Anatomy: Lower Limb — Comprehensive Study Notes Flashcards

Front

Lower limb overview

Back

The lower limb is specialized for weight-bearing and locomotion and includes the hip, thigh, knee, leg, ankle, and foot. Organizational flow is proximal-to-distal: pelvic girdle → femur → tibia/fibula → tarsals/metatarsals/phalanges. Understanding bones, joints, muscles, nerves, vessels, and surface landmarks together aids clinical application.

Front

Structural organization

Back

Structural organization follows a proximal-to-distal pattern from the pelvis to the foot, linking skeletal elements, joints, and soft tissues. This ordered pathway helps trace neurovascular bundles and biomechanical functions. It is essential for locating sites of injury or compression clinically.

Front

Pelvis

Back

The pelvis is formed by the ilium, ischium, and pubis, which together create the acetabulum to articulate with the femoral head. It provides muscular attachments and transmits weight from trunk to lower limbs. Surface landmarks such as the ASIS and PSIS help orient pelvic position.

Front

Femur

Back

The femur is the longest bone with key landmarks including the head, neck, greater and lesser trochanters, linea aspera, and distal condyles. It transmits body weight and provides attachment sites for powerful hip and thigh muscles. The neck is clinically important because fractures there can compromise femoral head blood supply.

Front

Patella

Back

The patella is a sesamoid bone within the quadriceps tendon that improves the leverage of the quadriceps during knee extension. It protects the anterior knee and articulates with the femoral trochlea. Patellar tracking and tendon attachments are common sources of anterior knee pain.

Front

Tibia

Back

The tibia is the principal weight-bearing bone of the leg with landmarks including the tibial tuberosity and medial malleolus. It forms the medial aspect of the ankle joint and provides extensive articular surfaces for the knee. The subcutaneous position makes it vulnerable to injury and palpation for alignment.

Front

Fibula

Back

The fibula is a slender lateral bone that provides muscular attachment and forms the lateral malleolus of the ankle. It bears little axial weight but stabilizes the ankle and serves as an attachment for ligaments. Its neck near the fibular head is a common site of common fibular nerve injury.

Front

Tarsals

Back

The tarsal bones include the talus and calcaneus in the hindfoot, plus the navicular, cuboid, and three cuneiforms in the midfoot. These bones form articulations that transmit forces between the leg and forefoot and contribute to arch architecture. The talus articulates superiorly with the tibia and fibula to form the ankle joint.

Front

Metatarsals & Phalanges

Back

The metatarsals and phalanges form the forefoot and provide lever arms for propulsion during gait. Metatarsal heads bear weight during toe-off and the phalanges enable toe flexion and extension for balance. Pathology in these bones affects gait mechanics and load distribution.

Front

Hip joint

Back

The hip (acetabulofemoral) is a ball-and-socket joint permitting flexion/extension, abduction/adduction, and rotation. It is stabilized by a deep acetabulum, labrum, and strong ligaments and surrounded by powerful muscles. Its stability makes it less prone to dislocation compared with the shoulder, but fractures and arthritis are clinically important.

Front

Knee joint

Back

The knee consists of tibiofemoral and patellofemoral articulations and primarily allows flexion and extension with limited rotation when flexed. Stability arises from ligaments, menisci, and surrounding musculature rather than bony congruence. It is vulnerable to ligamentous and meniscal injuries due to high loads and rotational stresses.

Front

Ankle joint

Back

The talocrural (ankle) joint is a hinge joint allowing dorsiflexion and plantarflexion, formed by the tibia, fibula, and talus. Its stability depends on bony mortise congruity and ligamentous support. Adjacent subtalar and midtarsal joints provide inversion/eversion and adaptability to uneven surfaces.

Front

Subtalar joint

Back

The subtalar joint, between the talus and calcaneus, primarily allows inversion and eversion of the foot. It contributes to the foot's ability to adapt to uneven ground and to convert tibial rotation into foot motion. Dysfunction here alters gait and predisposes to sprain-related instability.

Front

Forefoot joints

Back

Forefoot joints include the midtarsal, metatarsophalangeal (MTP), and interphalangeal (IP) joints that enable complex weight-bearing and propulsion. They allow toe dorsiflexion during push-off and adjust load distribution across the foot. Pathology produces pain, decreased propulsion, and altered gait mechanics.

Front

Gluteus Maximus

Back

The gluteus maximus is the primary hip extensor and lateral rotator, essential for rising from sitting and powerful movements like climbing. It stabilizes the pelvis and supports the iliotibial tract during weight-bearing. Weakness impairs extension and power during gait.

Front

Gluteus Medius/Minimus

Back

The gluteus medius and minimus abduct and medially rotate the thigh and play a critical role in pelvic stability during the stance phase of gait. Contraction prevents contralateral pelvic drop when standing on one leg. Dysfunction produces a Trendelenburg sign and gait disturbance.

Front

Tensor Fasciae Latae

Back

The tensor fasciae latae assists in hip abduction and medial rotation and tenses the iliotibial tract to stabilize the lateral knee. It works with gluteal muscles to maintain pelvic stability during gait. Overuse can contribute to lateral knee or hip pain.

Front

Deep External Rotators

Back

The deep external rotators (piriformis, obturator internus/externus, superior/inferior gemelli, quadratus femoris) externally rotate the hip and stabilize the femoral head within the acetabulum. They are small but important for fine control of hip rotation. The piriformis in particular can compress the sciatic nerve in piriformis syndrome.

Front

Anterior Compartment

Back

The anterior thigh compartment contains the quadriceps femoris group and sartorius, primarily functioning in knee extension and some hip flexion. These muscles are mainly innervated by the femoral nerve. The compartment architecture facilitates powerful knee extension used in standing and locomotion.

Front

Quadriceps Femoris

Back

The quadriceps femoris comprises rectus femoris and the three vasti (lateralis, medialis, intermedius) and is the primary knee extensor. Rectus femoris also crosses the hip to assist flexion. Strength and coordination of the quadriceps are essential for knee stability and gait.

Front

Sartorius

Back

The sartorius is a long, strap-like muscle that flexes, abducts, and laterally rotates the hip while assisting knee flexion. It crosses both hip and knee joints and contributes to the classic “tailor” sitting posture. Innervation is from the femoral nerve.

Front

Femoral Nerve

Back

The femoral nerve supplies motor innervation to the anterior thigh muscles and provides the saphenous nerve for sensory supply to the medial leg. It originates from the lumbar plexus (L2–L4) and travels under the inguinal ligament into the thigh. Injury produces weakness of hip flexion and knee extension plus sensory loss over the anterior thigh and medial leg.

Front

Medial Compartment

Back

The medial compartment contains the adductor muscles (longus, brevis, magnus), gracilis, and obturator externus, with primary action of hip adduction. Innervation is mainly via the obturator nerve. These muscles stabilize the thigh during stance and assist with medial rotation and extension as appropriate.

Front

Obturator Nerve

Back

The obturator nerve supplies motor innervation to most medial thigh (adductor) muscles and provides sensory fibers to a small medial thigh region. It arises from L2–L4 of the lumbar plexus and traverses the obturator canal. Injury causes weakened hip adduction and medial thigh sensory loss.

Front

Posterior Compartment

Back

The posterior thigh compartment contains the hamstrings (semitendinosus, semimembranosus, biceps femoris) that extend the hip and flex the knee. Innervation is primarily from the tibial division of the sciatic nerve, except the short head of biceps which is innervated by the common fibular division. These muscles are powerful contributors to propulsion and deceleration.

Front

Hamstrings

Back

Hamstrings include semitendinosus, semimembranosus, and biceps femoris and function in hip extension and knee flexion. They are important in running and controlling forward motion of the tibia. Tightness or strain commonly occurs with sudden sprinting or eccentric overload.

Front

Sciatic Nerve

Back

The sciatic nerve is the largest nerve in the body and divides into tibial and common fibular (peroneal) divisions near the popliteal fossa. It supplies the posterior thigh and all muscles below the knee via its branches. Sciatic injury causes variable patterns of motor and sensory loss depending on the level of lesion.

Front

Leg Anterior Compartment

Back

The anterior leg compartment contains tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius and is responsible for dorsiflexion and toe extension. It is innervated by the deep fibular nerve. Dysfunction causes foot drop and affects gait clearance.

Front

Lateral Compartment

Back

The lateral compartment contains fibularis longus and brevis, which evert the foot and assist in plantarflexion support. Innervation is by the superficial fibular nerve. These muscles help stabilize the lateral ankle and maintain the transverse and longitudinal arches.

Front

Posterior Leg Compartment

Back

The posterior leg compartment is divided into superficial (gastrocnemius, soleus, plantaris) and deep groups (tibialis posterior, flexor digitorum longus, flexor hallucis longus). Both groups are innervated by the tibial nerve and mainly function in plantarflexion, inversion, and toe flexion. They are essential for push-off during gait and arch support.

Front

Tom Dick Mnemonic

Back

The mnemonic “Tom, Dick, And Very Nervous Harry” helps remember structures posterior to the medial malleolus from anterior to posterior: tibialis posterior, flexor digitorum longus, posterior tibial artery/vein, tibial nerve, and flexor hallucis longus. This ordering is important when assessing tarsal tunnel anatomy and pulses. It aids localization of compressive or vascular lesions at the medial ankle.

Front

Anterior Cruciate Ligament

Back

The anterior cruciate ligament (ACL) prevents anterior translation of the tibia relative to the femur and controls rotational stability. It is commonly injured during pivoting or deceleration maneuvers. ACL tears cause instability, positive Lachman or anterior drawer tests, and often require surgical reconstruction for active patients.

Front

Posterior Cruciate Ligament

Back

The posterior cruciate ligament (PCL) prevents posterior translation of the tibia on the femur and stabilizes the knee during flexion. PCL injuries often occur from direct posterior force to the tibia (dashboard injury) and may be associated with other ligamentous damage. Isolated PCL tears can be managed nonoperatively if stable and low-demand.

Front

Collateral Ligaments

Back

The medial (MCL) and lateral (LCL) collateral ligaments resist valgus and varus stresses, respectively, at the knee. The MCL is more commonly injured due to valgus forces and has attachments that make the medial meniscus more fixed and vulnerable. Collateral injuries often occur with twisting or direct force and are graded by severity.

Front

Menisci

Back

The medial and lateral menisci deepen the tibial plateau, enhance congruency, and absorb shock within the knee. The medial meniscus is more firmly attached and therefore more commonly injured than the lateral. Meniscal tears produce joint line pain, clicking, or locking and can predispose to osteoarthritis if unrepaired.

Front

Popliteus

Back

The popliteus muscle unlocks the knee by rotating the femur laterally on the tibia (or medially rotating the tibia) to allow flexion from full extension. It provides dynamic posterolateral knee stability and resists external rotation. Dysfunction impairs the knee’s ability to ‘unlock’ and initiate flexion.

Front

Talocrural Joint

Back

The talocrural joint is a hinge joint formed by the tibia, fibula, and talus that permits dorsiflexion and plantarflexion. Stability is provided by the bony mortise of the distal tibia/fibula and collateral ligaments. Its range of motion is essential for the stance and swing phases of gait.

Front

Deltoid Ligament

Back

The deltoid (medial) ligament is a strong, fan-shaped complex that resists eversion of the ankle and stabilizes the medial side. It is less commonly injured than the lateral ligament complex due to its strength. Deltoid tears often occur with severe eversion injuries and may associate with medial malleolar fractures.

Front

Lateral Ligament Complex

Back

The lateral ligament complex includes the anterior talofibular (ATFL), calcaneofibular (CFL), and posterior talofibular (PTFL) ligaments, with the ATFL most commonly injured in inversion sprains. These ligaments stabilize the lateral ankle against inversion and anterior translation. Recurrent sprains can lead to chronic instability and peroneal tendon problems.

Front

Foot Arches

Back

The foot’s medial longitudinal, lateral longitudinal, and transverse arches are maintained by bone geometry, ligaments (including the plantar calcaneonavicular spring ligament), the plantar aponeurosis, and intrinsic and extrinsic muscles. Arches allow efficient load distribution, shock absorption, and energy storage during gait. Collapse or hyperpronation alters biomechanics and can cause pain.

Front

Plantar Aponeurosis

Back

The plantar aponeurosis (plantar fascia) is a thick fibrous band supporting the longitudinal arch and protecting plantar soft tissues. It stores and releases energy during gait and contributes to the windlass mechanism during toe dorsiflexion. Inflammation or microtears cause plantar fasciitis, a common cause of heel pain.

Front

Intrinsic Plantar Muscles

Back

Intrinsic plantar muscles are layered on the sole of the foot and support toe movements and the arches during stance and propulsion. They help stabilize the forefoot and fine-tune toe positioning for balance. Weakness contributes to deformities and reduced dynamic arch support.

Front

Dermatomes

Back

Cutaneous dermatomes of the lower limb span from L1 (upper groin) to S2 (posterior thigh/calf), with L4–S1 particularly important for mapping motor and sensory function. Knowledge of dermatomes assists in localizing neurological lesions and correlating radicular pain. Clinical testing of specific dermatomal sensation complements nerve conduction and imaging.

Front

Vascular Supply

Back

The external iliac becomes the femoral artery which supplies the thigh and gives off the profunda femoris (deep femoral) for muscular branches. Distally the femoral continues as the popliteal artery and divides into anterior tibial (continuing as dorsalis pedis) and posterior tibial (with fibular branch) arteries. Understanding this pathway is essential for pulse examination and identifying ischemic or traumatic vascular injuries.

Front

Profunda Femoris

Back

The profunda femoris (deep femoral artery) is a major branch of the femoral artery supplying the thigh musculature via perforating branches. It also contributes to collateral circulation around the hip and femur. Injury or occlusion affects thigh muscle perfusion but the main femoral trunk still supplies distal structures.

Front

Popliteal Branches

Back

The popliteal artery lies in the popliteal fossa and divides into the anterior tibial artery and the tibioperoneal trunk, which further gives posterior tibial and fibular arteries. These branches supply the leg and foot, with the anterior tibial continuing as the dorsalis pedis artery on the dorsum. Popliteal injury can compromise blood flow to the entire lower limb.

Front

Palpable Pulses

Back

Important palpable pulses in the lower limb include the femoral (midway between ASIS and pubic symphysis), popliteal (deep in the popliteal fossa), posterior tibial (posterior to the medial malleolus), and dorsalis pedis (on dorsum lateral to the extensor hallucis longus tendon). Pulse examination assesses arterial patency and perfusion. Absent or diminished pulses may indicate vascular occlusion or severe peripheral arterial disease.

Front

Superficial Veins

Back

Superficial venous return includes the great saphenous vein (medial leg to femoral vein) and the small saphenous vein (posterior leg to popliteal vein). Perforating veins connect superficial and deep systems and normally have valves to prevent reflux. Valve incompetence causes varicose veins and chronic venous insufficiency.

Front

Deep Veins & DVT

Back

Deep veins run with arteries and are the major pathway for lower limb venous return; they are the primary site for deep vein thrombosis (DVT). DVT presents with swelling, pain, and risk of pulmonary embolism if thrombus embolizes. Prompt diagnosis and anticoagulation are critical to reduce morbidity and mortality.

Front

Fractured Neck Femur

Back

A fractured neck of femur (intracapsular) risks disruption of the retinacular arteries supplying the femoral head, leading to avascular necrosis. These fractures often occur in elderly patients and may require fixation or arthroplasty depending on displacement and patient factors. Early recognition and appropriate management are essential to preserve hip function.

Front

Intertrochanteric Fractures

Back

Intertrochanteric fractures are extracapsular and typically bleed more but usually preserve the femoral head blood supply. They occur between the greater and lesser trochanters and often result from falls in older adults. Treatment commonly involves surgical fixation to restore alignment and allow early mobilization.

Front

ACL Tear Mechanism

Back

ACL tears commonly occur during pivoting, sudden deceleration, or noncontact twisting injuries that force rotational stress on the knee. The ACL provides anterior and rotational stability, so its rupture often produces immediate swelling, instability, and positive special tests. Management ranges from rehabilitation to surgical reconstruction based on activity level and instability.

Front

Meniscal Tear Presentation

Back

Meniscal tears typically cause joint line pain, swelling, locking, or catching, especially after twisting injuries with the foot planted. The medial meniscus is more commonly injured due to firmer attachments. Diagnosis combines clinical tests (McMurray), imaging, and sometimes arthroscopy for definitive management.

Front

Trendelenburg Sign

Back

A positive Trendelenburg sign is pelvic drop on the side contralateral to the stance leg indicating weakness of the gluteus medius/minimus or superior gluteal nerve lesion. It reflects inadequate hip abduction and pelvic stabilization during single-leg stance. This sign helps localize abductor dysfunction and guide rehabilitation or further evaluation.

Front

Common Fibular Injury

Back

Injury to the common fibular (peroneal) nerve at the fibular neck causes foot drop from loss of dorsiflexion and toe extension, plus sensory loss over the anterolateral leg and dorsum of the foot. The nerve’s superficial course around the fibular neck makes it vulnerable to trauma or compression. Management depends on cause and may include bracing and nerve repair if needed.

Front

Compartment Syndrome

Back

Compartment syndrome is increased pressure within a closed fascial compartment that compromises perfusion and nerve function, often after trauma or reperfusion. Symptoms include severe pain out of proportion, tense swelling, paresthesia, and pain with passive stretch; it is a surgical emergency requiring fasciotomy. Delayed treatment risks permanent muscle and nerve damage.

Front

Lateral Ankle Sprain

Back

Lateral ankle sprains, typically from inversion injuries, commonly damage the anterior talofibular ligament (ATFL) and may involve the calcaneofibular or posterior talofibular ligaments. They present with lateral ankle pain, swelling, and difficulty bearing weight. Early rehab, proprioceptive training, and in severe cases immobilization or ligament repair reduce chronic instability risk.

Front

Surface Landmarks

Back

Key surface landmarks include the ASIS and PSIS for pelvic orientation, the greater trochanter laterally, and the patella anteriorly. Palpating these landmarks helps locate underlying joints, tendons, and neurovascular structures for examination or procedures. Familiarity with landmarks improves accuracy during physical exam and ultrasound-guided interventions.

Front

Tibial Tuberosity

Back

The tibial tuberosity is the attachment site for the patellar tendon and is clinically important in conditions like Osgood–Schlatter disease and patellar tendinopathy. It is easily palpable on the anterior proximal tibia and used as a landmark for lower limb alignment. Pain or swelling here often relates to repetitive quadriceps loading.

Front

Study Tips

Back

Learn muscle origins, insertions, actions, and innervations together for each compartment to integrate structure and function. Trace neurovascular bundles from pelvis to foot and correlate surface landmarks with underlying anatomy during palpation and ultrasound. Practice clinical tests (Trendelenburg, Lachman, anterior drawer, Thompson squeeze) to link anatomy with function and pathology.