Biomechanics of Pelvis
What structures limit lateral rotation of the hip?
-Anterior joint capsule -Iliofemoral and pubofemoral ligaments
What structures limit hip extension?
-Anterior joint capsule -Three reinforcing ligaments of hip (ischiofemoral lig, pubofemoral lig, iliofemoral ligament)
What structures limit hip abduction?
-Hip adductor muscles -Pubofemoral ligament
What are the motions that the pubofemoral ligament restrict?
-Hyperextension -Abduction
What are the motions that the iliofemoral ligament restricts?
-Hyperextension -Lateral Rotation -Adduction
What structures limit medial rotation of the hip?
-Lateral rotator muscles -Posterior capsule -Ischiofemoral ligament
What functional activities would be limited by a weak psoas major?
-Lifting a limb in and out of the bathtub -Climbing stairs -(walking doesn't require much force from hip flexors)
Hip flexion end-feel is listed as soft but very few people have a soft end-feel at 120 degrees. What are the limiting structures for hip flexion?
-Posterior joint capsule -Gluteus maximus
What structures limit hip adduction?
-Superior part of iliofemoral ligament -hip abductor muscles
What are the two joint hip flexors?
-sartorius -rectus femoris -tensor fascia latae
In the normal erect posture, the acetabulum and femoral head are aligned so that the head of the femur...
...is directed anteriorly and superiorly in the acetabulum.
What is the capsular pattern for the hip?
1.) INTERNAL ROTATION 2.) FLEXION 3.) ABDUCTION 4.) Some limited might be present in extension but no limitation is present in external rotation or adduction.
What are two common compensations for hip flexor tightness?
1.) If the pt has a flexible lumbar spine, they will compensate with an anterior pelvic tilt. 2.) If the pt. has limited lumbar spine flexibility, they will exhibit a flattened lumbar lordosis and a forward lean. This can lead to muscle strain and injury to the IV disc from excessive loading.
What are the biomechanical implications for a patient with coxa vara?
1.) The decrease in the angle between the shaft and neck of the femur increases the bending moment applied to the femoral neck which increases the compressive forces on the medial aspect of the neck and increases the tensile forces on the lateral side of the neck. 2.) Moves the trochanter farther from the joint center which lengthens the moment arm of the hip abductors putting them at a mechanical advantage. This results in less force needed for them to keep the joint stable which, in turn, reduces the joint reaction force. (This is a good thing and is used by surgeons in osteotomies to reduce the loads on the hip) 3.) Increases the medial pull on the femur into the acetabulum. 4.) Increased bending moment on the femoral neck.
What are the biomechanical implications for patients with coxa valga?
1.) The joint reaction force on the femur is more parallel to the femoral neck which subjects the neck to more compressive forces and less of a bending moment. 2.) The perpendicular distance between the hip joint center and the trochanter is decreased which shortens the moment arm of the abductors (they insert on the greater trochanter). In turn, the abductors must generate larger contractile forces to support the hip joint which increases the joint reaction force and the stress put on the femoral head. 3.) Also, the joint reaction force is displaced laterally in the acetabulum and is applied over a smaller surface area which increases joint stress.
What composes the SI joint?
1.) lateral surface of combined upper 3 sacral segments (articular surface) articulating with aricular surface on ilium 2.) Sacral tuberosity on sacrum articulated with sacral tuberosity on ilim
What is normal femoral anteversion?
15 degrees. It refers to the transverse plane alignment the proximal femur (coxa valga and vara refer to frontal plane alignment). More specifically, anteversion refers to the angle between the femoral head/neck and the femoral condyles.
What is coxa vara?
A decrease in the angle of inclination (less than 120 degrees).
If you have a patient with weak abductors unilaterally, how might you advise them to hold weighted objects during ADLs: on the same side as the weak abductors or on the opposite side?
Advise them to hold the weight on the same side as their weakness because it produces an abduction moment on the stance hip which reduces the force required of the abductors.
Why does tightness in psoas major lead to anterior pelvic tilt?
Because the tight psoas pulls its origin (lumbar vertebrae) towards its insertion (the femur) and because another compensation is a backward-bend elsewhere in the spine to keep the eyes on the horizon.
What are the clinical implications for patients with coxa valga?
Coxa valga deformities are likely to increase the risk of degenerative joint disease within the hip by increasing the joint reaction force as well as the stress sustained by the femoral head. -Oatis 696
What are the clinical implications for a patient with coxa vara?
Coxa vara is a risk factor for stress fractures of the femoral neck.
What are the normal ranges for movements at the hip (according to AAOS)?
Flexion: 120 Extension: 20 Internal Rotation: 45 External Rotation: 45 Abduction: 45 Adduction: 10
Explain the actions of gluteus medius with both hip flexed and hip extended. What is the clinical significance?
Hip extended: - the anterior and middle portions of glut med. internally rotate the hip and the posterior fibers laterally rotate the hip. All segments abduct the hip. Hip flexed: - however, no portion of glut med abducts the hip or laterally rotates the hip. All of its portions does medial rotation. When a patient is quadruped or seated, their abduction exercises are not working gluteus medius or minimum. They are probably working TFL and gluteus maximus. The "fire hydrant," or seated abductor machine are good examples of abductor exercises that fail to target glut med and min. The best exercises are when a patient is in standing, supine, or side-lying.
What is the difference in motion at the hip in open chain vs closed chain?
In OKC, the femur moves on the pelvis but in CKC the pelvis moves on the femur. In ROM testing, you put the patient in OKC but in daily life people are usually in CKC.
What is the supracristal plane and how is it used clinically?
It is a horizontal line drawn through the highest points of the iliac crests. The transverse plane of the iliac crests is used clinically because it passes through the IVD between L4 and L5 in standing posture. It is also useful for locating the usual site of lumbar puncture.
What are the clinical implications for excessive femoral anteversion?
It places the head of the femur farther anteriorly in the acetabulum. Most patients will compensate by medially rotating the hip because this will place the femoral head in a more normal location within the acetabulum. The result is pigeon-toed stance. Over time, some patients may begin to compensate with lateral tibial torsion which turns the foot laterally with respect to the knee. Lateral tibial torsion will eliminate the in-toed stance but will not solve the medial rotation at the hip.
You are conducting a PROM assessment on a patient because, during the lower quarter screen, you noticed they had a lack of ROM at the hip. The patient presents with 90 degrees of PROM hip flexion, 46 degrees of internal rotation, 44 degrees of external rotation, and 18 degrees of extension. What would be your next steps?
Since the patient has average ranges for their PROM hip internal rotation, external rotation, and extension, this is not a capsular pattern (INT >FLEX>ABD). I would determine that the lack of flexion in PROM means that there may be a joint problem. I would follow-up with a test to measure the extensibility of the hip extensors (hamstrings) by doing a Straight Leg Raise test or a 90-90 Straight Leg Raise test. Since the patient was limited in PROM, I would not be concerned with muscle weakness. My intervention might consist of a joint mobilization for hip flexion (posterior glide of the femur on the acetabulum). I also might have the patient in a repeated stretching protocol on e-stim with electrodes on the hip flexors and the patient in a position allowing them to stretch their hamstrings during each contraction (you'd have to put the electrodes on the two-joint hip flexors since they have a larger PCSA and are closer to the surface).
What are the motions that the ischiofemoral ligament restricts?
Spiral fibers limit: -Hyperextension Posterior fibers limit: -Internal rotation -Adduction
What is the attachment of the psoas major?
The lesser trochanter.
What is the most stable position for the hip and how does this make sense with the location of the three major ligaments of the hip?
The most stable position for the hip is in flexion and abduction because it places the femoral head in the deepest part of the acetabulum. The three major ligaments of the hip (ischiofemoral, pubofemoral, and iliofemoral) are located to prevent extension, internal and external rotation, and adduction. Only one prevents too much abduction.
During the ROM section of the LQ screen you notice your patient has limited ROM at the hip so you decide to follow-up with PROM goniometric measurements. You find that they have 20 degrees of internal rotation on the right and 40 degrees on the left, 10 degrees of adduction on both sides, 80 degrees of flexion on the right and 110 on the left, 43 degrees of external rotation on the right and 42 degrees on the left, and 39 degrees of abduction on the right and 45 on the left. What do you conclude?
The patient has a capsular pattern ROM loss at the right hip (INT. ROT>FLEX>ABD). You would do a posterior joint mob for the medial rotation and flexion loss and an inferior joint mob for the abduction loss.
In closed kinetic chain, what action is occurring during flexion at the hip?
The pelvis is moving on the femur into anterior pelvic tilt. Ex.) Moving down into a squat.
How do patients with a fused or pathological hip substitute for the normal hip motions in walking?
They use their pelvis to move the limb instead of their femur. Since walking involves an open kinetic chain on the moving side, in extension they rely on an anterior pelvic tilt (during stance) and during swing they rely on posterior pelvic tilt to substitute for flexion.
What is coxa valga?
When the angle of inclination (the angle between the head and neck of the femur) is greater than the normal 125 degrees. The femoral head is directed more superiorly in the acetabulum than it is normally.
Explain the functional role of the hip abductors in CKC activities like walking and running.
While in a one-legged stance during a gait cycle, the weight of the unsupported leg and the HAT (head/arm/trunk) exerts an adduction moment on the stance hip which makes the body fall towards the unsupported side and adduct the hip on the supported side. The abductors are required to hold the pelvis and the HAT-L weight stable. They pull from their distal femur insertions to their proximal pelvic origins to keep the pelvis level. They also provide support to stabilize the femur to maintain frontal plane alignment of the knee and foot (thus knee pain is common in patients with weak abductors).
