The Arthritic Knee: Etiology and Patterns of Disease
Knee osteoarthritis (OA) is a multifactorial disease, and OA cases are affected by both genetics and environment to varying degrees. Knee OA is one of the leading causes of global disability. Idiopathic OA is the most common form of arthritis with still unknown pathogenic etiology and considerable contribution of genetic factors. One of the mechanisms of cartilage degradation in OA is enzymatic proteolysis of the extracellular matrix by metalloproteinases. MMP-1, produced by chondrocytes and synovial cells, is a major proteinase of the MMP family. Five phenotypes of knee OA have been identified: “minimal joint disease phenotype,” “strong muscle strength phenotype,” “severe radiographic OA phenotype,” “obese phenotype,” and “depressive mood phenotype.” Knees with degenerative changes in the medial compartment constituted the majority of cases (63 %). The average age of patients is 72 years for those with varus disease, 79 years for those with valgus disease, and 84 years for those with patellofemoral arthritis (PFA). Bilateral involvement was common only in patients with PFA (79 %). There is a female predominance in valgus and patellofemoral disease.
KeywordsKnee Osteoarthritis Etiology Idiopathic Patterns of disease
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