Great toe mobility : Anatomy
The 1st Metatarsophalangeal Joint (MPJ)
The 1st Metatarsophalangeal Joint (MPJ) is formed by the head of the first metatarsal and the base of
the proximal phalanx. This hinge joint plays a crucial role in movements such as walking, running, and jumping by allowing sagittal plane progression.
For optimal push-off during the gait cycle, the MPJ requires at least 30 degrees of dorsiflexion, with 65 to 75 degrees being ideal. Insufficient hallux dorsiflexion can lead to a low-gear push-off position, early heel rise, overactive adductors, and underactive gluteus maximus.
Complexity of Hallux Dorsiflexion
While hallux dorsiflexion may seem straightforward, it involves complex mechanics that fitness professionals must understand. Improving hallux dorsiflexion requires more than just toe stretches or using wedges under the big toe.
During closed-chain movements like walking, maximum great toe dorsiflexion occurs in the propulsive phase of gait. Here, the flexor hallucis longus (FHL) engages, anchoring the distal hallux to the ground. This stabilization allows the metatarsal head to move relative to the proximal phalanx.
Phases of Hallux Dorsiflexion
- Sliding Phase: The first 20 degrees of dorsiflexion involve the head of the 1st metatarsal sliding over the base of the proximal phalanx.
- Gliding Phase: The next 10 degrees (up to 50 degrees) require the metatarsal to plantarflex relative to the proximal phalanx, allowing the foot to glide over the hallux.
- Jamming Phase: The final stage stabilizes the joint position.
Effective hallux push-off relies on the precise timing of these phases. Disruptions in this sequence can limit dorsiflexion and lead to compensatory movements.
Ensuring Proper Function
To ensure proper sliding, gliding, and jamming, the stability of the 1st ray is essential. The gliding 
phase, where the 1st metatarsal head plantarflexes relative to the proximal phalanx, is particularly crucial.
Key Muscles for Stability
The peroneus longus is the primary muscle responsible for plantarflexing the 1st metatarsal. This muscle runs along the lateral aspect of the lower leg, behind the lateral malleolus, and under the cuboid, inserting primarily on the base of the 1st metatarsal. Its function is complemented by the tibialis anterior, which, along with peroneus longus, contributes to the Spiral Fascial Line.
Balancing the Antagonists
The balance between the tibialis anterior and peroneus longus is vital for 1st ray stability and hallux dorsiflexion. If the tibialis anterior becomes overly dominant, the 1st metatarsal may dorsiflex, hindering the gliding phase and causing premature jamming of the MPJ.
Influence of the Subtalar Joint
The subtalar joint (STJ) position significantly affects foot stability. Eversion of the STJ often leads to a hypermobile and unstable foot, which can give the tibialis anterior a mechanical advantage over the peroneus longus. This imbalance can compromise the stability of the 1st ray and limit hallux dorsiflexion.
