Hip Joint Biomechanics PDF

Structure of the hip joint 1- Bony Articulation Acetabular labrum Ilium and ischium contribute 75% of acetabulum and pupis contribute by 25 % joint: #The acetabulum : cuplike socket that accepts the femur. #The femoral head contacts the...

Structure of the hip joint 1- Bony Articulation Acetabular labrum Ilium and ischium contribute 75% of acetabulum and pupis contribute by 25 % joint: #The acetabulum : cuplike socket that accepts the femur. #The femoral head contacts the acetabulum only along its horseshoe-shaped. #The acetabular labrum is a flexible ring of primary fibrocartilage that surrounds the outer circumference The labrum of Acetabulum  The acetabular labrum provides significant stability to the hip by “gripping” the femoral head and by deepening the volume of the socket by approximately 30%.  The seal formed around the joint by the labrum helps maintain a negative intra- articular pressure, thereby creating a modest suction that resists distraction of the joint surfaces  A malshaped, dysplastic acetabulum that does not adequately cover the femoral head may lead to chronic dislocation and increased stress, often leading to osteoarthritis. 2- Angles within the hip joint:- 1- Angle of inclination of the Angles of the femur (Neck shaft angle) femur 2- Angle of femoral torsion (Anteversion angle of the femur) 3- Center edge angle Angles of the (Angle of wiberg) acetabulum 4- Acetabular anteversion angle  2- Angles within the hip joint:- 1- Angle of inclination of the femur (Neck shaft angle) Plane Frontal Between 2 1- Axis of femoral lines neck. 2- Axis of femoral (1) shaft Value 125° (140°- 150°) in infants (2) 120° in elderly Function Allows more degree of freedom. Medio-lateral stability. Abnormal ↑↑ Coxa valga  2- Angles within the hip joint:- 2- Angle of femoral (1) torsion (Anteversion angle of (2) the femur) Plane Transverse Between 2 1- Axis of femoral neck. lines 2- Axis of femoral condyles. Value 10°-15° (40° in newborn) Function Antero-posterior stability. Abnormal ↑↑ Toe in gait change ↓↓ Toe out gait  2- Angles within the hip joint:- 3- Acetabular Center edge (Angle of Wiberg) (1) (2) Plane Frontal Between 2 1- Line between lateral rim of lines acetabulum and center of femoral head. 2- Vertical line passing through femoral head center. Value 22°-42° Function Lateral and superior stability of the hip joint.  2- Angles within the hip joint:- 3- Acetabular Center edge (Angle of Wiberg) Abnormal change ↑ angle → ↑ femoral head covering and stability. - Abnormal increase causes femoral acetabular impingement. ↓ angle - In low demand activity → ↓ coverage, ↓ contact area, ↑ stress. - In high demand activity → Risk of superior  2- Angles within the hip joint:- 4- Acetabular anteversion angle Plane Transverse Between 2 1- Line passing through anterior (1) (2) lines and posterior rims of the acetabulum. 2- From posterior rim straight forward line. Value 20° Function Anterior stability of the hip joint.  2- Angles within the hip joint:- 4- Acetabular anteversion angle Abnormal change ↑ angle - In low demand activity → ↓ coverage, ↓ contact area, ↑ stress. - In high demand activity → Risk of anterior dislocation. ↓ angle - Abnormal decrease causes femoral acetabular impingement.  Case study :- During a posture examination, a physical therapist notes that both of the patient`s patella point inward when viewed from the front of the patient. The most likely cause of this problem is excessive….? Femoral anteversion angle.  Structure of the hip joint 2- Capsule of the hip joint Hip joint capsule is strong, dense and shaped like cylindrical sleeve. Cover femoral neck and attached to acetabular periphery. The four sets of fibers in the hip joint capsule; 1- longitudinal fibers (superficial), 2- oblique fibers, 3- arcuate fibers 4- circular fibers. (deep) – zona orbicularis. Structure of the hip joint 3- Ligaments of the hip joint The capsule of the hip is strengthened by powerful ligaments anteriorly and Iilliofemoral ligament posteriorly. Anteriorly two ligaments Ischiofemoral ligament are present, i.e. Pubofemoral Ischiofemoral ligament ligament iliofemoral and pubofemoral ligament. Posteriorly there is only one ligament i.e. ischiofemoral ligament.  Site  Attachment  Function Structure of the hip joint 4- Muscles of the hip joint Structure of the hip joint 4- Muscles of the hip joint Structure of the hip joint The Role Of Abdominal muscle in SLR Structure of the hip joint The Adductor muscle group Structure of the hip joint The Role of Adductor Longus Structure of the hip joint What happens when passing a ball ? Structure of the hip joint External rotation when standing in hip and trunk Structure of the hip joint What happen when lean forward ?(brush your teeth) Structure of the hip joint While climbing Function of the hip joint 1- It supports the weight of the head, arms, and trunk (HAT), both in static erect posture and in dynamic postures such as ambulation, running and stair climbing. 2- It commonly operates in a closed kinematic chain because the foot ( distal end of the chain) is frequently fixed by weight bearing. 3- It provides a pathway for the transmission of forces between the pelvis and the lower extremities and conversely the thrusting propulsive movements of the legs are transmitted to the body. Stability (1) Stability of the hip joint (1) Stability of the hip joint Factors affecting stability:- Atmospheric pressure Shape of articulating surfaces Labrum acetabular Capsule Ligaments and muscles (2) Surface motion of hip joint (Arthrokinematics) Spinning in all motions with minimal glide. (3) Osteokinematics of hip joint Open vs closed kinematic chain  Femoral on pelvic  Pelvic on femoral A. Ipsilateral lumpopelvic rhythm B. Contralateral lumpopelvic rhythm (3) Osteokinematics of hip joint Open kinematic chain (3) Osteokinematics of hip joint Closed kinematic chain  (3) Osteokinematics Lumbo-pelvic rhythm It is the kinematic relationship between the lumbar spine and hip joints during sagittal plane movements. Open kinematic chain Ipsidirectio Pelvis moves to the same direction nal of the lumbar spine Closed kinematic chain Contra- the pelvis rotates in one direction directional while the lumbar spine rotates in the opposite direction. (3) Osteokinematics Lumbo-pelvic rhythm Ipsidirectional -Trunk flexion- The motion is measured as a combination of about 40 degrees of lumbar flexion and 70 degrees of hip flexion. It is usually initiated at the lumbar spine followed by anterior tilting of the pelvis at the hip (A) joints. Normal lumbar pelvic rhythm during trunk flexion. (B) The rhythm with limited hip flexion. (C) The rhythm with limited lumbar flexion. (3) Osteokinematics Lumbo-pelvic rhythm Ipsidirectional -Trunk extension- (A) Early phase by extension hip. (B) Middle phase occurs by extension of the lumbar spine. (C) In the last phase the muscle activity reduced. (3) Osteokinematics Lumbo-pelvic rhythm Contra-directional Anterior pelvic tilt extends the lumbar spine and increases lordosis and posterior pelvic tilt flexes the lumbar spine and decreases lordosis. This rhythm is used during walking, dancing and activities requiring the supralumbar trunk to be fixed. (3) Osteokinematics Lumbo-pelvic rhythm  Case study :- A patient demonstrates unstable posture while sitting. The first body segment that the therapist/ would align is the: ….. pelvis  Case study :- After surgery a patient develops a stiff pelvis and limited pelvic-lower trunk mobility. The therapist decides to use sitting exercises on a therapy ball to correct these impairments. In order to improve the abdominal control, in which direction the therapist should move the ball? Moving the ball forward makes the patient raising his arms and moving his trunk forward (in direction of more stability) to avoid falling and that produces posterior tilting of the pelvis and activation of abdominal muscles. (4) Weight transmission Body weight Abductor Causing bending ms. force moment Tensile force Compressive force laterally medially (4) Weight transmission Trabecular system of the femoral head Zone of weakness These stresses will be counterbalanced by activity of abductor muscles and tensor fascia lata in addition to dynamic structure of the bone itself and its trabecular network.  Hip joint kinetics Statics Dynamics (A) Bilateral stance (B) Unilateral stance  Statics HAT weight (A)Bilateral stance Distribution of weight of HAT on the lower limbs through hip joints:- * weight of HAT= 2/3 BW = 4/6 BW * Weight of both lower limbs (LL) =2/6 BW * weight of each LL = 1/6 BW Each hip joint carries half of HAT weight; N.B 1/3 BW Each lower (2/6 BW). extremity constitutes 1/6 of the total body weight. So total body weight = 4/6 for HAT (2/3 BW) + 2/6 both lower extremities. For example; in an individual weighing 90 kg, the weight of the HAT equals 60 kg (2/3 of body weight). The compressive force acts on each femoral head will be 30 kg (1/3 of body Statics (A)Unilateral stance When one foot is lifted from the ground, the hip joint carries the weight of HAT in addition to the weight of the lifted limb. The magnitude of the body weight compressing the supporting hip joint is five sixths of the total body weight = 2/3( 4/6) + 1/6 = 5/6 BW. The force of gravity (weight of HAT and the lifted limb) creates an adduction torque around the supporting hip joint which tends to drop the pelvis downward on the unsupported This adduction side. moment. is counterbalanced by an abduction moment produced by hip abductors(gluteus medius and minimus)  Joint reaction force The main factors that affect the total hip joint compression or the joint reaction force on the hip joint are muscular force and ground reaction force (weight). To find the joint reaction force, there are two methods: 1- Graphical method: by drawing triangle of forces. 2- Mathematical method.  Joint reaction force (1) Graphical method There are three forces acting on the hip joint which are: (1) The force of gravity (W) or ground reaction force (GRF) (2) The muscular force (MF) (3) The joint reaction force (JRF) Magnitude of JRF and direction can be estimated graphically by drawing the triangle of forces. Joint reaction force (2) Mathematical method Using cosine and sine equations to calculate the magnitude and direction of the JRF respectively. Cosine equation for the magnitude:- (J² = W² + M²- 2W M cos 0) Sine equation for the direction:-  **Question** A subject weighing 90 Kg is standing on one leg and the abductors are active to keep pelvis stable. when the moment arm of the weight is 10 cm and the moment arm of the abductor muscles is 5 cm and its angle of pull is 70° with the horizontal. -Calculate the magnitude (in Newton) and the direction of the joint reaction force (JRF) of the hip joint mathematically and -Then draw the triangle of forces graphically in scale.  **Question** -Draw the triangle of forces in scale; each 200 N = 1 cm. -Start drawing from the dot (.) inside the chart.  Joint reaction force Reduction of joint reaction force Several options are available to decrease the compressive force on the hip joint such as:- (1) Weight loss Weight loss of 1 N of body weight will reduce the joint reaction force by 3 N or more. For example; if the patient lost 15 kg the JRF reduces by 450 N. (2) Lateral lean of the trunk to reduce abductor muscle force (3) Using cane ipsilaterally and contralaterally Joint reaction force (2) Lateral lean of the trunk to reduce abductor muscle force Reduction of abductor muscle force can be used by reducing the moment arm of the gravitational force. This can be done by laterally leaning the trunk towards the side of pain or weakness. When a lateral trunk lean is seen during gait and is due to hip abductor muscle weakness, it is known as gluteus medius gait. If it is due to hip joint pain it is called antalgic  Joint reaction force (3) Using cane ipsilaterally and contralaterally Using the cane ipsilaterally provides some benefits in energy expenditure and structural stress reduction but still the lateral lean of the trunk reduces the joint compressive force more than using the cane ipsilaterally. When a cane is placed contralaterally (in the hand opposite to the painful right supporting hip), the weight passing through the painful right hip is reduced and activation of the left Latissimus dorsi provides a counter torque to diminish the need for a contraction of the right hip abductors. Joint reaction force *The effect of carrying a load on hip abductor* Pathomechanics of the hip joint 1- Arthrosis and Arthritis 2- Fracture and dislocation 3- Bone abnormalities:- - Coxa valga and Coxa vara - Femoral anteversion and femoral retroversion 4- Muscular abnormalities - Hip abductor weakness - Hip flexor contracture - Hamstring strian Pathomechanics of the hip joint Pathomechanics of the hip joint Dashboard injury Pathomechanics of the hip joint  Pathomechanics of the hip joint 3- Bone abnormalities:- Changes in femoral neck shaft angle ( femoral inclination angle):-  Pathomechanics of the hip joint 3- Bone abnormalities:- Changes in angle of torsion of femur( femoral anteversion angle):- Toe in gait Toe out gait Pathomechanics of the hip joint A Pincer impingement occurs as a result of an over coverage of the acetabulum on the femoral head (A), causing compression of the superior labrum between the acetabular rim and the femoral head-neck junction with flexion or abduction (B)  Pathomechanics of the hip joint 3- Muscular abnormalities:- Hip abductor muscle weakness Hip flexor muscle contracture  Pathomechanics of the hip joint 3- Muscular abnormalities:- Hamstring & adductor strain