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Hip and Pelvis, Proximal attachment, Distal attachment, Movement it limits…
Hip and Pelvis
Hip Muscle Action
Primary Roles, ranked in strength
- Extensors
- Flexors
- Adductors
- Abductors
- Internal rotators
- External rotators
Secondary Roles
Depending on several factors
- Number of joints muscle crosses
- Hip position
- Fibres orientation
- Moment arms
- Pelvic-on-femoral or femoral-on-pelvic movements
- External load.
Innervation
Lumbar plexus
- Part of the lumbosacral plexus.
- Gives rise to the femoral and obturator nerves.
- Referencing the notes, have both anterior (yellow) and posterior (blue) divisions.
- Lumbar portion of the plexus is formed by the ventral divisions of the first four lumbar nerves (ventral rami L1 to L4) and from contributions of the last thoracic nerve (T12).
- Ventral rami of the L4 passes communicating branches to the sacral plexus.
- The nerves of the lumbar plexus pass anterior of the hip joint and support the anterior portion of the thigh
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Sacral Plexus
- L4 through S3 and S4 at the lumbosacral enlargement.
- Provides motor and sensory nerves for the posterior thigh, most of the lower leg, the entire foot, as well as part of the pelvis.
- The most clinically important branches arising from the plexus are the sciatic, tibial, and peroneal nerves.
- Referencing the notes, branches from the posterior division are in blue, and branches from the anterior division are in yellow.
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Tibial nerve
Foot plantar flexion and inversion, and toe flexion
- Posterior joint capsule
- Knee
Common peroneal nerve
Foot eversion (superficial peroneal n.) and foot dorsiflexion, toe extension (deep peroneal n.)
- Posterior joint capsule
- Knee
Muscles that Cross 2 Joints
Most muscles can only shorten to about 70% of their resting length, so the greatest force at one joint could only occur if the muscle is lengthened at the other joint. When a two-joint muscle shortens over both of its joints simultaneously, it encounters active insufficiency
- Rectus femoris
- Sartorius
- Tensor fascia lata
- Gracilis
- Hamstring group
Pelvic on Femoral Hip Flexion
- Erector Spinae, iliopsoas and sartorius shorten
- Force-couple between hip flexors and trunk extensors
- Excessive/reduced anterior pelvic tilt and lumbar lordosis may be due to:
- Postural habits
- Pain avoidance
- Poor sitting posture
- Compensation from thoracic lordosis/ excessive kyphosis
- Weak abdominals or tight trunk extensors
- Tight connective tissues
- Hip flexors usually work in open chain for moving the lower limb/body forward
- When standing, we are in closed chain position, so hip flexors such as iliopsoas tilts pelvis anteriorly.
- If muscle is tight, pelvis is in anterior pelvic tilt, and have compensatory excessive lumbar lordosis. Contradirectional rhythm.
- Iliopsoas is the only hip flexor producing enough force to flex the hip >90 degrees in sitting.
- Patient won't have control, or collapse, while attempting to sit if he has weak iliopsoas.
Hip Flexion Contracture
- Constant state of flexion
- Increased demand on hip extensors and increased metabolic cost
- Optimal overlap of regions with thickest articular cartilage does not occur, so increased wear on joint surfaces
- Physios should stretch the hip flexors
- People 75-86 years old walk with 30% less hip extension than younger people
Femoral-on-pelvic hip flexion
- Strong abdominal muscles are needed to stabilise the pelvis, so that you can do leg raises (hip flexion)
- Else, leg raises are limited because the stronger rectus femoris "overpowers" the abdominals resulting in anterior pelvic tilt.
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Sit-ups and Straight leg raises (SLRs)
- Abdominals and hip flexors work synergistically in that when one muscle group performs the activity, the other provides stabilization.
- ‘Abs crunch’: abdominals flexes trunk whilst iliopsoas stabilizes femur; both concentric actions. To go into full sitting, the abdominals stabilize trunk isometrically, further flexion is at the hip by iliopsoas concentrically.
- SLR: iliopsoas concentric action, abdominals concentrically stabilizes lumbar spine and pelvis.
- If performed unilaterally, the contralateral lower extremity is flexed at the hip and knee with the foot and pelvis stabilized (manually), so that abdominals can provide the stabilization of the lumbar spine and pelvis.
- A powerful iliopsoas can exert tremendous force on a vulnerable low back unless the abdominal muscles have sufficient strength to provide adequate support.
- Since the abdominals contract isometrically once the scapulae are off the floor, it is usually not necessary to perform a full sit-up to strengthen the abdominals.
- Maintaining hip flexion at 90°during the abdominal curl limits the amount of force the hip flexors produce during the exercise
Pelvic-on-femoral hip extension
- The force-couple between hip extensors (gluteus maximus and hamstrings) and abdominal muscles (rectus abdominis and obliquus externus abdominis) posteriorly tilts the pelvis.
- Decreased lordosis at the lumbar spine.
- The extension at the hip stretches the iliofemoral ligament.
- Anterior capsule and hip flexor muscles limit posterior pelvic tilt.
Hamstrings and Forward Lean
- Slight forward lean of the upper body displaces the body weight force slightly anterior to the medial-lateral axis of rotation at the hip, controlled by minimal gluteus maximus activation.
- A more significant forward lean displaces the body weight force even farther anteriorly. The greater flexion of the hips rotates the ischial tuberosities posteriorly, thereby increasing the hip extension moment arm of the hamstrings.
Femoral-on-pelvis hip extension
- Generally, high demand on many muscles
- Multifidus (intrinsic back muscles)
- Gluteus maximus
- Adductor magnus
- Rectus femoris
- Biceps femoris
- Gastrocnemius, to name a few
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Shoulder vs Hips
Shoulder for mobility, hip for stability
Challenges for the pelvis/hip
- Transmit large forces between trunk and ground, e.g. hip abductors on the WB leg must counterbalance about 85% of body’s weight with every step.
- Elevate and lower body.
- Locomote, or move.
Scapula for ROM, hip for mobility
Pelvis has an osteoligamentous ring
- Muscle attachment for trunk and lower limbs
- Transmission of weight of upper limbs/trunk
- Supports organs of bowel, bladder and reproductive functions
Deformities
- May result in hip instability, poor muscle leverage and reduced force production capability.
Angle of inclination
- Measured frontal, between femoral neck and shaft
- At birth, under 2-8 years: 165-170°
- Normal adult: 125°
- Coxa vara<125°, often seen in older people
- Coxa valga>125°, in cerebral palsy patients
- Deformity alters leverage of the muscles that connect the pelvis to the greater trochanter.
Femoral Torsion
- Measured from superior view, relative rotation between femoral shaft and neck
- At birth: 40°anteversion
- By 16 years: 15°normal anteversion
- Abnormal if:
- More than 15°: Excessive anteversion. May lead to in-toeing gait
- Less than 15°: Retroversion
Acetabular alignment
- Centre-edge angle
- More than 35°: impingement
- Less than 35°: degeneration
- Acetabular anteversion angle
- More than 20°: dislocation risk
- Less than 20°: abnormal stress, degeneration
Movement
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Lumbopelvic rhythms
An “ipsidirectional” rhythm describes a movement in which the lumbar spine and pelvis rotate in the same direction, thus amplifying overall trunk motion.
A “contradirectional” rhythm describes a movement in which the lumbar spine and pelvis rotate in opposite directions
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