Lecture 9 - Subtalar Joint (STJ) Flashcards
What articulations form the STJ?
What is it’s anatomical shape?
Articulation of talus & calcaneus
Convex/ concave shaped joint=
saddle shaped & very strong,
List the 3 ligaments of the STJ
Talocalcaneal
Lateral Talocalcaneal [cervical]
Posterior Talocalconeal
Where is the STJ Axis?
Tri-planar axis, large individual variation: average 42° from TP & 16° from SP
(With 10 degrees of rotation)
List STJ Motion
pronation/ supination in foot
Converts TP plane motion of tibia to FP motion in foot
ROM: 20°inversion & 10° eversion
Frontal plane motion measurable [2:1]
Normal gait requires how many degrees of STJ motion?
6°- 12° of ROM
Why is STJ important?
- Pronation produces pliable foot to adapt to ground & shock absorption during gait
- Supination turns foot into rigid lever for propulsion & support
- Compensates for abnormal forefoot/ rearfoot
- STJ motion is interdependent with MTJ motion (STJ pronation increases MTJ motion & vice versa)
- Forces medial to STJ (GRF/muscle) produce supination & forces lateral to STJ produce pronation
What is STJ neutral?
•Theorised position where STJ neither supinated or pronated
•2:1 ratio of inversion:eversion or supination:pronation from this position
-Pros vs cons 2:1 ratio: low reducibility amongst ppl & everyone different
•Neutral position is where foot functions most efficiently
•Varies person to person
How is STJ neutral clinically measured?
Talar head palpation
What is the motion of STJ in gait?
- Subject to controversy
- Pronates at heel contact & supinates at propulsion
- Root suggests foot achieves STJ Neutral position at heel lift
- Orthotic treatment aim/ backbone is to align STJ to neutral
What is the OKC motion of STJ in pronation & supination?
non weight bearing
DEAb
(DF, eversion & abduction) of calcaneus
in pronation
PlAd
(PF & Adduction) of calcaneus
in supination
What is the CKC motion of STJ in pronation & supination?
weight bearing
PAd of talus & Eversion of calcaneus in pronation
DAb of talus, Inversion of calcaneus in supination