Answer:
Transient Patellar Dislocation
Findings- Images demonstrates bone marrow contusions of medial patellar facet and lateral femoral condyle. There is also interruption of medial patellar retinaculum fibers with associated edema and fluid-like signal consistent with partial thickness tear . chondral defect also seen in inferomedial patella.
Discussion- Transient patellar dislocation (TPD) is a common cause of acute traumatic hemarthrosis in young active patients. TPD is thought to occur either as a result of a noncontact injury with internal rotation of the femur and valgus position of the knee while on a planted foot (most common), or direct blow to the medial aspect of the patella. When the patella spontaneously relocates after dislocation, bone marrow contusions of the medial patellar facet and lateral femoral condyle occur owing to impaction injury. In addition, chondral or osteochondral fractures may also be seen in one or both of these locations. Injury to the medial patellar retinaculum is typically seen after TPD.
Reference- MUSCULOSKELETAL IMAGING CASES The McGraw-Hill Radiology Series
Contributed By: Dr. Arun Chelladurai MD, Dr. Karunakaran M. Kalathi MD
Consultant Radiologists, Aarthi Scans, Thirunelveli, Tamilnadu, India
Transient Patellar Dislocation
Findings- Images demonstrates bone marrow contusions of medial patellar facet and lateral femoral condyle. There is also interruption of medial patellar retinaculum fibers with associated edema and fluid-like signal consistent with partial thickness tear . chondral defect also seen in inferomedial patella.
Discussion- Transient patellar dislocation (TPD) is a common cause of acute traumatic hemarthrosis in young active patients. TPD is thought to occur either as a result of a noncontact injury with internal rotation of the femur and valgus position of the knee while on a planted foot (most common), or direct blow to the medial aspect of the patella. When the patella spontaneously relocates after dislocation, bone marrow contusions of the medial patellar facet and lateral femoral condyle occur owing to impaction injury. In addition, chondral or osteochondral fractures may also be seen in one or both of these locations. Injury to the medial patellar retinaculum is typically seen after TPD.
Reference- MUSCULOSKELETAL IMAGING CASES The McGraw-Hill Radiology Series
Contributed By: Dr. Arun Chelladurai MD, Dr. Karunakaran M. Kalathi MD
Consultant Radiologists, Aarthi Scans, Thirunelveli, Tamilnadu, India