Anatomy & Bio-mechanics of the Musculoskeletal System

Question 1

Definition of Lever

Answer 1

Rotations of a rigid surface about an axis. There are three types of levers

Question 2

First Class Lever

Answer 2

Occurs when two forces are applied on either side of an axis.
Ex: Triceps at elbow joint, Neck.

Question 3

Second Class Lever

Answer 3

Occurs when two forces are applied on one side of an axis. Resistance lies between effort force and the axis of rotation
Ex: few, toe raises

Question 4

Third Class Lever

Answer 4

Occurs when two forces are applied on one side of an axis. Effort force lies closer to the axis than the resistance force.
Ex: most muscles in the human body, elbow flexion, knee extension, knee flexion, hip flexion, etc.

Question 5

Arthrokinematics

Answer 5

Defined as the movement between joint surfaces. Three motions describe the movement of one joint surface on another

Question 6

Roll

Answer 6

Consists of one joint surface rolling on another such as a tire rolling on the road.
Ex: Femoral condyles on tibial surface

Question 7

Glide

Answer 7

Consists of a pure translatory motion of one surface gliding on another, as when a braked wheel skids.
Ex: Proximal phalanx at the head of metacarpal bone of the hand

Question 8

Spin

Answer 8

Consists of a rotation of the movable component of the joint

Ex: radial head with humerus

Question 9

Osteokinematics

Answer 9

Movement between two bones

Question 10

Convex-Concave Rule

Answer 10

Convex on concave, the convex surface moves opposite to the direction of the bony lever. Concave on convex concave surface moves in the same direction as lever.
In spine convex rule applies at AO joint, below C2, all concave applies.

Question 11

Open Packed/Loose Packed Positions

Answer 11

Joint position where capsule and other soft tissues are in most relaxed position. Minimal joint surface contact where joint play and mobilizations are applied.
Hip is exception to the rule

Question 12

Closed Packed Position

Answer 12

Joint position where capsule and other soft tissues are maximally tensed. Maximal contact between joint surfaces, mobs cannot be properly applied here

Question 13

Normal End Feels

Answer 13

1. Soft: occurs with soft tissue approximation
2. Firm: capsular and ligamentous stretching
3. Hard: when bone and/or cartillage meet

Question 14

Pathological End Feels

Answer 14

1. Boggy: edema, joint swelling.
2. Firm w/decreased elasticity: fibrosis of soft tissues
3. Rubbery: muscle spasm
4. Empty: loose, then very hard: associated w/muscle guarding or patient avoiding painful part of range
5. Hypermobility: end-feel at a later time than on opposite side

Question 15

Manual Grading of Accessory Joint Motion

Answer 15

0 - Ankylosed
1 - Considerable hypomobility
2 - Slight hypomobility
3 - Normal
4 - Slight hypermobility
5 - Considerable hypermobility
6 - Unstable

Question 16

Muscular Substitutions

Answer 16

Occur when muscles have become shortened/lengthened, weakened, lost endurance, developed impaired coordination, or paralyzed. Stronger muscles compensate for loss of motion.

Question 17

Common Muscle Substitutions

Answer 17

Use of Scapular stabilizers to initiate shoulder motion when shoulder abductors are weakened (reverse scapulothoracic rhythm). Use of lateral trunk muslces or TFL when hip abductors weak. Use of passive finger flexion by contraction of wrist extensors when finger flexors are weak (tenodesis).
Use of long head of biceps, coracobrachialis and anterior deltoid when pectoralis major is weak. Use of lower back extensors, adductor magnus, and quadratus lumborum when hip extensors are weak. Use of lower abdominal, lower obliques, hip adductors, and latissimus dorsi when hip flexors are weak.