Lecture4 BIOMECHANICS OF HIP JOINT Prepared by Dr

Lecture-4 BIO-MECHANICS OF HIP JOINT Prepared by: Dr. Hazrat Bilal Malakandi DPT (IPMR, KMU), MSPT* (KMU)

Objectives At the end of this lecture the student shall be able to: • Enumerate the kinematics of hip complex • Describe the movement of the femur on pelvis. . • Describe the movement of the pelvis on femur. • Describe the lumbo-pelvis rhythm. 2

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Kinematics of hip joint 4

Motion of the Femur on the Acetabulum q The motions of the hip joint are easiest to visualize as movement of the convex femoral head within the concavity of the acetabulum as the femur moves through its three degrees of freedom: qflexion/extension, qabduction/adduction, and qmedial/lateral rotation. q The femoral head will glide within the acetabulum in a direction opposite to motion of the distal end of the femur. 5

• Flexion and extension of the femur occur from a neutral position as an almost pure spin of the femoral head around a coronal axis through the head and neck of the femur. • The head spins posteriorly in flexion and anteriorly in extension. • . 6

• The motions of abduction/adduction and medial/lateral rotation must include both spinning and gliding of the femoral head within the acetabulum, but the intra-articular motion again occurs in a direction opposite to motion of the distal end of the femur. 7

• Flexion of the hip is generally about 90° with the knee extended and 120 ° when the knee is flexed and when passive tension in the two-joint hamstrings muscle group is released. Hip extension is considered to have a range of 10 ° to 30°. • Hip extension ROM appears to diminish somewhat with age, whereas flexion remains relatively unchanged. 8

• When hip extension is combined with knee flexion, passive tension in the two-joint rectus femoris muscle may limit the movement. The femur can be abducted 45° to 50° and adducted 20° to 30°. • Abduction can be limited by the two-joint gracilis muscle and adduction limited by the tensor fascia lata (TFL) muscle and its associated iliotibial (IT) band. 9

• Medial and lateral rotation of the hip are usually measured with the hip joint in 90° of flexion; the typical range is 42° to 50°. • Femoral anteversion is correlated with decreased range of lateral rotation and less strongly with increased range of medial rotation. 10

• When the femoral head is torsioned anteriorly more than normal lateral rotation of the femur turns the head out even more, both risking subluxation and encountering capsuloligamentous and muscular restrictions on the anterior aspect of the joint as the head presses forward. • Hip joint rotation can similarly be affected by retroversion of the femur, as well as by acetabular anteversion and laxity of the joint capsule. 11

• Normal gait on level ground requires at least the following hip joint ranges: • 30° flexion, • 10° hyperextension, • 5° of both abduction and adduction, and • 5° of both medial and lateral rotation. • Walking on uneven terrain or stairs will increase the need for joint range beyond that required for level ground, as will activities such as sitting in a chair or sitting cross-legged. 12

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Motion of the Pelvis on the Femur • Whenever the hip joint is weight-bearing, the femur is relatively fixed, and, in fact, motion of the hip joint is produced by movement of the pelvis on the femur. 14

Anterior and Posterior Pelvic Tilt • Anterior and posterior pelvic tilt are motions of the entire pelvic ring in the sagittal plane. • In the normally aligned pelvis, the anterosuperior iliac spines (ASISs) of the pelvis lie on a horizontal line with the posterior superior iliac spines. 15

• Anterior and posterior tilting of the pelvis on the fixed femur produce hip flexion and extension, respectively. • Hip joint extension through posterior tilting of the pelvis brings the symphysis pubis up and the sacrum of the pelvis closer to the femur, rather than moving the femur posteriorly on the pelvis 16

• Hip flexion through anterior tilting of the pelvis moves the ASISs anteriorly and inferiorly; the inferior sacrum moves farther from the femur, rather than moving the femur away from the sacrum • Anterior and posterior tilting will result in flexion and extension of both hip joints simultaneously in bilateral stance or can occur at the stance hip joint alone if the opposite limb is non-weightbearing. 17

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Lateral Pelvic Tilt • Lateral pelvic tilt is a frontal plane motion of the entire pelvis around an antero-posterior axis. In the normally aligned pelvis, a line through the ASISs is horizontal. • Left pelvic tilt ; is when the right side of the pelvis is elevated higher than the left side. • Right pelvic tilt ; is when the left side of the pelvis is elevated higher than the right side. 21

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Lateral Shift of the Pelvis • Lateral pelvic tilt can also occur in bilateral stance. If both feet are on the ground and the hip and knee of one limb are flexed, the opposite limb is largely the weight-bearing limb and the terminology is the same as for unilateral stance. • However, if both limbs are weight-bearing, lateral tilt of the pelvis will cause the pelvis to shift to one side or the other. 23

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• If the pelvis is shifted to the right in bilateral stance, the left side of the pelvis will drop, the right hip joint will be adducted, and the left hip joint will be abducted. 25

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Anterior and Posterior Pelvic Rotation • Pelvic rotation is motion of the entire pelvic ring in the transverse plane around a vertical axis. • Although rotation can occur around a vertical axis through the middle of the pelvis in bilateral stance, it most commonly and more importantly occurs in single-limb support around the axis of the supporting hip joint. 28

Forward Rotation • Forward rotation of the pelvis occurs in unilateral stance when the side of the pelvis opposite to the supporting hip joint moves anteriorly. • Forward rotation of the pelvis produces medial rotation of the supporting hip joint. 29

Backward Rotation • Backward rotation of the pelvis occurs when the side of the pelvis opposite the supporting hip moves posteriorly. • Backward rotation of the pelvis produces lateral rotation of the supporting hip joint. 30

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Bilateral Pelvic Rotation • Pelvic rotation can occur in bilateral stance as well as unilateral stance, as is true for lateral pelvic tilt. • If both feet are bearing weight and the axis of motion occurs around a vertical axis through the center of the pelvis, the terms forward rotation and backward rotation must be used by referencing a side (e. g. , forward rotation on the right and backward rotation on the left). 32

Coordinated Motions of the Femur, Pelvis, and Lumbar Spine • When the pelvis moves on a relatively fixed femur, there are two possible outcomes to consider. • Either the head and trunk will follow the motion of the pelvis or the head will continue to remain relatively upright and vertical despite the pelvic motions. • These are open- and closed-chain responses, respectively. 33

Pelvifemoral Motion • When the femur, pelvis, and spine move in a coordinated manner to produce a larger ROM than is available to one segment alone, the hip joint is participating in what will predominantly be an open-chain motion termed pelvifemoral motion. 34

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• Table presents the compensatory motions of the lumbar spine that accompany given motions of the pelvis and hip joint. 37

Muscles Work in AT & PT 38

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