Keywords: Chapter 26, Bones and Joints
Achondroplasia
A failure of endochondral bone growth, usually caused by a Mendelian dominant defect, that results in shortened extremities.
Alkaline phosphatase
An enzyme that hydrolyses phosphate esters, is secreted into the serum by osteoblasts and is used as a diagnostic marker for increased osteoblastic metabolic activity.
Ankylosing spondylitis
An inflammatory, RA-like arthritis, of the spine and sacro-iliac joints, which is seronegative for rheumatoid factor. It is most common in young men in their 20s and is strongly associated with HLA-B27 antigen.
Ankylosis
Firm fixation of a joint due to fusion of the bones.
Apatite-associated crystal deposition arthritis
A type of crystal deposition disease in which crystals of hydroxyapatite are deposited in articular cartilage and joint capsule. Release of the crystals into the joint space causes severe acute arthritis. Milwaukee shoulder is a variant of apatite deposition arthritis occurring in a previously traumatized and torn rotator cuff of the shoulder.
Avascular (aseptic) necrosis of bone
Bone infarcts resulting from occlusion of small vessels, usually at the ends of the long bones, produce multiple subarticular bone defects. Pathogenesis Nitrogen embolization in divers with caisson disease fat emboli, in transplant and other patients on steroids for immunosuppression, idiopathic in Perthe disease (avascular necrosis of the femoral head), and osteochondritis dessicans (subarticular infarcts in a variety of weight-bearing bones).
Calcium phosphate deposition disease (CPDD, pseudogout or chondrocalcinosis)
An arthritis of unknown etiology resulting from excessive deposition of calcium pyrophosphate dihydrate crystals bilaterally within the midzone of articular cartilage of weight-bearing joints. This condition is common in the elderly, but is usually asymptomatic and discovered as an incidental finding on x-ray. An inflammatory arthritis may occur when calcium pyrophosphate crystals are released into the joint space where they provoke an inflammatory reaction.
Callus
New growth of incompletely organized bony tissue surrounding and uniting the broken ends of bone at a fracture site.
Charcot joint
Arthritis of neuropathic origin, usually seen in the knees and hips in patients with syringomyelia or tabetic syphilis who have lost pain sensation and position sense in these joints due to posterior column spinal cord degeneration.
Chondrosarcoma
The second most common primary malignant tumor of bone. It occurs in adults age 40 to 60, often in the medullary cavity of pelvis, ribs or long bones, and is cartilaginous.
Collagen, type II
The type of collagen that predominates in cartilage matrix
Diaphysis
The mid-portion or shaft of a long bone. It is composed of an outer dense cortex and an inner medullary region containing bone spicules and interspersed marrow.
Eburnation
The wearing away of articular cartilage to yield a hard, osseous articulating surface.
Enchondroma
benign, cartilaginous neoplasm usually arising within the medullary cavity of bone. It is usually solitary, most common from ages 20 to 50, and most often seen in the small bones of the hand or foot. Ollier multiple enchondromatosis is a rare, non-hereditary form of this disease.
Endochondral ossification
Process of bone formation at cartilaginous epiphyseal growth plates.
Epiphysis
A region of bone, located at the ends of long bones, composed of cartilage in embryonic life, but subsequently becoming osseous with the closure of the growth plates after adolescence.
Ewing sarcoma
A highly malignant, destructive bone tumor of childhood, arising more often in the medullary space of the diaphysis of long bones. The tumor is composed of small, poorly differentiated round cells with highly glycogenated cytoplasm, possibly of neuroectodermal origin. An 11:22 chromosomal translocation is often present in Ewing sarcoma.
Felty syndrome
RA plus splenomegaly and leukopenia.
Fibrillation
The formation of crevices and cracks in the articular cartilate in osteoarthritis.
Fibrous dysplasia
Expanding radiolucent mass lesion of bone primarily in children and adolescents. The lesion is often the site of a pathologic fracture. Microscopically there is replacement of bone by benign fibrous tissue containing dysplastic woven bone trabecula.
Ganglion cyst
Small, non-neoplastic cystic tumor arising in the joint capsule or adjacent tendon sheath, usually in the wrist.
Giant cell tumor of bone
Rapidly enlarging, radiolucent tumor of young adults, ages 30 40, most often arising at the junction of epiphysis and metaphysis in long bones.
Giant cell tumor of tendon sheath
Benign tumor of giant cells in the vicinity of a joint. This lesion is probably non-neoplastic, and is closely related to pigmented villonodular synovitis. The latter condition is characterized by an exuberant, heavily pigmented villous synovial overgrowth containing pigmented cells, lipid-laden histiocytes, and multinucleated giant cells.
Gout
A disorder of uric acid metabolism characterized by hyperuricemia, with resulting deposits of urates in joints, kidneys and soft tissues. The disorder is characterized by recurrent bouts of acute arthritis, usually in the lower extremities.
Growth Plate
A transverse disc of cartilage at the base of the epiphysis where all growth in length of the bone occurs. The cartilage cells of the growth plate are arranged in longitudinally oriented stacks.
Hebreden nodes
Fusiform enlargement of distal interphalangeal joints due to osteophyte formation in osteoarthritis. These painful nodular enlargements are seen mostly in women, in a familial pattern.
Hydroxyapatite
A complex crystal of calcium phosphate, (Ca)10 (P04)6(OH)2. Bone and cartilage mineral is composed almost exclusively of hydroxyapatite.
Hypertrophic osteoarthropathy
Periosteal inflammation and fibrosis leading to enlargement and clubbing of the distal phalanges. The etiology of this condition is unknown. It is usually associated with intrathoracic neoplasms such as bronchogenic carcinoma, thymoma or mesothelioma.
Intramembranous bone formation
Bone growth that occurs in the absence of cartilage in developing membrane bones such as skull.
Joint mouse
A broken and dislodged osteophyte that becomes a movable body in the joint space. With time, the dislodged bone fragment becomes coated with a layer of regenerative cartilage.
Lyme disease
A systemic disease, due to spirochetal infection by Borrelia burgdorferi, characterized by a RA-like arthritis, first identified in adults and children living in a wooded village of Connecticut (Lyme) near the Connecticut river. Clinically dangerous features of Lyme disease include myocarditis, cardiac arrhythmias and encephalitis.
Malignant fibrous histiocytoma (MFH)
A solitary malignant neoplasm of variable histology, composed primarily of fibroblastic cells arranged in a storiform (cartwheel) pattern, with interspersed, foamy histiocyte-like cells. The tumor occurs in a wide range of ages (10 to 80) and locations, more commonly arising in the metaphyses of long bones, but can arise in any site.
Matrix vesicles
Extracellular, membrane-bound vesicles in the matrix of bone, cartilage and dentin that serve as the initial nucleation site for biological mineralization.
Metaphysis
A region of rapidly growing trabecular bone underlying the base of the cartilaginous growth plate.
Myositis ossificans (fibrodysplasia ossificans progressiva)
Abnormal, ectopic cartilage and bone formation of muscles tendons and ligaments. Pathogenesis: Osteoprogenitor cells which are normally present but quiescent in skeletal muscle, give rise to masses of callus-like cartilage and bone in muscles and soft tissues following minimal trauma. The victims may be exhibited in carnival shows as petrified men.
Non-ossifying fibroma
A benign, usually solitary fibromatous lesion of childhood that arises in the metaphysis of long bones, most commonly in tibia and femur.
Osteoarthritis (degenerative joint disease)
A slowly progressive condition of unknown etiology, seen in almost everyone after the age of 50, and characterized by degeneration and thinning of articular cartilage surfaces, associated with the formation of bone spurs (osteophytes) at the articular margins.
Osteochondroma
The most common benign tumor of bone, appears as a cartilage-capped lateral bony projection from the metaphysis, just below the growth plate, also known as an exostosis.
Osteogenesis imperfecta
A hereditary defect in collagen type I synthesis causes deficient intramembranous and cortical bone formation. The result is fragile bones with frequent fractures and progressively worsening deformity of the weight-bearing bones.
Osteoid
Precalcified bone matrix composed mostly of type I collagen
Osteoid osteoma
Small, solitary, painful cortical lesion with radiolucent central nidus surrounded by a sclerotic, hyperdense zone of reactive bone formation.
Osteomalacia
Adult onset rickets. A failure of calcification resulting from inadequate serum levels of calcium or phosphate or both occurs after the closure of the growth plates.
Osteomyelitis
A chronic progressive bacterial infection localizing in bone with subsequent purulent inflammation, localized bone necrosis (sequestrum), reactive periosteal bone growth (involucrum), and deformity due to unilateral unbalanced inhibition of bone growth.
Osteopetrosis (marble bone disease)
A hereditary abnormality of osteoclasts causes defective bone resorption and a failure of bone remodeling. The result is bones that are excessively dense on x-ray due to unopposed osteoblastic activity. These bones become hard (like marble), but are brittle and more often fractured than are normal bones.
Osteoporosis
A diffuse reduction of bone mass and x-ray density, more often occurring in post-menopausal females. This is the most common metabolic disease in the world and is the underlying cause of 350,000 vertebral and hip fractures annually in the U.S., costing an estimated 1 billion dollars. Pathogenesis: bone resorption exceeds bone formation to a mild degree over a long period leading to osteopenia. There is no defect in bone mineralization.
Osteosarcoma
The most common primary malignant tumor of bone; peak incidence is at age 10 to 20 (except for osteosarcoma secondary to Paget disease which occurs in the 60s to 70s). This is an x-ray-dense tumor arising in the metaphysis that invades through the cortex, causing elevation of the adjacent periosteum (Codman triangle).
Paget disease of bone (osteitis deformans)
A disease of the elderly in which repeated episodes of bone resorption are closely followed by excessive and disorderly bone formation resulting in a deformed skeleton with increased bone mass.
Pannus
An inflammatory, hypertrophic synovial projection in rheumatoid arthritis that migrates from the joint capsule out over the articular surfaces causing chondrolysis of the underlying articular cartilage.
Potts disease
A destructive form of tuberculous arthritis that most frequently involves the spine.
Primary gout
Is gout of idiopathic origin, most often in males in a familial pattern, due to over-synthesis of uric acid from purine nucleotides.
Proteoglycan
(Formerly referred to as acid mucopolysaccharide), this is the predominant, non-collagenous component of cartilage matrix. Proteoglycans are large molecules with a central protein core and attached polysaccharide molecules extending from the protein core as do bristles in a bottle brush.
Reiter syndrome
Combined urethritis, polyarthritis and conjunctivitis of unknown etiology; associated with HLA-B27 antigen in up to 90% of patients. The condition usually follows a venereal exposure and is almost exclusively seen in males.
Remodeling
The final phase in healing of a fracture site in which the dead original bone ends and inefficiently placed spicules of callus are resorbed and replaced by osteoblastic action. The final result is new lamellar bone well-oriented to withstand mechanical forces across the fracture site.
Rheumatoid arthritis (RA)
A systemic, autoimmune inflammatory disorder affecting primarily multiple small joints of the hands and feet with production of synovitis followed by destructive changes in the articular cartilage. Females are affected three times more commonly than males. Onset is usually in the 30s to 40s.
Rheumatoid factor
An immune complex found in serum and synovial fluid of patients with RA, composed of immunoglobulin autoantibodies directed against and complexed with normal serum IgG. The titer of serum rheumatoid factor correlates directly with the severity of RA.
Rheumatoid nodule
A subcutaneous nodule, seen in RA, usually periarticular in location, and composed of a central zone of zone of fibrinoid necrosis surrounded by palisading histiocytes and fibroblasts.
Rickets
A failure of the calcification process in bone and cartilage seen in children and adolescents with functioning growth plates.
Secondary gout
A condition of hyperuricemia due to excessive synthesis and catabolism of purines by neoplasms with rapid cell turnover, as occurs in acute Leukemias.
Septic (suppurative) arthritis
Infectious arthritis is usually monarticular, involving one of the large joints and is most often caused by staphylococci, streptococci, pneumococci, gonococci or tuberculous organisms. In young adults, the gonococcus predominates. Typically, the affected joint is painful, shows redness and swelling and contains purulent synovial fluid.
Sjogren syndrome
RA associated with salivary gland enlargement and dryness of the eyes and mouth. The salivary glands are infiltrated with lymphocytes.
Still disease
RA in children. Rheumatoid factor is often absent.
Subluxation
Overriding dislocation of articulating bone ends.
Synovial sarcoma
A highly malignant soft tissue tumor arising in the vicinity of a joint. It is characterized by a biphasic microscopic pattern with intermixed atypical spindle cells and nests of epithelial cells with cleft-like spaces.
Tophus
A deposit of monosodium urate crystals in the soft tissues of the joint capsule, the ear lobe, or elsewhere.
Ulnar deviation
A deformity characteristic of RA in which the metacarpals and phalanges are displaced toward the ulnar side of the forearm (flipper hand).