GENERAL INFORMATION
The peroneus tertius, also known as the fibularis tertius, is a muscle in the lower leg’s anterior compartment. It is part of the peroneal muscle group, the fibular muscles. The peroneus tertius assists in dorsiflexion and eversion of the foot, as well as providing stability during walking and running.
ORIGIN
The peroneus tertius muscle originates from two locations:
- The lower third of the fibula (the smaller bone of the lower leg), specifically the anterior surface.
- The interosseous membrane is a fibrous tissue connecting the fibula and tibia (the more significant bone of the lower leg).
These origins provide the muscle with the necessary leverage for its functions.
INSERTION POINT
The peroneus tertius muscle inserts onto the dorsal surface of the base of the fifth metatarsal bone, which is located in the foot. Consequently, this insertion allows the muscle to perform its actions on the foot effectively.
MAJOR ARTERIES
The peroneus tertius muscle receives its blood supply from the perforating branches of the anterior tibial artery and the peroneal artery. These arteries provide oxygenated blood to the muscle to support its function.
NEURAL INNERVATION
The peroneus tertius muscle is innervated by the deep fibular (peroneal) nerve, which arises from the common fibular (peroneal) nerve. This nerve provides both motor innervation for muscle contraction and sensory innervation for transmitting sensations from the skin of the lower leg and dorsum of the foot.
TRIGGER POINT
Trigger points may develop in the peroneus tertius muscle, causing localised pain and tenderness. These trigger points can be associated with muscle overuse, strain or postural imbalances. Therefore, addressing these trigger points is essential for managing pain and ensuring proper muscle function.
CONCENTRIC FUNCTION
The concentric function of the peroneus tertius is to actively contract and generate force during dorsiflexion and eversion of the foot. This action involves lifting the front of the foot and turning it outward, which is crucial for walking and running.
ECCENTRIC FUNCTION
During controlled lowering of the foot and inversion, the peroneus tertius muscle functions eccentrically to resist the force of gravity and control the movement. As a result, this eccentric function helps in maintaining balance and stability.
ISOMETRIC FUNCTION
This muscle can contract isometrically to stabilise the ankle and foot during weight-bearing activities, maintaining alignment and preventing excessive movement. Consequently, this isometric function is essential for postural control and stability.
RELATED MUSCLE-SCIENTIFIC NAMES
The Peroneus Tertius muscle is also known as:
- Musculus Peroneus Tertius
ANTAGONIST MUSCLES
- Gastrocnemius: Located in the posterior compartment of the lower leg, responsible for plantar flexion (pointing the foot downward), opposing the dorsiflexion action of the Peroneus Tertius.
COMMON INJURIES
- Tendinitis or Tendon Rupture: Inflammation or tearing of the tendon, often due to overuse or sudden injury, leading to pain and impaired movement.
- Muscle Strains or Tears: Overstretching or excessive force can cause muscle fibres to tear, resulting in pain and reduced function.
- Ankle Sprains: Ligament injuries around the ankle joint can affect the Peroneus Tertius, causing pain and instability.
EXERCISES
- Ankle Dorsiflexion Exercises Using Resistance Bands: Secure a resistance band around the forefoot and pull the toes towards the shin against the band’s resistance. Strengthens the muscle and improves dorsiflexion strength.
- Balance Exercises on Unstable Surfaces: Stand on a balance board or cushion to challenge stability and engage the lower leg muscles. Enhances the strength and coordination of the Peroneus Tertius and other stabilising muscles.
- Lateral leg Raises: Lie on one side, lift the top leg upward, hold for a moment, then lower it back down. Strengthens the lateral muscles of the lower leg, including the Peroneus Tertius.
- Toe Taps: Sit with feet flat on the floor, lift the toes off the ground and tap them back down. Engages and strengthens the Peroneus Tertius and other lower leg muscles.
- Single-Leg Calf Raises: Stand on one leg and raise the heel off the ground, hold, then lower back down. Engages the calf muscles and the Peroneus Tertius for improved balance and strength.
STRETCHES
- Calf Stretches: Stand facing a wall, place one foot back with the heel on the ground and lean forward into the wall. Stretches the calf and lower leg muscles, including the Peroneus Tertius.
- Ankle Dorsiflexion Stretch: Sit with legs extended, loop a towel around the football and gently pull the toes towards the shin. Stretches the Tibialis Anterior and Peroneus Tertius, improving ankle mobility.
- Soleus Stretch: Stand with one foot back, slightly bent and push the heel into the ground. Targets the deeper calf muscles, including the soleus and the lower leg.
- Heel Drop Stretch: Stand on a step with the heels hanging off and slowly lower the heels below the step level. Stretches the calf muscles and lower leg muscles, including the Peroneus Tertius.
- Seated Forward Fold: Sit with legs extended, reach towards the toes and hold. Stretches the hamstrings and lower leg muscles, improving overall flexibility.