Regional Anesthesia: Knee & Leg
Kathryn Johns, MD, MS
Vanica Guignard, MD
- The femoral nerve arises from the lumbar plexus and consists of nerve roots from L2, L3 and L4. The nerve then travels inferiorly through the psoas muscle to exit the pelvis with the femoral bundle below the inguinal ligament. In the femoral triangle, the femoral nerve is lateral to the artery and vein, and unlike its paired vessels the nerve exists outside of the femoral sheath. It lies below the fascia iliaca. Approximately 4cm distal to the femoral triangle, near the level of the lateral circumflex femoral artery branch point, the femoral nerve splits into its anterior and posterior divisions.
- The femoral nerve provides sensation to the skin of the anteromedial aspect of the thigh and the anterior knee via the anterior cutaneous branches; additionally it provides sensation to the medial calf and foot via the saphenous nerve. The femoral nerve innervates the patella and patellofemoral joint via the suprapatellar and infrapatellar genicular branches from the saphenous nerve. The femoral nerve also supplies the medial tibial plateau. The majority of the articular surfaces of the knee and joint capsule are innervated through genicular branches of the sciatic and common peroneal nerves. The femoral nerve also provides motor innervation to the hip flexors and knee extensors.
Femoral Nerve/Fascia Iliaca Block
- The femoral nerve/fascia iliaca block provides regional anesthesia primarily to the hip and thigh, but can also be used for the anteromedial thigh/knee
- The femoral nerve block can be used to provide analgesia in both adult and pediatric patients for the following indications:
- Hip joint pathology
- Femur neck or shaft fractures
- Large laceration repairs to anteromedial surface of thigh or knee
- Patellar pathology
- Knee arthroplasty (knee replacement) pain
Popliteal-Sciatic Nerve Block
- The popliteal-sciatic nerve block provides regional anesthesia and analgesia to the lower extremity below the knee. The sciatic nerve arises from the lumbar and sacral plexus and consists of nerve roots from L4, L5, S1, S2 and S3.
- The distal sciatic nerve branches into the tibial nerve and the common peroneal (fibular) nerve. Although the anatomy in this region can be variable, this typically occurs just proximal to the popliteal fossa where these branches can be found in a more superficial position.
- The tibial nerve provides sensation to the posterior aspect of the leg below the knee and the plantar aspect of the foot. The common peroneal nerve provides sensation to the lateral aspect of the leg below the knee and the lateral/dorsal aspect of the foot and ankle. Note that sensation to the medial aspect of the distal leg, foot and ankle is provided by the saphenous nerve and is NOT covered with this blockade. The tibial nerve provides motor innervation to the muscles of the calf and flexion of the toes. The common peroneal nerve provides motor innervation to dorsiflexion of the ankle, eversion of the foot and extension of the toes.
Saphenous Nerve Block
- The purpose of the saphenous nerve block is to provide analgesia for the medial leg and ankle.
- The saphenous nerve originates from the L3-L4 nerve roots and is a terminal branch of the femoral nerve, separating from the femoral nerve in the proximal third of the thigh. It descends lateral to the femoral sheath in the adductor canal. It separates from and crosses anteromedial to the femoral artery to emerge from the canal with the saphenous branch of the descending genicular artery. It travels laterally to the great saphenous vein. After leaving the adductor canal, it pierces the fascia lata between the tendons of the gracilis and sartorius muscles to become subcutaneous. It divides into the infrapatellar branch and the sartorial branch before dividing into multiple small subcutaneous branches.
- The saphenous nerve is mainly sensory, innervating the medial, anteromedial, and posteromedial lower leg, ankle, and foot.
- The saphenous nerve block is indicated for anesthesia of the lower leg or foot along its neural distribution. It is commonly used in conjunction with a popliteal sciatic nerve block to provide complete anesthesia of the lower leg for various procedures, such as medial meniscectomy wound repair or exploration, foreign body removal, saphenous vein stripping or harvesting, abscess drainage and ankle fracture or dislocation reduction.
- Arnold, Cosby, Alvarado ,Andrea C, Brady, Mark F. Saphenous Nerve Block. National Center for Biotechnology Information. 2020.
- Horn, Jean-Louis, MD; Pitsch, Trevor, MD; Salinas, Francis, MD; Benninger, Brion, MD. Anatomic Basis to the Ultrasound-Guided Approach for Saphenous Nerve Blockade. Regional Anesthesia and Pain Medicine. 2009; 34(5) 486-489
- Bendtsen, Thomas F, Lopez, Ana M, Clark, Thomas B. Ultrasound-Guided Saphenous (Adductor Canal) Block. New York School of Regional Anesthesia [Internet].
- Akkaya, T., Ersan, O., Ozkan, D. et al. Saphenous nerve block is an effective regional technique for post-menisectomy pain. Knee Surg Sports Traumatol Arthr 16, 855–858 (2008).
Genicular Nerve Block
- The purpose of the genicular nerve block is to provide analgesia to the knee joint.
- The genicular nerve has 3 branches: superior lateral (SL), superior medial (SM), and inferior medial (IM) genicular nerves. They pass the periosteal areas connecting the shaft of the femur to the bilateral epicondyles and the shaft of the tibia to the medial epicondyle.
- The genicular nerve block provides analgesia to the knee joint only. Therefore it’s widest usage is to provide analgesia for patients suffering from chronic knee pain, most notably osteoarthritis.
- Place the patient supine with a pillow under the popliteal fossa to alleviate discomfort.
- Using a linear transducer (~12 MHz), place the probe parallel to the femur shaft and move up or down to identify the femoral condyle.
- It is easiest to identify the genicular nerves by identifying the accompanying arteries. Observe the pulsation of the genicular arteries, confirm with color Doppler US, and the nerve should like next to the artery.
- Identify the superior-medial genicular nerve/artery at the lower end of the femur and approximately 1–1.5 cm from the medial upper edge of the patella.
- Identify the superior-lateral genicular nerve/artery at the lower end of the femur and approximately 1–1.5 cm from the lateral upper edge of the patella.
- Identify the inferomedial genicular nerve/artery at the upper end of the tibia, 1–1.5 cm from the lower medial end of the patella.
- Position the patient as described above. Prepare the area and drape using standard sterile technique.
- Identify the genicular arteries as described above.
- Keep a short-axis view of the genicular arteries/nerves, and insert the needle using an in-plane technique.
- After confirming the placement of the needle-tip next to a genicular artery, aspirate to ensure no blood, and then inject 2-5mL of local anesthetic around the site.
- Reproduce for all three target sites: the superior lateral, superior medial, and inferior medial genicular nerves.
- Visualization of the genicular nerves is difficult, but genicular arteries can be used to help more easily identify the location of the genicular nerve, as the arteries, which are well visualized, travel alongside the genicular nerves.
- Demir et al. A Different Approach to the Management of Osteoarthritis in the Knee: Ultrasound Guided Genicular Nerve Block. Pain Medicine. 2017; 18: 181–183
- Doo-Hwan Kim, MD, Seong-Soo Choi, MD, PhD, Syn-Hae Yoon, MD, So-Hee Lee, MD, Dong-Kyun Seo, MD, In-Gyu Lee, MD, Woo-Jong Choi, MD, PhD, and Jin-Woo Shin, MD, PhD. Ultrasound-Guided Genicular Nerve Block for Knee Osteoarthritis: A Double-Blind, Randomized Controlled Trial of Local Anesthetic Alone or in Combination with Corticosteroid. Pain Physician. 2018; 21:41-51
- Sarı, S., Aydın, O.N., Turan, Y. et al. Which imaging method should be used for genicular nerve radio frequency thermocoagulation in chronic knee osteoarthritis?. J Clin Monit Comput 2017. 31, 797–803
- Serdar Kesikburun, MD, Evren Yaşar, MD, Ayça Uran, MD, Emre Adigüzel, MD, and Bilge Yilmaz, MD. Ultrasound-Guided Genicular Nerve Pulsed Radiofrequency Treatment For Painful Knee Osteoarthritis: A Preliminary Report. Pain Physician. 2016; 19:E751-E759
Infiltration of local anesthetic between the Popliteal Artery and Capsule of the Knee (IPACK) Block
- Indication – To provide analgesia to the posterior aspect of the knee.
- The posterior knee consists of the popliteal nerve plexus in the popliteal fossa, derived from the tibial nerve and the posterior branch of the obturator nerve.
- The tibial nerve runs superior to the popliteal vein and superolateral to the popliteal artery. The common peroneal nerve branches off from the sciatic nerve and is lateral to the tibial nerve. The femoral shaft and the two heads of the gastrocnemius muscles lie in the inferior region of the plexus.
- The posterior group supplies intra-articular innervation to the menisci, the peri-meniscular joint capsule, the cruciate ligaments, the infra-patellar fat pad, and the posterior part of the fibrous knee capsule.
- Uses – To provide analgesia to the posterior aspect of the knee after surgical procedures such as arthroplasty of the knee and cruciate ligament repair.
- Currently the efficacy of this block in the emergency department is unknown, further investigation is needed.
- Position the leg with the knee flexed and the hip externally rotated. Using a linear or curvilinear transducer, place the probe proximal to the popliteal crease, short axis to the femur
- If the femoral condyles are seen, align the probe proximal until the condyles disappear and the shaft is seen.
- The view that should be seen should include the femoral shaft, popliteal vein and artery, and common peroneal and tibial nerves. The common peroneal nerve will appear the most superior and lateral on the ultrasound view. The tibial nerve will appear medial to the common peroneal nerve. The popliteal vein will be slightly posteromedial to the tibial nerve. The popliteal artery will be slightly posteromedial to the popliteal vein. The inferior portion of the ultrasound will have the femoral shaft followed by the medial and lateral heads of the gastrocnemius muscles present.
- Position the patient to identify the anatomy as described above. Drape the affected area using standard sterile procedure.
- Take a medial approach, insert the needle via the medial thigh using an anteromedial to posterolateral direction between the popliteal artery and the femoral shaft until the needle tip is ~1 cm beyond the lateral edge of the popliteal artery .
- Inject 20-30cc of the anesthetic into the region in aliquots, and continue to inject as the needle is being retracted.
- Use color doppler to identify vessels
- Take an anteromedial approach to avoid hitting nerve structure and vessels
- Scimia et al. The ultrasound-guided iPACK block with continuous adductor canal block for total knee arthroplasty: Anaesthesia Cases. 2017; 0117: ISSN 2396-8397 http://dx.doi.org/10.21466/ac.TUIBWCA.2017
- Kampitak et al. Optimal location of local anesthetic injection in the interspace between the popliteal artery and posterior capsule of the knee (iPACK) for posterior knee pain after total knee arthroplasty: an anatomical and clinical study: Korean Journal of Anesthesiology. 2019 Oct; 72(5): 486–49.
- Thobhani et al. Novel Regional Techniques for Total Knee Arthroplasty Promote Reduced Hospital Length of Stay: An Analysis of 106 Patients: Ochsner Journal. 2017; 17:233–238.
- Kandarian et al. Implementation of the IPACK (Infiltration between the Popliteal Artery and Capsule of the Knee) block into a multimodal analgesic pathway for total knee replacement: Korean Journal of Anesthesiology. 2019 Jun; 72(3): 238–244.
Pearls & Pitfalls
|↑1||Image courtesy of https://teachmeanatomy.info/,”The Femoral Nerve”|
|↑2, ↑3, ↑6, ↑7||Credit to NYSORA, Accessed 12/19/2022. https://www.nysora.com/topics/regional-anesthesia-for-specific-surgical-procedures/lower-extremity-regional-anesthesia-for-specific-surgical-procedures/foot-and-anckle/ultrasound-guided-popliteal-sciatic-block/|
|↑4, ↑5||Credit to NYSORA, Accessed 10/31/2022. https://www.nysora.com/topics/regional-anesthesia-for-specific-surgical-procedures/lower-extremity-regional-anesthesia-for-specific-surgical-procedures/foot-and-anckle/ultrasound-guided-popliteal-sciatic-block/|
|↑8||Credit to ASRA, Accessed 12/19/2022. https://www.asra.com/news-publications/asra-newsletter/newsletter-item/asra-news/2020/05/03/how-i-do-it-infiltration-between-popliteal-artery-and-capsule-of-knee-(ipack)|