Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
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Achilles tendon
The thick, strong cord at the back of the ankle that joins the calf muscles to the heel bone. It lets you push off, rise on your toes, and absorb force when walking or running. Reports mention it when describing thickening, inflammation, or a tear, best seen on MRI or ultrasound.
Also: Achilles, calcaneal tendon, heel cord
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Acromion
This is the bony tip at the very top of your shoulder, the firm bump you can feel where the shoulder blade reaches over toward the collarbone. It forms a small roof above the shoulder joint. Reports name it to point to that top-of-shoulder spot when describing a finding.
Also: acromial process, acromial tip, shoulder blade tip
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Bone marrow edema
An area inside a bone where extra fluid has built up among the soft tissue that fills its core. It usually signals that the bone is reacting to something — a recent injury, repeated stress, inflammation, or a nearby joint problem — and shows up as a bright patch on MRI sequences sensitive to water.
Also: bone bruise, bone marrow edema syndrome, bone marrow lesion
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Bursa
A small, flat fluid-filled sac that sits between tissues such as tendon and bone, acting as a cushion so they glide without rubbing. Bursae are found around the shoulder, hip, knee, and elbow. Reports mention them when describing fluid or inflammation, called bursitis, best seen on MRI or ultrasound.
Also: bursae, bursal sac, fluid cushion
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Bursitis
Inflammation of a bursa — one of the small fluid-filled cushions that sit between bone and the soft tissues around joints. When a bursa becomes irritated, it fills with extra fluid and shows up on imaging as a fluid pocket. Most cases settle with rest and time; a smaller number are infected and need treatment.
Also: bursa inflammation, bursal distension, bursal inflammation
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Calcaneus
The heel bone — the large, sturdy bone at the back of your foot that you stand and land on. It forms the heel and anchors the Achilles tendon from your calf. On a report it is usually just naming the back of the foot. The word itself is plain anatomy.
Also: calcanei, heel, heel bone
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Carpal bones
These are the eight small bones of your wrist, packed in two rows between the forearm and the hand. They let your wrist bend, tilt, and rotate smoothly. Reports name them to point to the wrist region, or to a specific little wrist bone, when describing a finding.
Also: carpals, carpus bones, small wrist bones
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Cartilage
The smooth, slippery tissue that caps the ends of bones inside a joint and cushions them so they glide without grinding. It also forms structures like the meniscus, ear, and windpipe rings. Reports mention it when describing thinning, wear, or damage, best seen on MRI.
Also: articular cartilage, chondral surface, gristle
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Clavicle
The collarbone — the slim, slightly S-shaped bone you can feel running across the top of your chest from the breastbone to the shoulder. It props the shoulder out to the side and links the arm to the body. On a report it is usually just naming where near the shoulder or upper chest a finding sits.
Also: clavicles, collar bone, collarbone
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Collateral ligament
A strong band along the side of a joint that stops it bending sideways. In the knee, the MCL runs on the inner side and the LCL on the outer side. Similar ligaments brace the elbow and ankle. Reports mention them when describing a sprain or tear, best seen on MRI.
Also: LCL, MCL, collateral ligaments
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Condyle
This is the smooth, rounded knob at the end of a bone where it meets another bone to form a joint. You have them at the knee, elbow, jaw, and more. Reports use the word to point to that bulging, rounded end of a particular bone when describing a finding.
Also: bone knob, condyles, knuckle of bone
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Cortical bone
The hard, dense outer layer of bone — the part you would feel if you tapped a bone with your knuckle. It surrounds and protects the softer, spongy inner bone (called trabecular or medullary bone). Most of the strength of a bone comes from this outer shell, and radiologists pay close attention to it for fractures.
Also: bone cortex, compact bone, cortex
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Cruciate ligament
One of two strong bands deep inside the knee that cross each other like an X and stop the shin bone sliding too far forward or back on the thigh bone. The front one is the ACL, the back one the PCL. Reports mention them when describing a sprain or tear, best seen on MRI.
Also: ACL, PCL, anterior cruciate ligament
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Deltoid
The large triangular muscle that caps the outer shoulder and gives it its rounded shape. It is the main muscle that lifts the arm out, forward, and back. Reports mention it when describing the muscle bulk, a strain, or, less commonly, a tear, usually best seen on MRI.
Also: deltoid muscle, deltoids, outer shoulder muscle
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urgent
Dislocation
A joint where the bones are no longer lined up the way they should be. In the full form the bone surfaces have lost contact completely; in a partial form (subluxation) they are misaligned but still touch. Most need to be put back into place promptly, although the urgency varies by joint and whether nearby structures are injured.
Also: dislocated joint, displaced joint, joint displacement
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Femur
The thigh bone — the long, strong bone running from your hip down to your knee. It is the largest and strongest bone in the body, carrying your full weight with every step. On a report it is usually just naming where in the thigh or hip a finding sits. The word itself is plain anatomy.
Also: femora, thigh bone, thighbone
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Fibula
The calf bone — the thin, long bone running down the outer side of your lower leg, alongside the thicker shinbone. It carries little body weight but steadies the leg and forms the bony bump on the outer ankle. On a report it is usually just naming where in the lower leg a finding sits.
Also: calf bone, lower leg bone, outer leg bone
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I
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Impingement
A radiology word for pinching — when two structures inside a joint rub or compress each other during normal movement instead of gliding cleanly past each other. Most often described in the shoulder (between the bones at the top) and the hip (between the ball and the rim of the socket), and not always painful.
Also: FAI, femoroacetabular impingement, hip impingement
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Infraspinatus
One of the four rotator cuff muscles, sitting across the back of the shoulder blade. It turns the arm outward and helps hold the ball of the arm bone in its socket. Reports mention it when describing wear, inflammation, or a tear in its tendon, usually best seen on MRI.
Also: infraspinatus muscle, infraspinatus tendon, rotator cuff muscle
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Joint effusion
Extra fluid inside the capsule that wraps around a joint. A small amount of fluid is normal and keeps the joint lubricated; a larger amount usually signals that something has stirred up the lining — an injury, arthritis, infection, gout, or inflammation — and is making more fluid than the joint can absorb.
Also: fluid in the joint, fluid on the knee, intra-articular effusion
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normal
Joint space narrowing
A reduced gap between the two bones of a joint on x-ray, which usually means the cushioning cartilage between them has thinned. It is one of the most common signs of ordinary joint wear and ageing, and is very often mild, gradual, and manageable rather than alarming.
Also: cartilage thinning, joint space loss, loss of joint space
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Labral tear
A break in the labrum, the ring of soft fibrous cartilage that deepens the socket of the shoulder or hip and helps hold the ball of the joint in place. Tears can come from a sudden injury, from repeated load over years, or simply from the shape of the joint itself. Common, and often found on scans of pain-free adults.
Also: SLAP tear, hip labral tear, labrum tear
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Labrum
A rim of firm cartilage that deepens the shallow sockets of the shoulder and hip, helping to grip the ball of the joint and keep it stable. Reports mention it when describing a fray, a tear, or age-related wear of this rim, which is best seen on MRI.
Also: cartilage rim, glenoid labrum, hip labrum
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Ligament tear
A break in one of the tough fibrous bands that hold two bones together at a joint. Tears range from a few stretched fibres (a sprain) to a complete rupture across the whole band. Most happen during a sudden twist, pivot, or impact, and the joint involved shapes how serious it is.
Also: ACL tear, MCL tear, ligament rupture
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Malalignment
Bones or joints that do not line up in their normal position or angle on a scan. It is a broad descriptive term covering anything from minor age-related shifts and old healed injuries to fresh injuries needing attention, so its importance depends on the cause and site.
Also: abnormal alignment, alignment abnormality, bones out of alignment
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Malleolus
These are the two bony bumps on the sides of your ankle, the knobs you can feel and see on the inner and outer ankle. They are the lower tips of the shin bones that cradle the ankle joint. Reports name them to point to one of those ankle bumps when describing a finding.
Also: ankle bone, ankle bone bump, ankle bump
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Meniscal tear
A split in one of the two C-shaped pads of cartilage that sit between the thigh bone and the shin bone inside the knee. These pads cushion and stabilise the joint. Tears can follow a sudden twist or develop gradually with age, and not every tear seen on a scan causes pain.
Also: bucket-handle tear, lateral meniscus tear, medial meniscus tear
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Meniscus
One of two C-shaped pads of cartilage inside the knee that sit between the thigh bone and the shin bone. They cushion the joint, spread load, and add stability. Reports mention them when describing wear, a tear, or age-related thinning, all best seen on MRI.
Also: knee cartilage, knee meniscus, lateral meniscus
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Metacarpal
These are the long bones inside the palm of your hand, the ones whose knuckles you see when you make a fist. There are five, one running from the wrist to the base of each finger. Reports name them simply to mark where in the hand a finding sits.
Also: hand bones, knuckle bones, metacarpal bones
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Metatarsal
These are the long bones in the middle of your foot, the ones you can feel under the top of the foot running from the arch toward the toes. There are five of them, one leading to each toe. Reports name them simply to point to where a finding sits in the foot.
Also: foot bones, long foot bones, metatarsal bones
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Olecranon
This is the bony point of your elbow, the firm tip you lean on when you rest your elbow on a table. It is the upper end of the larger forearm bone, hooking around the back of the elbow joint. Reports name it to point to the elbow tip when describing a finding.
Also: elbow bone, elbow point, elbow tip
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normal
Osteoarthritis
The most common form of joint wear. The smooth cartilage that lines the ends of the bones inside a joint gradually thins, the joint space narrows, and small bony ridges form along the edges. Extremely common with age — most adults over 60 show some of it on imaging, and many feel nothing from it.
Also: DJD, OA, degenerative arthritis
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Patella
The kneecap — the small, flat, roughly triangular bone that sits at the front of your knee. You can feel it move when you straighten your leg. It protects the knee joint and gives the big thigh muscle leverage to extend the leg. On a report it is usually just naming the front of the knee.
Also: knee bone, knee cap, kneecap
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Periosteal reaction
New bone laid down by the thin outer wrapping of a bone when that bone is irritated by injury, infection, or another process. It shows up as a fine line or layer along the bone surface on x-ray, and its pattern helps the radiologist judge how concerning it is.
Also: bone surface reaction, periosteal bone reaction, periosteal change
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Phalanx
This is simply the medical word for a finger or toe bone. Each finger has three of these small bones and the thumb and big toe have two, stacked end to end. Reports use the term to point precisely to which finger or toe segment a finding sits in.
Also: digit bone, finger bone, finger bones
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Plantar fascia
A thick band of fibrous tissue along the sole of the foot, running from the heel to the base of the toes. It supports the arch and acts like a spring while you walk. Reports mention it when describing thickening or inflammation, often called plantar fasciitis, best seen on MRI or ultrasound.
Also: arch tendon, foot arch band, plantar aponeurosis
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Radius (forearm bone)
This is one of the two bones in your forearm, the one on the thumb side that runs from the elbow to the wrist. It does most of the work at the wrist and rotates your hand palm-up and palm-down. Reports name it to point to that forearm bone when describing a finding.
Also: forearm bone, radial bone, radius
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Rotator cuff
A group of four small muscles and their tendons that wrap over the top of the shoulder and keep the upper arm bone seated in its shallow socket. Together they let you lift, turn, and steady the arm. Reports mention it when describing wear, inflammation, or tears in one of its tendons.
Also: cuff muscles, cuff tendons, rotator cuff tendons
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Rotator cuff tear
Damage to one of the four small muscle-tendons that wrap around the top of the shoulder and keep the arm bone seated in its socket. The tear can be a thin partial fray on the surface or a full break through the tendon. Many are gradual age-related wear; others follow a sudden injury.
Also: cuff tear, partial-thickness cuff tear, rotator cuff injury
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Scapula
The shoulder blade — the flat, triangular bone on each side of your upper back. It connects the arm to the collarbone and forms the socket of the shoulder joint. Many muscles attach to it, letting your shoulder move freely. On a report it is usually just naming where in the upper back or shoulder a finding sits.
Also: scapulae, shoulder blade, shoulderblade
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Subluxation
A partial slipping of a joint, where the two bones have lost some of their normal alignment but are still partly in contact. It sits between a normal joint and a full dislocation, and depending on the joint and cause it can range from minor to something needing prompt care.
Also: joint malalignment, joint slipping, partial dislocation
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Subscapularis
The largest rotator cuff muscle, sitting on the front of the shoulder blade between it and the rib cage. It turns the arm inward and helps hold the ball of the arm bone in its socket. Reports mention it when describing wear, inflammation, or a tear in its tendon.
Also: rotator cuff muscle, shoulder muscle, subscapularis muscle
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Supraspinatus
The top muscle of the rotator cuff, running across the top of the shoulder blade and over the ball of the arm bone. It starts the movement of lifting the arm out to the side. Reports mention it often because its tendon is the most common spot for shoulder wear and tears.
Also: rotator cuff muscle, shoulder muscle, supraspinatus muscle
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Tarsal bones
These are the seven bones at the back and middle of your foot, between the ankle and the long foot bones. They include the heel bone and the bones that form the arch. Reports name them to point to the ankle and midfoot region, or to one specific bone, when describing a finding.
Also: ankle bones, hindfoot bones, midfoot bones
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Tendinopathy
A catch-all term for a tendon that's been irritated, overloaded, or worn down over time. The tissue thickens, loses some of its tidy fibre pattern, and may show small areas of damage inside it. Common in shoulders, elbows, knees, and ankles, and often linked to repeated load rather than a single injury.
Also: tendinitis, tendinosis, tendon degeneration
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Tendon
A tough, rope-like band of tissue that connects a muscle to a bone, transmitting the muscle's pull so the joint can move. Tendons are found throughout the body. Reports mention them when describing wear, inflammation, or a tear, all of which are best seen on MRI.
Also: fibrous cord, muscle tendon, sinew
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Tibia
The shinbone — the large, strong bone at the front of your lower leg, the one you feel just under the skin along your shin. It carries most of your body weight between the knee and the ankle. On a report it is usually just naming where in the lower leg a finding sits. The word itself is plain anatomy.
Also: lower leg bone, shin, shin bone
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