Biomechanics Review Flashcards
What is the plane of scaption?
35 degrees anterior to the ML axis.
What is the posterior inclination of the clavicle?
20 degrees posterior to the ML axis.
What is humeral head retroversion?
30 degrees retroverted to face the glenoid.
Describe the movement at the sternoclavicular joint during elevation.
- Longitudinally convex on concave
- Contralateral rolls and slides.
How does the acromioclavicular joint move with the scapula?
It coordinates movement with the scapula, primarily in upward and downward rotation.
What does the superior glenohumeral ligament check?
Adduction.
What does the middle glenohumeral ligament check?
- Anterior translation
- Especially with some abduction and external rotation.
What does the inferior glenohumeral ligament check?
- At 90 degrees abduction, the anterior band checks external rotation.
- The posterior band checks internal rotation, and the axillary pouch checks AP translation.
Describe the scapulohumeral rhythm during shoulder abduction.
- 120° GH joint abduction, and
- 60° scapulothoracic upward rotation.
What is the role of the clavicle during shoulder abduction?
The clavicle retracts and posteriorly rotates around its axis.
What muscles are primary upward rotators of the scapula?
- Serratus anterior
- Upper/lower fibers of the trapezius.
What muscle can become adaptively shortened with anteriorly tilted and internally rotated scapula?
Pectoralis minor.
What is a SLAP lesion and its causes?
A tear in the superior labrum due to large or repetitive forces within the biceps tendon.
What is subacromial impingement?
Decreased subacromial space due to improper biomechanics and repetitive loading.
What is GIRD?
Glenohumeral Internal Rotation Deficit, common in throwing athletes.
What causes scapular dyskinesis and winging?
Weakness in the muscles that move and stabilize the scapula.
What is thoracic outlet syndrome?
Compression of neuro-vasculature at the scalenes, clavicle, or pec minor, causing pain in the arm, shoulder, or neck.
Tennis elbow
- What is it ?
- Cause = ?
Lateral epicondylitis, caused by repetitive wrist extension movements.
What is golfer’s elbow?
Medial epicondylitis, often seen in adolescent male baseball pitchers.
What is carpal tunnel syndrome?
Compression of the median nerve within the carpal tunnel.
What joints are involved in elbow and forearm movements?
- Humeroulnar
- Humeroradial
- Proximal/distal radioulnar joints.
What is the primary function of the biceps brachii?
Supination and flexion of the elbow.
Describe the movement of the distal radioulnar joint in weight-bearing.
- Convex-on-concave movement
- Contralateral rolls and slides
What is ulnar nerve entrapment?
Irritation of the ulnar nerve, often at the cubital tunnel near the medial epicondyle or at the ulnar side of the wrist.
What is a common MOI for a scaphoid fracture?
Compression injury along the scaphoid’s waist, often from a fall on an outstretched hand (FOOSH).
What is the angle of inclination for coxa vara and coxa valga?
- Coxa vara: ~105 degrees
- Coxa valga: ~140 degrees.
Describe the pelvic on femoral movement.
Pelvic movement on femur involves concave on convex motion.
What is the relationship between anterior pelvic tilt and spine posture?
Anterior tilt leads to lumbar lordosis.
What are the hip ligaments and their functions?
- Iliofemoral (prevents hyperextension)
- Ischiofemoral (checks extension)
- Pubofemoral (checks abduction and extension).
What is femoral anteversion?
Anterior rotation of the femoral head, leading to less bony congruency with the acetabulum.
What is the screw home mechanism in the knee?
External rotation of the tibia during the final phase of knee extension.
What are the primary functions of the knee ligaments?
- MCL (checks adduction)
- LCL (checks abduction)
- ACL (checks forward translation of the tibia)
- PCL (checks backward translation of the tibia).
How do you improve dorsiflexion at the ankle?
Weight-bearing dorsiflexion mobilization with ipsilateral anterior roll and slide.
What are the components of pronation and supination at the subtalar joint?
- Pronation: eversion and abduction
- Supination: inversion and adduction
What are the divisions of the foot?
- Rearfoot (subtalar joint)
- Midfoot (cuboid and cuneiforms)
- Forefoot (metatarsals and phalanges).
What are the ground reaction forces during gait?
Highest with weight transfer after heel strike and during push off.
What are the “rockers” in gait?
- Heel rocker (initial contact to foot flat)
- Ankle rocker (foot flat to heel off)
- Forefoot rocker (heel off to toe off).
Describe Trendelenburg gait.
Compensation involving leaning towards the affected side due to weak gluteus medius.
What is the relationship between hip and knee alignments (coxa vara/valga)?
- Coxa vara = genu valgum
- Coxa valga = genu varum
What are the percentages of the gait cycle?
- 60% stance phase
- 40% swing phase
- with two periods of double limb support (10% each)
What is the most common mechanism of injury (MOI) for distal radius fractures?
Fall on an outstretched hand (FOOSH).
What are the close packed positions for the hip, knee, and ankle?
- Hip: extension, internal rotation
- Knee: terminal knee extension with screw home mechanism
- Ankle: maximum dorsiflexion
What is FOOSH?
Fall on an outstretched hand, a common cause of wrist and hand fractures.
Describe the position of the ankle in the close packed position.
Maximum dorsiflexion.
What are the symptoms of carpal tunnel syndrome?
Numbness, tingling, and weakness in the hand, primarily affecting the thumb, index, and middle fingers.
Define torque in biomechanics.
The rotational force applied around a joint axis, influenced by the line of force and moment arm.
What is the significance of the screw home mechanism in the knee?
It provides stability to the knee during the final phase of extension.
What is the role of the popliteus muscle in the knee?
It unlocks the knee from full extension by medially rotating the tibia or laterally rotating the femur.
Describe the difference between open and close packed positions in joints.
- Open packed positions have the least joint congruency and maximal joint play.
- Close packed positions have maximal congruency and stability.
What is the impact of hip flexion contracture on gait?
Leads to a crouched gait with increased lumbar lordosis and reduced stride length.
What is the cause of genu recurvatum?
- Quadriceps paralysis,
- Plantarflexion contracture, or
- Hamstring weakness.
What is a common compensation for weak dorsiflexors?
- Steppage gait, characterized by high knee lift to clear the foot during swing phase.
How does weak quadriceps affect gait?
Leads to forward lean at the hip to shift the center of gravity anterior to the knee, preventing knee buckling.
What is a common gait pattern in individuals with Parkinson’s disease?
Shuffling gait with decreased stride length and increased speed (festinating gait).
Describe the symptoms and cause of scissor gait.
Caused by hip adductor spasticity, resulting in a narrow base of support and leg crossing during swing phase.
What are the consequences of weak gluteus maximus on gait?
Backward trunk lean during early stance phase to shift the line of gravity posterior to the hip.
Explain the concept of ground reaction forces in biomechanics.
Forces exerted by the ground on the body during contact, varying in magnitude and direction during different phases of gait.
What is the role of the gastrocnemius and soleus in gait?
They are responsible for heel rise during push-off, contributing to step length and propulsion.
How does hip circumduction compensate for lower limb impairments?
Involves swinging the leg outward to clear the foot during swing phase, often due to inability to flex the hip or knee adequately.
What is the significance of proper arthrokinematics in joint function?
Ensures smooth, coordinated movement and minimizes wear and tear on joint structures.
Contents of the Carpal Tunnel = ?
Carpal Tunnel
- Median nerve
- Four tendons of the flexor digitorum profundus
- Four tendons of the flexor digitorum superficialis
- Flexor pollicis longus (FPL) tendon
