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Leg

The leg, in human anatomy, is the segment of the lower limb extending from the knee joint to the ankle joint, comprising the tibia and fibula bones along with their associated muscles, tendons, ligaments, nerves, and blood vessels that facilitate weight-bearing, propulsion, and balance during locomotion.^[1]^[2] This region, also known as the crural region, is distinct from the thigh (upper leg) and foot, and it plays a critical role in bipedal movement by transmitting forces from the body to the ground.^[3] The skeletal framework of the leg consists of two parallel long bones: the robust tibia, which serves as the primary weight-bearing structure and articulates proximally with the femur at the knee and distally with the talus bone of the foot at the ankle, and the slender fibula, which lies laterally and primarily provides attachment sites for muscles while contributing to ankle stability through its distal articulation.^[1]^[2] Surrounding these bones are four fascial compartments—anterior, lateral, superficial posterior, and deep posterior—each containing specific muscle groups innervated by branches of the sciatic nerve (tibial and common fibular divisions) and supplied by the posterior tibial and fibular arteries.^[4] The anterior compartment houses the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius muscles, which primarily function in dorsiflexion of the ankle and extension of the toes to prevent foot drop during walking.^[4] In contrast, the posterior compartment's superficial layer includes the gastrocnemius, soleus, and plantaris muscles, responsible for plantarflexion of the foot to propel the body forward, while the deep layer features the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which invert the foot and flex the toes.^[5] The lateral compartment contains the fibularis longus and brevis muscles, aiding in foot eversion and stability on uneven terrain.^[6] Collectively, these structures ensure coordinated gait, shock absorption, and postural control, with clinical significance in conditions like compartment syndrome where increased pressure can impair blood flow and nerve function.^[4]

Overview and Terminology

Definition

The leg, or hindlimb, in vertebrates refers to the posterior paired appendage primarily adapted for supporting body weight and enabling locomotion, such as walking, running, or jumping.^[7] This structure typically attaches to the pelvic girdle and extends distally to the foot, contrasting with the anterior forelimbs that connect to the pectoral girdle.^[8] Legs are distinguished from forelimbs (or arms) by their position and specialized functions, despite sharing evolutionary homology through common developmental pathways and genetic controls that establish serial homology between anterior and posterior appendages.^[9] In many vertebrates, including tetrapods, forelimbs have evolved for diverse roles like grasping, swimming, or aerial propulsion, whereas legs emphasize stability, propulsion, and load-bearing during terrestrial movement.^[10] The basic classification of legs in tetrapods follows the pentadactyl limb plan as the ancestral model, featuring a single proximal bone (e.g., femur), two parallel distal bones (e.g., tibia and fibula), wrist- or ankle-like elements, and a five-digited foot that provides a versatile template for adaptation.^[11]

Key Terms

In human anatomy, the lower limb is divided into proximal and distal regions for descriptive purposes. The proximal region, known as the thigh, extends from the hip joint to the knee and contains the femur as its primary bone. The distal region, known as the leg (or lower leg, shank, or crural region), spans from the knee to the ankle and includes the tibia and fibula.^[12] The femur is the longest and strongest bone in the human body, forming the structural core of the thigh and articulating proximally with the pelvis at the hip joint and distally with the tibia and patella at the knee joint.^[2] The tibia, commonly referred to as the shinbone, is the larger and weight-bearing bone of the lower leg, connecting proximally to the femur at the knee joint and distally to the talus at the ankle joint.^[13] Parallel and lateral to the tibia, the fibula serves as a slender bone that primarily provides muscle attachment sites and contributes to the ankle joint's stability, though it bears little weight.^[1] The patella, or kneecap, is a small sesamoid bone embedded in the tendon of the quadriceps femoris muscle, located anterior to the knee joint where it enhances leverage for knee extension.^[14] Key joints include the hip joint, a ball-and-socket synovial joint formed by the femoral head and the acetabulum of the pelvis; the knee joint, a hinge-type synovial joint involving the femur, tibia, and patella; and the ankle joint, a hinge synovial joint between the tibia, fibula, and talus bone of the foot.^[15] In medical contexts, "leg" specifically denotes the distal region (crus or shank) between the knee and ankle, emphasizing the tibia and fibula, whereas in broader zoological usage, it may describe the entire hindlimb or analogous structures in non-human species.^[16] The term crus, derived from Latin for "leg," is used in anatomical nomenclature to precisely refer to the shank or lower leg portion.^[17]

Anatomy and Physiology

Skeletal Components

The skeletal framework of the human leg provides structural support, leverage for movement, and protection for underlying tissues. The leg, defined as the segment from the knee to the ankle (crural region), consists of two parallel long bones: the robust tibia and the slender fibula.^[3] The tibia, also known as the shinbone, forms the medial, weight-bearing pillar of the leg. It articulates proximally with the femur at the knee joint via its tibial plateau and condyles, and distally with the talus bone of the foot at the ankle. The fibula lies laterally to the tibia, primarily providing attachment sites for muscles and contributing to ankle stability through its distal end, the lateral malleolus, which forms part of the ankle mortise. The proximal tibiofibular joint is a synovial plane joint that allows slight gliding, while the distal tibiofibular syndesmosis—a fibrous joint—binds the tibia and fibula to maintain alignment during weight transfer. These bones also serve as attachment sites for leg muscles, such as the tibialis anterior on the tibia and fibularis muscles on the fibula.^[1]^[3] Key joint articulations involving the leg include the knee and ankle. The knee joint functions primarily as a hinge (ginglymus) synovial joint between the distal femur, patella, and proximal tibia, permitting flexion and extension with limited rotation, reinforced by menisci and ligaments for shock absorption. At the ankle, the talocrural joint is a hinge-like synovial articulation between the distal tibia and fibula (forming the malleolar mortise) and the talus, enabling dorsiflexion and plantarflexion.^[14] The development of the leg's skeletal components occurs through endochondral ossification, where mesenchymal precursors form cartilaginous models that progressively mineralize into bone. Primary ossification centers appear in the diaphysis (shaft) during fetal development—around the seventh week for the tibia and fibula—expanding via vascular invasion and osteoblast activity to replace cartilage with trabecular bone. Secondary ossification begins postnatally in the epiphyses (ends), leaving growth plates (epiphyseal plates) as zones of persistent hyaline cartilage that facilitate longitudinal growth through chondrocyte proliferation and hypertrophy. These plates, rich in type II collagen and proteoglycans, close via ossification in late adolescence—typically ages 14-16 for females and 16-18 for males—converting to epiphyseal lines and halting further elongation. Disruptions to this process, such as fractures through the growth plates, can lead to angular deformities if not managed promptly.^[18]^[19]^[20]

Muscular and Soft Tissue Elements

The muscular system of the human leg comprises groups organized into four fascial compartments—anterior, lateral, superficial posterior, and deep posterior—that facilitate movements such as dorsiflexion, eversion, and plantarflexion. The anterior compartment includes the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius muscles, which primarily function in dorsiflexion of the ankle and extension of the toes. The lateral compartment contains the fibularis longus and brevis muscles, aiding in foot eversion and stability. The superficial posterior compartment features the gastrocnemius, soleus, and plantaris muscles, responsible for plantarflexion, while the deep posterior compartment includes the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which invert the foot and flex the toes. The gastrocnemius and soleus form the triceps surae complex, enabling propulsion at the ankle.^[4]^[5]^[6] Ligaments in the leg provide passive stability to the knee and ankle joints by limiting excessive motion and resisting shear forces. The knee joint is reinforced by four primary ligaments: the anterior cruciate ligament (ACL), which prevents anterior tibial translation relative to the femur; the posterior cruciate ligament (PCL), which restricts posterior tibial displacement; the medial collateral ligament (MCL), stabilizing against valgus stress on the medial side; and the lateral collateral ligament (LCL), countering varus stress laterally. These ligaments work in concert to maintain knee integrity during weight-bearing. The ankle is stabilized by the medial deltoid ligament and lateral ligaments (anterior talofibular, calcaneofibular, and posterior talofibular), which prevent excessive inversion and eversion. The Achilles tendon, the strongest tendon in the body, connects the gastrocnemius and soleus to the calcaneus bone, transmitting forces for plantarflexion and absorbing shock during locomotion.^[21] Fascia and other connective tissues envelop and interconnect these muscular and ligamentous elements, playing a vital role in force transmission and structural support in the leg. In the lower leg, the crural fascia surrounds the calf muscles, while intermuscular septa divide the four compartments to direct force vectors and protect neurovascular structures. These tissues, composed primarily of collagen fibers, distribute tensile loads across the leg, ensuring coordinated movement without isolated strain on individual components.^[4]

Innervation and Blood Supply

The innervation of the leg primarily derives from the sciatic nerve, the largest nerve in the human body, which originates from the lumbosacral plexus (L4-S3) and divides in the popliteal fossa into the tibial nerve and the common fibular (peroneal) nerve, providing motor and sensory innervation to the leg structures.^[22]^[23] The tibial nerve courses through the posterior compartment, innervating muscles such as the gastrocnemius, soleus, and tibialis posterior, while also supplying sensory fibers to the skin of the sole of the foot via its medial and lateral plantar branches.^[22] The common fibular nerve winds around the fibular head and divides into superficial and deep branches; the deep fibular nerve innervates the anterior compartment muscles like the tibialis anterior and extensor digitorum longus, and the superficial fibular nerve supplies the lateral compartment muscles such as the fibularis longus and brevis, with sensory distribution to the dorsum of the foot.^[22] Dermatomes represent areas of skin supplied by specific spinal nerves, with the lower leg primarily covered by L4 to S2 segments; for instance, the L4 dermatome includes the medial aspect of the leg, the L5 dermatome covers the dorsolateral leg and foot, and the S1 dermatome extends along the lateral foot.^[24] Myotomes, defined as groups of muscles innervated by a single spinal nerve root, facilitate clinical assessment of nerve function; examples include the L4 myotome for ankle dorsiflexion via tibialis anterior and the S1 myotome for ankle plantarflexion via gastrocnemius.^[25] These sensory and motor pathways from the sciatic nerve and its branches provide comprehensive innervation to the muscle groups of the leg.^[22] The blood supply to the leg derives from the popliteal artery, which bifurcates into the anterior tibial artery, descending along the anterior compartment to supply the tibialis anterior and extensor muscles, and the posterior tibial artery (accompanied by the fibular artery), which provides blood to the posterior and lateral compartments, including the soleus and flexor muscles.^[26] Venous drainage parallels the arterial system, with the anterior and posterior tibial veins merging to form the popliteal vein, facilitating return of deoxygenated blood to the heart via the deep venous system.^[26] Lymphatic drainage of the leg involves superficial and deep vessels that collect interstitial fluid and direct it toward regional nodes to prevent accumulation and swelling. Superficial lymphatics from the skin and subcutaneous tissues drain primarily to the inguinal lymph nodes, while deep lymphatics accompanying the blood vessels converge on the popliteal nodes before ascending to the iliac nodes.^[27] Venous return mechanisms in the leg rely on the calf muscle pump, where contraction of surrounding skeletal muscles compresses deep veins to propel blood upward, aided by one-way venous valves that prevent backflow and reduce hydrostatic pressure to minimize edema.^[28] Additional support comes from the respiratory pump, where intrathoracic pressure changes during breathing enhance overall venous flow from the lower extremities.^[29]

Function and Biomechanics

Role in Locomotion

The legs play a central role in human locomotion by enabling efficient forward progression through coordinated cyclic movements. In bipedal walking, the legs alternate between supporting the body's weight and propelling it forward, achieving a natural gait that minimizes energy expenditure while maintaining balance. This dynamic function relies on the interaction of skeletal, muscular, and neural systems to generate smooth, rhythmic motion.^[30] The gait cycle, which represents one complete sequence of limb movement, is divided into two primary phases: stance and swing. The stance phase, comprising approximately 60% of the cycle, begins with heel strike—when the heel contacts the ground—and ends with toe-off, during which the foot leaves the ground after propulsion. This phase includes subperiods such as loading response, mid-stance, and terminal stance, where the leg bears the body's weight and absorbs impact. The swing phase, lasting about 40%, follows toe-off and involves the leg advancing through the air toward the next heel strike, divided into initial, mid-, and terminal swing, allowing the limb to clear the ground and prepare for weight acceptance.^[31]^[32]^[33] Biomechanically, the legs manage ground reaction forces (GRFs) and joint torques to facilitate stable and efficient movement. During the stance phase, vertical GRFs peak at about 1.1–1.2 times body weight shortly after heel strike, providing the upward force necessary to support and accelerate the center of mass. Horizontal GRFs, particularly braking forces early in stance and propulsive forces late in the phase, drive forward progression. Joint torques, such as the knee flexion torque during the swing phase (peaking at around 0.5–1.0 Nm/kg to lift the leg), counteract these forces and control limb positioning, ensuring minimal deviation in trajectory. Ankle plantarflexor moments during late stance, for instance, peak at around 1.0-1.5 Nm/kg, contributing to propulsion.^[34]^[35]^[36] Energy efficiency in locomotion is enhanced by mechanical principles that reduce muscular work. In walking, the legs approximate an inverted pendulum model, where the stance leg acts as a rigid strut, allowing the body's center of mass to vault over it in a low-energy arc; this passive pendulum-like motion recovers gravitational potential energy, contributing up to 70% of the forward propulsion with minimal active muscle input. During running, elastic energy storage in tendons, such as the Achilles tendon, becomes prominent; tendons stretch during stance to store strain energy (up to 50% of the work required for bounce) and recoil elastically in early stance, returning it to assist propulsion and reducing the metabolic cost by 30–50% compared to non-elastic mechanisms.^[37]^[38]^[39]

Support and Stability

The human leg provides essential support and stability by efficiently distributing body weight and maintaining postural equilibrium during stationary positions. Complementing this, the mechanical axis aligns the tibia to optimize load transfer through the knee to the ankle, with the knee joint positioned such that the tibial plateau and ankle mortise form a relatively straight line under weight-bearing conditions, thereby minimizing shear forces and enhancing overall structural integrity.^[40] Balance mechanisms further contribute to leg stability through sensory and muscular feedback systems. Proprioception, mediated by mechanoreceptors in the joint capsules, ligaments, and muscles of the ankle and knee, provides continuous afferent input about limb position and orientation, allowing for rapid adjustments to maintain equilibrium against perturbations.^[41] This sensory information integrates with central nervous system processing to coordinate reflexive responses, ensuring precise control over joint angles during static standing.^[41] Additionally, muscle co-contraction—simultaneous activation of agonist and antagonist muscles around the joints—increases joint stiffness and damping, which stabilizes the lower limb by resisting unintended displacements without generating net torque, particularly in the knee and ankle during postural challenges.^[42] Pathological misalignments, such as genu varum (bowlegs) and genu valgum (knock-knees), disrupt normal load-bearing and compromise stability. In genu varum, the mechanical axis shifts medially, concentrating compressive forces on the medial knee compartment, which accelerates cartilage wear and increases the risk of osteoarthritis by altering force distribution across the joint.^[43] Conversely, genu valgum redirects loads laterally, elevating pressure on the lateral tibiofemoral compartment and predisposing it to degenerative changes.^[44] These deviations not only impair weight distribution but also heighten fall risk by reducing the base of support and overloading compensatory muscles.^[44]

Evolutionary and Comparative Biology

Origin and Evolution

The evolutionary origin of legs traces back to the Late Devonian period, approximately 375 million years ago, when sarcopterygian fishes began transitioning from aquatic to terrestrial environments, marking the emergence of early tetrapods capable of rudimentary limb-based locomotion.^[45] This key event involved the modification of robust, lobed fins into weight-bearing appendages, facilitated by environmental pressures such as shallow, vegetated freshwater habitats that favored animals able to navigate both water and land. The Devonian tetrapod radiation, exemplified by fossils like Acanthostega and Ichthyostega, represents the initial diversification of limbed vertebrates, with these early forms retaining fin-like traits while developing skeletal reinforcements for terrestrial support. A pivotal transitional fossil in this fin-to-limb evolution is Tiktaalik roseae, discovered in Late Devonian rocks of the Canadian Arctic, dated to about 375 million years ago. This sarcopterygian fish exhibits a mosaic of fish and tetrapod features, including a flattened skull for bottom-walking, a neck for head mobility, and pectoral fins with robust bones homologous to the tetrapod humerus, radius, and ulna, enabling it to prop itself up in shallow water.^[45] The pelvic fin of Tiktaalik further shows early limb-like patterning, with a sturdy girdle and fin elements suggesting preparatory adaptations for weight-bearing, bridging the gap between finned swimmers and limbed walkers.^[46] These fossils illustrate how incremental skeletal changes, such as the loss of fin rays and elaboration of internal bones, underpinned the shift to terrestrial locomotion.^[45] At the genetic level, Hox genes play a central role in regulating limb patterning, with their conserved expression patterns linking fin development in fishes to limb formation in tetrapods. Hox gene clusters, particularly Hoxa and Hoxd, control proximodistal and anteroposterior axes during embryogenesis, as seen in the nested expression domains that pattern both teleost fins and tetrapod limbs.^[47] Studies of Hox expression in basal gnathostomes reveal an ancestral fin-fold compartment where these genes orchestrated skeletal elements, later co-opted for digit-like structures in tetrapod autopodia during the fin-to-limb transition.^[48] This regulatory framework, evolving from ancient genomic architectures, provided the developmental flexibility for the morphological innovations observed in Devonian fossils.^[47]

Variations Across Species

Leg structures and functions vary widely across animal species, reflecting adaptations to diverse habitats, locomotion needs, and evolutionary pressures. In tetrapods, these variations manifest in locomotor modes such as bipedalism, quadrupedalism, and specialized cursorial forms, enabling efficient movement on land. Bipedal tetrapods, including birds and humans, have evolved hindlimbs that support the body's weight on two legs, with avian species featuring a reversed knee joint (actually an ankle) and elongated tarsometatarsus for striding gaits that scale with body mass to optimize energy use during walking and running.^[49]^[50] In contrast, quadrupedal mammals like dogs and horses utilize all four limbs for weight-bearing and propulsion, often with forelimbs shorter than hindlimbs to facilitate forward momentum and stability during trots or gallops.^[51] Cursorial adaptations in fast-running tetrapods, such as the cheetah, emphasize speed through elongated, slender limbs that minimize rotational inertia and maximize stride length, allowing bursts up to 100 km/h while resisting high ground reaction forces.^[52]^[53] These modifications include flexible spines and semi-retractable claws for traction, highlighting how leg morphology integrates with overall biomechanics for predatory pursuits. Among invertebrates, true legs—jointed appendages arising from segmented bodies—are characteristic of arthropods, particularly insects, whose exoskeletal legs facilitate versatile locomotion like walking on flat surfaces or climbing vertical ones via tarsal claws and adhesive pads.^[54] Insect tibiae, for instance, exhibit biomechanical reinforcements to withstand compressive loads during rapid terrestrial movement.^[54] Non-arthropod invertebrates, such as annelids and mollusks, lack homologous jointed legs; polychaete annelids employ paired parapodia—fleshy, paddle-like extensions—for undulating swimming or crawling, while mollusks rely on a ventral muscular foot for gliding or burrowing.^[55]^[56] Aquatic and terrestrial environments further drive leg modifications in vertebrates. In cetaceans like whales, hindlimbs have been reduced and integrated into the body, with forelimbs transformed into broad flippers featuring hyperphalangic digits for hydrodynamic lift and steering during swimming, an adaptation from terrestrial ancestors.^[57] Conversely, terrestrial marsupials such as kangaroos display saltatory hindlimbs—elongated femurs, tibiae, and Achilles tendons—that store elastic energy for efficient bipedal hopping, supporting high-speed travel across open plains with minimal metabolic cost.^[58] These contrasts underscore how leg evolution balances propulsion, stability, and energy efficiency in response to environmental demands.

Artificial and Mechanical Legs

Robotic Legs

Robotic legs represent engineered systems designed to enable locomotion in robots, mimicking or surpassing biological structures for enhanced mobility in complex environments. These legs typically incorporate actuators for motion, sensors for environmental perception and balance, and advanced control algorithms to ensure stability and adaptability. Key design principles emphasize energy efficiency, robustness, and scalability, allowing robots to navigate uneven terrain where wheeled alternatives fail.^[59] Actuators in robotic legs vary by application, with electric motors providing precise torque control and efficiency in modern designs, while hydraulic systems offer high power density for dynamic movements. For instance, Boston Dynamics' Atlas humanoid robot employs custom electric actuators in its legs to achieve whole-body mobility, enabling feats like running and jumping with a 50-degree-of-freedom configuration. Sensors such as inertial measurement units (IMUs), gyroscopes, and force/torque sensors are integral for detecting orientation, ground contact, and external forces, facilitating real-time adjustments during locomotion. Bipedal robots like Atlas prioritize human-like agility for manipulation tasks, whereas multi-legged designs, such as the quadrupedal ANYmal from ETH Zurich, distribute weight across more limbs for superior stability on rough surfaces. Recent advancements as of 2025 include integration of large behavior models using AI for more natural and adaptive locomotion in Atlas.^[60]^[61]^[62]^[63] Control systems for robotic legs rely on computational models to generate stable gaits. Inverse kinematics algorithms compute joint angles required to position the leg endpoints at desired locations, essential for trajectory planning in bipedal walking. Stability is maintained through criteria like the zero-moment point (ZMP), which identifies the point on the ground where the net moment of inertial and gravity forces is zero, preventing tipping during dynamic motion; this concept, introduced in the early 1970s, remains foundational for ensuring equilibrium in legged robots.^[64]^[65] Applications of robotic legs span hazardous and assistive scenarios. In search-and-rescue operations, quadrupedal robots like ANYmal autonomously inspect disaster sites, using leg compliance to traverse debris and stairs while carrying sensors for gas detection and thermal imaging. Exoskeletons with powered legs, such as NASA's X1, augment human mobility by providing torque assistance during lower-body exercises, originally developed for in-space countermeasures to mitigate muscle atrophy. For space exploration, NASA's Legged Locomotion and Movement Adaptation (LLAMA) robot features adaptable legs for traversing uneven extraterrestrial terrain.^[62]^[66]^[67]

Prosthetic Legs

Prosthetic legs, also known as lower-limb prostheses, have evolved significantly to restore mobility for amputees by mimicking the natural leg's biomechanical functions. The earliest known prosthetic leg dates back to around 300 BCE, when the Romans crafted the Capua leg from bronze, iron, and wood to provide basic support and mobility.^[68] Wooden peg legs, simple cylindrical devices attached via straps or sockets, emerged in ancient times and remained in use through the centuries for their durability and ease of construction, though they offered limited functionality compared to the human leg.^[69] Advancements accelerated after World War II, driven by the need to rehabilitate injured veterans; myoelectric prosthetics, which use electrical signals from residual muscles to control movement, were pioneered in the 1940s in Germany and further developed in the Soviet Union during the 1950s and in the West during the 1960s.^[70] Modern prosthetic legs consist of several key components designed for comfort, stability, and efficient gait. The socket, custom-molded to fit the residual limb, interfaces directly with the user's body and is typically made from lightweight materials like carbon fiber or thermoplastics to minimize pressure and skin irritation.^[71] A pylon, often constructed from aluminum or titanium, serves as the structural support connecting the socket to the foot or knee unit, providing the necessary length and alignment to replicate natural leg proportions.^[71] For above-knee amputations, a knee joint is included, while the terminal device—a prosthetic foot or ankle unit—incorporates energy-return features, such as flexible carbon-fiber keels that store and release kinetic energy during the gait cycle to reduce metabolic cost and improve walking efficiency.^[72] Recent innovations in prosthetic technology focus on enhancing integration and adaptability to user needs. Osseointegration involves surgically implanting a titanium fixture directly into the residual bone, allowing the prosthesis to attach without a socket and reducing issues like socket discomfort while improving proprioception and gait symmetry.^[73] Neural interfaces enable more intuitive control by decoding signals from peripheral nerves or the spinal cord, permitting users to achieve biomimetic gait patterns with reduced cognitive effort and better obstacle navigation; as of 2025, advancements include direct brain-computer interfaces for enhanced sensory feedback.^[74] Microprocessor-controlled knees, equipped with sensors and onboard computers, dynamically adjust resistance and flexion in real-time based on terrain, speed, and user intent, significantly lowering fall risk and enhancing stability during varied activities.^[75]

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Present and future of gait assessment in clinical practice
Dec 16, 2022 · The stance phase corresponds to the duration between heel strike and toe-off of the same foot, constituting approximately 60% of the gait cycle.
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[PDF] Normal Gait
▫ Stance/swing = 60/40. ▫ Single/double limb support = 80/20. ▫ Running has no double limb support. 2. Page 3. Step or Stride? 3. Page 4. Phases of the Gait ...
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Introduction to Human Gait – Neuromechanics of Human Movement
As mentioned earlier stance phase begins with initial contact (IC), leading into loading response, followed by mid-stance, and the terminal stance at the end.Gait In Younger Individuals · Gait In Older Individuals · Abnormal Gait Patterns
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Estimation of Ground Reaction Forces and Moments During Gait ...
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Joint Torque and Mechanical Power of Lower Extremity and Its ... - NIH
Jul 12, 2017 · Specifically, during the stance phase, the large ground reaction force (GRF) generates contact torques simultaneously on lower extremity joints.
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Biomechanical Analysis of Human Gait When Changing Velocity ...
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Humans exploit the biomechanics of bipedal gait during visually ...
An idealized inverted pendulum without friction or resistance is perfectly energetically efficient; no mechanical energy is lost throughout its motion.
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It pays to have a spring in your step - PMC - NIH
Humans produce mechanical work at the ankle joint during walking with an efficiency two to six times greater than isolated muscle efficiency.
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Elastic energy savings and active energy cost in a simple model of ...
Leg tendons act elastically to store and return energy to the body, thus saving the muscles from costly work with each running step. Although elasticity is ...
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Anatomy, Bony Pelvis and Lower Limb: Arches of the Foot - NCBI - NIH
Aug 27, 2025 · These structures distribute body weight proportionally across weight-bearing areas and function as segmented levers to propel the body during ...
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Radiological assessment of lower limb alignment - PMC
Jun 28, 2021 · When standard weight-bearing X-rays are used to calculate alignment, the estimated angle on the X-ray is called the anatomic tibiofemoral ...
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The Sensorimotor System, Part II: The Role of Proprioception in ...
Thus, it appears that proprioception is fundamental for sensorimotor control over joint stability, with articular receptors providing unique, subtle roles. With ...
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Muscle coactivation: definitions, mechanisms, and functions - PMC
Muscle co-contraction modulates damping and joint stability in a three-link biomechanical limb. ... Increased lower limb muscle coactivation reduces gait ...History, Definitions, And... · Coactivation Within The... · Fig. 6
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Analysis of Genu Varum in Young Male Professional Soccer Players
Apr 18, 2025 · Genu varum shifts the mechanical axis to the medial side, increasing the load on the medial compartment of the knee and raising the risk of ...Leg Axis Measurements · Static Leg Axis Alignment · Dynamic Leg Axis Alignment
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Valgus Malalignment is a Risk Factor for Lateral Knee Osteoarthritis ...
Valgus malalignment increases the risk of knee OA x-ray progression, incidence and of lateral cartilage damage. It may cause these effects, in part, by ...Missing: varum | Show results with:varum
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A Devonian tetrapod-like fish and the evolution of the ... - Nature
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Pelvic girdle and fin of Tiktaalik roseae - PNAS
The earliest tetrapods have robust limbs, particularly hind limbs that are enlarged and supported by a number of modifications to the pelvic girdle.
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Hox gene expression in teleost fins and the origin of vertebrate digits
Jun 22, 1995 · HOX genes are essential for growth and patterning of the tetrapod limb skeleton1–5. Mice mutant for the Hoxd-13gene have an important delay ...
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HoxD expression in the fin-fold compartment of basal gnathostomes ...
Mar 4, 2016 · Our results support an ancestral role for HoxD genes in patterning the fin-fold, bringing new information to current models for fin/limb ...
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Human and avian running on uneven ground: a model-based ...
Sep 1, 2016 · Birds and humans are successful bipedal runners, who have individually evolved bipedalism, but the extent of the similarities and ...
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Scaling of avian bipedal locomotion reveals independent effects of ...
May 22, 2018 · Here, we review the scaling of avian striding bipedal gaits to explore how body mass and leg morphology influence walking and running.
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Fore-Aft Asymmetry Improves the Stability of Trotting in the ... - NIH
Quadrupedal mammals have fore-aft asymmetry in their body structure. For example, their fore and hind legs have not only different skeletal structures but ...
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Functional anatomy of the cheetah (Acinonyx jubatus) forelimb - NIH
To maximise its speed, an animal must rapidly swing its limbs (to increase stride frequency) and support its body weight by resisting large ground reaction ...
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[PDF] Genetic Basis for Species Vulnerability in the Cheetah
a number of cursorial adaptations that make high-speed pursuit (up to 112 km/hour) possible (5): long, slender legs; enlarged respiratory, cardiovascular ...
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Biomechanical Factors in the Adaptations of Insect Tibia Cuticle - PMC
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[PDF] Chapter 33 Invertebrates
Concept 33.1 Sponges are basal animals that lack true tissues. • Animals in the phyla Calcarea and Silicea are known informally as “sponges.”.Missing: non- | Show results with:non-<|control11|><|separator|>
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Mollusks and Annelids – Introductory Biology
Although mollusk body forms vary, they share key characteristics, such as a ventral, muscular foot that is typically used for locomotion; the visceral mass, ...
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Evolutionary genetics of flipper forelimb and hindlimb loss from limb ...
Dec 2, 2022 · Cetacean hindlimbs were lost and their forelimb changed into flippers characterized by webbed digits and hyperphalangy, thus allowing them ...
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Divergent locomotor evolution in “giant” kangaroos - PubMed Central
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Scientific exploration of challenging planetary analog environments ...
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Atlas | Boston Dynamics
Atlas, the world's most dynamic humanoid robot, enables Boston Dynamics to push the limits of whole-body mobility and manipulation.An Electric New Era for Atlas · Atlas Goes Hands On · Legacy Robots
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Explosive Electric Actuator and Control for Legged Robots
Therefore, legged robots require high explosive power actuators to provide high peak speed or high peak torque at specific moments during their dynamic motion.
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ANYmal – Robotic Systems Lab | ETH Zurich
ANYmal is a quadrupedal robot designed for autonomous operation in challenging environments. Driven by special compliant and precisely torque controllable ...
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[PDF] Inverse Kinematics Solution for Biped Robot - IOSR Journal
In this paper, we proposed a inverse method by viewing the kinematic chain of a leg of a biped in reverse order and finally employing the inverse technique ...
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[PDF] Zero-moment Point: Thirty five years of its life.
This paper is devoted to the permanence of the concept of Zero-Moment Point, widely- known by the acronym ZMP. Thirty-five years have elapsed since its ...
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[PDF] X1: A Robotic Exoskeleton for In-Space Countermeasures and ...
X1 is a new robotic exoskeleton that not only provides mobility for humans on earth, but is also being evaluated as an in-space countermeasures and dynamometry ...
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LLAMA | NASA Jet Propulsion Laboratory (JPL)
The innovative Legged Locomotion and Movement Adaptation (LLAMA). Still under development, LLAMA could be used on rough, uneven terrain, and in other ...
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Prosthetics through the ages | NIH MedlinePlus Magazine
May 11, 2023 · Approximately 300 years later—300 B.C.—in Italy, an ancient Roman nobleman used a prosthetic leg known as the “Capua leg.” The leg was made of ...
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Historical Development of Lower-Extremity Prostheses - O&P Library
The peg leg, the invention of the earliest times of history, has proved its usefulness through the centuries up to the present.
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Prosthetics in Orthopedics - StatPearls - NCBI Bookshelf - NIH
Jul 24, 2023 · The major components of a lower extremity prosthesis include the socket, suspension mechanism, knee joint (if needed), pylon, and the terminal ...Continuing Education Activity · Function · Issues of Concern · Clinical Significance
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Evidence Summary - Lower Limb Prostheses - NCBI - NIH
In adults who use a lower limb prosthesis, how do ambulatory, functional, and patient-centered outcomes with different prosthetic components vary based on study ...
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Osseointegrated Prosthetic Implants for People With Lower-Limb ...
We conducted a health technology assessment of osseointegrated prosthetic implants, compared with conventional socket prostheses, for people with lower-limb ...
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Continuous neural control of a bionic limb restores biomimetic gait ...
Jul 1, 2024 · Preliminary results suggested improved neural control of swing-phase kinematics compared with those without the neuroprosthetic interface.
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Effects of microprocessor-controlled prosthetic knees on self ... - NIH
A microprocessor-controlled prosthetic knee (MPK) continuously controls the flexion and extension of the knee joint using a microcomputer system throughout the ...