Roll, Slide and Spin mechanism Flashcards
Principles of Concave/convex arthrokinematics
For a convex-concave surface movement, the convex surface rolls and slides in opposite directions. EG. GH
For the concave-convex surface movement, the concave surface rolls and slides in the same direction. EG; Elbow
Convex always active, concave passive - except for Elbow
Function
Helps to maintain articular surface contact
Helps to maintain joint congruity through range of movement
Convex on concave examples
Atlantooccipital; flexion/extension
Glenohumeral; abduction
Sternoclavicular; elevation
Wrist carpals on radial/ulnar deviation
Knee, flexion into extension (Getting up from sitting)
Knee extension into flexion (Sitting down)
Talocrural Dorsi/plantar flexion
Concave on convex
Elbow, ulnar humeral joint; flexion/extension
When do you see Spin mechanism
Glenohumeral flexion/extension
Screw home mechanism of knee on full extension.
Occipitoatlanto Joint into flexion/extension
Concave surface - Atlas facet
Convex surface:
- During extension the Occipital facet rolls posteriorly and slides anteriorly.
- During flexion the Occipital facet rolls anteriorly and slides posteriorly.
Occiput is active, C1, passive/fixed
Sternoclavicular Joint into abduction
Concave surface - Menubrium
Convex surface - Proximal clavicle
Both clavicle and manubrium are passive, active movement is driven by humerus and scapular.
Glenohumeral joint into abduction
Concave surface - Glenoid fossa of scapular
Convex surface - Head of humerus, both rolls superiorly and slides inferiorly simultaneously.
The humerus spins during flexion/extension.
Scapular is fixed. Active movement is driven by humerus.
GH added
For the humerus to slide inferiorily, there needs to be healthy rotation and depression of scapular from Lattisimus dorsi. And depression of humerus by subscapularis.
Plus, there needs to be an accompanying rotation of clavicle.
Elbow into flexion/extension
Rolls and slides in the same direction
Concave surface - Ulnar
Convex surface - Humerus
The humerus is passive in both flexion and extension, which is driven by active movement of the ulnar and radius
Carpals into radial deviation
Concave surface - Radius
Convex surface - Proximal carpals
Movement driven actively by carpals, and passively allowed by distal radius and ulnar.
Knee flexion in extension. (Getting up from sitting)
Tibia is fixed and quadricep’s brings femur into extension.
The femur rolls anteriorly whilst sliding posteriorly.
The healthy force transmission through the patella and gradual relaxation of hamstrings to allow controlled elevation.
It is the cruciate ligaments that control the anterior/posterior slide of the tibia.
Knee extension into flexion (sitting down)
First for a knee to flex it must ‘unlock’ this is done by Politeus which medially rotates knee.
It is the Tibia that is fixed and the femur that is moving.
The femur is rolling posteriorly whilst sliding anteriorly.
There is an interplay between gradual contraction of hamstrings to flex knee and gradual controlled relaxation of quadriceps group to allowed controlled descent.
It is the cruciate ligaments that control the anterior/posterior slide of the tibia.
Talocrural into plantar and dorsi flexion
Concave surface - Tibia
Convex surface - Talus
During dorsi flexion, the talus rolls anteriorly whilst it slides posteriorly on the calcaneum.
During plantar flexion, the talus rolls posteriorly and simultaneously slides anteriorly on calcaneum.
Screw-Home mechanism of Knee
Stabilising mechanism for tibiofemoral joint during extension.
Requires 10 degrees of external rotation during the last 30 degrees of extension.
It is mechanically linked to extension and flexion of knee and cannot be performed independently.
It maximizes overall contact area of adult knee.
Thus, favouring joint congruence and stability.
Remember Popliteus is the muscles that ‘unlocks’ the knee, prior to locomotion
