This chapter divided into two parts first parts is on the knee injuries and another part is medial collateral ligament injuries of the knee. Knee injuries in India are common, mostly and increasing because of road traffic accidents especially by two wheelers and sports injuries. The knee is one of the most commonly injured joints because of its anatomic situation, its structure and exposure to external forces, knowledge of basic anatomy is important to understand the complicated injury; because the knee has many important ligaments, meniscal and muscles around. Osseous structures, extra-articular structures and intra-articular structures are three broad categories of knee injuries. The medial collateral ligament (MCL) is the commonest injured ligament around the knee. The main focus of this chapter is on motion of the normal knee joint and function of the ligaments, acute traumatic lesions of ligaments, clinical assessment of knee injuries, radiologic evaluation of knee injuries, nonoperative treatment of knee injuries, classification of ligaments injuries, injuries of posterolateral complex of the knee joint, treatment of the knee joint, rehabilitation, knee dislocations, medial collateral ligament injuries of the knee, etc.