Foot Orthotics Assessment

Original Editor - Carin Hunter based on the course by Donna Fisher
Top Contributors - Carin Hunter, Jess Bell, Kim Jackson, Ewa Jaraczewska, Lucinda hampton and Tarina van der Stockt

Introduction

Orthotics is a branch of medicine that deals with the making and fitting of orthotic devices. There are many interchangeable terms for this, a few being foot orthotic/orthosis/insole/shoe insert. Before an orthosis can be prescribed, a comprehensive assessment needs to be conducted to correctly prescribe a device that will meet all the requirements. Selecting an orthotic device can be complicated as there are many factors that need to be considered aside from biomechanical considerations, including comfort and aesthetics to enhance patient compliance.

Three Main Types of Foot Orthoses

1. Off the shelf (OTS) insoles
2. Functional foot orthoses (FFO)
3. Custom moulded total contact insoles (TCI)

Purpose of Foot Orthoses

A foot orthosis is generally referred to as an "externally applied apparatus that can be inserted in a shoe to help support or improve the function of the foot and/or ankle." The two main goals of an orthotic device are to reduce pressure across an area or to accommodate congenital or acquired deformities. The ultimate aim is to achieve / maintain near-neutral subtalar joint alignment during the gait cycle or the individual's highest functional level.

1. Support
2. Correct, if mobile
3. Accommodate if not
4. Shock absorption
5. Re-distribute pressure

Basic Foot Anatomy

1. 28 bones
2. 33 joints
3. Ligaments
4. Tendons
5. Muscles
6. Joints
7. Plantar fascia

Plantar Fascia

• The plantar fascia is a strong, fibrous tissue. It is not a nerve, tendon or muscle. Because it is stiff and largely impermeable, it is able to help protect the muscles of the sole of the foot.
• Its origins are deep within the plantar surface of the calcaneus and it fans out across the metatarsal heads. It divides and attaches to the base of the phalanges of each toe.
• During walking, as the toes dorsiflex at push off, the plantar fascia wraps around the metatarsal heads and tightens. This pulls the calcaneus towards the metatarsal heads and in turn maintains the shape of the longitudinal arch and supports the foot to enable propulsion. This is a phenomenon known as the windlass mechanism.

Windlass Mechanism

The windlass mechanism was first described by JH Hicks in 1954. Essentially it is: "a one-to-one coupling between metatarsal joint dorsiflexion and medial longitudinal arch rise." Based on an engineering concept of lifting weights via a pulley system, Hicks noted that during dorsiflexion of the toes, the plantar aponeurosis tightens. This draws the metatarsal heads towards the calcaneus, which increases the height of the longitudinal arch. This action occurs naturally at push off in gait cycle as toes dorsiflex and the foot becomes stiffer to aid propulsion. During loading and mid stance, the arch will stretch. The human foot is flexible due to its many articulations. However, it needs to be both flexible and rigid to promote normal gait. It is important to remember that the plantar fascia will stretch and recoil at different stages of the gait cycle.

Important Joints to Consider for Foot Orthosis

1. Hindfoot
   1. Talocrural Joint
   2. Sub Talar joint
2. Mid Foot
   1. Tarsometatarsal Joint
   2. Calcaneocuboid Joint
   3. Talonavicular Joint
3. Fore Foot
   1. 1st Metatarsal Phalangeal Joint

Terminology used in Orthotics

Valgus –everted
Neutral
Varus –inverted
Pronation – eversion, abduction, dorsiflexion & medially rotated subtalar joint
Supination – inversion, adduction, plantarflexion and laterally rotated subtalar joint.

Purpose of the Human Foot

“[The human foot] enables propulsion through space, adaptation to uneven terrain, absorption of shock, and support of body weight.”

There are a number of biomechanical theories in relation to the human foot. Its structure, function and position leave it exposed to injury. To understand the foot, it is key to assess it in non-weight-bearing and weight-bearing positions, and during gait.

Orthotic Foot Ankle Assessment

During a foot and ankle assessment for orthotics selection, you will need to look at:

1. Patient history
2. Range of motion
3. Muscle power
4. Sensation / pain
5. Proprioception
6. Biomechanical analysis
7. Leg length

1. Patient History

• Gait pattern and biomechanical analysis on entrance
• Type of shoes
• Assistive devices
• History of underlying conditions, foot problems and the primary problem affecting the individual on consultation.

2. Range of Motion

When considering foot orthosis design, the following range of motion tests should be carried out:

1. Active
2. Passive
3. Weight-bearing
4. Non-weight-bearing

Active and passive movements of the foot and ankle

• Dorsiflexion/ plantarflexion = a quick test for the ankle joint
• Pronation/ supination = a quick test for the subtalar joint
• Eversion/ inversion
• Abduction / adduction
• Toe flexion/ extension = a quick test for the Metatarsal Phalangeal joints

Non-weight-bearing assessment

• Windlass Test - can be effective for examining dysfunction of the plantar fascia although specificity has not been proved.
  • Passively extend hallux at the MTP joint
    • The plantar aponeurosis should tighten and reduce the distance between the calcaneus and metatarsals.
    • Please note that the angle of extension to initiate the arch can vary
    • Increase medial longitudinal arch
  • Positive Test: a test is considered positive if passive extension continues to end range or until the patient's pain is reproduced in plantar fasciitis
• Pain in medial calcaneus and plantar fascia on palpation

• Hallux limitus/rigidus
• Both affect the windlass mechanism, gait pattern and normal functioning of the foot.
  • Hallux Rigidus
    • Very limited dorsiflexion mobility or no movement. There is crepitation with joint mobilisation and pain associated with any movement of the first MTP joint.
  • Hallux Limitus (FnHL)
    • Reduced dorsiflexion movement, resulting in reduced range of dorsiflexion of the first MTP joint.
    • In gait, there is a loss of metatarsophalangeal joint extension during the second half of the single-support phase, when the weightbearing foot is in maximal dorsiflexion.

3. Muscles of the Foot and Ankle

There are four muscle compartments in the lower leg. These muscles are all tested using the standardised Oxford Scale.

Superficial Posterior Muscle Compartment
Action: Plantarflexion

Muscles: Gastrocnemius, Soleus and Plantaris

Deep Posterior Muscle Compartment

Action: Plantarflexion, Adduction and Inversion

Muscles: Tibialis Posterior, Flexor Hallicus Longus and Flexor Digitorum Longus

Lateral Muscle Compartment

Action: Dorsiflexion, Abduction and Eversion

Muscles: Peroneus Longus and Peroneus Brevis

Anterior Muscle Compartment

Action: Dorsiflexion, Abduction and Inversion

Muscles: Tibialis Anterior, Extensor Hallicus Longus and Extensor Digitorum Longus

See the following pages for more information on the muscle testing of:

• Dorsiflexion
• Plantarflexion
• Eversion
• Inversion

4. Sensation/Pain

Please see page on Sensation, Sensory Examination

5. Proprioception

Please see page on Proprioception, Assessing Proprioception

6. Biomechanical Analysis

Static

• Too many toes/ too few toes

• Jacks Test

• Windlass test

• Rear foot and forefoot alignment
• Normal/ideal foot alignment occurs when:
  • Distal 1/3 of leg is vertical
  • Calcaneus is vertical to the supporting surface
  • Plantar forefoot is parallel to the plantar rearfoot
  • Variations from this “normal’ foot alignment (‘intrinsic foot deformities’) lead to abnormal foot function

Dynamic Normal Walking

• Phases of Normal Walking
  • Heel strike
  • Mid stance
  • Terminal stance
  • Pre swing
  • Swing Phase
• Ground clearance is important in Swing phase
• Proprioception and balance are important for approximately 40% of the gait pattern where an individual is standing on one leg.

7. Leg Length Discrepancy (LLD)

1. Dipping
2. Pelvic obliquity
3. Retraction
4. Scoliosis
5. Apparent leg length
6. Actual leg length