The knee joint is the largest and most complex joint in the human body. Its functional stability is ensured by the joint action of body joints, ligaments, meniscus and surrounding muscles. The appearance of instability in just one of the above-mentioned structures leads to disruption of the knee function itself. In this paper the anatomy and biomechanics of the knee is discussed and the most important parts of the knee are described. In the following is described the etiology of patellar disorders - instability of the patella in the mediolateral direction (luxation, subluxation) and instability of the patella in the proximal-distal direction (patella alta and patella infera), as well as the etiology of chondromalacia of the patella, gonarthrosis, genu varum - knee deformation better known as "O" legs, genu valgus ("X" legs) and the etiology of ligament rupture (anterior and posterior cruciate ligament and medial and lateral collateral ligament). Furthermore, an analysis of the market was carried out, in terms of structural solutions that help in recovery from knee injuries, and a brief review of their effectiveness and quality was carried out. The knee joint is, unfortunately, one of the most frequently injured joints of the human body, which would mean that there are many structural solutions to this problem, but the fact that new products are constantly appearing on the market means that not all problems have been solved.