Consequences
Why your hip suffers from FHL
The hip and the subtalar joint are sister joints, anatomically comparable and functionally linked. When FHL blocks the foot, the hip compensates, its gluteus medius loses its effectiveness, and the joint slides toward impingement, labral injury, and even osteoarthritis.
The cascade to the hip
The hip is the first rotational joint above the foot. When FHL locks the subtalar joint, tibial rotation is disrupted, and the hip suffers the consequences with every step.
The biomechanical chain involved
The hip and the subtalar joint, two sister joints
To understand the involvement of FHL in the hip, one must first grasp a little-known anatomical reality. The hip and the subtalar joint (the joint between the talus and the calcaneus at the back of the foot) are two structurally similar joints. English speakers call them ball-in-the-socket joints. Professor Pisani named them coxa femoris for the hip and coxa pedis for the subtalar joint.
Prof. Pisani’s concept
Coxa pedis and coxa femoris, two interdependent joints
The hip and the subtalar joint are anatomically and functionally linked. When one locks, the other must follow the imposed direction of movement or resist through the strength of the stabilizing muscles. This is precisely what happens in FHL, where the subtalar joint, locked by the tenodesis effect, forces the hip to compensate.
A new way of looking at hip mobility
The classic hip examination measures the movement of the femur relative to the pelvis. This view is static and does not reflect what happens during walking, where it is the pelvis that moves over a single femoral head, in single-leg stance.
Classic approach
The femur moves under the pelvis
A static examination in the lying position, measuring the joint range of motion of the femur. Convenient for quantifying, but it does not capture the dynamic function.
Dynamic approach
The pelvis moves over the femoral head
During walking, this is how the hip actually works. This view makes it possible to visualize the muscle vectors of the gluteus medius, which is decisive for pelvic stabilization.
This paradigm shift is essential to understanding the role of FHL. When the hip is observed from the moving pelvis, one immediately perceives the imbalance created by the anterior pelvic tilt and the loss of effectiveness of the gluteus medius.
Three movements disrupted by FHL
FHL disrupts three axes of hip movement. Each has its own clinical consequences and contributes to long-term joint suffering.
1 · sagittal plane
Anterior pelvic tilt
- Increased flexion moment
- Constant forward tilt of the pelvis
- Compensation through core muscle engagement
2 · stance phase
Medial collapse
- Hip in adduction
- Internal rotation during stance
- Rotational imbalance with every step
3 · heel strike
Excessive external rotation
- Mistiming of the pronation–supination transition moments
- Excessive external rotation of the femur at heel strike
The gluteus medius, a key muscle deactivated
The gluteus medius is decisive in stabilizing the pelvis during walking. When you are standing on one leg, it is the muscle that prevents your pelvis from dropping on the opposite side. Its effectiveness depends on the position of the femur under the pelvis and on the timing of its contraction.
With FHL, the lever arm of the gluteus medius is altered. The anterior pelvic tilt changes the muscle vector, which now passes in front. The gluteus medius becomes less effective, and it is the piriformis that takes over to stabilize the pelvis in single-leg stance. Loaded beyond its function, it gradually develops a chronic contracture.
Clinical consequence
The contracture of the piriformis and the muscle tightening that follows limit the excursion of the sacroiliac joint, which becomes vulnerable and can become fixed in a malposition. This is one of the mechanisms by which FHL affects the lower back.
Long-term overload injuries
Over time, the abnormal stresses generated by the compensations end up damaging the joint structures. Four injuries are observed, in isolation or in combination, and can progress to osteoarthritis if the biomechanical cause is not corrected.
Cartilage injury — Premature wear of the articular cartilage under the effect of abnormal rotational stresses and asymmetric loading.
Labral injury — Damage to the fibrocartilaginous rim that surrounds the hip, a source of deep groin pain and joint locking.
Femoroacetabular impingement — Mechanical conflict between the femoral head and the acetabular rim in rotation, a source of pain on forced flexion and when walking.
Osteoarthritic progression — Without correction of the biomechanical cause, repeated overload injuries can evolve into progressive hip osteoarthritis.
Important
Not all cases of hip osteoarthritis are linked to FHL, but biomechanical analysis makes it possible to identify the cases in which the dysfunction of the big toe contributes to the deterioration. This identification changes the management, by adding a treatment of the cause to the treatment of the symptoms.
And after a hip replacement
A hip replacement corrects the joint, but it does not correct FHL if it was present before the operation. If the biomechanical dysfunction of the big toe persists, the compensations continue, and some patients feel residual or unexpected pain despite a perfectly placed prosthesis.
Analysis of FHL before and after a hip replacement is a complementary clinical approach that makes it possible to optimize the long-term functional outcome and to prevent residual pain of biomechanical origin.
« The hip and the foot are in constant dialogue during walking. To ignore this dialogue is to deprive oneself of half the understanding of a hip pain. »
Dr Jacques Vallotton, Centre Orthopédique d’Ouchy
Understanding through video
Two lectures explore the consequences of FHL on the hip in greater depth: the differential diagnosis of a hip dysfunction, and the insertional tendinopathies of the gluteal muscles (tears of the hip rotator cuff).
Consequences of a hip dysfunction and differential diagnosis
Insertional gluteal tendinopathies, or tears of the hip rotator cuff
Do you have hip pain?
Take stock of the biomechanical cause
If your hip pain is accompanied by signs described elsewhere (knee, back, lower back), a mobility assessment at the Centre du pied makes it possible to objectively document any underlying FHL that is the cause.
At a glance
Sister joint
subtalar joint
Concept
coxa pedis (Pisani)
Key movement
medial collapse
Deactivated muscle
gluteus medius
Compensating muscle
piriformis
Long-term risk
hip osteoarthritis
Going further
Other consequences and useful pages
Knee
The joint downstream that suffers the consequences of the hip’s rotational imbalance.