Orthopaedics Defined

Source: American Academy of Orthopaedic Surgeons

a b c d e f g h i j k l m n o p q r s t u v


  • Abduction: Movement of an extremity such as your arm or leg away from the body.
  • Acetabulum: The socket in the hip bone which is shaped like a cup. The top of the femur, the thigh bone, fits into the socket; it is formed by the ilium, ischium, and pubis.
  • Achilles tendinitis: Inflammation of the Achilles tendon behind the ankle, often caused by increased activity, improper footwear, or tight hamstrings.
  • Adduction: Movement of an extremity such as your arm or leg toward the body.
  • Agonists: Muscles that produce body movement in the same direction.
  • Anterior surface: Surface at the front of your body
  • Arthrodesis: The surgical fusion of a joint. The procedure removes any remaining articular cartilage and positions the adjacent bones to promote bone growth across a joint. A successful fusion eliminates the joint and stops motion. The usual purpose is pain relief or stabilization of an undependable joint
  • Arthrography: A procedure in which a contrast medium is injected into a joint to outline soft tissues such as the meniscus in the knee, or a torn structure such as the rotator cuff in the shoulder. MR arthrography is a technique in which a diluted contrast medium such as gadolinium is injected into a joint to improve the delineation of soft tissues. Standard MRI is obtained following the injection.
  • Arthroplasty: surgery to replace or mobilize a joint, typically performed by removing the arthritic surfaces and replacing them with an implant. Total joint arthroplasty is replacement of both sides of the joint. Hemiarthroplasty replaces only one side of a joint
  • Arthroscopy: A form of minimally invasive surgery in which a fiberoptic camera, the arthroscope, is inserted into an area of the body through a small incision.
  • Articular cartilage: A smooth, glistening surface that covers the ends of bones that articulate with each other to form a joint.
  • Atlantoaxial subluxation (AAS): An orthopaedic problem seen frequently in athletes with Down syndrome, which can pose a significant risk to athletes participating in contact sports. Joint looseness or malformation of the vertebrae or surrounding structures causes the first vertebra (C1) in the neck to slip forward and compress the spinal cord, particularly when the neck is in flexion or extension.
  • Autonomic dysreflexia: A health concern for athletes with a spinal cord injury above the upper chest (vertebra T8) in which the athlete experiences dizziness, sweating, headaches, and potentially severe hypertension. A plugged urethral catheter is the most common trigger; however, kidney stones or infections, pressure sores, and a blockage of feces in the rectum can also cause the condition.
  • Avulsion fracture: A fracture that occurs when a ligament or tendon pulls off a sliver of the bone.
  • Avulsion fracture: A fracture caused by a violent muscle contraction or sudden passive stretch.
  • Axial compression: A force directed along the vertical axis of the cervical spine (neck) that is part of almost every serious injury.
  • Axial loading: A load directed vertically along the axis of the cervical spine during a compression force, such as spearing or a head-on collision.


  • Bankart fracture: A small chip fracture off the anterior and inferior rims of a shallow extension of the shoulder blade (glenoid). This fracture occurs after an anterior dislocation of the shoulder, in which the upper arm bone comes out of the socket to the front side of the joint.
  • Baseball finger: Rupture of the extensor tendon caused by a sudden flexion force on the end of the finger while it is actively extended; also known as mallet finger.
  • Biceps tendinitis: Inflammation of the biceps tendon.
  • Bone densitometry: A procedure used to detect osteopenia in which a special density gradient plate is used to evaluate the comparative density of the spine, femur, or the end of the large bone in the forearm near the wrist. Photons from a single- or dual-emitting source are used to measure the density of the bone. These are then compared with normal values for a large patient population based on sex and age.
  • Bone scan: A study used to identify fractures, infections, or tumors in bones. A radioisotope is injected into a vein and allowed to circulate through the body. The distribution of radioactivity in the skeleton is measured by a special camera that can detect the emission of gamma rays. Fractures, tumors, or infections will show increased uptake of the radioisotope and appear as dark areas in the bone.
  • Burner (stinger) syndrome: An injury to the brachial plexus nerves in the neck and shoulder, often resulting from head, neck, or shoulder contact in football.
  • Bursa: A sac formed by two layers of tissue located where there is friction between tendon and bone or skin and bone
  • Burst fracture: A compression-type fracture of a vertebra in the spine, which forces the fragments to the rear, often into the spinal canal.
  • Burst laceration: A facial injury where the skin is compressed against underlying bone at impact and a jagged opening occurs.


  • Carpal tunnel syndrome: Nerve compression at the wrist. It is characterized by pain, numbness, and weakness in the median nerve in the hand.
  • Carrying angle of the elbow: The angle formed by the bone in the upper arm (humerus) and one of the bones in the forearm (ulna). This causes the forearm to stick out too much from the body.
  • Cartilage: A cellular tissue that, in the adult, is specific to joints, but in children forms a template for bone formation and growth. Hyaline cartilage is a low-friction cellular tissue that coats joint surfaces. Fibrocartilage is tough and has high collagen content, such as found in the meniscus of the knee, or the anulus fibrosus portion of the disks between the vertebrae in the spine.
  • Cavus: Describes a very high arch in the foot.
  • Cellulitis: Inflammation of tissue below the skin. This can be caused by trauma or infection.
  • Chronic rotator cuff tear: Tear of the rotator cuff in the shoulder resulting from degeneration within the rotator cuff tendon.
  • Clavicular epiphyseal fracture: Fracture of the growth plate of the collarbone (clavicle); the fracture may medically appear as a dislocation, especially if some displacement is present.
  • Closed reduction: A procedure to restore the normal position of a broken bone or dislocated joint. The fractured bones are simply manipulated and no incision is needed.


  • Degenerative joint disease (DJD): Deterioration of the cartilage that lines a joint, which results in narrowing of the joint space and pain; osteoarthritis
  • Diarthrodial joint: A specialized joint in the body that allows more or less free movement. Most of the body’s joints are this type. Also called synovial joint.
  • Discography (diskography): A procedure in which sterile x-ray dye (contrast material) is injected into one or more lumbar or cervical disks. This is done in conjunction with CT to help identify disks that are causing pain. The pain produced by the injection is correlated with the patient’s symptoms.
  • Discoid meniscus: A congenital deformity in young athletes in which the meniscus is an oval shape instead of its normal resemblance to a crescent moon.
  • Diskectomy: A surgical decompression in which the damaged part, or all, of a herniated disk is removed from the spine.
  • Dislocation: An injury that causes a joint and the ends of the bones there to be forced out of normal position.
  • Displaced fracture: A fracture in which the two ends of a bone are separated.


  • Electrical muscle stimulation (EMS): Treatment in which electric current delivers stimulation to muscles in a variety of ways, including pulse, surged, or tetanizing contractions
  • Electrocardiogram (EKG): A recording of electrical currents that flow through the heart in the form of a regular series of waves and complexes.
  • Electromyography (EMG): A test that measures the electrical response of muscle contraction.
  • Enchondral bone healing: Process in which a fibrovascular tissue known as callus grows and develops to bridge a gap between the ends of two bones
  • Enchondral ossification: The process of long bone formation where cartilage is replaced by bone.
  • Endochondral ossification: The formation of bone within a cartilage model
  • Extension: Movement of an extremity posterior to or behind the body.
  • Extensor: Any muscle that can contract and create movement at a joint that increases the angle between the parts of a limb. Exs: straightening the elbow or knee or bending the wrist, with the arm, leg, or hand assuming a more straight line.
  • Extensor mechanism: Complex interaction of muscles, ligaments, and tendons that stabilizes the knee joint and acts to extend the knee.
  • External fixation: Stabilization of a fracture or unstable joint by inserting pins into bone that are then attached to an external frame.


  • Fascia: Sheet or band of tough fibrous deep under the skin; the fascia form an outer layer for the muscles.
  • Fatigue fracture: Microfracture that occurs when the bone is subjected to frequent, repeated stresses, such as in running or marching long distances. With a microfracture, the rate of bone breakdown exceeds the rate of bone repair.
  • Femoral head: The top end of the thighbone (femur) which moves within the acetabulum socket in the hip
  • Femoral neck: The bone connecting the head and the shaft of the thighbone (femur); fractures frequently occur in this area
  • Fusion (arthrodesis): The joining of two bones into one unit, eliminating motion between them. Fusion may occur at or before birth, by injury, or as a surgical procedure.


  • Gout: An inflammatory arthritis associated with deposits of a salt in a joint, that are derived from uric acid which the body cannot metabolize.


  • Hamstrings: Made up of three muscles in the buttock and back of the thigh between the hip and the knee.


  • Iliotibial band (ITB): It runs along the outside of the thigh and helps stabilize the knee.
  • Iliotibial band (ITB) syndrome: An overuse injury of the outside thigh and knee. Can occur among runners and cyclists, with pain noticed on the outside of the knee. Develops with repeated movement of the leg and knee when inflammation of the ITB ensues as it rubs over the bottom of the thighbone (femur).
  • Inflammation: A response by the body’s white blood cells to protect from infection. Inflammation can produce heat, redness, swelling, and pain when an injury occurs to muscle or other tissue.
  • Internal fixation: Surgery to insert a device that stops motion around a fracture or joint, in order to encourage healing or fusion of the bone.
  • Intervertebral disk: Located between each of the vertebrae in the spine, made of cartilage and providing a cushion between the bones.
  • Intramedullary nailing or rodding: A procedure to fix fractures. In this procedure, a nail or rod is inserted into the bone from one of its two ends.
  • Intramembranous ossification: A type of bone formation.
  • Inversion injury: Ankle injury resulting from landing on the outside part of the foot.


  • Joint: The junction between the ends of two adjacent bones.
  • Joint capsule: A thin, but strong structure in the elbow that plays a role in ligamentous restraint.
  • Joint manipulation: Skilled, passive movement of a joint (or spinal segment) either within or beyond its active range of motion; also known as joint mobilization.
  • Joint mobilization: Passive movement techniques used to treat joint conditions, such as stiffness, reversible joint hypomobility, and pain.
  • Jones fracture: Stress fracture of the bone on the outside of the foot that connects to the little toe. Jones fracture occurs at the end of the metatarsal that is closer to the ankle. This fracture often can heal with difficulty
  • Jumper’s knee: Breakdown of the collagen in the patellar tendon (kneecap) due to overuse. The patellar tendon works with the thigh muscles to straighten the leg.


  • Kinematics: The study of the movement of rigid structures without reference to the cause of motion, i.e., independent of the forces that produce the motion.
  • Kinesiology: The study of motion of the human body.


  • Lamellar bone: Mature, well-organized form of cortical bone, one of three layers of bone.
  • Laminectomy: A surgery that decompresses the spinal cord/nerves by removing the back part of the vertebra. The surgery enlarges the spinal canal and allows access to the disk.
  • Lateral: Toward the side, away from the midline
  • Lateral articular surface: A bony process on each end of the collarbone (clavicle).
  • Lateral condyle: Forms the side of the upper surface of a joint.
  • Lateral epicondylitis: Also known as tennis elbow. Inflammation of the tendons that join the forearm muscles on the outside of the elbow. An overuse injury to the lateral epicondyle.
  • Lateral malleolus: Bony prominence at the end of the fibula in the lower leg that is part of the ankle joint.
  • Lateral meniscus: The lateral C-shaped cartilage structure of the knee.
  • Lateral view: A view that passes from side to side.
  • Ligament: A collagenous tissue that connects two bones to stabilize a joint.


  • Magnetic resonance imaging (MRI): In orthopaedics, an MRI scan is useful in diagnosing muscle-tendon-ligament injuries, tumors, stress fractures, and infections. MRI’s depend on the movement of protons in water molecules. Protons normally become randomly aligned in the scannner’s magnetic field. Radiowaves change the alignment of these photons. When the radiowaves are turned off, the protons emit a signal that is picked up by a computer and processed into an image.
  • Medial collateral ligament injuries: Knee injury to the ligament on the inside of the knee. The MCL connects the inside of the shin bone to the inside of the bottom of the thigh bone. MCL injuries occur with a blow to the outside of the knee, when the foot is planted. They are commonly seen in football players and snow skiers.
  • Metacarpals: The five bones of the hand that extend from the wrist to the fingers.
  • Metaphysis: The broad portion of a long bone adjacent to a joint.
  • Metatarsus valgus: Congenital deformity of the forefoot in which the bones are shifted outward from the body while the heel remains straight. Sometimes referred to as duck walk.
  • Metatarsus varus: Congenital deformity of the forefoot which causes the toes to point inward. Sometimes referred to as pigeon-toed.
  • Morton’s neuroma: A condition that affects the ball of the foot, especially between the third and fourth toes. Can result in pain, numbness, and tingling.


  • Navicular bone: A bone in the foot and in the wrist. The navicular bone lies at the top of the foot; with it, the talus bone in the ankle moves. In the wrist, the navicular lies on the inside, or thumb side, of the wrist. It is commonly fractured.
  • Navicular stress fracture: A fracture that occurs with repetitive stress activities and results in foot pain and tenderness.
  • Nerve conduction studies: Tests that measure the speed in which motor or sensory nerves transmit impulses.


  • Osteolysis: Dissolving of bone, especially as a result of its breakdown. This can be due to disease or infection, for example.
  • Osteomyelitis: Infection of the bone, either bacterial or fungal.
  • Osteon: In thin plates of bone, a concentric series of layers of minerals surrounding the central canal.
  • Osteonecrosis: The death of bone, often as a result of obstruction of its blood supply.
  • Osteopenia: Bone fragility as the result of a low-calcium diet.
  • Osteoperiostitis: A painful inflammation of the lining of bone.
  • Osteophytes: Overgrowth of bone, common in osteoarthritis and spinal stenosis.
  • Osteoporosis: Deterioration of bone tissue, due to a low-calcium diet. Osteoporosis causes an increased risk of fracture.
  • Osteoporosis: Deterioration of bone tissue, due to a low-calcium diet. Osteoporosis causes an increased risk of fracture.
  • Osteosynthesis: The process of bony union, as in fracture healing. It is a biologic welding process that is sometimes facilitated with grafts of bone from the hip and insertion of fixation devices.
  • Osteotomy: Literally, cutting a bone. Used to describe surgery in which bone is cut and realigned.


  • Paget disease: A condition of abnormally increased and disorganized bone remodeling.
  • Pain: A sensory and emotional reaction caused by an actual or anticipated injury. It is caused by damage to tissue or nerves, and is made worse by pressure or inflammation.
  • Palmar: The palm side of the hand and front side of the wrist and forearm.
  • Patellar tendinitis: A condition that results in pain and inflammation of the patella (knee cap) tendon; a common problem in jumping sports.
  • Pelvis: A bony ring, consisting of the sacrum, coccyx, and innominate bones, that connects the trunk of the body to the legs, supports the abdomen, and performs other functions.
  • Percutaneous pinning: Insertion of pins into bone through small openings created in the skin. The pins stabilize a fracture or a dislocated joint that was realigned by closed reduction.
  • Peroneal tendon injuries: A classification of injuries that includes tendinitis, dislocations, long tears, and tendon ruptures.
  • Phalanges: Bones of the fingers (three in each finger and two in the thumb).
  • Plantar: The sole, or flexor surface, of the foot.
  • Plantar fasciitis: Irritation of the plantar fascia where it joins the plantar part of the heel; a common cause of heel pain.
  • Posterior glenohumeral dislocation: Disruption of the shoulder joint toward the back.
  • Posterior process: The part of each vertebra that can be examined by touch. It lies just under the skin in the midline of the back.
  • Posterior sternoclavicular dislocation: Disruption of the joint between the collarbone, the sternum, and the first rib.
  • Posterior tibial syndrome: Pain along the back side of the tibia (lower leg). It is thought to be due to a tight posterior tibial muscle “pulling” on the membrane that covers the bone this area; associated with running.


  • Quadriceps tendinitis: A condition that results in tendon pain near the patella (knee cap); commonly occurs in running and jumping sports that involve changing directions.


  • Range of motion (ROM): The amount of movement available at a joint.
  • Regeneration: The production of tissue that is structurally and functionally identical to tissue damaged by injury.
  • Rehabilitation: After disease, illness, or injury, restoration of the ability to function in a normal or nearly normal manner.
  • Rotator cuff: The rotator cuff is made up of four muscles and their tendons. These combine to form a “cuff” over the head of the upper arm bone (humerus). The four muscles — the supraspinatus, infraspinatus, subscapularis, and teres minor — originate from the shoulder blade (scapula) and together form a single tendon unit. The rotator cuff helps to lift and rotate the arm and stabilize the ball of the shoulder within the joint.
  • Rotator cuff impingement: The rotator cuff can become trapped, due to repetitive overhead motion, leading to local inflammation, pain, and impaired function of the cuff.


  • Sacroiliac joint: The joint formed by the sacrum at the bottom of the spine and the ilium in the hip bone.
  • Sacrum: One of the three bones (sacrum and two pelvic bones) that make up the pelvic ring
  • Scoliosis: Condition marked by side to side curve of the spine.
  • Secondary osteoarthritis: Osteoarthritis resulting from such causes as trauma and neuropathy.
  • Secondary osteoporosis: Osteoporosis in which the bone loss is due to another condition such as hormonal imbalance, malignancy, gastrointestinal disorder, or because of corticosteroid use.
  • Spinal column: The column of vertebrae in the spine.
  • Spinal cord: Extension of the brain, it comprises virtually all nerves carrying messages between the brain and the rest of the body. It lies inside vertebrae and the spinal column.
  • Spinal stenosis, cervical: Developmental narrowing of the spinal canal in the neck (cervical spine).
  • Spinal stenosis: Narrowing of the opening that contains the spinal cord; commonly caused by encroachment of bone.
  • Spine: Column of 33 vertebrae extending from the base of the skull to the tip of the coccyx.
  • Spinous processes: Prominent parts of the vertebrae that can be examined by touch.
  • Spiral fracture: A fracture in which the force has caused a bone to twist apart.
  • Spondylolisthesis: A condition in the spine in which a vertebra moves forward over the vertebra below it. It often occurs in the lower parts of the spine (lumbar, for ex.). Can lead to pressure on the spinal cord or nerve roots.
  • Spondylolysis: A defect (possibly a type of stress fracture) in the pars interarticularis, which is a small bone in the back of the spine. Also, an overuse injury to the the spine of a young athlete.
  • Sports medicine: The practice of medicine and medical care that physicians and athletic trainers, for ex., provide to athletes.
  • Sprain: Partial or complete tear of a ligament.
  • Stress fracture: An overuse injury which creates microscopic damage to the bone.


  • Tarsal coalition: An abnormality joining two or more of the major tarsal bones in the foot (talus, navicular, calcaneus, and cuboid).
  • Thoracic kyphosis: Backward curvature of the cervical spine (neck).
  • Thoracic outlet syndrome: Disorders that develop with pressure on the blood vessels or nerves between the collar bone and first rib.
  • Tibial stress fracture: A fracture of the tibia (lower leg bone) caused by repetitive force on the bone, often after an increase or change in the training regimen.


  • Ultrasound (Ultrasonography): Ultrasound uses pictures created by high-frequency sound waves that reflect off different tissues. The reflected sound waves are recorded and processed by a computer and then converted into an image. Ultrasound is used to evaluate infant hip disorders and tears of the rotator cuff.


  • Valgus: A bone is turned outward. Can also be used to describe abnormal bend in fractures or bony deformities.
  • Varus: Abnormal inward curve of a bone.
  • Vertebral arch: Part of the vertebra composed of the right and left pedicles and the right and left laminae; also called neural arch
  • Vertebral column: Segments of the spinal column, which is composed of 24 movable vertebrae, 5 fixed sacral vertebrae, and 4 fixed coccygeal vertebrae.

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