Foot/Ankle

Question 1

What is the AOR for the talocrural joint?

Answer 1

Passes through the lateral and medial malleoli; medial malleolus is more anterior and superior than the lateral one, so the AOR deviates from a purely medial-lateral axis about 10 degrees from the transverse plane and 6 degrees from the frontal plane

Question 2

What plane does the majority of movement occur in in the talocrural joint? What motions?

Answer 2

Sagittal plane; dorsiflexion and plantarflexion

Question 3

What is the AOR for the subtalar joint?

Answer 3

42˚ superior anteriorly from the transverse plane and 16˚ medial anteriorly from the sagittal plane.

Question 4

In an OKC, which sagittal, frontal, and transverse plane motions contribute to pronation?

Answer 4

Abduction (talus) , eversion (calcaneus), dorsiflexion (talocrural)

Question 5

What are the differences between a high axis and low axis sub talar joint?

Answer 5

High-axis subtalar joint motions primarily occur in the transverse/horizontal plane (abduction/adduction).

Low-axis subtalar joint motions primarily occur in the frontal plane (inversion/eversion).

Question 6

In an OKC, which sagittal, frontal, and transverse plane motions contribute to supination?

Answer 6

Adduction (talus), Inversion (calcaneus), Plantarflexion (talocrural)

Question 7

In a CKC, which sagittal, frontal and transverse plane motions contribute to pronation?

Answer 7

Adduction (talus), eversion (calcaneus), plantarflexion (talocrural)

Question 8

In a CKC, which sagittal, frontal, transverse plane motions contribute to supination?

Answer 8

Abduction (talus), inversion (calcaneus), dorsiflexion (talocrural)

Question 9

What is torque equal to?

Answer 9

Moment arm times force

Question 10

What are the three anterior compartment muscles?

Answer 10

Anterior Tibialis, Extensor Hallucis Longus, Extensor Digitorum Longus

Question 11

What are the lateral compartment muscles?

Answer 11

Peroneals (Longus and Brevis)

Question 12

What are the posterior compartment muscles?

Answer 12

Deep: Tibiais Posterior, Flexor Digitorum Longus, Flexor Hallucis Longus

Superficial: Gastrocnemius, Soleus

Question 13

What are the functions of the anterior compartment muscles?

Answer 13

All are dorsiflexors.

Tibialis Anterior also inverts.

EDL also everts.

Question 14

Compare the torque generation of the muscles of the anterior compartment.

Answer 14

TA has a larger PCSA and therefore can be a strong dorsiflexor.

EHL has longer moment arm for DF, therefore it can also be a strong dorsiflexor.

Length of moment arms of these muscles are not much different to each other even though they have different insertion because they are all restrained by the extensor retinaculum.

Question 15

What are the functions of the muscles of the lateral compartment?

Answer 15

Plantarflexors and evertors

Question 16

Compare the torque generation of the muscles of the lateral compartment.

Answer 16

Peroneus longus and peroneus brevis have the same moment arm for eversion/PFor, while PL has a slightly larger PCSA. Therefore, PL is the stronger evertor/PFor of the two.

Question 17

What are the functions of the posterior compartment muscles?

Answer 17

Achilles tendon: PF, slight inversion

Tibialis Posterior: PF, inversion

FDL: Flex digits, PF

FHL: Flex hallucis, plantarflexion

Question 18

Compare the torque generation for plantarflexion of the posterior compartment muscles.

Answer 18

Achilles tendon has the longest moment arm and also the largest PCSA.

Question 19

Compare the torque generation for inversion for the posterior compartment muscles.

Answer 19

Tibialis Posterior has the longest moment arm with middle size PCSA.

Achilles tendon has short moment arm for inversion but large PCSA.

Both TP and Achilles tendon can be a strong invertor.

Question 20

What are the major joints of the foot?

Answer 20

Subtalar, transverse tarsal (calcaneocuboid, talonavicular), tarsometatarsal, metatarsalphalyngeal

Question 21

During loading response, what is occurring at the subtalar joint? Where does the navicular travel with this? What does this then mean is happening at the transverse tarsal joint and why is this important?

Answer 21

Pronation: Talus plantarflexion and adduction, calcaneal eversion

Navicular travels plantar (downward)

Transverse tarsal joint: Axes become parallel allowing for a compliant foot. Important for shock absorption and allows body to adapt to different surfaces and uneven terrain.

Question 22

During terminal stance, what is occuring at the subtalar joint? And the transverse tarsal joint? What does this result in?

Answer 22

Supination: talus dorsiflexion and abduction, calcaneal inversion

Transverse Tarsal Joint: Navicular travels upward resulting in crossing of the axes and therefore a rigid foot.

Question 23

What strucutral or muscular control factors help with the rigid foot?

Answer 23

Extension at the MTP joint (hallux dorsiflexion) leads to increased tension/”tightening” of the plantar fascia (Windlass mechanism), elevating the arch and adding to the stability of the transverse tarsal joint.

Contraction of the plantarflexors causes some inversion.

Posterior tibalis (attahces to navicular) also contracts. This muscle is a powerful invertor and also assists in supination of the foot.

Question 24

Why is the locking of the transverse tarsal joint important for gait mechanics?

Answer 24

It shifts the fulcrum of rotation anteriorly to the MTP joint, and thus increases the moment arm for the gastrocnemius/soleus assisting in propelling the body forward.

Question 25

Desribe the possible implciations of Posterior Tibialis Tendon Dysfunction. How does a flat foot deformity develop? Discuss what mechanics of specific phases of gait it could impair. What about the case of extreme flat foot deformity?

Answer 25

In those with PTTD, a flat foot deformity develops as the a**ction of the peroneus longus is unopposed allowing for pronation**. The dysfunction of this tendon limits the ability to supinate, which can greatly alter gait mechanics. During the propulsive phase of gait, the limited ability to supinate limits the individual's ability to lock the transverse tarsal joint. If the foot doesn't become rigid, during push off, the fulcrum will shift posteriorly to the transverse tarsal joint (talonavicular joint) as opposed to the typical rotation around the MTP. This **impairs the Windlass mechanism and will lead to stress of the spring ligament**. In **extreme flat foot deformity, the Gastroc/Soleus line of pull moves lateral to the subtalar joint axis and thus becomes an evertor**, further impiaring supination ability. Persons with **stage 1 or 2 post tib tendinopathy are not able to perform a heel raise.**

Question 26

During pronation in WB, what is occuring at the tibia? What does this allow to occur at the knee?

Answer 26

Internal Rotation, it follows talus rotation. Knee flexion (reverse of screw home mechanism)

Question 27

What is happening at the foot/ankle, tibia and knee during the absorption phase of gait?

Answer 27

**Pronation, tibial IR, knee flexion.** They occur relatively synchronously. When we look at joint kinematic curves, we see that peak eversion, peak tibial IR, peak knee flexion, and peak hip IR occur at relatively the same time.

Question 28

What would happen if we had prolonged pronation during the absorption phases of gait? What is supposed to occur at these proximal joints during terminal stance?

Answer 28

During terminal stance, the knee is extending. For this to happen, relative tibial ER has to occur. With prolonged pronation, however, tibia remains IR. **In order to acheive relative tibial ER, the femur must IR.** Excessive femoral IR has been associated with PFJ pain!

Question 29

How many degrees of tibial internal rotation should theoretically occur with every degree of calcaneal eversion?

Answer 29

If the axis was oriented at 45˚, for every 1˚ of eversion, we would have 1˚ of tibial IR. In coupling, this can be represented as the EV/TIR ratio. If we plug these numbers in an axis oriented at 45˚ would have a ratio of 1. **Since 42˚ allows for slightly more EV and slightly less TIR rotation, research suggests a mean EV/TIR ratio of 1.72 (supporting more EV).** This ratio is calculated based on total excursion from the initial contact to peak in each of the associated movements (EV and TIR) which we know occur relatively simultaneously.

Question 30

How can foot arch height potentially change the EV/TIR ratio? In high-arch versus low-arch runners, does research support more differences in TIR or EV excursion?

Answer 30

A **high arch** will **shift the AOR more vertically**, and thus there will be relatively **more tibial IR** and realtively less eversion or a **lower EV/TIR ratio**. A **low arch** will result in a more **A-P axis** and thus **less TIR** and relatively more eversion, or a **higher EV/TIR ratio.** When examining the EV/TIR ratios in high arch versus low arch runners, **the majority of the research suggests that any changes to the ratio are due to differences in tibial IR** as compared to differences in eversion. Most runners had similar rearfoot eversion excursion, however high arch runners had higher TIR ecursion.

Question 31

Clubfoot Anatomy. Position? What joints are involved?

Answer 31

**Cavus, adduction, varus/inversion, equinus/PF.** Talocrural, subtalar, midtarsal joints involved. **Navicular:** medially and inferiorly displaced on talus. **Cuboid:** medially displaced on calcaneus

Question 32

Clubfoot. What are some bony and muscular components that may accompany this? Which tendons/ligaments become thick and fibrotic?

Answer 32

Accompanied by: **internal tibial torsion.** Soft tissue abnormalities and contractures. Atrophy of muscularature around calf. Achilles and posterior tibialis tendons, posterior and medial ligaments between calcaneus, talus, and navicular, become thick and fibrotic.

Question 33

Clubfoot. Vascularature affected?

Answer 33

Up to 85% have an insufficient or absent anterior tibial artery.

Question 34

Clubfoot Non-Surgical Treatment? What is the order of deformity correction? Why is there an order?

Answer 34

**Ponseti method.** Serial weekly manipulation of casting. Order of deformity correction (to avoid development of rocker bottom): **forefoot cavus and adduction, heel varus, hindfoot equinus**

Question 35

Clubfoot. Surgical Treatment?

Answer 35

**Percutaneous Achilles tenotomy** (tendon release): lengthening tendon. Tendon transfers and/or osteotomies may be performed residual deformity still present. **Anterior Tibial Tendon Transfer.** Used for children 2-3 years old with residual deformity. **Prereq: flexible forefoot supination because won't corect restricted subtalar motion**. Tibialis anterior line of action may have moved posterior to frontal (medial-lateral) axis of talocrural joint because of navicular subluxation. Loses DF ability and exacerbates deformity in frontal and sagittal planes. **Procedure:** incision at tib ant tendon at medial cuneiform. insertion detached distally. **incision made over lateral cuneiform and hole drilled through; tendon passed through lateral cuneiform and brought onto plantar aspect of foot; must be in DF!** Third incision may need to be made lateral to tibial crest for tendon to pass through subcutaneously (may be done if tendon not flexible enough).

Question 36

In which position is the calcaneofibular ligament taut? In which is it relaxed? What about the Anferior Talofibular Ligament? Which one is the "First line of defense"?

Answer 36

**Dorsiflexion:** Calcaneofibular ligament taut because rotates into a more vertical orientation. Anterior Talofibular is lax because it is horixontally oriented. **Plantarflexion:** Anterior Talofibular Ligament becomes taut rotates into a more vertical position. Calcanofibular ligament is lax because it is oriented horizontally. **Anterior Talofibular Ligament is the "first line of defense"** for most inversion ankle sprains because most of them occur in plantarflexion. If ATFL is torn, eventually the CF ligament becomes taut and is susceptible to injury.

Question 37

What is the most common MOI for high ankle sprains? What happens at the distal tibiofibular joint?

Answer 37

High ankle ligaments are located above ankle, connecting tibia, fibula (A/P tibiofibular ligaments, and IO membrane). When these are injured = high ankle sprain. Involves excessive DF and/or rotation on a planted foot that causes gapping at the distal tibiofibular joint (talus spreads mortise).

Question 38

Which possible ligaments can be injured in a high ankle sprain? What test is used to assess and how is it perforemd? Which tissues are taut upon compression? Upon release?

Answer 38

Squeeze test is used to diagnose a high ankle sprain and differentiate injury site. Performed by squeezing the leg just below the knee to **see if pain radiates to high ankle ligament area, which would suggest a high ankle sprain.** **Possible injured sites: inferior tibiofibular ligaments (a&p),** **or IO membrane.** Squeeze = inferior tibiofibular ligaments become taut and IO structures become lax. Release = inferior tibiofibular ligaments lax and IO strcutures become taut. High ankle sprain is unlikely to result in an isolated injury bur rather is generally sore in distal third of tibiofibular complex with compression and/or palpation at the tibiofibular ligament.

Question 39

Subtalar Joint. Describe the articulations that exist between the talus and the calcaneus. What plane and what motions dictated?

Answer 39

Three articulations (posterior, middle, and anterior) between talus and calcaneus. Lie mostly in frontal and transverse planes. Orientation primarily dictates inversion/eversion and abduction/adduction.

Question 40

What are the main functions of the subtalar joint?

Answer 40

Mobility and maintaining balance

Question 41

What triplanar motions occur at the subtalar joint? Compare each WB vs. NWB.

Answer 41

Pronation and supination. **NWB Pronation:** Calcaneus abducts, everts, DF. **WB Pronation:** Talus adducts/IR, PF ; Calcaneus everts **NWB Supination:** Calcaneus adducts, inverts, plantarflexion **WB Supination:** Talus adducts and dorsiflexion; calcaneus inverts

Question 42

Describe why subtalar joint neutral is clinically important. How is this used for orthotics? How can it help someone with a pronated foot?

Answer 42

Biomechanically, in the subtalar neutral position, the subtalar joint has the **most ROM, and surrounding ligaments and tendons bear the least stress.** Foot orthoses usually molded in STJ neutral to make a proper wedge. **Pronated foot:** surrounding ligaments on medial aspect of subtalar joint and tib post tendon (navicular drops) will be stretched. **Wedge can maintain the STJ neutral position, providing greater ROM and avoiding excessive stress on ligaments & tendons.**