Osteoarthritis (OA) is one of the most common causes of disability around the globe, especially in aging populations. The main symptoms of OA are pain and loss of motion and function of the affected joint. Hyaline cartilage has limited ability for regeneration due to its avascularity, lack of nerve endings, and very slow metabolism. Total joint replacement (TJR) has to date been used as the treatment of end-stage disease. Various joint-sparing alternatives, including conservative and surgical treatment, have been proposed in the literature; however, no treatment to date has been fully successful in restoring hyaline cartilage. The mechanical and frictional properties of the cartilage are of paramount importance in terms of cartilage resistance to continuous loading. OA causes numerous changes in the macro- and microstructure of cartilage, affecting its mechanical properties. Increased friction and reduced load-bearing capability of the cartilage accelerate further degradation of tissue by exerting increased loads on the healthy surrounding tissues. Cartilage repair techniques aim to restore function and reduce pain in the affected joint. Numerous studies have investigated the biological aspects of OA progression and cartilage repair techniques. However, the mechanical properties of cartilage repair techniques are of vital importance and must be addressed too. This review, therefore, addresses the mechanical and frictional properties of articular cartilage and its changes during OA, and it summarizes the mechanical outcomes of cartilage repair techniques.

Talar avascular necrosis (AVN) is a devastating condition that frequently follows type III and IV talar neck fractures. As 60% of the talus is covered by hyaline cartilage, its vascular supply is limited and prone to trauma, which may eventually lead to AVN development. Early detection of AVN (Hawkins sign, MRI) is crucial, as it may prevent the development of the irreversible stages III and IV of AVN. Alertness is advised regarding non-obvious conditions that may cause this complication (sub chondroplasty, systemic lupus erythematosus, diabetes mellitus). Although, in stages I–II, AVN may be treated with non-surgical procedures (ESWT therapy, non-weight bearing) or joint-sparing techniques (core drilling, bone marrow aspirate injections), stages III–IV require more advanced procedures, such as joint-sacrificing procedures (hindfoot arthrodesis/ankle arthrodesis), or replacement surgery, including total talar replacement (TTR) or combined total ankle replacement (TAR). The advancement of 3D-printing technology and increased access to implant manufacturing are contributing to a rise in the production rates of third-generation total talar prostheses. As a result, there is a growing frequency of alloplasty procedures and combined total ankle replacement (TAR) surgeries. By performing TTR as opposed to deses, the operator avoids (i) delayed union, (ii) a shortening of the limb, (iii) a lack of mobility, and (iv) the stiffening of adjacent joints, which are the main disadvantages of joint-sacrificing procedures. Simultaneously, TTR and combined TAR offer (i) a brief period of weight-bearing restriction, (ii) quick pain relief, and (iii) preservation of the length of the limb. Here, we summarize the most up-to-date knowledge regarding AVN diagnosis and treatment, with a special focus on the role of TTR.