Gross Anatomy
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FUNCTIONAL ANATOMY OF THE HIP JOINT

Required Reading: 637 -662 (The Anteromedial Thigh); 672 -75 ( The Posterior Thigh)

Review Chapter 7.2 (Gluteal Region) and the lecture on the Gluteal region given during the Abdomen and Pelvis unit

I. BONY ANATOMY

  1. Proximal femur (637 -40)
    1. Head, Neck Trochanters
    2. Alignment of the femur (Fig.1)
      1. Angle of Inclination
        1. Angle between neck and shaft of femur
        2. 1250 - 1300 angle in adults
      2. Coxa Vera
        1. Angle less than 1000
        2. Results in shortening of limb on affected side
      3. Coxa Valga
        1. Angle greater than 1300
        2. Results lengthening of limb on affected side sulcus
  2. Pelvic / Hip Bone (Os Coxa) (663) (Fig. 2)
    1. Ilium
      1. Iliac crest
        1. L-4
      2. Fossa
      3. Anterior Superior Iliac Spine (ASIS)
        1. Pelvic alignment
        2. Measurement of leg length
      4. Posterior Superior Iliac Spine
        1. S - 2
        2. Location of Sacroiliac joint ( dimples)
    2. Pubis
      1. Symphysis
        1. strong, slightly moveable joint between right and left public bones
        2. supported by fibrocartilage and ligaments
      2. Body
      3. Rami
        1. Superior ramus
        2. Inferior ramus
    3. Ischium
      1. Spine
        1. Landmark for pudendal vessels and nerve
      2. Tuberosity
    4. Obturator Foramen
      1. Opening between ischium and pubis
      2. Covered by obturator membrane
    5. Acetabulum
      1. Socket on lateral aspect of pelvic bone
      2. Formed by parts of all 3 components of the pelvic bone
      3. Forms socket portion of hip joint with the femoral head
    6. Notches
      1. Greater sciatic
        1. Between ilium and ischium
      2. Lesser sciatic
        1. Between ischial spine and tuberosity
    7. Ligaments
      1. Sacrotuberous
        1. Sacrum to ischial tuberosity
        2. Weight bearing when seated
      2. Sacrospinous
        1. Sacrum to ischial spine
      3. Sacroiliac
        1. Bind sacrum to Ilium
        2. (2) Support sacroiliac joint

II. FUNCTIONAL COMPARTMENTS OF THE THIGH

The thigh is subdivided by the attachments of the fascia lata ( deep fascia of the thigh) into 3 functional compartments). Each compartment contains a primary functional group of muscles, the innervation to theses muscles and a major source of arterial blood. It is necessary to understand the attachments, innervation and actions of these muscles in order to appreciate how the hip functions. The anatomy of the compartments of the thigh are covered in the text. The attachments, innervation and functions of the thigh muscles are outlined in Chart 1.

  1. A. Anterior Compartment
    1. Muscles
      1. Sartorius
      2. Tensor fascia lata
      3. Quadriceps femoris
        1. Rectus femoris
        2. Vastus lateralis
        3. Vastus medialis
        4. Vastus intermedius
      4. Pectineus
      5. Iliopsoas
        1. Iliacus
        2. Psoas
    2. Nerve Supply
      1. Femoral ( L 2,3,4 )
      2. (1) Motor
      3. Quadriceps femoris
      4. Sartorius
      5. Pectineus
      6. Sensory
      7. Anterior and lateral portion of thigh
      8. Medial portion of leg
    3. Blood Supply
      1. Femoral Artery
        1. Anterior Abdominal Wall
        2. Deep ( profunda ) femoral
        3. Muscular to muscles in anterior compartment
        4. Descending Genicular
      2. Deep ( Profunda ) Femoral
        1. Lateral femoral circumflex
        2. Medial femoral circumflex
        3. Perforating
          1. Muscles in posterior compartment
  2. B. Medial Compartment
    1. Muscles
      1. Pectineus
      2. Adductor longus
      3. Adductor brevis
      4. Adductor magnus
      5. Gracilis
    2. Nerve Supply
      1. Obturator ( L 2, 3, 4 )
        1. Motor to muscles in medial compartment
        2. Sensory to medial portion of thigh
    3. Bloody Supply
      1. Obturator Artery
        1. Muscular branches to muscles in medial compartment of thigh
        2. Acetabular branch
        3. Head of Femur
          1. Important in children
  3. Posterior Compartment
    1. Muscles
      1. Hamstrings
        1. Biceps femoris
        2. Semimembranosus
        3. Semitendinosus
    2. Nerve Supply
      1. Sciatic ( L 4 - S 3 )
        1. Motor to hamstring muscles
        2. Sensory - see unit on The Leg and Foot
        3. Motor deficits
    3. Blood Supply
      1. Perforating branches of Deep femoral artery

Hip Joint

  1. Type
    1. A multiaxial ball and socket synovial joint between the head of the femur and the acetabulum of the coxal ( pelvic ) bone.
  2. Fibrous Capsule
    1. 1. Proximal attachment - encircles rim of acetabulum
    2. 2. Distal Attachment
    3. a. anterior - greater trochanter, intertrochanteric line
    4. b. posterior - neck of femur
    5. i) capsule incomplete posteriorly
  3. Ligaments
    1. 1. Iliofemoral
      1. a. Covers hip joint anteriorly
      2. b. Arises from anterior inferior iliac spine
      3. c. Inserts into intertrochanteric line
    2. 2. Pubofemoral
      1. a. Covers hip joint anteriorly
      2. b. Arises from pubic bone and margin of obturator foramen
      3. c. Inserts into femoral neck deep to iliofemoral ligament
    3. 3. Ischiofemoral
      1. a. Covers hip joint posteriorly
      2. b. Arises from ischium
      3. c. Inserts into greater trochanter of femur
    4. 4 Functions
      1. Limit Motion
        1. Pubofemoral ligament limits abduction
        2. Lateral band of iliofemoral ligament limits adduction
        3. Medial band of iliofemoral ligament limits lateral rotation
        4. Ischiofemoral ligament limits medial rotation
      2. Stability
        1. Iliofemoral Ligament becomes taut in extension preventing the femur from moving past vertical position ( resists hyperextension)
        2. Maintains hip in locked or stable configuration
  4. Intracapsular
    1. Ligament of the head of the femur
      1. Very Weak
      2. Conveys branches of obturator artery to head of femur
  5. Retinacula
    1. Composed of fibers derived from fibrous capsule
    2. Retinacula fibers reflect back along femoral neck towards the femoral head
    3. Convey small arteries to head of femur
      1. Branches of medial and lateral femoral circumflex arteries
      2. Main blood supply to femoral head
      3. Commonly found on anterior surface of femoral neck
  6. Fractures/ Dislocation
    1. Fracture of femoral neck
      1. Could disrupt retinacula and blood supply to femoral head
      2. Avascular necrosis of femoral head
      3. Limb outwardly rotated
        1. Pull of lateral rotator muscles
    2. Dislocation
      1. Limb is shortened and inwardly rotated
  7. Cruciate anastomosis ( collateral circulation posterior to hip joint)
    1. Deep Femoral
      1. Transverse branch of lateral femoral circumflex a.
      2. Medial femoral circumflex a.
      3. Recurrent branch of 1st. perforating a.
    2. Inferior gluteal artery

III. LOCKING OF THE HIP JOINT

  1. Function
    1. Permits standing upright with little expenditure of energy in the form of muscle contraction
    2. Occurs when the head of the femur and the acetabulum are congruent ( fit tightly together and the iliofemoral ligament becomes taut.
  2. Mechanism
    1. Fibrous Capsule
      1. Iliofemoral Ligament
        1. Covers hip joint anteriorly and interiorly
        2. Tightens during hip extension
        3. Prevents femur from moving past vertical position ( resists hyperextension)
      2. Ischiofemoral ligament
        1. Winds transversely across posterior aspect of hip
        2. Tightens upon hip extension
        3. Much weaker than iliofemoral ligament
  3. C. Process
    1. Center of mass of the body falls behind hip joint
    2. Gravity forces the hip posteriorly into a position of extension
    3. In the extended position, the hip joint locks
      1. The femoral head fits tightly into the acetabulum
      2. Iliofemoral ligament becomes taut preventing hyperextension
    4. Weight of the body supported by iliofemoral ligament

IV.MOVEMENTS OF THE HIP (Chart 2)

  1. Properties of the Hip Joint
    1. Multiaxial ball and socket joint
    2. Types of Movement - Movements of the lower limb can best be understand if one realizes that different bones will move depending upon whether the limb is in weight bearing or non weight bearing. In either case the movement is the same and the same muscles act. It just that different bones can move given the different situations
      1. Weight bearing (fixed) -foot in contact with ground and the limb is supporting weight of body
        1. Pelvis moves on a fixed femur
        2. Bending down to touch toes
      2. Non Weight bearing (free) - foot free of ground and the limb is unable to support weight of body
        1. Femur free to move on a fixed pelvis
        2. Kicking a ball
  2. Movements at the Hip
    1. Flexion / Extension
      1. Occurs in sagittal plane
      2. Transverse ( side to side) axis through head of femur
    2. Adduction / Abduction
      1. Occurs in frontal plane
      2. Anterior / posterior axis through head of femur
    3. Inward / Outward Rotation
      1. Occurs in transverse plane
      2. b. Vertical axis through head of femur and lateral femoral condyle
  3. Muscle Actions
    1. Muscles acting to move the hip include the gluteal muscles, the iliopsoas , and muscles of the thigh. The Chart lists the movements that can occur at the hip joint and the muscles acting as prime movers for each motion

V. CLINICAL CONSIDERATIONS

  1. Actions of the Hip Joint During Gait (Review the video "The Anatomical Gait Cycle")
    1. Acceleration and Heel Strike
      1. Restraining the forward movement of the lower limb occurs during this interval through the eccentric contractions of hamstring and gluteus maximus muscles acting on the hip joint. This restraining action leaves the hip in a flexed position.
      2. The gluteus medius and gluteus minimus contract concentricly abducting the reference limb from a weight bearing position. This involves moving the iliac crest of the reference limb away from the midline (abduction). The iliac crest moves instead of the femur because at heel strike, the foot of the reference limb is in contact with the ground and in a weight bearing position. The femur can not move so the muscles act on the iliac crest which can move. Concomitantly, the non weight bearing hip is "hiked" upward counterbalancing the effect that gravity wants to exert on the non reference limb which is about to attain a non weight bearing position . Without the concentric contraction of the hip abductors on the weight bearing reference limb, the opposite hip would tilt downward making it very difficult to swing the limb forward in order to take a step. This type of gait is called "Trendelenburg Gait"
    2. Heel Strike to Midstance
      1. The torso is being pulled over the center of the reference limb as the non reference limb swings forward. This puts the hip in a neutral position without any direct actions of muscles acting on the hip.
    3. Midstance to Toe Off
      1. The non reference limb is in a non weight bearing stage and is swinging forward as a step is taken. This process "drags" the torso in front of the reference limb forcing the hip joint of the weight bearing reference limb into an extended position. Once again, this occurs without the direct action of the muscles acting on the reference limb.
    4. Toe Off to Acceleration
      1. During this interval, the reference limb goes from a weight bearing to a non weight bearing position as the reference limb begins to swing forward ahead of the torso as a step is being taken. Powerful concentric contractions of the hip flexors, mainly the iliopsoas muscle with help from the adductor muscles bring the hip into a position of flexion.
      2. The hip adductors also helps the swinging limb move in an inward direction. This enables the foot to be placed under the pelvis rather than in a position that would be parallel with the shoulder.
  2. The Effect of Nerve Lesions on the Hip Joint During Gait
    1. Superior gluteal nerve
      1. Trendelenburg Gait
        1. Marked downward tilting of the hip on the non weight bearing side due to inability of the gluteus medius and minimus to actively abduct the hip on the weight bearing side during walking
      2. Trendelenburg Sign
        1. Clinical test to determine the integrity of the superior gluteal nerve
        2. Patient's hip tilts down when the limb is non weight bearing because of superior gluteal nerve is damaged on weight bearing side.
    2. Obturator nerve
      1. "Waddling gait"
        1. Hip is in a marked abducted position due to paralysis of hip adductor muscles
        2. When walking, the foot on the affected side, can not be placed under pelvis. Patient has to "throw" their weight laterally when taking a step thus, waddling to the affected side.
  3. Lumbar and Lumbosacral Nerve Root Involvement
    1. L 1,2
      1. These roots are mainly involved with innervating the iliopsoas muscle. Damage to these roots would result in very weak hip flexion
      2. To test for the integrity of these roots, ask the patient to sit. Then have them try and flex the hip from a sitting position. Weak hip flexion indicates a problem with the L 1,2 nerve roots
    2. L 2,3
      1. These roots are concerned with the innervation of the hip abductors. Damage to these roots can lead to a waddling type of gait.
      2. To test for the integrity of these roots, have the patient lie on their side with their body in a straight line. Place the upper hip into abduction and place each hand on the inside of each thigh. Have the patient try and bring the hips into adduction. Weakness could indicate a lesion of the L 2,3 nerve roots
    3. L 5
      1. This is the main root innervating the gluteus medius and minimus muscles. A positive Trendelenburg Sign could indicate damage to this root


  1. Chart I - MUSCLES OF THE THIGH

Compartment Joint Main

Function(s)

Nerve Segment(s)
ANTERIOR:
Vastus Medialis 1 Knee Extend Femoral L 2,3*
Vastus Lateralis 1 Knee Extend Femoral L 2,3
Vastus Intermedius 1 Knee Extend Femoral L 2,3
Rectus femoris 1 Hip

Knee

Flex

Extend

Femoral L 2,3
Sartorius Knee

Hip

Flex

Flexes,Abducts, Outward Rotation

Femoral L 2,3
Iliacus 2 Hip Flexor Lumbar Plexus L 1,2
Psoas 2 Hip Flexor Lumbar Plexus L 1,2
Pectineus Hip Flexor

Adductor

Femoral

Obturator

L 2,3
MEDIAL
Adductor Longus Hip Adduct; flex Obturator L 2,3
Adductor Brevis Hip Adduct; flex Obturator L 2,3
Adductor Magnus 3 Hip Adduct; flex Obturator L 2,3
Gracilis Hip

Knee

Flex, adduct

Flex

Obturator L 2,3
POSTERIOR 4
Semimembranosus Hip

Knee

Extend

Flex

Sciatic(T) L5,S1 ,2
Semitendinosus Hip

Knee

Extend

Flex

Sciatic(T) L5,S1 ,2
Biceps Femoris -Long Hip

Knee

Extend

Flex

Sciatic(T) L5,S1 ,2
Biceps Femoris -Short Hip

Knee

Extend

Flex

Sciatic(CF) L5,S1 ,2

    1 =Quadriceps femoris

    2 = Iliacus + Psoas muscles join to form a common tendon = Iliopsoas

    3 = Posterior portion of Adductor Magnus can help extend hip and is innervated by sciatic nerve.

    4 = Posterior compartment muscles = Hamstring muscles

    * Bold numbers indicate which ventral rami provide the most important motor axons innervating each muscle


Chart 2 -PRIME MOVERS OF THE HIP JOINT

ACTION MUSCLES NERVE SEGMENTS
Flexion- Initiate Tensor Fascia Lata Superior Gluteal L 4, 5, S 1
Pectineus Femoral;Obturator L 2,3,4
Sartorius Femoral L 2,3,4
Gracilis Obturator L 2,3,4
Flexion - Complete Iliopsoas Lumbar Plexus L 1,2
Extension Gluteus Maximus Inferior Gluteal L 5 S 1, 2
Hamstrings Sciatic L 5 S 1, 2
Adductor Magnus-

Posterior

Sciatic L 3,4
Adduction Adductors Longus Obturator L 2, 3,4
Adductors Brevis Obturator L 2, 3,4
Adductors Magnus Obturator L 2, 3,4
Gracilis Obturator L 2, 3,4
Abduction Gluteus medius Superior Gluteal L 4, 5, S 1
Gluteus minimus Superior Gluteal L 4, 5, S 1
Inward Rotation Gluteus minimus Superior Gluteal L 4, 5, S 1
Tensor Fascia Lata Superior Gluteal L 4, 5, S 1
Outward Rotation Gluteus Maximus Inferior Gluteal L 5 S 1, 2
Piriformis Nerve to Piriformis S 1, 2
Obturator Externus Obturator Nerve L 3, 4
Obturator Internus Nerve to Obturator Internus L 5 ,S 1, 2
Superior Gemellus Nerve to Obturator

Internus

L 5 ,S 1, 2
Inferior Gemellus Nerve to Inferior

Gemellus

L 4,5, S 1
Quadratus Femoris Nerve to Inferior

Gemellus

L 4,5, S 1
Gluteus medius Superior Gluteal L 4, 5, S 1


Figure 1 Alignment of the Femur
a. = pubic bone

b. = ischium

c. = ilium

1 = Lesser trochanter of femur

2 = Greater trochanter of femur

3 = Neck of femur

4 = Shaft of Femur

Angle of inclination is the angle between the neck and shaft of the femur.


Figure 2 - Bony Female Pelvis


VII. OBJECTIVES:

  1. Know the bony and ligamentous structures that comprise the hip joint.
    1. Be able to define coxa valga and coxa vera and know what is meant by the angle of inclination of the femur
  2. Know the blood supply and innervation of the hip joint
    1. Understand the clinical significance of the cruciate anastomosis
  3. Understand the mechanism involved in hip stability and how the hip is locked.
    1. Know the role of the following in these processes:
      1. Center of gravity
      2. Bony surface
      3. Ligaments
  4. Know how the ligaments act to restrain hip motion
  5. Be able to differentiate between hip fractures and hip dislocation by the position of the limb.
  6. Know the attachments, innervation and function(s) of the muscles acting on the hip joint .
    1. Be able to apply this information to determine if there are any functional deficits affecting the normal range of motion of the hip
  7. Understand the factors that affect the hip during the gait cycle
    1. Know the position of the hip joint at the various stages of the gait cycle
    2. Be able to determine which muscles are acting on the hip at the different stages of the gait cycle and if they are acting in a concentric or eccentric manner.
  8. Know how nerve lesions may affect movements of the hip joint.
    1. Be able to localize the site of peripheral nerve damage by testing to see if there are any deficits in motion at the hip.
    2. Be able to distinguish between the effects of peripheral nerve lesions on the functioning of the hip from lesions to the roots of the lumbosacral plexus.
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