We report a study of 28 women with severe primary gonarthrosis followed for 1 year. Variations in bone mineral density and in functional behaviour of knee extensors and flexors were studied before and after implantation of uncemented total knee prosthesis. A functional deficit was noted in the extensor apparatus, which increased in the first 6 months following surgery. This strength was not improved 1 year following the arthroplasty, but it was more efficient as shown by the reduction of muscle fatigue. Flexor strength was conserved and a pathological muscle balance was maintained, reaching maximum efficiency over a smaller joint range.Résumé Etude des variations de la densité minérale osseuse et du comportement des extenseurs et fléchisseurs du genou avant et après implantation d'une prothèse totale non cimentée chez 28 femmes souffrant d'une gonarthrose primaire sévère et suivies pendant une année. Un déficit fonctionnel de l'appareil de l'extenseur à été noté avant l'intervention et a augmenté dans les six premiers mois suivant la chirurgie. La force d'extension n'était pas améliorée une année après l'arthroplastie, mais l'action était meilleure à cause d'une moindre fatiguabilité du muscle. La force des fléchisseurs a été conservée et un équilibre musculaire a été maintenu, en arrivant à l'efficacité maximale sur une plus petite amplitude articulaire.

Articular cartilage (AC) has an essential function in the best performance of the human body's joints, but it has a limited capacity of regeneration and the initial cause that develops the pathological degenerative process is still unknown. It is believed that cartilage damage due to knee osteoarthritis is mechanically induced. Thus, to investigate such a phenomenon and analyze and simulate the biomechanical behavior of the knee joint, a virtual 3D knee prototype was created using a commercial finite element code, which includes the femur, tibia and AC as a deformable solid model. This paper shows the stress distribution found in AC in the femur and the tibia. The factors were obtained by applying a load range of 700 to 2800 N, 0º in flexion and different cases with physiological valgus variation and a graphical model of stress prediction to the femur cartilage was created using the stress behavior with the different factors. In general, the results show that different factors like being overweight (load> 700N) and misalignment (valgus variation) could damage the AC because they increase the stress magnitude and it comes into the cyclic damage range (5-10 MPa), which progressively produces articular cartilage damage and enhances the osteoarthritis phenomenon due to mechanical factors.