This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
[{'content': 'Locking of knee joint can be caused by -a) Osgood shalterb) Loose body in knee jointc) Tuberculosis of kneed) Medial meniscal partial tear \nSelect and explain. \nA. c, B. d, C. bd, D. ac', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Pathological locking of knee joint\n\nIt has already been explained that physiological locking of knee occur in full extension. It is due to action of muscle and geometry of articular surfaces of the knee.\nHowever some pathology of knee joint can cause locking of the knee, i.e., the knee is locked in partial flexion and there is inability to extend the knee for the last few degrees. This is frequently known as locking of the knee joint.\nLocking occurs because the fragments (bone or cartilage) get nipped between the condyles of tibia and femur and do not allow the extension : Knee is held in flexion.\nCauses of locking are : -\n\n\nMeniscal tear\nOsteochondral fracture\nLoose body in the knee\nOsteophytes fracture in osteoarthritis\nFractures tibial spine fragment\xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0\n\n\nHamstring spasm also does not allow the knee to get extended. However, this is not true locking as the pathology is outside the knee joint. Therefore, it is known as pseudolocking.', 'role': 'assistant'}]