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Chapter 3
Considerations of Sex Differences
in Musculoskeletal Anatomy
Phillip S. Sizer, PT, PhD
and
C. Roger James, PhD, FACSM
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Learning Objectives
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After completing this chapter, you should
understand:
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sexual dimorphism and how it applies to humans
sex differences in general morphology
sex differences in skeletal geometry
sex differences in collagenous, cartilage, & bone tissue
sex differences in upper extremity anatomy &
mechanics
sex differences in lower extremity anatomy &
mechanics
sex differences in spine anatomy & mechanics
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Musculoskeletal Anatomy of Men
and Women
• Sexual dimorphism is
prominent in many
species, but more
subtle in humans
• There are generally
recognized differences
in body structure
Symbolic representation of men and women as
depicted on the plaque of the Pioneer 10 spacecraft in
1972. Source: NASA. Adapted with permission.
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Differences in General Body
Characteristics
• Sex differences are age dependent:
• Before puberty, boys and girls at the 50th
percentile are approximately the same height
and weight.
• After puberty, men are approximately 14 cm
taller and have 12 kg more mass than women.
• General appearance (body shape) changes, as
well.
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Selected Sex Differences in Skeletal
Geometry: Pelvis
• Women have
• Larger inlet and outlet
• Greater interacetabular distance
• Greater hip width normalized to femur length
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Selected Sex Differences in Skeletal
Geometry: Femur
• Women have
• Greater femoral anteversion
• Narrower intercondylar notch width
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Selected Sex Differences in Skeletal
Geometry: Knee, Tibia, and Foot
• Women have
• Greater genu recurvatum
• Greater quadriceps (Q) angle
• More lateral patellar alignment
• Greater tibial torsion
• More bunions and deformities of the toes
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Evidence of Sexual Dimorphism from
Forensic Anthropology & Archeology
• Characteristics of skeletal geometry have
been used to predict an individual’s sex
from their skeletal remains.
• The humerus, pelvis, femur, tibia, talus, and
calcaneus all have been used for this
purpose.
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Evidence of Sexual Dimorphism from
Forensic Anthropology & Archeology
• The ability to predict an individual’s sex
from skeletal remains differs by bone.
• The strongest predictors are the tibia, femur,
and calcaneus, followed by the pelvis and
talus.
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Evidence of Sexual Dimorphism from
Forensic Anthropology & Archeology
• Some anatomic characteristics of a bone are better
predictors of sex than other characteristics.
• The characteristics of the femur that best predict
sex include those that are associated with the
femoral head.
• Combinations of characteristics are the best
predictors.
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Factors Influencing Sex Differences
in Skeletal Geometry
• Skeletal maturity
• Environmental stresses
• Genetics
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Sex Differences in Musculoskeletal
Tissues: Collagenous Tissues
• There are several sex differences in collagenous
tissues (e.g., tendon, ligament, skin):
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Collagen thickness
Collagen orientation
Collagen content
Collagen diameter
Collagen volume
Collagen metabolism
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Sex Differences in Musculoskeletal
Tissues: Cartilage Tissue
• Women have 1.5-4 times greater risk of
osteoarthritis
• There are several sex differences in cartilage,
women having:
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Less cartilage volume
Less cartilage thickness
Less cartilage surface area
Slower cartilage accrual rate in youth
Greater cartilage degradation in older age
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Sex Differences in Musculoskeletal
Tissues: Bone Tissue
• Women have greater risk of bone fracture,
especially after menopause.
• There are several sex differences in bone, women
having:
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Slower bone accrual rate in youth
Less peak bone mass in adulthood
Slower bone turn-over in adulthood
Less volumetric bone mineral density at some sites
Less bone area at some sites
Less cortical thickness at some sites
Less compressive and bending strength at some sites
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Shoulder Anatomy
Sex-Based Differences
• Incidence of external impingement is likely
related to differences in:
• Acromion process shape
• Posterior capsule shortening
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Shoulder Anatomy
Sex-Based Differences
• Increased incidence of glenohumeral
instability in women is likely related to
differences in:
• Glenoid fossa inclination
• Anterior capsular laxity
• Decreased joint stiffness
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Shoulder Anatomy
Sex-Based Differences
• Increased incidence of idiopathic capsulitis
in women is likely related to differences in:
• Increased thickening of the anterior-superior
joint capsule at the coracohumeral ligament
• Non-inflammatory synovial reaction in the area
of the subscapularis tendon
• Active fibroblastic proliferation and tissue
transformation
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Elbow Anatomy
Sex-Based Differences
• Increased incidence of tennis elbow in
women is likely related to differences in:
• Decreases in estrogen production
• Mesenchymal changes in the tendon structure
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Wrist & Hand Anatomy
Sex-Based Differences
• Increased incidence of carpal tunnel
syndrome in women is likely related to
differences in:
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Tunnel architecture and volume
Shape of the hamate hook
Digital features
Hand-length ratios
Body mass index
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Wrist & Hand Anatomy
Sex-Based Differences
• Female architectural differences likely
result in the following Carpal Tunnel
Syndrome precipitating factors:
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Increased tunnel pressure
Perineural edema & fibrosis
Deficits in neurophysiological function
Autonomic disturbances
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Hip Joint Anatomy
Sex-Based Differences
• A woman’s predisposition to stress & frank
fracture at the hip are likely related to:
• Architectural differences in the hip & pelvis
• Reduced acetabular depth and femoral head
width
• Narrowed CD angle
• Decreased femoral neck strength
• Decreased bone mass
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Hip Joint Anatomy
Sex-Based Differences
• A woman’s predisposition to labral tears at
the hip are likely related to:
• Decreased labral tensile strength
• Increased femoral neck thickness
• Decreased CD angulation
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Knee Joint Anatomy
Sex-Based Differences
• A woman’s predisposition to ACL Injuries
at the knee are likely related to:
• Reduced femoral intercondylar notch width
(controversial)
• Altered biomechanical behaviors
• Altered motor control strategies
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Knee Joint Anatomy
Sex-Based Differences
• Biomechanical differences in women during
landing and cutting:
• Reduced knee flexion angle at contact
• Increased knee valgus motion
• Increased knee joint laxity and anterior tibial
translation
• Increased subtalar joint pronation
• Greater ACL ligament creep
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Knee Joint Anatomy
Sex-Based Differences
• Control strategy differences in women
during landing and cutting:
• Reduced protective hamstring activity
• Increased quadriceps activity
• Decreased cocontractive control
• Increased soleus and gastrocnemius activity
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Knee Joint Anatomy
Sex-Based Differences
• Hormonal differences in women during
landing and cutting:
• Menstrual fluctuations in estrogen and
progesterone concentrations and receptors
• Resultant fluctuations in metallomatrix protease
activity and decrease fibroblastic activity within
the ligament
• Resultant ligament laxity
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Ankle & Foot Anatomy
Sex-Based Differences
• Women differ from men in the incidence of
• Achilles tendopathy
• Inversion trauma
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Ankle & Foot Anatomy
Sex-Based Differences
• A woman’s predisposition related to
differences in:
• Cartilage thickness differences
• Architectural differences, such as the obliquity
of the 1st MT base
• Tissue property differences
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Cervical Spine Anatomy
Sex-Based Differences
• A woman’s predisposition to cervical spine
affliction related to differences in:
• Architectural differences, such as the shape of
the pedicles, laminae, and cartilage coverage on
articular processes
• Tissue property differences, such as loading
response of the intervertebral disc
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Thoracic Spine Anatomy
Sex-Based Differences
• A girl’s predisposition to adolescent
idiopathic scoliosis (AIS) related to:
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Genetics
Skeletal maturation
Postmenarchal status
Psychosocial factors that include self-esteem
and body image
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Lumbar Spine
Sex-Based Differences
• A woman’s predisposition to lumbar
affliction may be related to:
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Increased lordosis
Structural differences in the articular facets
Cross-sectional diameter of muscles
Control strategy differences during static
posture, transition, and loading
• Increased segmental motion and decreased
segmental stiffness
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Sacroiliac Joint Anatomy
Sex-Based Differences
• A woman’s predisposition to Sacroiliac joint
affliction is related to:
• Hormone fluctuation
• Architectural differences
• Tissue responses
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Conclusion
• The musculoskeletal anatomy of men and
women is grossly similar, yet important
differences exist that may influence the way
in which the general public views and
health care professionals respond to
women’s musculoskeletal health issues.
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