Chapter 20
The Hip Joint Complex


The hip joint complex is the critical link between the lower extremity and the trunk. This system must absorb and transmit enormous forces while also allowing a large arc of motion. As such, the hip joint complex presents as a fascinating dichotomy of stability and mobility. The fundamental clinical question, relative to the hip is, "what are the threats to my patient's stability and mobility?"

  1. Factors favoring stability are:
    1. joint surfaces are nearly congruent during WB,
    2. the acetabulum forms a bony ring around the femoral head, this is reinforced by the capsule and labrum,
    3. bony trabeculae reinforce the femur and pelvis in the direction of WB, and
    4. there is a large muscle mass acting through well-placed, bony lever arms.
  2. Factors favoring mobility are:
    1. large surface area of joint,
    2. no barriers to motion from adjacent joints, and
    3. capsular redundancy.
The purpose of this presentation is to review the anatomy and mechanics of the hip joint complex from the perspective of mobility vs. stability. This concept will be used as a model to also discuss the common developmental, traumatic and degenerative conditions which affect the hip. A hip examination will be reviewed, followed by treatment options using the case study approach.

  1. Bony anatomy
    1. proximal femur: femoral head, neck, greater and lesser trochanters
      1. intertrochanteric line and crest, quadrate tubercle
      2. trochanteric fossa
      3. spiral line, pectineal line, gluteal tuberosity
    2. inominate bone: ischium, ilium, pubis
      1. acetabulum: rim, notch
      2. ASIS, AIIS, iliopubic eminence
      3. pubic rami: pectineal line, crest, tubercle
      4. ischial tuberosity, spine
      5. gluteal line: anterior, posterior, inferior

  2. Arthrology of the hip
    1. joint structure: convex femoral head articulates with the concave acetabulum to form a "ball and socket" type joint. Despite its great mobility, the hip joint is quite stable.
      1. femoral head: roughly semi-spherical shape, the geometric center is traversed by the three axes of the joint. Faces superior, anterior and medial within the acetabulum.
      2. femoral neck: "overhang" system, trabecular arrangement well-suited for resisting compressive, tensile, and bending forces. Forms with the shaft of the femur the angle of inclination = (125-135 degrees on frontal plane), and the angle of anteversion =15 degrees on the transverse plane.
        1. the width of the femoral neck determines the length of the moment arm of the hip abductor muscles.
        2. abnormalities: excessive anteversion, retroversion, coxa vara, coxa valga.
      3. acetabulum: hemispherical shaped, the articular surface is horseshoe-shaped, inferiorly has notch, and centrally a fossa.
        1. reinforced superiorly by rim and labrum.
        2. axis faces interiorly 30-40 degrees (angle of Wriberg) this creates an overhang of the superior rim.
      4. capsule: large and strong, it covers much of femoral neck, and has a small inferior redundancy.
      5. ligaments: strongly reinforce capsule, "twisted" taut in extension, loose in flexion
        1. Ilio-femoral ligament
        2. pubo-femoral ligament
        3. ischio-femoral ligament
    2. Arthrokinematics: 3 degrees of freedom. Consider the femur moving relative to the pelvis or the pelvis moving relative to the femur.
      1. close-packed: extension
      2. maximum loose packed: mid - to full flexion
      3. joint geometry: lack of precise fit, eg. incongruity when unloaded. When fully loaded develops congruity between joint surfaces, with specific areas of weight-bearing.
        1. important for nutrition
        2. arthrosis: changes joint geometry, alters this mechanism
      4. joint forces:
        1. external: gravity, inertia due to acceleration of body parts
        2. internal: primarily from musculotendonius unit, small contribution from ligaments, joint capsule.
        3. the resultant of internal and external forces is balanced by the joint reaction force (JRF)
          1. peak JRF during walking occur just after mid-stance ( 4 X body weight)
          2. least JRF "touch down" weight-bearing

  3. Osteokinematics and Muscle Activity

    1. Cardinal plane motion

      Motion ROM Muscles active (agonists) Motion Limiters
      Flexion 125-135 lliopsoas
      Rectus Femoris
      Adductor L & B
      Tensor Fascia Latae
      Gluteus Minimus
      hip extensor muscles
      posterior capsule
      femoral neck on the acetabulum
      Extension 20-30 Gluteus Maximus
      Gluteus Medius
      Ham Strings
      Adductor Magnus (post.)
      hip flexor muscles
      anterior capsule
      Ilio-femoral liga
      pubo-femoral liga
      ischio-femoral liga
      Abduction 40-45 Gluteus Medius
      Tensor Fascia Latae
      Gluteus Minimus
      Gluteus Medius
      Gemelli, Obturator Int.
      Adductor muscles
      inferior capsule
      femoral neck on the superior rim of the acetabulum
      Adduction 30 Adductor L & B
      Adductor magnus

      Gracilis, Obturator Ext
      abductor muscles
      superior capsule
      Medial Rot 30-40 Tensor fascia latae
      Gluteus medius (ant.)
      Adductor L & B
      Gluteus Minimus
      lateral rot. muscles
      posterior capsule
      Lateral Rot 60-70 Piriformis
      Obturator Int. & Ext.
      Quadratus Femoris

      Gluteus Maximus
      Biceps Femoris, long head
      Posterior Gluteus Medius
      Medial rot. muscles
      Anterior Capsule

    2. Motion required for gait
        10-15 degrees of extension, 30-40 degrees of flexion.
        10 degrees of ER, 3-5 degrees of IR
        5 degrees of ADD to 6-8 degrees of IR

    3. Hip joint function during normal gait
Most hip joint disorders result in some form of gait impairment, thus analysis of gait is critical when evaluating a person with hip joint dysfunction. Additionally, restoration of normal gait is often the main goal of PT treatment. While an in depth discussion of gait is beyond the scope of this presentation, a brief review will be presented.

  1. Normal Gait
    1. The primary function of the lower extremities (LE's) is locomotion, ie. gait.
    2. Walking or running can be considered as series of losing and gaining one's balance in a controlled fashion.
      1. This happens through restraint, support and propulsion
      2. This is an extremely complex activity which combines muscle activity and joint motion (internal forces) in response to inertia and gravity (external forces).
    3. Normal gait is energy efficient, this involves minimal non-forward displacement of the center of gravity (COG).
    4. Abnormal gait occurs due to paralysis, contracture, sensory impairment, discoordination, and a variety of other causes.
      1. this results in a disruption of the normal sequence of events.
      2. manifests as: abnormal timing, unequal step length, and/or abnormal displacement of the COG.

  2. Hip joint kinematics during gait (approximate values)
    1. Swing phase

        Early Mid Late
      sagittal 20 flex 30 flex 30 flex
      frontal 3 ABD 8 ABD 3 ABD
      transverse 10 ER 2 ER 0

    2. Stance phase

        HS FF MS HO TO
      sagittal 30 flex 25 flex 0 flex 10-20 ext 0
      frontal 2 ABD 0 ABD 0-2 ADD 5 ADD 5 ABD
      transverse 0-2 IR 2 IR 2 LR 2 LR 10 LR

  3. Hip joint kinetics during gait: (Kinetics: the study of forces)
    1. Muscle contractions occur in response to external forces. The goal is to keep the COG going in the desired direction.
    2. Stance phase: applies Newton's 3rd Law (the Law of Reaction)
      1. Ground Reaction Force (GRF): the forces which occur in response to limb which is in contact with the ground.
        1. can be horizontal, vertical, fore and aft shear, lateral, shear, transverse.
        2. GRF affected by:
          1. body weight
          2. nature of terrain (geography, friction)
          3. velocity (rule of 3's)
          4. foot mechanics
      2. relate the Ground Reaction Force to the COG to determine muscle actions. Consider turning moment

        Muscular contraction resists this turning moment.

      3. Joint Forces: the contact force at the hip during stance is 5 times that of body weight. This is primarily due to the force from muscular contractions.
        1. the use of assistive gait devices reduces this. The use of a cane can reduce this by 60% (Brand 1980).
        2. reducing cadence will also reduce this force.
        3. the least joint force through the hip occurs with "toe touch weight-bearing". ie. Resting the foot on the ground to reduce the distractive load.

  4. Neurovascular anatomy
    1. The primary peripheral nerves associated with the hip are:
      1. femoral
      2. obturator
      3. sciatic
      4. superior gluteal
      5. inferior gluteal
      6. other
    2. The innervation of the hip joint (Hilton's Law)

    3. Cutaneous innervation of the hip, buttock and thigh
      1. peripheral nerves
      2. dermatomes
    4. Primary vascular structures
      1. femoral artery
      2. femoral circumflex system
      3. superior and inferior gluteal arteries

  5. Pathokinesiology

    Dysfunction of the hip joint and its associated tissues is common in all age groups. It is one of the major causes of gait impairment in both the pediatric and geriatric populations.

    1. Epidemiological factors
      1. The hip joint transmits large forces repetitively, therefore it is subjected to great "wear and tear" throughout life. This is probably a predisposing factor for arthrosis.
      2. The blood supply to the femoral head is tenuous and can be compromised by trauma, disease and aging. This can lead to avascular necrosis.
      3. The bone tissue in the femoral neck is primarily cancellous. The loss of bone cells (osteopenia) in this area is common in elderly people and can predispose to fractures here.
      4. The abductor muscle mechanism relies on a normally functioning hip joint. With dysfunction of the hip this is usually impaired. This alters the joint reaction forces acting upon the hip which can lead to further problems.

    2. Dysfunction of the hip joint typically presents as:
      1. pain perceived in the inguinal area which can refer to the medial knee.
      2. limited ROM of the hip
      3. gait disturbance

    3. The following are common hip problems which are encountered by PT's
      1. Pediatric
        1. developmental: congenital dislocation, Leg Calve Perthe's
        2. traumatic: epiphyseal injuries, soft tissue injury
      2. Young and middle-age adults
        1. traumatic: dislocation, femoral Fx, soft tissue injuries
        2. overuse syndromes: stress Fx, tendonitis
        3. inflammatory and infectious disorders
        4. avascular necrosis (AVN)
      3. Elderly
        1. osteoarthrosis
        2. hip Fx

  6. Pathokinesiology: arthrosis

    Arthrosis refers to degeneration of a joint, typically this refers to morphological changes occurring in the articular surfaces, followed by changes of the other joint structures such as synovium, capsule, subchrondral bone.

    1. Etiological factors for the development of arthrosis
      1. microtrauma: "wear and tear", primarily due to impulse loading
      2. macrotrauma: joint injury, dislocation
      3. impaired nutrition
        1. limited motion
        2. injury to subchrondral bone
        3. AVN
      4. aging process?
    2. Histological and mechanical
      1. structure of normal articular cartilage
        1. hyaline cartilage without a perichondral layer, roughly 2-7mm thick. Contains:
          1. chondrocytes
          2. collagen
          3. proteoglycans (PG) and bound water: PG's consist of a core protein (5%) to which are attached glycosaminoglycans (GAG's) (95%). The GAG's are said to hydrophilic, eg they exert a (-) electrical charge and thus attract H (+), thereby binding large amounts of water.
        2. Collagen fibers act as a mesh-work within matrix
      2. Function: acts as a mantle or barrier to protect bone ends
        1. distribute loads
        2. low friction surface
      3. proposed mechanism of arthrosis:
        1. alteration or loss of proteoglycans results in loss of bound water,
        2. increased stiffness,
        3. decreased load-bearing capacity,
        4. increased stress on sub-chondral bone,
        5. disruption of cartilage.
    3. Pathological changes
      1. disruption of tangential layer (fibrillation)
      2. formation of large defects (fissuring)
      3. exposed sub-chrondral bone (eburnation)
    4. Radiographic
      1. loss of joint space
      2. sclerosis of sub-chrondral bone
      3. formation of osteophytes and bone cysts
    5. Clinical examples of hip joint arthritis
      1. inquinal pain
      2. gait impairment
      3. limited ROM, fixed deformity
      4. disuse weakness
    6. Treatments
      1. non-surgical
        1. prevention?
        2. ROM exercises
        3. strengthening
        4. reduced load-bearing: assistive device, weight loss
        5. joint, soft tissue mobilization? TENS? Foot orthotics?
        6. NSAIDS
      2. surgical
        1. osteotomy
        2. arthroplasty


  1. Assessment: ask yourself, "what information do I need to develop a safe, effective treatment plan for this patient?"
    Considerations are:
    1. reliability of:
      1. patient as a historian
      2. measurements obtained
        1. goniometry
        2. muscle testing
        3. other
    2. musculoskeletal problem or not?
      1. abnormal motion
      2. malalignment
      3. "non-neurological muscular weakness"
      4. structural impairment of the spine or LE
    3. neurological impairment?
    4. associated problems: precautions, contraindications?
    5. risk factors: occupational, recreational
    6. for patients with a complaint of pain:
      1. habitual activities which increase pain
      2. referred pain?
      3. level of irritability
      4. psychological stress level
    7. for patients with mobility problems
      1. distance ambulated
      2. surfaces
      3. assistive devices
    8. other:
      1. secondary gain
      2. health attitude
      3. classification: acute, acute recurrent, chronic, disabled or not?

  2. The subjective exam
    1. Goals of the subjective exam for hip dysfunction
      1. establish patient's identity, lifestyle, daily stresses
      2. cc symptoms
      3. past medical history, current medical/surgical problems
      4. patient goals
    2. Suggested procedure
      1. age, occupation, recreation
      2. current cc (pain, stiffness, weakness, gait disturbance)
        1. location of pain: local vs diffuse
        2. * behavior: "what makes it better, what makes it worse?"
        3. functional questions: walking, standing, sitting, sit to stand, self-care, unique occupational demands, disabled or not?
        4. potential of nerve root compression: true weakness, anesthesia, bowel and bladder problems
      3. onset of symptoms
        1. when and how?
        2. single traumatic episode:
          1. radiographs
          2. associated injuries
          3. care of associated injuries
        3. gradual onset
          1. postural stresses, arthrosis, overuse
          2. potential for non-musculoskeletal cause
        4. behavior since onset
          1. better or worse?
          2. previous care
        5. previous problems with this hip, is this the same or different?
        6. other musculo-skeletal problems
      4. past and current medical/surgical history
        1. chronic diseases: DM, RA, ETOH, heart disease, HT, lung disease
        2. other: seizure disorder, PVD
        3. any systemic inflammatory disease
        4. osteoporosis
        5. surgeries: spinal, hysterectomy, cancer
        6. medications: steroids, opiates, psychotrophic, tricylics, NSAIDS
      5. patient goals
        1. measurable
        2. reasonable

      6. Examiner's impression
        1. reliability?
        2. musculoskeletal problem?
        3. level of irritability?
        4. precautions and contraindications?
        5. potential for non-PT related problems?
        6. disabled or not?

    1. Goals of the objective exam for Hip Dysfunction
      1. identify structural abnormalities
      2. identify movements and positions which reproduce the patient's symptoms
      3. identify the presence of neuromuscular impairment
    2. Suggested procedure
      1. exam maneuvers are performed in the following sequence of positions:
        1. standing, gait analysis if WB
        2. sitting
        3. supine
        4. prone and if indicated, sidelying
    3. Standing (if FWB)
      1. inspection
        1. iliac crest height, femoral-pelvic relationship
        2. symmetry of trunk and lower extremities (bony, soft tissue)
      2. patient identifies painful area
      3. ROM of trunk (rule out referred pain from spine)
        1. forward bending
        2. backward bending
        3. side bending
        4. three dimensional
        5. repeated motions
      4. special tests
        1. unilateral leg stand (L4,5)
        2. heel raise (S1,2)
    4. Sitting
      1. sitting posture
      2. ROM: rotation of trunk and hips
      3. Motor: hip rotation
      4. functional activities: putting on shoes, etc.
    5. Supine
      1. inspection
        1. leg length
        2. alignment of LE's
        3. symmetry of soft tissue
        4. skin condition
      2. ROM (active followed by overpressure)
        1. hip flexion (extension of opposite hip) (also knee flexion here)
        2. hip rotation
        3. abduction, adduction
        4. knee extension
        5. SLR
        6. ankle dorsi flexion (Homan's)
      3. Motor
        1. hip flexion (L2,3)
        2. knee extension (L3,4)
        3. ankle dorsi flexion (L4,5)
        4. sub-talar eversion (L5,S1)
        5. great toe extension (L5)
        6. great toe flexion (S1)
      4. Sensory and reflex
        1. light touch L2-S2
        2. patellar tendon (L3,4)
        3. achilles tendon (S1,2)
        4. Babinski, Clonus
      5. Palpation
        1. bony
          1. ASIS, AIIS, pubic tubercles, femoral head
        2. soft tissue
          1. iliopsoas, sartorius, rectus femoris, TFL, adductor longus
        3. pulses: femoral, popliteal, posterior tibial, dorsalis pedis
      6. Special tests
        1. SI compression and distraction
        2. spinal distraction
        3. Patrick's
        4. accessory motion: inferior glide, lateral glide, "perimeter"
    6. Prone
      1. inspection: spine and buttock soft tissues
      2. ROM
          knee flexion (femoral nerve stretch test)
      3. motor
        1. knee flexion (S1,2)
        2. hip extension (L4,5;S1,2)
      4. palpation (static)
        1. bony
          1. iliac crest, PSIS, sacrum, ischial tuberosity, greater trochanter
          2. spinous processes L5-T12
        2. soft tissue
          1. Ligamentous: sacrotuberous ligament, supraspinious ligament
          2. muscles and fascia
            1. buttock: TFL, gluteus max, mm, piriformis, quadratus femoris
            2. spinal: lateral abdominals, quadratus lumborum, erector spinae
      5. palpation (dynamic)
        1. articular: PA pressures
        2. soft tissue mobility
    7. Sidelying
      1. palpation (dynamic)
        1. spinal joints
          1. distraction
          2. flexion
          3. extension
          4. side-bending
          5. rotation
        2. sacro-iliac joint
          1. upward rotation
          2. downward rotation
      2. special tests
          Ober's test
      3. motor: hip abductors
    1. Common fractures and dislocations (mechanism, surgical management, weight-bearing progression, other)
      1. inter-trochanteric Fx
      2. femoral neck Fx
      3. acetabular Fx
      4. femoral shaft Fx
      5. pelvic ring Fx
      6. stress Fx
      7. posterior dislocations
    2. Common soft tissue problems (etiological factors, unique findings, treatment options)
      1. "hip pointer"
      2. adductor longus tendonitis
      3. piriformis muscle strain

[Back] [Ortho II] [Next]