Biomechanics of foot and ankle

Question 1

Talocrural joint

Answer 1

Articulation between the talus and tibia

Axis at at the malleoli

DF and PF

ROM required for walking-
10 DF
20 PF

Usually 23 degrees of external rotation compared to knee joint axis.

Question 2

Subtalar Joint

Answer 2

Between Talus and Calcaneus

Triplanar joint

Supination/ Pronation

Normal is 10 degrees of Eversion and 20 inversion (2x as eversion usually).

Need 5 degrees eversion and 10 degrees inversion for normal.

Question 3

Transverse Midtarsal Joints

Answer 3

Talonavicular and calcaneocuboid

Adduction and abduction

Forefoot varies and values.

Inversion of STJ makes mid tarsal joints rigid and eversion makes joints flexible (parallel axes).

Question 4

Plantar aponeurosis

Answer 4

Extends from calcaneus to proximal toes

Stabilizes the longitudinal arch of the foot

Question 5

Windlass effect

Answer 5

As MTP is DF, aponeurosis is drawn forward and depresses met heads, elevates arch and invest the calcaneus for stability in push off.

Question 6

Closed chain/Open chain supination

Answer 6

Open chain- inversion, plantar flexion and forefoot adduction

Closed chain- Inversion, Dorsiflexion and adduction of the talus

Question 7

Closed chain-open chain pronation

Answer 7

Open chain- Eversion, Dorsifelxion and forefoot abduction

Closed chain- eversion, PF and adduction of talus.

Question 8

Loading response mechanics

Answer 8

Calcaneus inverted at heel strike 2-3

LE internally rotates and pronates

Question 9

Midstance mechanics

Answer 9

LE externally rotates

Calcaneus inverts to 4-6

Question 10

Feiss Line

Answer 10

Line from distal apex of medial malleolus to plantar surface of first met head.

Navicular should be on line. Positive is 10mm below line for pet planes.