Podcast
Questions and Answers
What is the primary role of synovial fluid in the joints?
Which structures make up the shoulder girdle?
What proportion of rotation occurs in the shoulder girdle for every 2° of glenohumeral abduction?
What is the role of the glenoid labrum in the glenohumeral joint?
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What is the strength-to-balance ratio between internal and external rotators?
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Which of the following movements is NOT associated with the glenohumeral joint?
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What effect does trunk extension have on shoulder flexion?
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What is the relationship between active and passive range of motion?
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What type of joint is the Humeroulnar joint classified as?
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Which ligament stabilizes the elbow by preventing radial head rotation against the ulna?
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Which movement is associated with the Proximal Radioulnar Joint?
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What is the primary function of the Radial Collateral Ligament at the elbow?
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How many synovial joints are part of the elbow complex?
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Which statement about the Humeroradial joint is accurate?
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What is true regarding the normal range of motion for shoulder flexion?
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What type of movement does the Ulna Collateral Ligament primarily assist in providing?
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What is the primary function of the meniscus in the knee joint?
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What does the screw home mechanism describe in the knee joint?
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Which factor significantly affects patella tracking during knee movement?
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What is the normal Q-angle range for females?
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What happens to the patella during flexion of the knee?
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What is a consequence of an imbalance in the vastus medialis muscle?
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What is one of the key benefits of the patella in the knee joint?
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What would be the likely outcome of a torn meniscus during knee extension?
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Study Notes
Levers
- First Class: Load → Fulcrum → Effort; Advantage: Force + Distance
- Second Class: Effort → Load → Fulcrum; Advantage: Force
- Third Class: Fulcrum → Effort → Load; Advantage: Distance
- If unsure, assume Third Class.
Basic Movement Analysis Rules
- Action + Concentric = Muscle Group (e.g., flexion + concentric = flexors)
- Action + Eccentric = Muscle Group (e.g., flexion + eccentric = extensors)
- Isometric = Muscle group working against gravity
Bone Remodeling
- Wolff's Law: Bone responds to stress.
- Examples: Increased humerus width in tennis players, larger metatarsals/tarsals/phalanges in ballet dancers.
- Bone resorption: Bone breakdown.
- Example: Reduced bone density in astronauts due to lack of gravity.
- Adult bone maintenance stage lasts 7-10 years.
Biomechanics of Bone
- Loading Modes & Descriptions:
- Tension: Pulled at ends, elongates (e.g., Calcaneal tensile fracture)
- Compression: Gravity puts pressure on body, widens in the middle (e.g., vertebral compressive fracture)
- Shear: Horizontally opposing forces (e.g., leg extension machine)
- Torsion: Twisting, fracture line diagonal; (e.g., 3-point or 4-point fracture of the tibia)
- Bending: 3-point or 4-point fracture, (e.g., 3-point tendon fracture of the tibia)
- Muscle Activity Influence on Bone Loading:
- Tibia falling forward
- Ski boot in the way
- 3 point bending
- Bone is weaker under compression
- Soleus muscles compress the tibia
- Reduces damage in falls
Bones and Articulations of the Shoulder Complex
- Shoulder Girdle: Scapula + clavicle (sternoclavicular + acromioclavicular)
- Movements: Protraction/Retraction, Elevation/Depression, Upward/Downward Rotation
- Scapulo-humeral Rhythm: 2º glenohumeral abduction = 1º of upward scapular rotation
- Glenohumeral Joint: Scapula + humerus
- Movements: Flexion/Extension, Adduction/Abduction, Horizontal abduction/adduction, Internal/External rotation, Circumduction
- Glenoid Labrum: Fibrocartilage, increases glenoid depth by 50%
Strength to Balance Ratio Between Internal and External Rotators
- 3:2 ratio (internal: external)
- Rotators: Infraspinatus, Teres Minor, Supraspinatus, Subscapularis, Deltoid.
Shoulder Girdle Actions
- Elevation/Depression
- Retraction/Protraction
- Upward/Downward Rotation
Spinal Contributions to Shoulder Movement
- Trunk extension & flexion
- Lateral flexion & rotation
Range of Motion (ROM)
- Flexibility of a joint
- Measured in degrees using a goniometer.
- Active ROM: Muscle contraction
- Passive ROM: External force
The Elbow Complex
- Synovial joints:
- Humeroulnar: Hinge
- Humeroradial: Plane
- Proximal Radioulnar: Pivot
- Ligaments: Annular, Radial collateral, Ulnar collateral
- Valgus: Distal end of limb more lateral
- Varus: Distal end of limb more medial
The Wrist
- Triangular Fibrocartilage Complex (TFCC): Load-bearing structure, pulley for wrist movements
- Wrist Movements: Flexion, extension, abduction, adduction
- Palmar Intercarpal Ligament, Ulnotriquetral, Radiocarpal.
- Arches of the hand are Proximal Transverse (carpals to metacarpals), Distal Transverse (Metacarpals to phalanges), Longitudinal.
Carpal Tunnel
- Retinaculum completes tunnel
- Median nerve involved
- Phalen's Test: Wrist flexion for 30-60 seconds
- Prehension: Grasping objects (Power grip, Pinch grip)
Pelvis, Hip and Knee
- Acetabular Labrum: Cartilage ring that deepens the acetabulum.
- Transverse ligament: Stabilizes hip.
- Ligamentum Teres: Intra-articular structure, supports & lubricates hip joint.
- Acetabular alignment: Centre-edge (Wiberg) angle; acetabular anteversion angle
- Hip extension and internal rotation will tighten the ligaments
- Types of prehension are Tip pinch, Lateral pinch, Pulp pinch, Palmar pinch
Active Range of Motion (ROM)
- Hip Flexion: Supine position, to prevent hamstring stretch.
- Hip Hyperextension: Supine position, keep knee joint extended, avoid lumbosacral motion
Assessing Leg Length Discrepancy
- True leg length: Bone length measured using anterior superior iliac spine (ASIS) and medial malleolus (MM).
- Apparent leg length: Pelvic rotation, sacroiliac dysfunction, foot pronation/supination
- Measure from umbilicus to medial malleolus
Surface Motion of the Knee
- Sagittal plane motion (flexion & extension):
- Example: flexion 15 degrees
Patella Mechanism
- Functions: Protection, leverage, shock absorption, reducing friction
- Tracking: Medial/lateral tracking in flexion
Foot and Ankle
- Windlass mechanism: Plantarflexion increases arch height.
- Gait cycle:
- Stance Phase: Heel strike, foot flat, heel rise, push off, toe off
- Swing Phase: Acceleration, toe clearance
Biomechanical Assessment of Foot and Ankle
- Knee to wall test assesses dorsiflexion ROM
Spine and Posture
- Ligaments: Anterior longitudinal ligament, Posterior longitudinal ligament, Ligamentum flavum,.
- Spinal curvatures: Normal (lordosis, kyphosis) & Abnormal (hypo/hyperlordosis, hypo/hyperkyphosis)
- Normal line of gravity passes anterior to spinal column if kyphosis exists
Pelvic Tilt
- Anterior tilt increase load on lumbar spine.
- Erector spinae control posture.
- Lying down and raising legs helps reduce load.
Spinal Nerves
- Nerve plexus: 5 main (Cervical, Brachial, Lumbar, Sacral, Coccygeal)
- Spinal nerves: 31 pairs total
Spinal Nerve Diagram
- Dorsal root: Sensory neurons
- Ventral root: Motor neurons
- Reflex arc: Unconscious response loop.
Components of a Reflex Arc
- Receptor: Receives stimulus
- Sensory neuron: Transmits signal
- Integration centre: Relays signal
- Motor neuron: Carries signal to effector
- Effector: Carries out response
Brachial Plexus
- Spinal nerves C5-T1 (superior to clavicle).
- Innervates upper limbs and associated dermatomes.
Lumbar Plexus
- Spinal nerves L1-L4
- Innervates anterior and medial thigh, associated dermatomes
- Also innervates some hip muscles
Sacral Plexus
- Spinal nerves L4-S4
- Longest, thickest plexus
- Pain along sciatic nerve, possible numbness/shooting pain/leg pain.
Innervation of Skin
- Dermatomes: Areas of skin innervated by a specific spinal nerve.
Somatotyping
- Quantifies body shape and composition.
- Endomorphy: Fatness
- Mesomorphy: Musculoskeletal robustness
- Ectomorphy: Linearity/slenderness
Measuring Somatotypes – Heath Carter Method
- Body measurements for somatotyping (height, weight, skin folds, bone breadth, girth).
- Measurements are taken on the Right side of the body to avoid left-right asymmetry.
- Skinfolds: Triceps, Subscapular, Supraspinale, Medial Calf
- Bone Breadth: Humerus, Femur
- Girth: Arm, Calf
Plotting Somatotypes
- Plotting methods: Determining body type from measurements.
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Description
Test your understanding of the biomechanics of levers, muscle movements, and bone remodeling. This quiz covers first, second, and third class levers, as well as the effects of stress on bone structure. Dive into the fundamental principles that govern human movement and skeletal adaptation.
