Deformation due to arthrosis of the hip joint affects 40 % of the total number of patients with osteoarthritis, which is from 7 to 25 % of the adult population. For the activity of the pathological process evaluation we studied biochemical changes in the metabolism of collagen, namely: glycosaminoglycans (GAG), hydroxyproline (HP) fractions, collagenase, hyaluronidase activity, etc. Objective. To determine the biochemical changes in blood serum and articular cartilage depending on the form of progression of idiopathic coxarthrosis. Methods. 23 patients were examined (8 (34.8 %) men, 15 (65.2 %) women, age 45‒75 years and more) with idiopathic arthrosis of the hip joint IV stage (Kellgren–Lawrence). Progression forms of idiopathic coxarthrosis were distinguished: group I — rapid (the period from the initial to the final stage of the disease was 5 years and less), II — moderate (5‒10 years), III — slow (over 10 years). Collagenase activity, HP fractions, total GAG content were determined in patients’ blood serum, and collagen content was determined in the cartilage tissue of the femoral head. Results. Compared with the age reference norm in the blood serum of patients of group I activity collagenase increased to 114 %, in II and III — 122 and 135 %, respectively; the content of the free fraction of GP — up to 111, 169, 128 %, respectively; GAG concentrations — up to 110, 122, and 135 %, respectively; protein-bound HP was reduced to 60% in group II, up to 84 % — in group III. In cartilage tissue, the GAG content decreased in group III to 63 %, II — 55 %, I — 47 %; collagen — 32, 25, 24 % in accordance. Conclusions. The course of idiopathic coxarthrosis is determined by metabolic changes in the components of the organic basis of connective and cartilaginous tissues in blood serum. The most profound changes were found in the synthetic phase of HP metabolism, especially in the group with a rapid course disease. A decrease in the content of organic components of connective tissue (GAG and collagen) was determined