0.375% bupivacaine), clinicians can reliably anesthetize the medial knee down to the medial malleolus. More distal injections at the level of the knee or below can concentrate coverage to the ankle and medial foot. Continuous infusions deliver steady analgesia and can extend coverage for days; typical infusion regimens use dilute ropivacaine (0.1–0.2%) at 3–8 mL/hr depending on target density and institutional protocols.
Limitations in coverage must be recognized: saphenous block does not affect posterior knee pain or plantar foot sensation. If the surgical area extends beyond the saphenous territory, additional blocks (e.g., sciatic, tibial, sural, or superficial peroneal nerves) are required for complete analgesia. Risks that may influence coverage include incomplete spread due to fascial confines and anatomic variation. When planning analgesia, the clinician should choose the site that best balances desired sensory blockade with preservation of motor function to minimize fall risk while achieving adequate pain control for the planned procedure.
Saphenous Nerve Block — Procedure Guide
A practical procedure guide begins with patient preparation: explain the block, obtain informed consent, check allergies, and ensure appropriate monitoring (pulse oximetry, blood pressure, ECG). Position the patient supine with the leg slightly externally rotated. Prepare a sterile field and place the ultrasound probe (with sterile cover) over the mid-thigh to identify the femoral artery within the adductor canal beneath the sartorius muscle. Using an in-plane lateral-to-medial needle approach, advance a 50–100 mm block needle toward the target adjacent to the femoral artery where the saphenous nerve typically resides. After careful aspiration to exclude intravascular placement, inject a small test dose and then incrementally deposit local anesthetic while observing spread around the nerve and artery. Hydrodissection may help confirm correct plane.
Document the local anesthetic type and volume, needle path, and any immediate complications. Observe the patient for 20–30 minutes to confirm sensory loss in the medial leg and absence of significant motor weakness. For catheter placement, thread the catheter 2–5 cm beyond the needle tip and secure it with adhesive and dressing; set infusion parameters per protocol. Provide post-procedure instructions about limb numbness, fall precautions, and signs of infection or catheter malfunction. If unexpected pain or neurologic symptoms occur, stop infusion and reassess. With meticulous ultrasound technique and appropriate dosing, the saphenous nerve block is a safe, effective tool to deliver targeted analgesia for many knee, ankle, and medial lower-limb procedures.
Reviewed by Simon Albert
on
May 22, 2025
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