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

Orthotics is a branch of medicine dealing with the making and fitting of orthotic devices. There are many interchangeable terms for this, a few being foot orthotic/orthosis/insole/shoe insert.

Three Main Types of Foot Orthoses

1. Off the shelf (OTS) Insoles
2. Functional Foot Orthoses (FFO)
3. Custom Molded Total Contact Insoles (TCI)

What do foot orthoses do?

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 not a nerve, tendon or muscle, but a strong fibrous tissue. This stiff and relatively impermeable covering helps to protect the muscles of the sole of the foot.

• This tissue originates deep within the plantar surface of the calcaneus fanning out across the met 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

Hicks first described the windlass mechanism in 1954 as 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. He proposed that dorsiflexion of the toes tightens the plantar aponeurosis and pulls the metatarsal heads towards the calcaneus thereby increasing the structural 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 by its nature of many articulations and requires to be flexible at times and rigid at other times to promote normal gait. Important to remember that the plantar fascia will stretch and recoil at different stages of the gait cycle.

Important Joints with regards to Foot Orthosis for ROM in the Foot/Ankle

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 & laterally rotated subtalar joint

Purpose of human foot

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

The human foot is a complex mechanism with a number of theories of biomechanics. The structure, function and position leave the foot exposed to risk of injury. When understanding the foot biomechanics, it is key to assess in non weight bearing, weight bearing and during gait.

Orthotic Foot Ankle Assessment

1. Patient History
2. ROM
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

o Passive and Active

Weightbearing and Non weightbering

o Active

Orthotic Foot Ankle Assessment

Movements in foot/ankle

o Dorsiflexion/ Plantarflexion - Ankle Joint

o Pronation/ Supination – Subtalar joint

o Eversion/ Inversion

o Abduction/ Adduction

o Toe flexion/ extension – MTP joints

Non weight bearing assessment

•Windlass Test- can be effective in examining dysfunction of the plantar fascia,

although specificity has not been proved.

o Non-weight bearing or weight bearing

o Passively extend hallux at MTP joint

o Plantar aponeurosis should tighten and reduces dist between calcaneus and Metatarsals.

o Note angle of extension to initiate arch, can vary

o Increase MLA

o Positive test= A positive test is considered if passive extension is continued to end range or until the patient's pain is reproduced in Plantarfascitis

o Pain in medial calcaneus and plantarfascia on palpation

Hallux Limitus/rigidus

• Hallux Rigidus
  • Very limited dorsiflexion mobility or no mvt. there is crepitation with joint mobilization 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, loss of metatarsophalangeal joint extension during the second half of the single-support phase, when the weightbearing foot is in maximal dorsiflexion.

• Both affect the windlass mechanism and gait pattern and normal functioning of the foot.

3. Muscles around foot/ankle- oxford scale

There are 5 muscle compartments in the lower leg

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

6. Biomechanical Analysis

Static

o Overall biomechanics of standing, knees hips pelvis

o STJt alignment – medial/lateral devn- supination

resistance test

o Too many toes, 1 & 4/5, more lateral more pronated

o Rear foot/forefoot

o Hallux extension – Jacks, Windlass test

Root V STJt equilibrium

• Sub Talar Joint Equilibrium -K. Kirby

(2001)

• Spatial location of the subtalar joint

axis in relation to the weightbearing

structures of the plantar foot

• concept of subtalar joint rotational

equilibrium

• externally generated forces, such as

GRF and internally generated forces,

such as ligamentous and tendon

tensile forces and joint compression

forces, affect the mechanical

behavior of the foot and lower

extremity

• Root Theory Model -Root (1954 – 1966)

• Basis was to classify normal & abnormal foot

types (osseous alignment). › “

• Normal/ideal foot alignment occurs when:

• Distal 1/3 of leg vertical

• Calcaneus vertical to supporting surface

• Plantar forefoot parallel to plantar rearfoot

• Variations from this “normal’ foot alignment

(‘intrinsic foot deformities’) lead to abnormal

foot function

Sub Talar Joint Equilibruim

Kirby 2001

Biomechanical Analysis - Dynamic Normal walking,

o IC heel strike,

o Loading response

o MS mid stance, single

o Terminal stance, single

o Pre swing

o Swing Phase

o ground clearance,

o Single 40% /

double support

60%

o Timing- load rate=

stress

7. Leg Length Discrepancy (LLD)

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