Intrinsic Foot Muscles

Original Editor - Lucinda hampton

Top Contributors - Lucinda hampton  

Introduction

The main functions of the intrinsic muscles of the foot are stabilisation of the arches and the metatarsophalangeal (MTP) and interphalangeal (IP) joints. Additionally these muscles: assist with tension regulation and counteract extrinsic muscle force production; and provide critical stabilisation of the foot allowing its transition from rigid to flexible during the gait cycle.

These muscles are arranged in four layers on the plantar (bottom) aspect of the foot. They originate and insert within the foot itself and are responsible for moving the toes and providing stability to the foot structure, particularly the arches.

• Quadratus plantae helps with toe flexion in the sagittal plane;
• Lumbricals extend the interphalangeal joint;
• Interosseus assist with the MTP joint flexion,
• IP joint extension, toe abduction and adduction.

The intrinsic foot muscles include:

Intrinsic Foot Muscles

Intrinsic Foot muscles

1. Abductor hallucis
2. Flexor digitorum brevis
3. Abductor digiti minimi
4. Quadratus plantae
5. Lumbricals (four muscles)
6. Flexor hallucis brevis
7. Adductor hallucis (oblique and transverse heads)
8. Flexor digiti minimi brevis
9. Dorsal interossei (four muscles)
10. Plantar interossei (three muscles)

See also Basic Foot and Ankle Anatomy - Muscles and Fascia.

"Core" Muscles of the Foot

The intrinsic muscles of the foot (IFM) are vital for good foot function. The intrinsic muscles are similar in function to the abdominal and paraspinal muscles of the lumbopelvic-hip core muscles, who are responsible for maintaining posture and stability to the body during gait. Likewise, the intrinsic muscles, provide support by maintaining and stabilizing the arches of the foot. Improving the strength and function of weak intrinsic muscles is important for many reasons. eg IFM exercises effectively improve outcomes such as foot morphology and function, balance, strength and running mechanics. Specific exercises to targeting strengthening of these muscles, improving muscle activation, mobilization (massage and manual therapy), and proprioceptive training (balance and stability exercises) are treatment options for IFM disfunction.

Physiotherapy Assessment

To assess the intrinsic foot muscles, you can use several methods:

1. Visual inspection:

• Look for flat toes when standing, which indicates good intrinsic muscle strength
• When pointing the foot, the toes should remain straight. Curling toes suggest weak intrinsic muscles

1. Paper pull-out test:

• Place a piece of paper under the toes
• Ask the patient to grip the paper with their toes
• Attempt to pull the paper out
• This tests the strength of toe or digital purchase

1. Manual muscle testing:

• Test specific muscles like flexor hallucis brevis and intrinsics
• Perform both isometric and through-range tests

1. Functional tests:

• Observe toe control during activities like walking or standing on tiptoes
• Look for the ability to keep toes flat on the ground when walking on various surfaces

1. Range of motion testing:

• Assess individual joint mobility using gliding motions
• Compare to the opposite side and normal values

1. Dynamometer testing: Use specialized equipment to measure muscle strength more precisely
2. Slow-motion video analysis: Examine joint axis locations and foot mechanics during movement
3. Gait analysis: Observe foot and lower extremity mechanics during walking or running
4. Plantar load distribution: Inspect the plantar aspect of the foot for callus patterns

Remember, a comprehensive assessment should include patient history, pain evaluation, and consideration of the entire lower extremity, not just the foot in isolation.

Physiotherapy Management

Strengthening Exercises include:

To strengthen the intrinsic foot muscles, also known as the core muscles of the foot, you can perform the following exercises:

1. 1st toe extension while stabilizing through 2nd-5th toes
2. 2nd - 5th toe flexion
3. Short foot exercise (also called make an arch exercise or doming exercise):

• Keep the foot on the floor and flex the toes without curling them
• Perform this in weight-bearing positions

Isometric contractions:

• Start with the muscles at their shortest length
• Progress to performing while sitting
• Advance to performing while standing

1. "Dance step to nowhere" exercise: Maintain an isometric contraction in the foot while mimicking a dance step
2. TheraBand exercises:

• Place a TheraBand under the front part of the foot
• Press the toes down and pull the TheraBand back
• Maintain extended toes while pressing down and gently drawing toes back to lift the arch

1. Combined intrinsic and flexor muscle exercise:

• Place TheraBand under the foot
• Press down with intrinsics while flexors keep toe tips on the ground
• Resist as the band is pulled up, pushing toes down towards the floor

1. Toe pressing exercise:

• Sit in a chair
• Press the foot and toes down, keeping toes as extended as possible
• Gently draw toes back while lifting the arch

Remember to progress gradually from easier to more challenging exercises as strength improves. These exercises help improve foot function, stability, and can aid in alleviating foot-related issues.

Flexibility and Coordination Exercises include:

You can try the following exercises:

1. Toe spreading:

• Actively spread your toes apart as wide as possible
• Hold for a few seconds, then relax
• This exercise helps stretch and improve control of the intrinsic muscles

1. Toe yoga:

• Lift your big toe while keeping the other toes down
• Then reverse, lifting the other toes while keeping the big toe down
• Alternate between these positions to improve coordination
• Marble pickup: Place marbles on the floor and try to pick them up with your toes This improves dexterity and coordination of the intrinsic muscles

1. Towel scrunches:

• Place a small towel on the floor
• Use your toes to scrunch the towel towards you
• This exercise combines stretching and coordination

1. Doming with straight toes:

• Create a dome effect with your foot while keeping your toes straight
• Focus on lifting the transverse arch without curling the toes
• This exercise improves both strength and coordination

1. Foot massage:

• Gently massage the bottom of your foot
• This can help relax tight intrinsic muscles and improve flexibility

1. Toe stretching:

• Gently pull each toe back towards the top of your foot
• Hold for a few seconds to stretch the intrinsic muscles

Remember, because intrinsic foot muscles are small and often tight from frequent use, especially in activities like ballet, they benefit greatly from regular stretching and massage. These exercises can help improve flexibility, coordination, and overall foot function.

When IFM Physiotherapy may be needed.

• IFM exercises improve foot strength and morphology in athletes, helping in injury prevention.
• Benefits, both clinical and functional, of IFM exercises in rehabilitation of the lower extremities include improving balance and strength, reducing self perceived disability, and lowered navicular drop and foot posture index. Sensory and motor function also improves with IFM exercise.
• Sarcopenic changes are evident on MRI of the foot in patients with diabetes and is profound in patients with diabetic neuropathy. The general extent and severity of sarcopenia correlates with clinical scores to assess neuropathy and is implicated in the development of diabetic foot disease. IFM strengthening and ankle mobility exercises on the foot and ankle joints can enhance ROM in the foot and hallux grip force in patient groups with DN.
• Increasing the strength of intrinsic foot muscles is effective in promoting positive biomechanical changes in the longitudinal arch of the foot
• Strengthening the plantar intrinsic foot muscles has benefits for the mobility of older adults, and can contribute to the reduction of fall risk. Evidence shows that improved IFM strength may be appropriate to incorporate in falls risk rehabilitation program.
• There is a significant association between foot pain and muscle weakness, primarily related to toe flexion and foot pain, when the pain is of frequent disabling intensity.