Generation of torques around the joints of lower limb during gait!

Generation of torques around the joints of lower limb during gait!
Nur Rachmat

Introduction

Torque is the rotational potential of the forces acting on the joint. It is also define as a force that produces or tends to produce rotation. Torque is also called moment or moment of force. The internal joint moment is the net result of all of the internal forces acting about the joint, including moments due to muscles, ligaments, joint friction and structural constraints.

The joint moment usually is calculated around a joint center. When we think in terms of internal moments, for example, a net knee extensor moment means the knee extensors (quadriceps) are dominant at the knee joint, and the knee extensors are creating a greater moment than the knee flexors (hamstrings and gastrocnemius). The units used to express moments or torques are Newton-meters (N-m). Normalized to the subject’s body mass, Newton-meters are expressed as N-m/kg.
Torque about a point is the product of a force and the perpendicular distance from the line of action of the force to the point. We will not discussing more on the amount of torque, but more over we will discuss it more on the generation of torque by means of torque demand on each joint of lower limb during gait.

Generation of torques around the joints of lower limb during gait

To facilitate observational gait analysis, the gait cycle is divided into eight phases. On each phases, the generation of torques around the joint of lower limb will be discuss.

Figure No.1. Periods, task, & phases of gait cycle adopted from Ed Ayyappa (1997). Page.13. Note the timing relationship between the functional tasks of gait and the phases of gait

Initial Contact
At initial contact, the ankle is at the neutral position; the ground-reaction force vector is posterior to the ankle joint center creates a plantar flexion torque. On Subtalar joint, an inversion torque occurs because the calcaneus is lateral to the weight bearing axis of tibia. At the knee, the vector is anterior to the joint axis, creating a brief passive extensor torque. A rapid, high intensity flexion torque begins on hip joint as the vector falls anterior to the joint, placing great demand on the hip extensors.

Figure No.2. At initial contact, the ground-reaction force line is posterior to the ankle and anterior to the knee and hip with activation of the pretibials, quadriceps, hamstrings and gluteus maximus. The gluteus medius is active in preparing to limit pelvis tilt in the coronal plane. Adopted from Edmond A. (1997). Page No. 49.

Figure No.3. At initial contact, Hip is in 200 flexion,
Knee is in 50 flexion, and Ankle is in neutral position.
Adopted from Jabeen U. (2008). Page No. 20.

Loading response

During loading responses, heel rocker action occurs as the pretibial pull the tibia forward over the fulcrum of the os calcis even as the foot is moving into a plantar grade position. This movement enables forward momentum of the tibia relative to the foot, but it also flexes the knee. The position of the body behind the foot creates plantar flexion torque which quickly forces the foot to the floor, and then diminishes in late loading response. It is also creates a rapid moderate intensity flexion torque on knee joint. The hip maintains its posture of about 30 degrees of flexion, creating a rapid, high-intensity flexion torque, the second-highest joint torque in normal gait. A hip adduction torque begins as body weight is assumed by the stance leg. On Subtalar joint, an inversion torque continues, because the calcaneus is still lateral to the weight bearing axis of tibia.

Figure No. 4. During loading response, flexion torque at the knee is caused by the heel rocker action and position of the body behind the foot. Shock is absorbed and stability established while maintaining forward progression.
Adopted from Edmond A. (1997). Page No. 50.

Figure No.5. At loading response, Hip is in 200 flexion,
Knee is in 150 flexion, and Ankle is in 50 plantar flexion.
Adopted from Jabeen U. (2008). Page No. 21.

Mid stance

As the lower limb rolls forward over the stance foot, the body weight vector becomes anterior to the ankle joint, creating an increasing dorsiflexion torque. Momentum of the contra lateral swing leg creates an extension torque on the ipsilateral knee that decreases demand on the quadriceps and extends the knee without muscle action. The contra lateral swing limb moves the body past the stance limb, this leads to a change from a hip flexion torque to an extension torque by the end of mid stance. The adduction torque continues as the body mass and the ground-reaction force are quite medial to the structural support point at the head of the femur. The Subtalar joint eversion torque diminishes.

Figure No.6. In early midstance, the vertical force begins to decrease and the triceps surae, quadriceps, and gluteus medius and maximus are active.
Adopted from Edmond A. (1997). Page No. 51.

Figure No.7. At Mid stance, Hip is in neutral position,
Knee is in 50 flexion, and Ankle is in 50 dorsi flexion.
Adopted from Jabeen U. (2008). Page No. 21.

Terminal stance

In terminal stance, forward fall of the body moves the vector further anterior to the ankle, creating a large dorsiflexion torque, this dorsiflexion torque reaches peak. This torque creates the greatest muscle demand at any joint during gait cycle. The knee achieves an angular position of full extension accompanied by a mild extension torque which reach peaks than diminishes in the latter part of terminal stance. The trailing posture of the limb and the presence of the vector posterior to the hip create hip extension torque which provides passive stability at the hip joint. The adduction torque rapidly diminishes. On Subtalar joint, an inversion torque is created as the heel rises. This is caused by body weight progressing onto the obliquely aligned metatarsal heads and the pull of the soleus.

Figure No. 8. Terminal stance produces a second peak in vertical force exceeding body weight with high activity of the triceps surae, which maintain the third rocker while the tensor fascia lata restrains the increasing posterior hip vector.
Adopted from Edmond A. (1997). Page No. 52.

Figure No.9. At Terminal stance, Hip is in 200Apparent hyperextension,
Knee is in 50 flexion, and Ankle is in 100 dorsi flexion.
Adopted from Jabeen U. (2008). Page No. 22.

Pre-swing

In this phase, the dorsiflexion torque present at the beginning of preswing diminishes rapidly as the metatarsophalangeal joints extend to 60 degrees. Rapid unloading of the limb by transfer the body to the outer of the foot to the other foot allows the residual plantar flexion at ankle to generate a flexion torque at the knee. As the limb unloaded, the hip extension torque diminishes. The subtalar joint inversion torque diminishes to zero and remains in this level through out swing limb advancement.

Figure No. 10. Contralateral loading results in limited muscle activity during preswing. The rectus femoris and adductor longus initiate hip flexion. Knee flexion is passive, resulting from the planted forefoot and mobile proximal segments.
Adopted from Edmond A. (1997). Page No. 53.

Figure No.11. At Pre-swing, Hip is in 100Apparent hyperextension,
Knee is in 400 flexion, and Ankle is in 150 plantar flexion.
Adopted from Jabeen U. (2008). Page No. 22.

Initial swing

A very low level plantar flexion torque is present. Thigh advancement by active hip flexion combined with tibia inertia creates a knee flexion torque. Tibial inertia initially maintains the hip extension torque, and then by the end of initial swing the hip extension torque approaches zero.

Figure No.12. During initial swing, the short head of the biceps, iliacus and pretibials are active in initiating limb advancement and providing swing clearance.
Adopted from Edmond A. (1997). Page No. 54

Figure No.13. At initial-swing, Hip is in 150flexion,
Knee is in 600 flexion, and Ankle is in 50 plantar flexion.
Adopted from Jabeen U. (2008). Page No. 23.

Mid swing

The knee extends as the ankle dorsiflexes, contributing to foot clearance while advancing the tibia, a very low level plantar flexion torque is present. Due to tibia momentum, assists with knee extension, creates transition to a knee extension torque in late mid swing. Limb inertia, due to rapidly advancing tibia, creates a gradually increasing hip flexion.

Figure No.14. A vertical tibia identifies the terminal period of midswing. Iliacus preserves hip flexion, and the hamstrings are active in decelerating the thigh while the pretibials maintain foot clearance.
Adopted from Edmond A. (1997). Page No. 55

Figure No.15. At mid-swing, Hip is in 250flexion,
Knee is in 250 flexion, and Ankle is in neutral position.
Adopted from Jabeen U. (2008). Page No. 23
Terminal swing

During terminal swing the low level plantar flexion torque diminishes to zero as the function of pretibial activity changes from one of foot clearance in swing to more appropriate limb placement and positioning for initial contact. The knee extension torque, generated by rapidly advancing tibia, continues. The hip flexion torque diminishes at the end of terminal swing.

Figure No.16. At terminal swing, the gluteus maximus, hamstrings, quadriceps and pretibials are active in preparing for limb placement and the ensuing loading response.
Adopted from Edmond A. (1997). Page No. 56

Figure No.17. At terminal-swing, Hip is in 200flexion,
Knee is in 50 flexion, and Ankle is in neutral position.
Adopted from Jabeen U. (2008). Page No. 23

Figure No.16. Generation of torque during gait.
Adopted and modified from Jabeen U. (2008). Page No. 7, 13 & 17

Concussion

Torque is force that produces or tends to produce rotation. The generation of torques around the joints of lower limb during gait is easily observable on sagital plane, but also observable on frontal plane. The joint involve are subtalar joint, ankle joint, knee joint, and hip joint. For easy understanding the generation of torque is discussed on each phases of gait cycle separately. The generation of torques is influenced by muscle strength, dynamic range of motion, and shape, position and function of numerous neuromuscular and musculoskeletal structures, inertia of limb, and ground reaction force.
Normal human locomotion requires a complex interactive control between multiple limb and body segments that work congruently to provide the most shock-absorbing and energy-efficient forward movement possible which apposes the torque generated on the joints. The primary goal is energy efficiency in progression using a stable kinetic chain of joints and limb segments that work congruently to transport the passenger unit forward

Acknowledgements
The author would like to express appreciation to Madam Uzma Jabeen, lecturer of Pakistan Institute of Prosthetic and Orthotic Sciences for her book, “ A manual of Biomechanics III” which is Basic concept on article.

References:

1. Edmond A. Normal Human Locomotion, Part 2: Motion, Ground Reaction Force and Muscle Activity, JPO: American Academy of Orthotists & Prosthetists, 1997, Vol. 9, Num. 2: 42-57
2. Ed Ayyappa, Normal Human Locomotion, Part 1: Basic Concepts and Terminology, JPO: American Academy of Orthotists & Prosthetists, 1997, Vol. 9, Num. 1: 10-17
3. Jabeen Uzma. manual of biomechanics III, PIPOS, 2008: 2-31

Terima kasih telah memberi komentar, untuk mendapat balasan komentar lebih cepat, silakan kirim email ke info@kuspito.com

Isikan data di bawah atau klik salah satu ikon untuk log in:

Logo WordPress.com

You are commenting using your WordPress.com account. Logout / Ubah )

Gambar Twitter

You are commenting using your Twitter account. Logout / Ubah )

Foto Facebook

You are commenting using your Facebook account. Logout / Ubah )

Foto Google+

You are commenting using your Google+ account. Logout / Ubah )

Connecting to %s