Hip 2

Hip joint capsule & ligaments: Capsule: • Strong & dense • Substantial contributor for joint stability • It is attached to the entire periphery of the acetabulum • It covers the femoral neck like a sleeve and attaches to the base of the neck – femoral neck is intracapsular whereas greater and lesser trochanters are extracapsular • It is thick anterosuperiorly where predominant stresses occur while it is thin and loose posteroinferiorly

Ligaments: Ligamentum teres/ligament of head of femur Doesn't play a significant role in stabilization Functions primarily as a conduit for the secondary blood supply from the obturator artery and for the nerves that travel along the ligament to reach the head through the fovea

• Hip joint capsule is reinforced by 3 ligaments

– 2 anteriorly and 1 posteriorly Anterior: • Ilio femoral ligament(Y lig.of Bigelow) • Pubofemoral ligament • Fibers of both these ligaments form a Z on the anterior capsule

Posterior: • Ischiofemoral ligament

• Hip joint capsule and ligaments are quite

strong • Joint is difficult to traumatically dislocate • In bilateral stance, hip is typically in neutral position or slight extension – in this position ligaments and capsule are under some tension • LOG in bilateral stance falls behind the hip joint axis, creating a gravitational extension torque

Weight-bearing structure of Hip Joint: • Internal architecture of pelvis and femur reveal remarkable adaptations occurred to accommodate mechanical stresses ‘n’ strains created by transmission of forces between femur and pelvis • Trabeculae of bone line up along lines of stress and form systems to meet stress requirements • Weight bearing occurs through vertebrae to the sacral promontory and on through the sacroiliac joints • Weight bearing lines of both pelvis and femur are evident by the arrangement of trabeculae

•

Most of the weight bearing stresses in the pelvis pass from the sacroiliac joints to the acetabulum, although the trabeculae show evidence of some forces along the pubic ramus and along the ischial tuberosities • The pelvic trabeculae that pass through the acetabulum of the pelvis form two major systems within the femur: c) Medial trabecular system d) Lateral trabecular system • There are two minor accessory systems of trabeculae

Trabecular system

• In bilateral static stance, weight of HAT is

distributed between left and right hip joints with the force of at least half the superimposed body weight, travelling down the femoral head, while the ground reaction force (GRF) travels up the shaft • The distance between the super imposed body weight on the head and the GRF up the shaft creates a bending force at the femoral neck • The trabecular systems must resist this bending force

Medial and lateral trabecular systems not only contribute to the structure of head and neck of femur but also help resist bending stresses as the weight of HAT passes down on the femoral head Areas in which various trabecular systems cross each other at right angles are areas that offer greatest resistance to stress and strain An area in the femoral neck in which trabeculae are relatively thin and do not cross over is called as ‘Zone of weakness’

Zone of weakness: Area where trabeculae don't cross at right angels Less reinforcement by trabeculae More potential for injury This zone is susceptible to bending forces and can fracture when forces are excessive or when tissues are no longer able to resist normal forces

Functions of Hip Joint: Arthrokinematics: • Hip joint involves movement of a convex femoral head within the concave acetabulum • Head glides within the acetabulum in a direction opposite to the motion of distal end of femur • From a neutral position flexion and extension occurs as almost pure “spin” of femoral head around a coronal axis through the head and neck of femur • Head spins posteriorly in flexion and anteriorly in extension

• However, flexion and extension from other

positions must include both “spinning” and “gliding” of articular surfaces • Motions of abduction/adduction and medial/ lateral rotation must include both spinning and gliding of one surface over the other,but again occur opposite to motion of distal end of femur when femur is the moving segment • Whenever hip joint is weight bearing (femur is relatively fixed) and motion of hip joint is produced by movement of pelvis on femur

Osteokinematics: Motion of femur at hip joint: • ROM available at hip joint is most commonly described by movement of femur • ROM is influenced by whether it is performed actively or passively and whether passive tension in two joint muscles is encountered or avoided • Following are the ranges of passive motion: Flexion :90° with knee extended and 120°-135° when knee is flexed & passive tension in hamstrings is released Extension :10°-30°, when hip extension is combined with knee flexion, passive tension in rectus femoris may limit the movement

Abduction:45°-50° can be limited by gracilis muscle Adduction:20°-30° can be limited by TFL and associated IT band Medial rotation: 30-45°(hip in 90° flexion) Lateral rotation: 45-60°  Normal gait on level ground requires at least the following ranges: • 30° flexion • 10° hyperextension • 5° of abduction and adduction • 5° of medial and lateral rotation

Motion of pelvis at hip joint: When proximal segment of joint moves on distal part, the motion is the same as if the distal segment were the moving part However, the direction of movement of the lever reverses For e.g. elbow flexion can be a movement of distal forearm upwards or conversely a rotation of proximal humerus downward

• At the hip joint, this reversal of motion of

lever is complicated by the horizontal orientation and nonlever shape of pelvis • Unlike at other joints there is a new set of terms to identify joint motion when pelvis is the moving segment • Terms of pelvic motion are used with weightbearing hip motion because these are the motions that are visible • These motions are also key to what occurs at above or below joints of pelvis

Anterior and Posterior Pelvic Tilt: • Are motions of pelvis in saggital plane around a coronal axis • In a normally aligned pelvis the ASIS lie on a horizontal line with PSIS and on a vertical line with symphysis pubis • Anterior and posterior tilting of the pelvis on a fixed femur produces hip flexion & extension respectively

Posterior tilting: • Posterior tilting of the pelvis moves symphysis pubis superiorly and the lumbar spine flexes slightly, hip joint extends • Hip extension via posterior tilting brings symphysis pubis up and posterior part of the pelvis closer to the femur rather than moving femur posteriorly

Anterior tilting: • Anterior tilting of pelvis moves symphysis pubis inferiorly and lumbar spine is hyper extended ,hip joint is flexed • Hip flexion through anterior tilting of the pelvis brings ASIS anterior and inferiorly, symphysis pubis moves down and closer to the femur

• Anterior and posterior tilting can result in

flexion and extension of both hip joints simultaneously or can occur at a stance hip joint if the opposite limb is non weight bearing

Lateral Pelvic tilt: Occurs in a frontal lane and around A-P axis In a normally aligned pelvis line passing through both the ASIS is horizontal If this line is not horizontal lateral tilt has occurred This can occur in unilateral or bilateral stance

• In lateral tilt of pelvis in unilateral stance,

one hip joint is the pivot point or axis of motion of the opposite side of the pelvis as it elevates(hiking) or drops(pelvic drops)

Pelvic Rotation: • Rotation of entire pelvis in a transverse lane around a vertical axis • Forward rotation of pelvis occurs when the side of the pelvis opposite to the supporting hip joint moves anteriorly.This produces medial rotation of the supporting hip joint

• Backward rotation of the pelvis occurs

when the side of pelvis opposite the supporting limb moves posteriorly.This produces lateral rotation of supporting hip joint