ICB Lower Limb Biomechanics – Neutral or Ideal Positioning

ICB Lower limb biomechanics

One of the most profound changes to affect the study of foot function was the theory proposed by Root etal (Root 1964, Root et al 1971) which outlined the concept of a measurable neutral position about which the foot was supposed to function.1


There has been much conjecture about the relevance of Neutral Calcaneal Stance position (NCSP), other-wise described as a patients unique Ideal position. However, still today the ‘Root Theory’ has stood the test of time albeit with alternate theories and modifications to ensure that the process works in a clinical setting.

The Foot Posture Index (FPI) 2 is useful in establishing several methodology’s to manipulate the weight bearing foot into a posture that can be considered functionally neutral and quantify the frontal plane position of the foot.3

For clinicians the challenge is to find a fast, effective method of establishing the patients position in which, they are neither excessively pronated or excessively supinated otherwise defined as NCSP or Ideal as opposed to a resting Calcaneal Stance position RCSP. Using of the FPI in a clinical setting could be quite cumbersome as the 6 steps need to be correlated with each other and the time taken could be excessive and highly inefficient.

Most practitioners using orthotic therapy around the world have de-faulted to the Talo navicular method which, at times, made finding congruency difficult due to a lateral osseous exostosis on the talar head often being present Equal ness or congruency is not instance easy to establish.

Therefore a method which can use the FPI and additional method combining together to overcome any anatomical variances such as the ICB Anterior Line Method (ICBAAM) is of particular benefit.

The ICB AAM uses the Talo Navicular reference points aligning the tibia with the 2nd MTPJ by drawing an anterior line.

The Talo Navicular method uses talar head congruency to establish the neutral position.
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The TN Reference points can be established by placing the foot in a dorsiflexed position4

It may be useful in some cases to move the foot into inversion and eversion while palpating for the talar head This way both eversion and inversion can be clearly identified.

In the resting position the Anterior line will deviate medially indicating that pronation is evident and Laterally if the foot is supinating.

TN reference points

TN reference points are exposed when the foot is dorsiflexed with the heel on the ground.

At rest the tibial varum alignment aligns with the 1stMTPJ on a excessively pronated foot.

The Rearfoot position can also assist in establishing neutral in conjunction with ICB AAM.

There is a direct correlation between rearfoot alignment and anterior alignment position.
Calcaneal bisection

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When finding the tibial varum angle the practitioner is conceptualising where the Tibia sits within the soft tissue and the same process is undertaken when bisecting the calcaneus.

The ICB Anterior Alignment Method is especially useful when moulding and fitting orthotics as it provides reference points that can be clearly identified when wearing shoes and socks.

Fitting Orthotics

Using the ICB Anterior Alignment Method ICB AAM to establish neutral is also useful when taking a foam box casts for custom made orthotics.

Neutral Foot Position

NB: every patients neutral may be different, use the established parameters to identify the patients ideal position. and compare with their resting position.

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1. Merrimans Assessment of the lower Limb 3rd ed p289
2. Development and validation of a novel rating system for scoring standing foot posture: The Foot Posture Index An-thony C. Redmond a,b,*, Jack Crosbie c , Robert A. Ouvrier b 10 May 2005
3. Merrimans Assessment of the lower Limb 3rd ed p290
4. The Orthotic Solution p 29
Michaud T.C., 1993 Foot Orthoses and Other Forms of Conserva-tive Foot Care. Williams and Wilkins, Baltimore, pp.93-105.
Root M L, Orien W P, Weed J H., 1977 Normal and Abnormal Func-tion of the Foot. Clinical Biomechanics Vol 2, Los Angeles
Valmassy, R.L.. Pathomechanics of Lower Extremity Function. Clinical Biomechanics of the Lower Extremity. Mosby, St Louis.