Root Origin
- Spinal nerve roots: L4, L5, S1, S2, S3
- Plexus: Sacral plexus (lumbosacral trunk L4-L5 + ventral rami S1-S3)
- Formation: The nerve roots converge within the pelvis on the anterior surface of the piriformis muscle. The sciatic nerve is actually two nerves bundled together in a common connective tissue sheath — the tibial division (from the anterior branches of L4-S3) and the common peroneal division (from the posterior branches of L4-S2). These two divisions travel together but supply different muscles and can be affected independently.
- Type: Mixed (motor and sensory)
Course
The sciatic nerve follows a predictable path from the pelvis to the knee, with one key landmark — the piriformis muscle — that every MT must know.- Pelvis. The nerve roots converge on the anterior (pelvic) surface of the piriformis. The complete nerve exits the pelvis through the greater sciatic foramen, emerging inferior to the piriformis in approximately 85% of people. In the remaining 12-15%, the nerve or one of its divisions passes through the piriformis muscle belly itself — this anatomical variant is the basis for conditions/piriformis-syndrome. Other rare variants include the nerve passing superior to the piriformis or splitting, with one division above and one below.
- Gluteal region. After exiting beneath the piriformis, the nerve descends across the posterior surface of the obturator internus, gemelli, and quadratus femoris (the deep hip external rotators). It lies deep to the gluteus maximus at this level. The nerve passes roughly midway between the greater trochanter and the ischial tuberosity — this is the key palpation landmark. You can approximate the nerve's location by drawing an imaginary line between these two bony points; the nerve crosses near the midpoint.
- Posterior thigh. The nerve descends vertically through the posterior thigh, deep to the long head of the biceps femoris. It lies on the adductor magnus, which acts as the nerve's "floor" in the thigh. Along this course, the nerve gives off muscular branches to the hamstrings. The tibial division supplies three of the four hamstrings (semimembranosus, semitendinosus, and biceps femoris long head). The common peroneal division supplies the biceps femoris short head — the only hamstring innervated by the peroneal division. This is clinically relevant: isolated short head weakness points to common peroneal involvement, not tibial.
- Popliteal fossa (division point). The nerve divides into its two terminal branches — the tibial nerve and the common peroneal (fibular) nerve — at the superior angle of the popliteal fossa, typically about two-thirds of the way down the thigh. However, this division point is highly variable. In approximately 10-12% of people, the nerve divides much higher — even in the pelvis or gluteal region. When the division occurs high, the two branches may pass on either side of the piriformis, creating a variant that predisposes to piriformis syndrome.
- Below the knee (via terminal branches). The tibial nerve continues straight down through the popliteal fossa and posterior leg, eventually passing behind the medial malleolus into the foot. The common peroneal nerve wraps laterally around the neck of the fibula — the most superficially exposed point of any major lower extremity nerve — before entering the anterior and lateral leg compartments.
Motor Distribution
The sciatic nerve innervates all muscles of the posterior thigh and, through its terminal branches, all muscles below the knee. Nothing in the anterior thigh (that is the femoral nerve) or medial thigh (that is the obturator nerve).Posterior Thigh — Tibial Division
| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/semimembranosus | Knee flexion, hip extension, medial rotation of tibia | Deepest hamstring; attaches broadly to posterior medial tibial condyle |
| anatomy/muscles/semitendinosus | Knee flexion, hip extension, medial rotation of tibia | Part of the pes anserine group (with sartorius and gracilis) |
| anatomy/muscles/biceps-femoris-long-head | Knee flexion, hip extension, lateral rotation of tibia | Shares the ischial tuberosity origin with semitendinosus |
| anatomy/muscles/adductor-magnus (hamstring portion) | Hip extension | Only the posterior (ischial) portion is sciatic — the anterior (adductor) portion is obturator nerve |
Posterior Thigh — Common Peroneal Division
| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/biceps-femoris-short-head | Knee flexion, lateral rotation of tibia | The ONLY hamstring from the peroneal division; isolated weakness here localizes to the peroneal branch |
Below the Knee — Tibial Nerve (Terminal Branch)
All posterior and plantar muscles of the leg and foot:| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/gastrocnemius | Plantar flexion, knee flexion | Two-joint muscle — crosses both knee and ankle |
| anatomy/muscles/soleus | Plantar flexion | Deep to gastroc; the primary plantar flexor during stance |
| anatomy/muscles/plantaris | Weak plantar flexion | Vestigial muscle; tendon often harvested for surgical grafts |
| anatomy/muscles/popliteus | Unlocks the knee from full extension, medial rotation of tibia | The "key" that unlocks the screw-home mechanism |
| anatomy/muscles/tibialis-posterior | Plantar flexion, inversion | Primary dynamic support for the medial longitudinal arch |
| anatomy/muscles/flexor-digitorum-longus | Flexes toes 2-5, plantar flexion | Deep posterior compartment |
| anatomy/muscles/flexor-hallucis-longus | Flexes great toe, plantar flexion | Critical for push-off in gait |
| Intrinsic foot muscles (plantar) | Various toe movements, arch support | Supplied by the medial and lateral plantar nerves (tibial branches) |
Below the Knee — Common Peroneal Nerve (Terminal Branch)
All anterior and lateral muscles of the leg: Deep Peroneal Branch:| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/tibialis-anterior | Dorsiflexion, inversion | The muscle that lifts your foot so you do not trip while walking |
| anatomy/muscles/extensor-digitorum-longus | Extends toes 2-5, dorsiflexion | Anterior compartment |
| anatomy/muscles/extensor-hallucis-longus | Extends great toe, dorsiflexion | Palpable tendon on dorsum of foot |
| anatomy/muscles/peroneus-tertius | Dorsiflexion, eversion | Not always present; lies lateral to EDL |
| anatomy/muscles/extensor-digitorum-brevis | Extends toes 2-4 | Only intrinsic muscle on the dorsum of the foot |
| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/peroneus-longus | Eversion, plantar flexion | Tendon crosses under the foot to stabilize the first ray |
| anatomy/muscles/peroneus-brevis | Eversion, plantar flexion | Attaches to the base of the 5th metatarsal |
Sensory Distribution
The sciatic nerve provides sensation to the entire lower leg and foot — the only part of the leg it does NOT supply is the medial leg (that is the saphenous nerve, a branch of the femoral nerve).- Posterior thigh. Often attributed to the sciatic nerve, but the posterior thigh skin is actually supplied by the posterior cutaneous nerve of the thigh (S1-S3) — a separate nerve that exits the pelvis alongside the sciatic nerve and is frequently confused with it. True sciatic sensory territory begins below the knee.
- Tibial nerve sensory territory:
- Sural nerve (formed from tibial contribution + communicating branch from common peroneal) — posterolateral leg and lateral foot
- Medial plantar nerve — medial sole, great toe, and second/third toes (analogous to the median nerve in the hand)
- Lateral plantar nerve — lateral sole, fourth toe, little toe (analogous to the ulnar nerve in the hand)
- Medial calcaneal nerve — medial heel
- Common peroneal nerve sensory territory:
- Superficial peroneal nerve — anterolateral leg and dorsum of the foot (except the first web space)
- Deep peroneal nerve — first web space only (the small patch of skin between the great toe and second toe)
- Lateral sural cutaneous nerve — lateral proximal leg
- Clinical significance of sensory mapping: Dermatomal testing of the foot helps localize the level of nerve root compression. L4 dermatome covers the medial leg and foot; L5 covers the lateral leg and dorsum of the foot; S1 covers the lateral foot and sole. When a patient says "my foot is numb," asking exactly where narrows the differential significantly.
Entrapment Sites
1. Piriformis Muscle
- Location: Greater sciatic foramen, where the nerve exits the pelvis inferior to the piriformis
- Structure: The piriformis muscle itself compresses the nerve. In the normal variant (~85%), compression occurs between the piriformis and the underlying bony pelvis. In the through-muscle variant (~12-15%), the nerve or one division passes directly through the piriformis belly, making it vulnerable to even mild muscular hypertrophy or spasm.
- Condition: conditions/piriformis-syndrome
- Presentation: Deep buttock pain radiating down the posterior thigh. Pain increases with prolonged sitting, hip flexion with adduction and internal rotation (which stretches and compresses the piriformis against the nerve). May mimic L5 or S1 radiculopathy.
- Key differentiator from disc herniation: SLR is typically negative in piriformis syndrome; the FAIR test is the specific provocation. Lumbar ROM is full and painless.
- MT relevance: Piriformis syndrome is a muscular compression problem — first-line treatment includes specific compression, myofascial release, and muscle energy techniques (see Clinical Notes).
2. Sciatic Notch Compression
- Location: Greater sciatic notch, the bony groove in the posterior pelvis
- Structure: The nerve can be compressed against the bony notch by external forces — most commonly prolonged sitting on hard surfaces or trauma to the buttock region
- Presentation: "Wallet sciatica" or "back pocket syndrome" — posterior thigh and leg symptoms that develop after prolonged sitting, especially on hard surfaces with a wallet or object in the back pocket. Also seen after falls directly onto the buttock.
- MT relevance: Identify and remove the external compression source (wallet, hard surface, recent fall). Manual therapy addresses reactive muscle guarding.
3. Ischial Tuberosity (Hamstring Origin)
- Location: Proximal posterior thigh, at the ischial tuberosity where the hamstrings originate
- Structure: Hamstring tendinopathy, bursitis, or scar tissue from hamstring origin injuries can compress the sciatic nerve as it passes alongside the ischial tuberosity
- Presentation: Deep buttock pain and sitting pain that overlaps with both proximal hamstring tendinopathy and piriformis syndrome. The distinguishing feature is tenderness localized to the ischial tuberosity (not the piriformis) and pain with resisted knee flexion.
- MT relevance: Post-injury scar tissue management around the ischial tuberosity can prevent entrapment. Distinguish sources: resisted knee flexion loads the tendon; SLR loads the nerve.
Clinical Tests
| Test | Procedure | Positive Finding | What It Tells You |
|---|---|---|---|
| SLR / Lasegue's test | Patient supine. Lift the extended leg passively by the heel. | Reproduction of sciatic symptoms (radiating pain below the knee) between 30-70 degrees of hip flexion. Pain above 70 degrees is more likely hamstring tightness, not neural. | Tension on the sciatic nerve and dural sleeve reproduces the radicular pain. The most well-known neural tension test. Sensitivity ~91% for disc herniation, specificity only ~26% — many false positives. |
| Crossed SLR (well-leg raise) | Same as SLR, but lift the uninvolved leg. | Pain reproduces in the symptomatic leg. | Much more specific (~88%) than the standard SLR. A positive crossed SLR strongly suggests a large disc herniation compressing the nerve root medially. If this is positive, the lesion is likely significant. |
| Slump test | Patient sitting at the edge of the table. Flex the thoracic and lumbar spine (slump), flex the cervical spine (chin to chest), extend the knee, dorsiflex the ankle. Applied sequentially to progressively tension the neural structures. | Reproduction of symptoms. Symptoms should decrease when cervical flexion is released — this confirms the neural origin of the pain (releasing the proximal end of the neural chain reduces tension on the whole system). | A comprehensive neurodynamic test for the entire spinal cord, nerve roots, and sciatic nerve. More sensitive than SLR alone because it adds thoracic and cervical tension to the chain. |
| FAIR test | Patient side-lying with the affected side up. Hip flexed to 60 degrees, adducted and internally rotated. Apply downward pressure on the knee. | Reproduction of sciatic symptoms in the buttock and posterior thigh. | Specific to piriformis syndrome — this position stretches the piriformis across the sciatic nerve. Combines compression (adduction) with elongation (internal rotation). |
| Lower extremity neuro screen | Test myotomes (L4: ankle dorsiflexion; L5: great toe extension; S1: plantar flexion/eversion), dermatomes (pin-prick along L4, L5, S1 distributions), and reflexes (L4: patellar; S1: Achilles). | Specific myotomal weakness, dermatomal sensory loss, or reflex diminution at a single level. | Localizes the nerve root level. A positive neuro screen combined with a positive SLR strongly supports radiculopathy at a specific level. Normal neuro screen with buttock pain suggests piriformis, not root compression. |
| Bowstring sign (popliteal compression) | During a positive SLR, lower the leg slightly until symptoms decrease, then flex the knee slightly. Apply direct pressure to the tibial nerve in the popliteal fossa. | Return of sciatic symptoms with popliteal pressure. | Confirms that the sciatic nerve (not the hamstrings or hip joint) is the source of the positive SLR. A useful confirmatory test when SLR results are equivocal. |
Clinical Notes
These are the observations that shape how an MT should think about the sciatic nerve in daily practice.- "Sciatica" is a symptom, not a diagnosis. When a patient says "I have sciatica," what they mean is "I have pain going down my leg." Your job is to figure out why. The causes include lumbar disc herniation (most common), piriformis syndrome, spinal stenosis, spondylolisthesis, and gluteal trigger points. Each requires a different treatment approach. Do not treat "sciatica" — treat the cause.
- Gluteus minimus trigger points mimic sciatic distribution almost exactly. This is possibly the most under-recognized cause of leg pain in clinical practice. Trigger points in the gluteus minimus refer pain down the lateral leg all the way to the ankle, perfectly mimicking L5 sciatica. If SLR is negative, the neuro screen is normal, and the pain pattern follows L5, palpate the gluteus minimus. This is the classic pseudo-sciatica — and it responds dramatically to trigger point treatment.
- Piriformis variant anatomy matters. In approximately 12-15% of the population, the sciatic nerve or one of its divisions passes through the piriformis muscle belly instead of beneath it. These individuals are predisposed to piriformis syndrome, and their symptoms may be more resistant to treatment because the compression is intramuscular rather than external. You cannot determine the variant from physical examination — but if piriformis release produces inconsistent results, the through-muscle variant may explain why.
- The division point varies — and it matters. The sciatic nerve normally divides into the tibial and common peroneal nerves near the top of the popliteal fossa. But in 10-12% of people, this division happens much higher — even within the pelvis. When the division occurs high, the two branches may straddle the piriformis (one above, one below), and selective compression of one division can produce confusing clinical pictures (e.g., peroneal symptoms without tibial involvement).
- Foot drop is an emergency sign. If a patient presents with inability to dorsiflex the foot or "slapping" gait (foot drops during swing phase), this indicates common peroneal nerve dysfunction. While foot drop can result from peroneal compression at the fibular head (external cause — crossed legs, tight cast), acute foot drop with back pain suggests a large disc herniation compressing the L4-L5 nerve root. This is a medical emergency if accompanied by bowel or bladder changes — suspect cauda equina syndrome and refer immediately.
- SLR sensitivity vs. specificity — know the tradeoff. SLR is very sensitive (~91%) but not very specific (~26%) for disc herniation. This means a negative SLR makes disc herniation unlikely (good for ruling out), but a positive SLR does not confirm it (many false positives from hamstring tightness, hip pathology, or neural irritability from any cause). The crossed SLR has the opposite profile — low sensitivity but high specificity (~88%). When both are positive, you can be reasonably confident the disc is involved.
- Posterior cutaneous nerve of thigh gets blamed on the sciatic. Pain and paresthesia limited to the posterior thigh — without extending below the knee — is more likely the posterior cutaneous nerve of thigh than the sciatic nerve. This nerve exits the pelvis alongside the sciatic and can be compressed by the same structures (piriformis, ischial tuberosity). But its territory is the posterior thigh and buttock, not the leg. If symptoms do not extend below the knee, reconsider the diagnosis.
- The sitting vs. standing question differentiates causes. Disc herniations typically worsen with sitting (increased intradiscal pressure) and improve with standing or walking. Spinal stenosis does the opposite — symptoms worsen with standing and walking (spinal extension narrows the canal) and improve with sitting or forward flexion. This single question — "Does it get worse when you sit or when you stand?" — is one of the most efficient differentiators in clinical practice.
Related Nerves
- anatomy/nerves/tibial-nerve — Terminal branch of the sciatic nerve (from the tibial division). Continues the sciatic path through the posterior leg. Supplies the calf muscles and plantar foot muscles. Entrapment at the tarsal tunnel behind the medial malleolus produces conditions/tarsal-tunnel-syndrome — the lower extremity equivalent of carpal tunnel syndrome.
- anatomy/nerves/common-peroneal-nerve — Terminal branch of the sciatic nerve (from the common peroneal division). Wraps around the fibular head — the most vulnerable point of any lower extremity nerve. Supplies the anterior and lateral leg compartments. Damage here causes foot drop.
- anatomy/nerves/posterior-cutaneous-nerve-of-thigh — S1-S3, exits the pelvis with the sciatic nerve. Supplies posterior thigh skin. Frequently confused with the sciatic nerve because they share the same exit point and the same compression by the piriformis. The key difference: posterior cutaneous nerve symptoms stay in the thigh; sciatic symptoms extend below the knee.
- anatomy/nerves/femoral-nerve — L2-L4, lumbar plexus. Supplies the anterior thigh (quadriceps). The main differential when leg symptoms do not fit the sciatic pattern — anterior thigh pain, weak knee extension, and diminished patellar reflex suggest femoral rather than sciatic involvement.
- anatomy/nerves/superior-gluteal-nerve — L4-S1. Exits above the piriformis (the sciatic exits below). Supplies the gluteus medius, gluteus minimus, and TFL. Damage causes Trendelenburg gait — the pelvis drops on the unsupported side during single-leg stance.
Key Takeaways
- "Sciatica" is a symptom, not a diagnosis — the MT must differentiate disc herniation, piriformis syndrome, stenosis, and pseudo-sciatica from trigger points.
- Gluteus minimus TrPs are the most commonly missed pseudo-sciatica source — they mimic L5 dermatomal pain and respond dramatically to treatment.
- SLR is sensitive but not specific; crossed SLR is specific but not sensitive. Use both.
- Foot drop with back pain and bowel/bladder changes = suspect cauda equina. Refer immediately.
- Sitting vs. standing pain differentiates disc herniation (worse sitting) from spinal stenosis (worse standing).