What is SSI?

Shoe Stability Index (SSI) is an indicator of shoe stability, as an index. SSI is derived through mathematically combining the quantified measurements of midfoot stability (TCI) and hindfoot stability (VCI), indicating the shoe’s overall ability to control the motion of the foot.

What is TCI?

Torsion Control Index (TCI) is a measurement of midfoot shoe stability, in inch-pound units (in.-lbs.). TCI is measured through actively twisting a shoe around the longitudinal axis of the shoe, from the heel to the area of the toes joints, simulating rotational forces of the foot, and measuring the shoe’s resistance to this motion.

The higher the TCI, the firmer the midfoot and more torsional stability. The lower the TCI, the softer the midfoot and less torsional stability.

What is VCI?

Vertical Compression Index (VCI) is a measurement of hindfoot shoe stability, in millimeters (mm). VCI is measured through compression of the heel portion of the shoe under a fixed amount of pressure, thereby measuring how the structure of the shoe controls rearfoot motion.

The higher the VCI, the softer the midsole and less hindfoot stability. The lower the VCI, the firmer the midsole and more hindfoot stability.

What is Loaded Heel to Toe Drop?

Loaded Heel to Toe Drop is the measurement in millimeters of the height of the heel relative to the fore foot when compressed to a fixed poundage. This can be defined as vertical support.

What is RI?

Rebound Index (RI) is an indicator of energy return of shoe to the foot, in millimeters (mm). RI is measured through compression of the heel portion of the shoe under a fixed amount of pressure, and then determining how much force the shoe exerts on the foot.


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  • Tenderness and pain between the metatarsal heads
  • Increased pain with walking and running activities

Possible Causes

  • Pronation may increase symptoms
  • Shoes with tight fitting toe box and insufficient torsional support in midsole

Shoe Profile

For moderate to excessive pronators, the long axis of the shoe should provide maximum torsional control of foot rotation (pronation) and the midsole should provide proper vertical support. Proper support reduces shearing forces on the metatarsal heads that leads to pain and tenderness. Shoes should have a wide toe box to reduce compression of the metatarsals.


Neutral (mild pronators) – Over-the-counter orthotics with appropriately placed metatarsal support
Moderate to excessive prontators – Custom orthotics

Shoe Recommendations

The following shoes meet these criteria. Please click on the appropriate link to see the shoes and their test data.

personal_male_2 personal_female_2

Recommended Accessories

SuperFeet arch supports

Stabilizes the foot to reduce pronation and shearing forces in the forefoot resulting in less irritation of the neuroma.

Neuroma pads

Separates and displays the bones in the ball of the foot (metatarsal heads) to reduce pressure on the neuromas. Pads should be placed just behind the affected metatarsals.

October 2023 test data is now live!