Biomechanics Flashcards
Kinematics
Study of Motion…not the causes of it! (KineMaticsKM=M[otion])
Kinetics
Study of Forces that cause motion.
Translation
All parts move through the same distance, at the same time, in parallel paths at equal velocity. Rotation is translation around a joint. If there is no rotation, translation is zero (think of arm hanging straight at side while standing).
Traction
The force is used to pull along the long axis for the limb. E.g. the long axis for the GH joint is parallel to the glenoid fossa, or along the length of the arm
Distraction
A special case of traction that is perpendicular to the joint surface. Example: pulling the head of the humerus away from the capsule before pulling it inferiorly (traction).
Rotation
A special case of translation that occurs around a joint.
Osteokinematics:
the motion of bones relative to the three cardinal planes of the body. (Ex. Frontal plane is where lateral flexion, ab-/adduction occur.
Arthrokinematics:
describes the motion that occurs between the articular surfaces of joints (ex. Concave convex rule).
Do the axes of joint motions fall perpendicular to cardinal planes? Explain
No, they do not. It is only possible with a perfect sphere for the convex part of the joint. All convex members of joints in the body are imperfect spheres with changing surface curvatures.
Horizontal (Transverse) Plane
Axial rotation, Internal (medial)/External (lateral) rotation (bisects the body into top and bottom halves).
Frontal Plane
Ab-/Adduction, Lateral flexion, Radial/Ulnar deviation, Eversion/Inversion (bisects the body into front and back).
Sagittal Plane
(bisects the body into right and left sides) Flexion/Extension, Dorsiflexion/Plantarflexion.
What might altar degrees of freedom?
- Pain
- Joint effusion
- Soft tissue tightness
Ovoid
convex on concave joint, but in the shape of an egg (imperfect sphere) and an egg cup. Most joints in the body actually fit this description, contributing to their accessory motions that are outside their given planes of movement.
Sellar
surface looks convex in one view and concave in another, corresponding surface is the opposite. (Saddle joint)
Roll-
each point on the convex surface articulates with a different spot on the concave surface as it moves along
Slide-
a single point on the convex surface articulates with different spots on the concave surface as it moves along.
Spin-
single point on the convex surface articulates with the single point on the concave surface (ex. A top spinning on one point of the table).
Roll is always…
In the direction of skeletal movement.
What is the concave/convex rule?
concave moving on convex= roll and slide are in the same direction.
convex moving on concave= the roll and slide are in the opposite direction.
What happens if you have roll without slide?
Dislocation
What happens if you get slide without roll?
Impingement
List 4 ways to classify joint mobility:
- Normal
- Hypermobile
- Hypomobile
- Instability
What determines the amount of movement available in the joint?
- Joint structure
- Integrity of joint surface
- Mobility and pliability of soft tissues
- Degree of soft tissue approximation
- Health of surrounding tissue, scarring
- Load- deformation history of the joint
- Age/Gender (range is greatest in infancy and decreases with aging)
Normal End Feels:
- Hard (bony)
- Firm (capsular, muscle/tendon)
- Soft (soft tissue approximation)
Abnormal End Feels:
- Empty (pain limited)
- Springy/springy block
- Spasm (muscle guarding)
- Boggy (squishier than you’d expect)
- Normal end feel found where it shouldn’t be
Hypomobility
=restricted motion
- Capsular pattern of restriction= pain and limitation of motion in a predictable pattern to that joint
- Non capsular pattern= maybe derangement, extra-articular problem
Closed packed-
tissues stretched, decreasing movements in many directions
Open Packed-
tissue loose, increasing movement.
Passive insufficiency-
when a 2-joint muscle is too short to perform the normal ROM in the opposite direction at all joints crossed (stretched at one joint but can’t stretch at 2nd joint)
Active insufficiency-
muscle cannot generate force due to the shortened state the muscle is positioned in
Hypermobility:
over-mobility that is generalized to multiple joints across the body and can be caused by genetic diseases. If it is only at one joint (localized), it can be due to adjacent joint hypomobility.
Functional Instability:
disrupted articular/ligamentous structures with functional loss. Key word: Compensation.
Anatomical Instability:
no compensation seen and may not have functional loss.
