abduction Movement away from the midline. Lifting one’s arms to either side abducts them.
abductor hallucis A muscle that brings the great toe away from the other toes, originating at the calcaneus and the soft tissues nearby, and inserting at the outside of the proximal bone of the great toe.
acetabulum The large spherical indentation in the pelvic bone that forms the pelvic side of the hip joint.
Achilles bursitis See bursitis.
Achilles tendonitis Inflammation of the Achilles tendon, generally occurring just above the heel bone, into which the tendon inserts, attaching the gastrocnemius and soleus muscles to the calcaneus.
acromioclavicular joint The joint connecting the clavicle with the acromion, a superolateral boney projection of the scapula.
acromion A boney projection of the scapula, or shoulder blade, that joins it to the lateral clavicle, or collarbone.
adduction Movement toward the midline, even crossing it. To touch one’s left shoulder with the right hand, one must adduct the right arm.
ankle mortise The space between the distal ends of the tibia and fibula into which the uppermost bone of the foot, the talus, just fits.
ankylosing spondylitis Hereditary progressive inflammation and eventual fusion of vertebral bodies, largely in males. Fusion and virtual rigidity of the spine are frequently complete by the early twenties, yielding a stooped or hunched thorax.
anterior In the front.
Anusara Yoga principles of alignment See Appendix III.
arterial insufficiency A condition chiefly affecting older individuals in which the vascular system is unable to transport enough blood to supply adequate oxygen and nutrients to the periphery, including the muscles.
arthritis Destructive inflammation of a joint or joints. When one is referring to types of arthritis, the plural is arthritides, in the manner of ancient Greek.
asana Sanskrit term for yoga pose or poses, literally translated as “seat”or “posture.”The term is both singular and plural.
axon The thin extended outgrowth from a neuron that normally propagates impulses away from that neuron toward another neuron, a muscle, or a gland. The term derives from the Greek word for “axis.”
brachial plexus The complex rearrangement of cervical nerve roots after they leave the cervical spine, taking place in the lateral neck and upper inner chest area. In the course of this reorganization, the nerve fibers form trunks, divisions, and cords—all part of the plexus—which subsequently become the major nerves to the upper extremities (e.g., the median, ulnar, and radial nerves).
bridging spondylitis An arthritic condition in which two or more vertebrae are either fused together or have dangerously large osteophytes, in either case severely limiting range of motion at that joint. Usually this occurs in the cervical spine of older people, where it may or may not be associated with HLA-B27 as a very mild form of ankylosing spondylitis; it need not be genetic.
bursa A closed sac with synovial lining and joint fluid within, generally separating a bone from a tendon. The bursae are thought to have evolved from joints, since they have the same basic structure, and to have been retained because they prevent the tendon from bruising the bone, and the bone from fraying the tendon. The Latin word bursa means “purse.”
bursitis Inflammation of a bursa (see above), which can become quite painful. Examples are Achilles bursitis (between the tendon and the ankle bone), prepatellar bursitis (external to the kneecap), pes anserinus bursitis (separating the sartorius, gracilis, and semitendinosus tendons from the tibia just below the inner knee), and ischial bursitis (between the bones on which one sits and the hamstring muscles that attach to them).
carpal tunnel syndrome Entrapment of the median nerve in a tight-fitting passageway between the bones of the wrist. Tendons also pass through the carpal tunnel and injure the nerve when they become inflamed or swollen (e.g., when swelling in pregnancy congests the compartment). This syndrome causes pain and numbness of the palmar side of the thumb, index, and middle fingers, and the thumb side of the ring finger, and weakness in lifting the thumb perpendicular to the plane of the palm.
cartilage The semi-stiff substance that lines joints and forms movable tubes in the body such as the trachea, the nasal cavity, and the Adam’s apple. There are three forms: hyaline cartilage, elastic cartilage, and fibrocartilage.
cauda equina Collections of nerve fibers, rootlets, that descend through the lumbar portion of the canal, giving the appearance of a horse’s tail, hence, the name cauda equina. In adults, the spinal cord proper ends at the lower thoracic levels, far above where lumbar nerve roots exit the spinal canal.
cerebrovascular disease Blood vessel abnormalities in the brain, including aneurysm, stroke, intracranial hemorrhage, and changes in small blood vessels of the brain caused by hypertension.
cervical spine The seven vertebrae of the neck.
cervical vertebral instability When, because of fracture or serious disruption, the cervical vertebral column is vulnerable to gross malalignment, exposing the spinal column within to sudden catastrophic injury.
Chiari malformations A range of congenital defects at the base of the skull that might be mild, with dizziness, neuromuscular symptoms, and impaired coordination (type I); might involve defects of the cervical vertebrae and spinal canal, which might lead to paralysis (type II, Arnold-Chiari); or might even be more serious, causing hydrocephalus and similar difficulties (type III).
chondrocytes Cells that secrete the fibers that constitute cartilage.
chondromalacia patellae Softening of the cartilage of the kneecap. Because the knee is an elliptical joint involving three bones, the back of the kneecap is cut with fine facets, almost like a precious jewel, so that it fits properly over the joint between the tibia and the femur at all angles. Malalignment in the knee, which then contributes to degenerative changes in the cartilage, can cause pain. Also known as runner’s knee, it is more common in women, with onset usually before age forty.
coccygodynia Pain in the region of the coccyx, frequently due to a fracture or dislocation at the sacrococcygeal junction, itself often the result of trauma such as a fall.
collagen A component of connective tissue that is pervasive throughout the body. It is a triple helix of three long protein chains that wrap around one another. Cross-linked molecules of collagen greatly resist stretch and are stronger than many metals.
collateral ligaments, medial and lateral Tough cartilaginous thongs that attach the tibia and fibula to the femur at the inner and outer areas of the knee. The most common pathology of these ligaments is sprain. They can also be stretched, giving the knee “wiggle room”and leading to valgum and varus deformities. In addition, they can tear along with the menisci.
contralateral The opposite side (e.g., the right is contralateral to the left).
conus medullaris The enlargement of the spinal cord at the lowest thoracic level, where it gives rise to the fibers for all five lumbar levels that make up the cauda equina. The conus medullaris is where the spinal cord proper terminates.
cruciate ligaments, anterior and posterior Strong cords of fibrous tissue that restrain the tibia from moving forward and backward, respectively, at the knee.
de Quervain’s syndrome Inflammation (tenosynovitis) of the tendons of the thumb muscles—the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus—at the radial bone’s styloid process (dorsal wrist).
dendrite The branching outgrowth from a neuron that acquires impulses, which are then transmitted through the cell body to the axon and, hence, to another cell. The Greek word for dendrites means “pertaining to a tree.”
distal Farther from the point of reference or axis (e.g., the hand is distal to the elbow).
Dupuytren’s contracture Hereditary shortening and thickening of the flexor tendons of the hand, generally beginning after middle age with the fourth digit and sometimes progressing to involve several.
effusion Collection of fluid beyond what is physiologically required. This can occur in joints, distorting the relationships and movement patterns of the bones, or in other places (e.g., pulmonary effusion).
elastin A component of connective tissue made up of polypeptide (protein) chains that cross-link like collagen but with the opposite effect: they coil into a form that may uncoil when the fiber is stretched, and resile (recoil) when the stretch is terminated.
eversion Lateral movement of the foot toward the little toe side and a lifting up of that side, producing an outward-facing sole.
extension Motion of bones at a joint away from each other or away from the torso. Exception: Ankle and toe extension bring the foot and toes upward.
facet syndrome Painful spinal condition resulting from arthritis or other mechanical problems in the facet joints of the vertebrae. There are no neurological sequelae such as paresthesias, numbness, weakness, or sciatica. Recent literature suggests that many cases identified as facet syndrome are actually segmental rigidity, simple tightening of the longitudinal muscles along the spine.
external rotation Clockwise revolving motion of the right arm and leg; counterclockwise revolving of the left limbs. At the ankle and wrist, these movements are termed supination.
fibrocartilaginous triangle Tough diagonal tendinous bands that essentially hold the skeleton of the hand together from the palm side.
flexion Motion of bones toward one another at a joint generally to the functional position, toward the front. One exception is ankle and toe flexion, which to physicians means pointing the foot and toes downward.
gait cycle The repetitive series of movements that each foot, ankle, knee, and hip and the trunk and arms go through with each pair of steps.
gastroesophageal reflux Nonphysiological flow of digestive juices and eaten material back to the esophagus from the stomach. This can be due to weak gastroesophageal sphincter muscles, but rarely occurs after inverted yoga poses unless it also occurs when the practitioner is right-side up. Those with GERD (gastroesophageal reflux disease) should not do yoga for five hours after eating.
genu valgum Inward tilting of the knee joint, toward the other knee.
genu varus Outward tilting of the knee joint, away from the other knee.
glenoid fossa The shallow cup-shaped part of the scapula into which the humerus (upper arm bone) fits to form the shoulder joint.
golfer’s elbow Inflammation of the inside (medial side) of the elbow, generally involving the tendons of the muscles that flex the wrist, or the connective tissue to which they are attached.
Golgi tendon organs Sensory nerve endings embedded in each tendon’s fibers that send signals inhibiting the contraction of the muscle to which the tendon is attached. The Golgi tendon organs are stimulated by passive stretch or active contraction of the muscle—anything that stretches the tendon. Their inhibitory output is proportional to the stretch and does not change regardless of how long the muscle remains stretched. They are named after their discoverer, Nobel laureate Camillo Golgi (1843–1926).
gout Generally intermittent, extremely painful condition deriving from the body’s overproduction of uric acid, a derivative of the nucleic acid purine. It is associated with a protein-rich diet and related to obesity.
herniated nucleus pulposus Rupture of a protruding nucleus pulposus, the soft inner mass (jello-like) of an intervertebral disc, through the annulus fibrosus, the relatively stiff outer (rice paper–like) membrane of the disc. Unfortunately these herniations almost invariably occur in a posterior direction, where the neurological material within the spine is located.
Hill-Sachs deformity Fracture of the medial humeral head, usually requiring special posterior oblique X-rays or MRI to detect.
humerus The bone of the upper arm.
hyperlordosis Abnormal arching of the spine with convexity forward. It is found most commonly in the lumbar spine, but can occur in the cervical and even (rarely) the thoracic spine.
idiopathic Without cause.
iliopsoas Primary hip flexing muscles originating at the lateral edges of the lumbar vertebrae (psoas) and the inner surface of the pelvis (iliacus) and attaching to the inner upper region of the femurs.
impingement syndrome Where movement or positioning causes compression, usually of a tendon. In shoulder impingement, the supraspinatus tendon is pressed between the acromion and the head of the humerus.
inferior Below.
inguinal hernia Often painful protrusion of the abdominal cavity linings, and possibly some intestine, through the abdominal wall at the groin. This hernia is more common in men. There is usually an abdominal bulge that resolves with lying down. Bulges that do not resolve may become lodged between the abdominal wall and the deeper muscles and skin, a dangerous condition, known as incarceration, demanding immediate medical attention.
internal rotation Counterclockwise revolving motion of the right arm and leg; clockwise revolving of the left limbs. At the ankle and wrist, these movements are termed pronation.
intertriginous dermatitis Skin condition located in the skin between the digits.
intrafusal fibers Sensory nerve endings embedded in tiny muscle fibers, themselves embedded in every skeletal muscle. When stretched, the intrafusal fibers send facilitatory signals affecting the large muscle in which they are embedded, stimulating that particular muscle to contract more strongly. The tiny muscles adjust the sensitivity of the intrafusal fibers to stretch, damping down their facilitatory signal output if a muscle is stretched for any length of time. They are responsible for the stretch, or myotatic, reflex.
intrinsic muscles Muscles of the hands and feet that are located entirely in the hands and feet themselves. In contrast, most muscles that move the extremities, especially those used for more powerful actions, are located in the forearms and lower legs, with long tendons to the fingers and toes. Any other arrangement would be too bulky and produce too much momentum in the hands and feet for the deft movements required of the extremities.
inversion Movement of the foot in which the inner arch lifts up and the foot turns in toward the midline.
ischial bursitis See bursitis.
labral tear Injury to the fibrocartilaginous ring around most major joints. The shoulder joint, for example, has posterior, anterior, superior, and lateral labra. The superior labrum is often damaged in an anterior-posterior direction (SLAP lesion). In the hip, labral tears are common in dancers and yoga students. However, the anterior joint capsular fibers are very strong and resist tearing, as they counterbalance the trunk’s weight during walking. Labral tears are painful, and difficult to diagnose without MRI.
lateral Toward the side.
latissimus dorsi Large muscles connecting the back of the pelvis to the inner upper area of the humerus. Their primary action is to rotate and bring the arms inward and behind the body.
ligamentum flavum A yellowish ligament that extends the entire length of the spine, lining the rear portion of the long spinal canal that the nerves pass through on their way from the brain to the arms and legs and body.
longitudinal arch The rising curve of the inner foot that distributes weight to the heel and ball of the foot. Its keystone is the navicular bone.
lordosis The normal convexity-forward arching of the lumbar and cervical spine.
lumbar spine The five vertebrae at the lower end of the spine, from the level of the twelfth rib to the sacrum.
macular degeneration Loss of cellular function in the most sensitive part of the eye. In the wet form of macular degeneration, new blood vessel formation crowds out some of the light-sensitive cells. Their rupture and subsequent hemorrhage damages the macula, potentially causing vision to deteriorate substantially. In the more common dry form, pigmented areas (drusen) impair vision much less.
medial Toward the midline.
meniscus, medial and lateral The cartilage inside the knee joint that improves the fit between the tibia and the femur and cushions both during weight bearing.
myotatic reflex Contraction of a muscle in response to a sudden stretching force, due to stretch of the intrafusal fibers (e.g., the patellar reflex, the Achilles tendon reflex).
neck of the femur The diagonal part at the upper end of the femur, from the greater trochanter at the side to the rounded head in the actual hip socket. This buttress shape allows for greater stability in walking than we would have if the femur were one long straight bone. Wolff’s law describes how the sideward forces generated during walking gradually remodel the femur to have a diagonal neck. Babies are born without that angle at the greater trochanter.
neuroforamen Space through which a nerve root passes that is created by the fit of two adjoining vertebrae. Plural: neuroforamina.
Neutral The position of limbs or torso that is without flexion, extension, abduction, adduction, or external or internal rotation. The entire body in neutral is also known as the “anatomical position.”This is different from the yogi’s Savasana, in which arms and legs are somewhat externally rotated.
nonsteroidal anti-inflammatory drugs Medications related to aspirin which interfere with the prostaglandin-mediated pathways that generate pain and enhance inflammation. These medicines reduce both pain and inflammatory responses, such as swelling and redness. However, their use is associated with varying degrees of side effects, such as gastric irritation, ulcer, and prolonged bleeding time. Examples are Motrin, Relafen, Voltaren, Celebrex, and Mobic.
nutation Movement of the sacrum in any plane. Some researchers give evidence that the sacrum actually moves around diagonal axes (i.e., from lower right to upper left or lower left to upper right).
osteoarthritis Erosion of the cartilage at joints, either without single cause or due to trauma. It is characterized by irregular boney outgrowths at the joint, and painful restrictions of movement and swelling mainly of weight-bearing and very active joints. Since chronic conditions are cumulative, it is more common in older persons.
osteoarthropathy Any disorder that affects bones and joints. Its origins are Greek: osteo (bone) + arthron (joint) + pathos (suffering).
osteoblasts Cells that line the outside of bones and are destined to make the protein matrix of the bones.
osteocytes Cells descended from osteoblasts, located within the bones, that actively secrete the protein matrix and are surrounded by it.
osteophytes Irregular nonanatomical boney growths at or near joints, associated with osteoarthritis. They may limit range of motion of the joints and in the spine. Since the facet joints are so near the neuroforamina, they can also painfully compress the nerve roots as they exit the spinal canal. Greek: osteo (bone) + phyton (plant).
osteoporosis Reduction of bone mineral, and thereby bone strength beyond 2.5 standard deviations of the mean, which is equivalent to bones weaker than 99 percent of healthy thirty-year-old women.
paraspinal muscles Near-midline longitudinal muscles that attach to and move the vertebrae.
paresthesias Strange sensations such as tingling, of being stuck by pins and needles, or of insects crawling on the skin. Numbness is when you do not feel what is there; paresthesias are when you feel what is not there.
patellofemoral arthralgia Pain brought about by improper fitting of the underside of the kneecap, or patella, and the forward face of the femoral condyles at the knee joint.
pectoralis major and minor Muscles connecting the scapula and upper humerus to the ribs and sternum.
perichondrium Lining such as that between the ends of bones and the cartilage that supplies oxygen and nourishes the chondrocytes, cells that make cartilage.
plantar fascia The tough membrane that connects the heel to the toes. Like a bowstring, the plantar fascia puts the foot under tension that bends the middle of its underside upward, maintaining the longitudinal arch of the foot.
plantar fasciitis Painful inflammation of the insertion of the plantar fascia into the calcaneus, also known as “heel spur.”
pontine Related to the pons, part of the brain that integrates motor and sensory signals between the spinal cord and higher brain regions such as the cerebral cortex.
posterior In the rear.
prepatellar bursitis See bursitis.
protraction Movement of the scapulae (shoulder blades) forward, toward the ventral, or navel-bearing side of the body. In human anatomy, it is nearly equivalent to abducting them, that is, bringing them away from the spine.
proximal Closer to the point of reference or axis.
pseudogout Goutlike episodes caused by calcium pyrophosphate crystals, rather than the urate crystals that irritate the synovial membrane in true gout. It is also associated with calcification of the articular cartilage, known as chondrocalcinosis.
quadriceps The prominent muscle at the front of the thigh that straightens the knee.
radiculopathy Compression or injury to the nerve roots that exit the spine.
Reiter’s syndrome Autoimmune arthritis following a bacterial infection of the intestines or genitourinary system, generally affecting joints of the lower extremities and the ligaments and tendons that cross them. Also known as reactive arthritis, it may be accompanied by palmar or plantar rash, oral or genital sores, and inflammation of the eyes.
retraction Movement of the scapulae (shoulder blades) backward, toward the dorsal aspect of the thorax. In human anatomy, it is nearly equivalent to adducting them, that is, bringing them toward the spine.
retrolisthesis See spondylolisthesis.
rheumatoid arthritis Arthritic damage to joints resulting from the immune system’s actions, generally on the joint capsules’ lining or synovium.
rotator cuff syndrome or tear The rotator cuff consists of the supraspinatus, infraspinatus, teres minor, and subscapularis muscles, which secure the humerus into the shoulder socket. A rip in the fabric of any of these technically qualifies as rotator cuff syndrome. Usually rotator cuff syndrome includes the supraspinatus tendon, whether other muscles or tendons are involved or not. Supraspinatus tears cause pain when lifting the arm between 80 and 120 degrees.
sacroiliac joint A bilateral synovial joint between the outer edges of the sacrum and the inner edges of the iliac bones.
sacroiliitis Inflammation of the sacroiliac joint.
sacrum Spade-shaped central posterior pelvic bone that articulates with the iliac bones on either side (the sacroiliac joints), with the lowest lumbar vertebra above (L5-S1 joint), and with the coccyx below.
scapulothoracic The large area between the shoulder blade, or scapula, and the backs of ribs 2 through 6, over which the shoulder blade normally moves. It is often referred to as a joint, although its size and structure are quite different from any other joint.
scoliosis Lateral curvature of the spine, often with a rotation as well. The curve is described by its location, as in “left thoracolumbar scoliosis.”Idiopathic scoliosis disappears with forward bending.
sesamoid bone A bone encapsulated within a tendon and named for its shape, which resembles a sesame seed. There is one in the flexor tendon of the big toe as it rounds the joint that connects the toe to the foot. The patella is the largest sesamoid bone in the human body.
SLAP lesion Tear of the superior labrum of the shoulder joint, occurring in an anterior-posterior direction where the long head of the biceps tendon crosses just above the joint.
spinal cord The part of the central nervous system that descends within the vertebral column, conducting nearly all motor and sensory communications between the body and the brain. The cord is divided into cervical (neck), thoracic (where the ribs are), and lumbar (from the ribs to the pelvis) regions.
spinal stenosis Narrowing of the inside of the central canal of the spine, which is formed by the column of vertebrae. This canal houses the spinal cord (see above). The narrowing can be due to an intervertebral disc that bulges or has herniated at a specific level; a thickening of the bones, which can narrow whole sections of the spinal canal; or a swollen ligamentum flavum, which can narrow variable stretches of the canal. The pain, numbness, weakness, and paresthesias that result from this type of compression of the nerve fibers are usually somewhat symmetrical.
spondyloarthropathy See ankylosing spondylitis.
spondylolisthesis The undesired sliding of one vertebra (generally forward) on the one below it. The displacement is graded (grade I = 1–25 percent, grade II = 25–50 percent, etc.). It can result in narrowing of the central canal (stenosis) or it may narrow a neuroforamen, causing radiculopathy. Displacement may also be posterior (retrolisthesis) or sideways (lateral listhesis).
spondylolysis Separation of the facet-bearing part of a vertebra from the vertebral body. This can occur by traumatic fracture of the pars intraarticularis and is believed to be congenital in some cases.
sprain Where at least some of the fibers of the ligaments that bind a joint together are torn apart. A strain is stretching without a tear.
stretch reflex The same as the myotatic reflex (see above).
superior Above.
suprascapular nerve entrapment Rupture of the ligament that holds the suprascapular nerve, which reaches from its origins at C5–C6 over the top of the scapula through the suprascapular notch to serve the supraspinatus and infraspinatus muscles, within the suprascapular notch, causing the nerve to slide back and forth or even leave the notch altogether, subjecting it to damage. This is sometimes seen in pitchers and back-bending yogis.
synapse The site where impulses are passed from one neuron to another, generally by neurotransmitter molecules but sometimes by direct (electronic) propagation of the signal. This communication involves a one-way, all-or-nothing excitation of the stimulated neuron, though recent observations question the all-or-nothing, the one-way, and other aspects of the Hodgkin-Huxley theory that lies at the foundation of most computational neurobiology. (For more on this, see B. Gutkin and G. B. Ermentrout, “Spikes too kinky in the cortex?”Nature 440 [April 20, 2006]: 999–1000.) The word originates from the Greek syn (together) and hapto (to clasp).
synovial fluid The yellowish white fluid that bathes each joint. This fluid serves three essential purposes: it is a first-class lubricant; it brings oxygen, food, and protein-building blocks to the cartilage of the joint; and it protects the joint from many mechanical and biological causes of disruption.
synovial membrane A membrane, similar to a gasket, that seals the synovial fluid in the joint. It is quite vascular and richly invested with nerves, secretes and resorbs the synovial fluid, and is exquisitely sensitive, causing pain with distention, inflammation, or disruption.
tennis elbow A small but painful tear in the forearm’s extensor aponeurosis, a broad flat tendon on the dorsal forearm. It occurs when the muscles that lift the hand and fingers are stressed, as in backhand.
teres major and minor Small muscles attaching the outer scapula to the humerus, rotating it internally and externally, respectively.
thoracic outlet syndrome Entrapment of the brachial plexus, or the nerves that emerge from it, at the neck or upper chest (generally either between the scalenii, by an anomalous rib that is attached to a cervical vertebra, beneath the clavicle, or at the coracoid process). Except when the nerves are entrapped between two cervical muscles, blood vessels may be involved.
thoracic spine The twelve vertebrae at the level of the chest, between the neck and the lower back, to which the ribs attach.
vagus nerve A nerve that exits the brain through the skull and descends bilaterally through the neck and torso to influence the heart, lungs, and digestive system. This nerve is an exception to the rule that all communication between the body and the brain occurs by virtue of the spinal cord.
vasovagal episode Abrupt changes in abdominal or thoracic pressure (e.g., when voiding, or when in an airplane or headstand) that can trigger the vagus nerve to slow down the heart, at times causing fainting.
voluntary subluxation Repeated separation of the humerus from the glenoid fossa, a very painful form of shoulder joint abnormality that can happen without trauma in people prone to it. If it happens twice, corrective surgery is suggested.
zygapophyseal joints Referring to the facet joints that link each vertebra to the one above and the one below it. From the Greek root zugon, meaning “yoke,”possibly because these joint surfaces are somewhat ovoid.