Consequences
Why your ankle always twists on the same side
A recurrent ankle sprain is not inevitable. When FHL locks the subtalar joint and distorts heel strike, the ankle loses its ability to adjust and tips predictably into supination. A tenolysis of the tendon can then stabilize the ankle more effectively than a ligament reconstruction.
The cascade to the ankle
The ankle is the joint closest to the foot. It is also the first to suffer the mechanical consequences of FHL. The tendon blockage and the desynchronization of the step create the perfect conditions for the recurrent sprain.
The biomechanical chain involved
The classic mechanism of the sprain
The ankle sprain most often occurs in inversion, which corresponds to a combined movement of supination, adduction and plantar flexion of the foot. This twisting causes excessive tension on the lateral ligaments of the ankle.
Lateral ligament anatomy — two lateral ligaments account for the majority of injuries in an inversion sprain. The anterior bundle is almost always affected. The middle calcaneofibular bundle, for its part, ruptures only in severe sprains.
The calcaneofibular bundle bridges both the talocrural joint and the subtalar joint. Its injury signals a more severe sprain and explains why some sprains leave more lasting sequelae than others.
How FHL promotes the sprain
FHL creates two biomechanical conditions that directly predispose to the inversion sprain. These two factors add up and explain repeated sprains.
Factor 1 · roll-through of the step
Desynchronization of the gait cycle
- Excessive, prolonged pronation at propulsion
- Sweeping effect during the swing phase
- Excessive supination at heel strike
- Ankle in a position vulnerable to inversion
Factor 2 · FHL tendon cord
Locking of the subtalar joint in varus
- Tenodesis effect of the flexor hallucis longus tendon
- Subtalar joint locked in varus
- Loss of varus–valgus adjustment
- Ankle unable to adapt to uneven ground
Direct consequence
An ankle that can no longer adjust can no longer adapt to variations in the ground. The slightest loss of balance becomes a sprain, and the sprain becomes recurrent. The groundwork is laid well before the first injury.
When the sprain becomes recurrent
When sprains repeat or a chronic instability sets in despite well-conducted rehabilitation, it is often because the underlying biomechanical factor has not been identified. Classic rehabilitation (proprioception, peroneal strengthening, elastic bracing) targets the ankle. It ignores the foot.
As long as the subtalar joint remains locked by FHL and the gait cycle remains desynchronized, the ankle keeps moving into a vulnerable position with every step. The sprains return as soon as sport is resumed or at the first unexpected demand.
Practical recommendation
For any ankle rehabilitation after a sprain, incorporating release of the subtalar joint and gliding of the FHL is essential. These steps must be part of the protocol, not an option. Without them, the risk of recurrence remains high.
Tenolysis, an alternative to ligament reconstruction
When chronic instability persists despite well-conducted conservative treatment, surgery becomes an option. Two approaches exist, with very different philosophies.
classic approach
Ligament reconstruction
Reconstruction or reinforcement of the injured ligaments. Aims to restore the passive stability of the ankle. Does not treat the biomechanical cause of the imbalance. Risk of recurrence if FHL persists.
FHL approach
Arthroscopic tenolysis of FHL
Release of the tendon by endoscopic approach. Frees the subtalar joint, eases the supination posture and resynchronizes the pronation–supination timing. Treats the cause, not just the symptom.
Tenolysis is a minimally invasive procedure that, in this indication, is often more effective than a ligament reconstruction. It offers the advantage of treating the biomechanical cause instead of repairing an effect, and restores the adjustment function of the ankle rather than its passive stability.
« An ankle that twists repeatedly is not a weak ankle. It is an ankle poorly informed by a foot that no longer transmits the right information about ground contact. »
Centre Orthopédique d’Ouchy
Key scientific article
The Centre du pied has published an article that completely repositions the understanding of the ankle sprain in light of FHL.
Article
The ankle sprain revisited
The ankle sprain revisited — scientific article from the Centre du pied, professional reading.
Understanding through video
A lecture from the Centre du pied details chronic ankle instability, its origins and its management.
Chronic ankle instability: origin(s), prevention, treatment
Do you have repeated sprains?
Identify the biomechanical cause
If your ankles always twist on the same side despite rehabilitation, the mobility assessment at the Centre du pied makes it possible to objectively document any underlying FHL that is the cause.
At a glance
Mechanism
inversion
Main ligament
anterior bundle
FHL factors
2 conditions
Recurrence risk
high if FHL untreated
Indicated surgery
FHL tenolysis
Surgical approach
arthroscopic
Going further
Other consequences and useful pages
Foot
The origin of the cascade, where the imbalance that ultimately destabilizes the ankle begins.
Knee
The joint downstream of the ankle that shares the consequences of the rotational imbalance.