The deep lateral femoral notch sign, although uncommon, is subchondral fracture lines or cortical contour flattening appreciated in sagittal planes or lateral radiographs and is quite specific for ACL tear. It is caused by impact injury of the lateral femoral condylopatellar notch onto the tibia. A notch depth of over 1.5–2 mm is diagnostic.

Discoid meniscus is a normal anatomic variant that is seen in 0.8–3.0 % of knees, characterized by a wider than normal meniscal body that results in greater coverage of the tibia. It may lead to abnormal biomechanical forces across the knee. Watanabe and Takeda described three types of discoid menisci: incomplete, complete, and Wrisberg variant.

Two main causes are recognized in distal femoral fractures: high-energy trauma in young population (<40 years; male predominance) and low-energy trauma in osteoporotic population (>50 years; female predominance). Identification of articular surface involvement, fragmentation, and deformation of metaphysis and epiphysis in distal femur fracture are crucial in terms of surgical and nonsurgical procedures. Osteoporotic fractures can be problematic for fixation. Soft tissue injuries can be associated as meniscal and ligaments tears; neurovascular injuries can also occur but rarely. Femur fractures may be classified on the basis of Müller classification, in which category A are the extra-articular fractures, category B are partial articular factures (part of the articular surface remains attached to the diaphysis), and category C are the complete articular fractures (both condyles separated from diaphysis). Every category is subdivided based on fracture direction, grade, and complexity of fragmentation.