Lower-Extremity Anatomy, Joint Mechanics, Injuries, and Gait

What bones make up the talocrural joint?

Distal tibia, fibula, and talus

What are the movements and range of motion of the talocrural joint?

Plantar flexion (~50°) and dorsiflexion (~20°)

What is the closed-packed position of the talocrural joint?

Full dorsiflexion and eversion

What bones comprise the subtalar joint?

Talus and calcaneus

What are the shapes of the subtalar joint facets?

Concave posterior facet; convex anterior and medial facets

What components are involved in subtalar pronation?

Eversion + Abduction + Dorsiflexion

What components are involved in subtalar supination?

Inversion + Adduction + Plantar flexion

What is the closed-packed position of the subtalar joint?

Full supination

What bones are found in the rearfoot?

Calcaneus and talus

What bones are found in the midfoot?

Navicular, cuboid, and 3 cuneiforms

What bones are found in the forefoot?

Metatarsals and phalanges

What is the keystone of the medial longitudinal arch?

Head of the talus

What structures support the medial longitudinal arch?

Spring ligament and plantar fascia

What is the keystone of the lateral longitudinal arch?

Cuboid

What structures support the lateral longitudinal arch?

Long plantar ligament and plantar calcaneocuboid ligament

What supports the transverse arch?

Tendon of fibularis (peroneus) longus

What is the function of foot arch mobility?

Dampens rotational motions; allows foot to adapt to terrain surfaces

What is the function of foot arch stability?

Mitigates weight-bearing impact; distributes weight; creates a rigid lever for propulsion

Where do the plantar fascia attach?

Medial calcaneal tubercle to metatarsal heads

What is the most commonly sprained ligament in the body?

Anterior talofibular ligament (ATFL)

What are the features of an inversion ankle sprain?

Most common ankle sprain; tears ATFL; pain/swelling at anterolateral ankle

What are the features of an eversion ankle sprain?

Tears deltoid ligament; often causes avulsion fracture; pain/swelling inferior to medial malleolus

What is the mechanism of a high ankle sprain (syndesmotic)?

External rotation of the foot/ankle (plant and twist)

What happens anatomically in pes planus (flat feet)?

Head of talus shifts medially and inferiorly (palpable in the arch)

What is associated with pes cavus (high arch)?

Curling of the toes (claw toes)

What ligament is key in plantar fasciitis?

Spring ligament (navicular to sustentaculum tali)

Where is the heel spur located?

Medial tubercle of the calcaneus

Where is Morton's neuroma most commonly located?

Between the 3rd and 4th metatarsals

What is the difference between a bunion and a tailor's bunion?

Bunion = 1st MTP joint (hallux valgus); Tailor's bunion = 5th MTP joint

What type of joint is the tibiofemoral joint?

Double condyloid joint (modified hinge)

What is the shape of the medial meniscus compared to the lateral meniscus?

Medial = C-shaped; Lateral = almost a complete circle

What is the blood supply rule for the meniscus?

Outer 1/3 has a rich blood supply (heals well with conservative care)

What is the closed-packed position of the tibiofemoral joint?

Full extension with full external rotation

What is the loose-packed position of the tibiofemoral joint?

25° of flexion

What is the normal physiologic valgus angle of the knee?

170°-175°

What is the difference between genu valgum, genu varum, and genu recurvatum?

Genu valgum = knock-kneed; Genu varum = bowlegged; Genu recurvatum = hyperextension ('back knee')

What is the normal Q-angle and its gender difference?

~15° normal; smaller in men, larger in women

How does genu valgum affect the Q-angle?

Increases Q-angle

How does genu varum affect the Q-angle?

Decreases Q-angle

What are the connections and primary function of the MCL?

Attached to medial meniscus; resists valgus force and external rotation

What is the insertion and primary function of the LCL?

Inserts on fibular head with biceps femoris tendon; resists varus force

What is the primary function of the ACL and its mechanism of injury?

Resists anterior translation of tibia; plant-and-twist motion (more common in females)

What is the primary function of the PCL and its mechanism of injury?

Resists posterior tibial shear; dashboard injury or hyperflexion

What structures are involved in the Terrible Triad (Unhappy Triad)?

ACL + MCL + Medial meniscus

Which patellar plica is most commonly injured?

Medial plica

What is the term for cartilage damage in patellofemoral pain syndrome?

Chondromalacia patellae

What is Osgood-Schlatter disease?

Apophysitis of the tibial tubercle (common in adolescent boys 9-16)

What causes IT band syndrome pain?

Connects with knee retinaculum (often due to overactive TFL compensating for weak abductors)

What is Baker's cyst (popliteal cyst)?

Swelling of semimembranosus/popliteal bursa (secondary to intra-articular knee pathology)

In which direction does a patellar dislocation occur and who is more affected?

Dislocates laterally; more common in adolescent females

What are the bone percentages of the acetabulum?

Ilium (40%), Ischium (40%), Pubis (20%)

What is the strongest ligament and largest muscle in the body?

Iliofemoral ligament (strongest ligament); Gluteus maximus (largest muscle)

What is the most common direction of hip dislocation?

Posterior dislocation (90%)

What is the normal femoral angle of inclination and its deviations?

Normal = 125°; >125° = coxa valga;

What is the normal femoral angle of anteversion and its deviations?

Normal = 12°; >12° = excessive anteversion (toe-in);

What is the closed-packed position of the hip?

Full extension, internal rotation, and abduction

What is the loose-packed position of the hip?

30° flexion, 30° abduction, slight external rotation

What happens when the gluteus medius is inhibited?

Leads to an overactive TFL

What happens when the gluteus maximus is inhibited?

Leads to overactive hamstrings and lumbar erectors

What does an early hip hike fault in the hip abduction test indicate?

Indicates overactive quadratus lumborum (QL) before 30° abduction

What does an overactive TFL fault in the hip abduction test indicate?

Hip flexion and internal rotation

What does an overactive psoas fault in the hip abduction test indicate?

Hip flexion and external rotation

What is the normal muscle firing sequence in the hip extension test?

1. Ipsilateral glute max → 2. Ipsilateral hamstrings → 3. Contralateral lumbar erectors → 4. Ipsilateral lumbar erectors

What does knee bending fault in the hip extension test indicate?

Indicates tight/short hamstrings

What nerve is involved in meralgia paresthetica?

Lateral femoral cutaneous nerve (burning on anterolateral thigh)

What is the difference between Cam and Pincer impingement?

Cam = femoral head overgrowth; Pincer = acetabulum rim overgrowth

What is Slipped Capital Femoral Epiphysis (SCFE) and its referral pain?

Growth plate fracture in adolescent males; often presents solely as medial knee pain

What are the percentages of gait cycle phases?

Stance phase = 60%; Swing phase = 40%

What is the double limb support percentage in the gait cycle?

20% total stride (10% during each step)

What are the three tasks of Rancho Los Amigos gait?

Weight Acceptance (WA), Single Limb Support (SLS), Swing Limb Advancement (SLA)

When is the center of gravity (COG) lowest and highest during the gait cycle?

Lowest during Loading Response; highest during Mid-Stance

What muscle actions occur during initial contact?

Tibialis anterior and quadriceps contract eccentrically

What happens to the subtalar joint during loading response?

Subtalar joint pronates to absorb shock

What muscle action occurs during terminal swing (late swing)?

Hamstrings contract eccentrically to decelerate forward limb motion

What causes Trendelenburg gait and what is the sign?

Weak hip abductors (gluteus medius); pelvis drops on the opposite (swinging) side

What causes scissor gait?

Spastic or contracted hip adductors (legs cross midline)

What causes foot slap?

Weak pretibials (tibialis anterior) failing to control plantar flexion at loading response

What causes contralateral vaulting?

Compensates for an inability to shorten or flex the opposite swing limb