Saphenous Nerve Block: The Same Nerve Under Two Names

The saphenous nerve is the largest sensory branch of the femoral nerve and the only one that reaches below the knee. It is purely sensory, which is the single most useful fact about it: blocking it anaesthetises the medial leg, ankle and midfoot without weakening the quadriceps.

That property is why the block has quietly become one of the most-performed regional techniques in orthopaedic practice — though usually under a different name. This reference explains the relationship between the saphenous nerve block and the adductor canal block, where each is used, and what the evidence supports. It sits under our clinical reference to nerve blocks in outpatient pain practice.

The adductor canal block is a saphenous nerve block

This causes more confusion than any other point in the topic, so it is worth stating directly. The adductor canal block targets the saphenous nerve within the adductor (Hunter’s) canal in the mid-thigh. It is the same nerve, named for the compartment rather than the nerve.

The distinction that does matter is what else is in the canal. Injectate placed there may also reach the nerve to vastus medialis and, with proximal spread, other femoral branches — which is why the adductor canal block is described as motor-sparing rather than motor-free. A block placed more distally, at or above the knee, is more reliably confined to sensory fibres.

So the clinical choice is a trade: a proximal approach gives wider knee coverage with some risk of quadriceps weakness, and a distal approach gives cleaner sensory selectivity with narrower coverage. Neither is simply better.

Around the knee

The saphenous nerve supplies the medial knee, which is why the adductor canal approach is a standard component of analgesia after knee arthroplasty, where preserving quadriceps strength for early mobilisation is the whole point.

The evidence here is largely about what is added to the block rather than the block itself. A 2025 meta-analysis of four randomised trials in 343 patients found that liposomal bupivacaine in the adductor canal produced statistically significant reductions in pain on the day of surgery and the first postoperative day, and lower opioid consumption on both days, with no significant difference in pain, opioid use, length of stay or adverse events beyond the first postoperative day. A 2026 randomised trial in 58 patients found that adding perineural dexmedetomidine to dexamethasone reduced 24-hour and 48-hour morphine consumption without affecting quadriceps strength or timed-up-and-go performance.

Read together, the adjuncts buy a short extension of a short block. That is worth having, and it is not the durable effect the marketing around sustained-release formulations sometimes implies.

Where the saphenous block sits among the alternatives after knee replacement — and why adductor canal block combined with infiltration between the popliteal artery and knee capsule tends to win on function rather than pain score — is covered in genicular nerve block.

At the ankle and foot

Below the knee the saphenous nerve supplies a strip along the medial leg down to the medial malleolus and often onto the medial midfoot. It is one of the five nerves blocked in a complete ankle block, and the only one of the five that is not a branch of the sciatic nerve.

This is where its sensory-only character is most useful: medial foot and ankle procedures, or medial ankle pain, can be addressed without any motor consequence at all. The full five-nerve approach at the ankle, and its use in diabetic peripheral neuropathy, is covered in the ankle block for diabetic peripheral neuropathy.

Safety

This is a comparatively forgiving block. The nerve is superficial at the knee and ankle, there is no motor consequence when blocked distally, and no body cavity is nearby.

The two considerations that remain are the femoral artery in the adductor canal — the nerve lies lateral to it, and the artery is the landmark that makes the block findable on ultrasound as well as the structure to avoid — and the general architecture of local anaesthetic systemic toxicity and asepsis set out in the nerve blocks reference.

Patients should be warned that numbness along the medial leg and foot is expected, and that it affects their awareness of the limb until it wears off.

For clinicians

The saphenous nerve is small and not reliably found by landmark alone, which is why the artery is used as the reference point and why this block is taught with ultrasound. What guidance improves — accuracy and safety rather than pain scores — is covered in musculoskeletal ultrasound for pain practice. This reference carries no needle depths or trajectories.

Empire teaches the saphenous nerve block under ultrasound guidance within Advanced Musculoskeletal Ultrasound Guided Injections, part of the pain management academy.