Medical words often describe a structure, a change in that structure or a category of care. This glossary keeps those meanings separate. A definition explains a word; it does not establish a diagnosis or determine what care is appropriate. Sources appear at the end of each letter section. The anatomy guide puts tissue terms in context, while disc conditions and osteoarthritis explain related diagnostic language.

A

Aggrecan
A large molecule in cartilage’s extracellular matrix that carries carbohydrate chains. It belongs to the proteoglycan family and contributes to cartilage’s resistance to compression.
Annulus fibrosus
The fibrous outer ring of an intervertebral disc. Its layered structure surrounds the gel-like nucleus pulposus and helps the disc withstand forces placed on it.
Antibiotic
A category of medicine used against bacterial infections. Antibiotics act by killing bacteria or making it harder for them to grow and multiply within the body.
Antibiotic resistance
A change in bacteria that allows them to resist an antibiotic’s effects and continue growing. The term refers to bacteria, rather than a person becoming resistant.
Arthroplasty
An operation that replaces, reshapes or realigns a joint surface. Joint replacement is a form of arthroplasty, but the broader term also includes other surgical approaches.
Articular cartilage
The smooth layer of hyaline cartilage covering the surfaces of bones within a synovial joint. It lies inside the joint cavity and is bathed in synovial fluid.

Sources: Aggrecan, Annulus fibrosus, Antibiotic, Antibiotic resistance, Arthroplasty, Articular cartilage.

B

Biocompatibility
How a material performs in a particular use in the body, including the body’s response to it. The meaning depends on the material’s setting and purpose.
Biofilm
A community of microorganisms embedded in a matrix they produce. The cells stick together and often attach to a surface, rather than floating separately in fluid.
Bone spur
An extra growth of bone, also called an osteophyte. In osteoarthritis, NIAMS describes these growths at joint edges as part of changes involving bone and other tissues.

Sources: Biocompatibility, Biofilm, Bone spur.

C

Cartilage
A smooth, resilient connective tissue. It covers bone ends at many joints and has a matrix containing collagen and other molecules; it is distinct from bone.
Cervical
Relating to the neck region of the spine. The term identifies a location: a cervical disc or cervical nerve root is located in that region.
Chondrocyte
A specialized cartilage cell that produces and maintains the surrounding matrix. That matrix is made mainly from collagen and proteoglycans, rather than being composed of cells alone.
Collagen
A structural protein in the extracellular matrix of connective tissues. It is present in cartilage, bone, tendons, ligaments and skin, whose overall tissue properties differ.

Sources: Cartilage, Cervical, Chondrocyte, Collagen.

D

Decompression
An approach intended to make more space around a nerve or the spinal cord. Laminectomy is an operation that can remove tissue to relieve this pressure.
Degenerative disc disease
A term for disc degeneration associated with pain. The disc degeneration review distinguishes a painful degenerate disc from structural or age-related changes in a disc without pain.
Discectomy
An operation removing all or part of a spinal disc. The spelling diskectomy describes the same operation; it is different from replacing a disc with an implant.
Discography
A diagnostic procedure examining a disc’s possible role in pain. The sciatica reference describes measuring disc-space pressure and using contrast material to examine changes within the disc.

Sources: Decompression, Degenerative disc disease, Discectomy, Discography.

E

Extracellular matrix
The network of material outside cells that provides structural and biochemical support. Its composition varies between tissues and can include collagen and water-binding carbohydrate-containing molecules.

Sources: Extracellular matrix.

F

Facet joint
A synovial joint between neighboring vertebrae at the back of a spinal segment. Facet joints help guide and limit the movement of the segment.
Fibroblast
A connective-tissue cell that makes extracellular matrix and collagen. Fibroblasts contribute to the tissue framework and have an important role in the process of wound healing.
Foramen
An opening in bone. In the spine, the term is used for openings through which nerve roots branch away from the spinal cord and leave the spine.
Fusion
Surgery joining spinal bones permanently so that movement between the joined bones stops. Bone graft material is used to help establish the union of the bones.

Sources: Facet joint, Fibroblast, Foramen, Fusion.

H

Herniated disc
A disc in which material pushes through a weakened part of its outer structure. It may press on a nearby nerve or on the spinal cord.
Hip resurfacing
An operation covering the head of the thighbone with a cap and placing a cup in the hip socket. It differs from a total hip replacement.

Sources: Herniated disc, Hip resurfacing.

I

Imaging
Tests that create pictures of body structures. NIAMS describes magnetic resonance imaging as producing images that can show soft tissues, including discs, ligaments and nerve roots.
Inflammation
A response involving immune cells after tissue damage. The wound-healing reference describes this stage as clearing damaged cells, bacteria and debris from the affected tissue.
Intervertebral disc
The cartilaginous structure between neighboring vertebrae. It permits slight movement, helps hold the vertebrae together and acts as a shock absorber within the spine.

Sources: Imaging, Inflammation, Intervertebral disc.

L

Laminectomy
Surgery removing some or all of the lamina, part of the bone forming a vertebra. The operation can make more room for spinal nerves or the cord.
Lumbar
Relating to the lower back region of the spine. The location is different from the cervical spine in the neck and the thoracic spine in the chest.

Sources: Laminectomy, Lumbar.

M

Mesenchymal stem cell
A cell type also described as a mesenchymal stromal cell. The reference describes its capacity to develop into various specialized cells, including cartilage and bone-forming cells.

Sources: Mesenchymal stem cell.

N

Nerve root
A nerve branching from the spinal cord and leaving the spine. Pressure on or irritation of a root can be associated with pain, numbness or weakness.
Nucleus pulposus
The gel-like center of a spinal disc, surrounded by the annulus fibrosus. The disc reference describes its role in distributing pressure and absorbing impact.

Sources: Nerve root, Nucleus pulposus.

O

Orthobiologics
A category of biologic substances studied or used in orthopedic care. OrthoInfo discusses the term in relation to fracture healing and distinguishes stronger evidence from limited evidence.
Osseointegration
A direct connection between living bone and the surface of an implant. The reference distinguishes this contact from an interface with soft tissue between bone and implant.
Osteoarthritis
A joint disease involving changes and breakdown in joint tissues over time. It can affect cartilage, bone and other structures and may cause pain, stiffness and reduced movement.
Osteonecrosis
Death of bone tissue after its blood supply is disrupted. NIAMS describes how affected bone can break down and how involvement of a joint can cause arthritis.
Osteotomy
Surgery that cuts a bone to change alignment. For the knee, MedlinePlus describes approaches involving the shinbone or thighbone rather than replacing the joint surfaces.

Sources: Orthobiologics, Osseointegration, Osteoarthritis, Osteonecrosis, Osteotomy.

P

Partial knee replacement
An operation replacing the damaged surface in a limited part of the knee. It is also called unicompartmental replacement and differs from replacing all damaged compartments.
Physiatrist
A doctor specializing in physical medicine and rehabilitation. NIAMS includes physiatrists among professionals involved in osteoarthritis care and describes them as supervising exercise programs.
Physical therapy
Care addressing movement and daily function, also called physiotherapy. It is a health profession that includes assessment, patient education and physical approaches tailored to an individual.
Platelet-rich plasma
A preparation of blood plasma containing a higher concentration of platelets than usual. This is a description of its composition, rather than a claim about clinical benefit.
Polyethylene
A plastic used in artificial joint bearings. The ultra-high-molecular-weight form is described in the materials reference as having long molecular chains and resistance to wear.
Premarket approval
An FDA regulatory process requiring scientific evidence to provide reasonable assurance of safety and effectiveness for an intended use. It concerns a defined device and use.
Prosthesis
An artificial part replacing a body structure. MedlinePlus uses this term for an artificial hip joint; a prosthesis is distinct from the body’s own bone or cartilage.
Proteoglycan
A protein carrying carbohydrate chains called glycosaminoglycans. Proteoglycans form part of the extracellular matrix, where they interact with collagen and contribute to its water-rich character.

Sources: Partial knee replacement, Physiatrist, Physical therapy, Platelet-rich plasma, Polyethylene, Premarket approval, Prosthesis, Proteoglycan.

Q

Quorum sensing
Communication between bacterial cells that allows responses to the density of a local bacterial population. The reference describes it as a way bacteria coordinate gene activity.

Sources: Quorum sensing.

R

Radiculopathy
A condition affecting a spinal nerve root. MedlinePlus describes disc herniation as a possible cause; symptoms depend on where the affected root is located.
Registry
A collection of information about care and its outcomes. Joint replacement registries use collected data to monitor performance and support work on quality and patient safety.
Rehabilitation
Care concerned with keeping, regaining or improving abilities needed in daily life. MedlinePlus notes that goals vary according to the condition, affected abilities and their severity.
Revision surgery
An operation performed again on an artificial joint. NIAMS describes revision in relation to complications such as loosening, dislocation, wear or infection after hip replacement.
Rheumatoid arthritis
An autoimmune disease in which the immune system attacks the body’s tissues. It often affects the joint lining and can cause pain, swelling, stiffness and loss of function.

Sources: Radiculopathy, Registry, Rehabilitation, Revision surgery, Rheumatoid arthritis.

S

Sciatica
Pain extending down the leg from the lower back. It may occur with weakness or numbness; the word describes a pattern of symptoms rather than an operation.
Spinal stenosis
Narrowing of spaces in the spine that can put pressure on nerves or the spinal cord. The condition may produce symptoms or be present without noticeable symptoms.
Spondylosis
A term for degenerative changes in the spinal column. Cervical spondylosis concerns the neck; changes can involve vertebrae, nerve openings and facet joints.
Synovial fluid
Fluid within the cavity of a synovial joint. It lubricates the cartilage-covered moving surfaces and participates in transporting nutrients and waste for nearby cartilage cells.
Synovial joint
A freely movable joint enclosed by a capsule and containing a fluid-filled cavity. The bone ends have articular cartilage, and a synovial membrane lines the capsule.

Sources: Sciatica, Spinal stenosis, Spondylosis, Synovial fluid, Synovial joint.

T

Total disc replacement
An operation replacing a degenerated spinal disc with an artificial implant. The disc replacement reference describes an aim of retaining movement as an alternative to spinal fusion.
Total hip replacement
An operation replacing the hip’s ball and socket surfaces with artificial components. It is distinct from replacing only part of the hip or covering existing surfaces.
Total knee replacement
An operation replacing damaged knee joint surfaces with artificial parts. The components attach to bone and provide bearing surfaces; partial replacement addresses a more limited area.

Sources: Total disc replacement, Total hip replacement, Total knee replacement.

V

Vertebra
A bone of the spinal column; vertebrae is the plural. The bones form the segmented spine, with a canal that surrounds and protects the spinal cord.

Sources: Vertebra.