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Measuring  Subtalar Joint (STJ) Neutral
The STJ is neutral when it it is neither pronated nor supinated. Because the STJ's axis is oriented obliquely, the joint's motion is triplanar. In an open chain, the calcaneus and forefoot move simultaneously. In closed chain, when body weight stabilizes the foot against the floor, the STJ motion requires motion in proximal segments and joints like the talus, tibia and knee.
Easy Way
1. Palpate medial and lateral aspects of the head of talus.
2. Invert and evert the rearfoot in the frontal plane.
3. The STJ Neutral is where the talar head protrudes equally on medial and lateral sides.

Hard (and more precise) Way
1. Using a skin pencil, draw a line that bisects the posterior calcaneus and lower 1/3 leg.
2. With the patient prone, let the ankle and foot hang over end of table.
3. Place the calcaneus in the frontal plane.
4. Center a goniometer's axis between the malleoli in the frontal plane.
5. Align the goniometer's stationary arm so that it parallels the line on the leg's distal third.
6. Align the moving arm so that it parallels the line on the calcaneus.
7. Lock the forefoot by grasping the fourth and fifth metatarsal heads and moving them dorsally.
8. Maximally supinate the STJ, realign the goniometer's arms and read the degrees of inversion.
9. Maximally pronate the STJ, realign the goniometer and read the degrees of eversion.
10. Measure total STJ range of motion (inversion + eversion).
11. Divide that number by 3, to get X degrees.
12. The STJ Neutral Position is when the rearfoot is inverted by X degrees from maximally everted.  

Regardless of the method used to measure STJ Neutral Position, it is universally accepted as the position used for the fabrication of orthotic devices.   
  

Short Leg Syndrome
The presence of short leg syndrome is usually associated with pelvic or lumbar misalignment. The short leg may be functional, anatomical, or a combination of both. Studies have found that the majority presenting to our offices are functional, but a growing number seen are anatomical, the result of post hip or knee replacement surgeries.

FUNCTIONAL SHORT LEG:
1) Sacroiliac joint that is misaligned causing the sacral base to drop to one side.
2) There is a flexion or extension with one of the iliac bones out of its normal anatomical position.
3) Posterior tibial tendon dysfunction causing the subtalar joint to over pronate effectively shorting the limb.

ANATOMICAL SHORT LEG:
1) Hip or knee replacement surgery.
2) Polio
3) Congenital, birth injuries and infections to the growth plates.
4) Fractures

BIOMECHANICS OF THE SHORT LIMB:
1) Supination of the subtalar joint.
2) External rotation of the tibia.
3) External rotation of the knee.
4) Abnormal patella tracking.
5) Pelvic tilt.
6) Shifting of the center of gravity to the short side.

BIOMECHANICS OF THE LONG LIMB:
1) Pronation of the subtalar joint.
2) Internal rotation of the tibia and knee.
3) Abnormal patella tracking.
4) Vaulting over the hip joint.

GAIT EVALUATION
1) Center of gravity shifted to the short side.
2) Unilateral early heel lift.
3) Pelvic tilt.
4) Shoulder drop.
5) Unilateral subtalar pronation.
6) Unilateral shoe wear (lateral heel)
7) Abnormal knee rotation and patella tracking.