1. MUSCLE FACTS
An external rotator, weak abductor, and weak flexor of the hip
Provides postural stability during ambulation and standing
Originates at the anterior surface of the sacrum, usually at the levels of vertebrae S2 through S4, at or near the sacroiliac joint capsule.
Attaches to the superior medial aspect of the greater trochanter via a round tendon
In many individuals, the tendon merges with the tendons of the obturator internus and gemelli muscles
The piriformis muscle is innervated by spinal nerves S1 and S2—and occasionally also by L5.
PIRIFORMIS SYNDROME

2. Piriformis Syndrome Features
A chronic nagging ache, pain, tingling, or numbness
starts in the buttocks
can extend along the course of the sciatic nerve
down the entire back of the thigh and calf, and sometimes into the foot
Pain worsens when the piriformis is pressed against the sciatic nerve-
(eg, while sitting on a toilet, a car seat, or a narrow bicycle seat or while running).

3. The piriformis syndrome is a rare entrapment
neuropathy in which the sciatic nerve is
compromised by an abnormal piriformis muscle.
Approximately 6% of lower back pain and
sciatica cases seen in a general practice may be
caused by piriformis syndrome

4. Signs and symptoms of pain in the sciatic nerve distribution:
Gluteal area
Posterior thigh
Posterior leg
Lateral aspect of the foot.
1) The nerve passes anteriorly to the piriformis between the rims of the greater sciatic foramen.
(2) The peroneal portion of the sciatic nerve passes through the piriformis; the tibial portion passes anterior to the piriformis muscle. (3) The peroneal branch of the sciatic nerve loops above and posterior to the piriformis muscle, whereas the tibial branch passes anterior to the piriformis muscle.
(4) The undivided sciatic nerve penetrates the piriformis muscle.

5. Demography and features of Piriformis Syndrome
Female-to-Male incidence ratio of piriformis syndrome is 6:1
Positive Lasegue sign-straight leg raising test
Sausage-shaped mass over the piriformis muscle
Gluteal atrophy in chronic cases
Trauma to the region
Pain in the sacroiliac region, gluteal muscles, or greater sciatic notch
Pain exacerbated by lifting the leg and relieved by traction on the affected extremity

6. Causes of Piriformis syndrome
Trauma to the buttocks or gluteal region is the most common cause of piriformis syndrome.
Skiers, truck drivers, tennis players, and long-distance bikers are at high risk.
In Morton foot, the prominent head of the second metatarsal causes foot instability and a reactive contraction of the external rotators of the hip during gait.
Spinal Stenosis can lead to bilateral piriformis tenderness.
Anatomic variations of the divisions of the sciatic nerve above, below, and through the belly of the piriformis muscle may be causative factors.

7. 40-year-old man with piriformis syndrome
40-year-old man with piriformis syndrome. Unenhanced axial T1-weighted MR image of sacrum- shows accessory fibers of right piriformis muscle (a) overlying right S2 nerve (arrow) and attaching medially.
Note that accessory fibers of right piriformis muscle and right S2 nerve are of normal signal intensity.
p = normal left piriformis muscle at sacral attachment.

8. 40-year-old man with piriformis syndrome.
Unenhanced oblique coronal T1-weighted MR image shows accessory fibers of right piriformis muscle (a) anterior to and obscuring right S2 nerve.
p = normal right and left piriformis muscles.

9. Symptoms
Pain with sitting, standing, or lying longer than 15 to 20 minutes
Pain and/or paresthesia radiating from sacrum through gluteal area and down posterior aspect of thigh, usually stopping above knee
Pain improves with ambulation and worsens with no movement
Pain when rising from seated or squatting position
Change of position does not relieve pain completely
Contralateral sacroiliac pain
Difficulty walking (eg, antalgic gait, foot drop)
Numbness in foot
Weakness in ipsilateral lower extremity
Headache
Neck pain
Abdominal, pelvic, and inguinal pain
Dyspareunia in women
Pain with bowel movements

10. Signs
Tenderness in region of sacroiliac joint, greater sciatic notch, and piriformis muscle
Tenderness over piriformis muscle
Palpable mass in ipsilateral buttock
Traction of affected limb provides moderate relief of pain
Asymmetrical weakness in affected limb
Lasègue sign positive
Localized pain when pressure is applied over the piriformis muscle and its tendon, especially when the hip is flexed at an angle of 90 degrees and the knee is extended

11. Tests for Piriformis Syndrome
The involved hip is flexed, passively adducted, and internally rotated in a standing position.
The involved hip is flexed, passively adducted, and internally rotated while the patient is reclined

12. The involved hip is flexed, passively adducted, and internally rotated while the patient is reclined.

13. Freiberg test: Forceful internal rotation of the affected side elicits pain.
Beatty maneuver: Patient lies on the uninvolved side and abducts the involved thigh upward, which elicits pain.

14. Piriformis Stretch
Place the right knee on the ground roughly in line with your left shoulder
The right foot should be just in front of the left knee
Press your hips towards the ground so that your bodyweight is on your right leg.
As you move (torso) down the right knee comes closer to the left shoulder.
You should feel a gentle pull deep in the right hip / buttocks.