Biological aspects of early osteoarthritis.
OBJECTIVE
Early OA primarily affects articular cartilage and involves the entire joint, including the subchondral bone, synovial membrane, menisci and periarticular structures. The aim of this review is to highlight the molecular basis and histopathological features of early OA.


METHODS
Selective review of literature.


RESULTS
Risk factors for developing early OA include, but are not limited to, a genetic predisposition, mechanical factors such as axial malalignment, and aging. In early OA, the articular cartilage surface is progressively becoming discontinuous, showing fibrillation and vertical fissures that extend not deeper than into the mid-zone of the articular cartilage, reflective of OARSI grades 1.0-3.0. Early changes in the subchondral bone comprise a progressive increase in subchondral plate and subarticular spongiosa thickness. Early OA affects not only the articular cartilage and the subchondral bone but also other structures of the joint, such as the menisci, the synovial membrane, the joint capsule, ligaments, muscles and the infrapatellar fat pad. Genetic markers or marker combinations may become useful in the future to identify early OA and patients at risk.


CONCLUSIONS
The high socioeconomic impact of OA suggests that a better insight into the mechanisms of early OA may be a key to develop more targeted reconstructive therapies at this first stage of the disease.


METHODS
Systematic review, Level II.
Experimental Orthopaedics and Osteoarthritis Research, Saarland University, Kirrbergerstrasse, Building 37, 66421, Homburg, Germany. henning.madry@uks.eu
Henning
H
Madry
Frank P
FP
Luyten
Andrea
A
Facchini
D000818:Animals; D001696:Biomechanical Phenomena; D001842:Bone and Bones / Q000473:pathology; D002358:Cartilage, Articular / Q000473:pathology; D018925:Chemokines / Q000502:physiology; D019902:Chondrocytes; D003094:Collagen / Q000502:physiology; D004195:Disease Models, Animal; D018450:Disease Progression; D005109:Extracellular Matrix / Q000473:pathology; D020022:Genetic Predisposition to Disease; D006801:Humans; D007378:Interleukins / Q000502:physiology; D008592:Menisci, Tibial / Q000473:pathology; D010003:Osteoarthritis / Q000235:genetics / Q000473:pathology / Q000503:physiopathology*; D011509:Proteoglycans / Q000502:physiology; D013583:Synovial Membrane / Q000473:pathology
D018925:Chemokines; D007378:Interleukins; D011509:Proteoglycans; D003094:Collagen