The lower limbs, aka the legs, act as pillars when we stand. Like any other pillar, they require both strength and stability to prevent collapse under the weight above. The bones, joints, and muscles work together to convert each leg into reliable support connected to the trunk by the pelvic girdle. Each leg is divided into segments: thigh, calf, and foot; these are linked by joints, the hip, knee, ankle, and joints of the foot, which can accommodate changes in line of weight as the head and trunk move overhead. The muscles surrounding the joints counteract gravity and any external forces that upset the body’s equilibrium.
Characterized by forwarding propulsion, the legs assist in supporting the head, arms, and trunk while they propel the body ahead. The limbs execute continuous movements of one limb in support while the other swings forward. This back-and-forth swing and support require that each limb as a whole combine strength with mobility. Walking sideways, up and down slopes, and on varied types of ground need different movement patterns.
The lower limbs transfer the body from one posture to another in functional activities like getting out of bed and standing up from a chair. Muscles or joint mobility loss makes these transfer activities impossible, so the upper limb has to compensate. Pressure receptors in the foot’s sole and proprioceptors in the lower limb muscles assist in maintaining balance by providing information. Feedback from these sensors maintains an efficient gait mode.
Functions of the Lower Limb
- The orderly movement of the body from a lying position to sitting and then standing.
- Postures and motions are supported by the head, arms, and trunk.
- Walking, running, and climbing stairs.
- Sensory communication for posture and maintaining balance.
Joints and Motions of the Pelvis, Thigh, and Leg
The pelvis is the link between the vertebral column and the thigh, which transmits body weight from the trunk to the hip and knee joints and then to the feet. The thigh and leg joints work in tandem to provide stability for postural support while also providing a broad range of movement for the limb as a whole.
The hip’s movement lets the thigh shift in different directions, similar to how the elbow mainly bends and extends in one plane. The knee allows us to push our feet off the ground when we walk quickly by shortening the lower limb. Finally, the ankle helps support our weight as it places our foot on various surfaces before propelling us forward.
The Pelvic Girdle
Position and Function
The pelvis is an irregular ring of bone made up of two innominate bones and the sacrum. Five fused vertebrae form the sacrum, and each innominate bone consists of the ilium, ischium, and pubis. These fuse at the socket for the hip joint. You can feel the iliac crest when you place your hands on your hips. The ischium, which can be regarded as a hard seat when sitting upright, inferiorly ends with a roughened ischial tuberosity. The pubis meets in the midline on either side to anteriorly complete the ring of bone. The sacrum articulates superiorly at the lumbosacral joint with the fifth lumbar vertebra.
The Hip Joint
The hip joint, like the glenohumeral joint at the shoulder, is a synovial ball-and-socket type of joint, but it differs in several respects. The shoulder joint is intended for mobility, but the hip joint must also maintain stability. The acetabulum is the hip joint socket, which means “little vinegar cup.” The labrum is a rim of fibrocartilage tissue that encircles the acetabulum and forms a deep, outward-facing cup with a rim.
The ball is formed by the head of the femur, two-thirds of a sphere in volume. The labrum curves inwards beyond the head of the femur’s equator to grip it and assist in its retention when the ball is within the socket.
The hip joint capsule is robust and includes most of the femoral neck. This capsule is further strengthened by anterior ligaments that are very strong and by small muscles in the rotator cuff posteriorly. The iliofemoral ligament is among the strongest in the body; it has a Y-shape and passes across the front of this joint.
The ligament in question limits how far the hip can extend, which allows the trunk to be supported on the lower limb. Additionally, orbicular fibers within the capsule and circular-shaped help with stability by holding the capsule together tightly around the waist area–increasing suction and tightening your hold on the head of the femur.
Mr. James Letko is the President and CEO of Vertaloc Inc., which provide spinal support products to improve people’s quality of life. In this blog post, we’ve looked at the different functions of the lower limb, how joints and motions work together to create movement and some of the issues that can occur when these systems are not working properly. We hope you have found this information helpful and informative. If you have any questions about our products or want more information, please don’t hesitate to contact us.