This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Joint disorders, Subject name: Orthopaedics
The deformity that is most commonly seen in primary osteoahritis of knee joint? 
Select and explain. 
A. Genu valgum, B. Genu recurratum, C. Genu varus, D. Procurvatum
C: Genu varus
Answer: C: Genu varus 
Explanation: Deformity seen is varus of the knee, flexion-abduction external rotation of the hip Osteoahritis occurs in elderly people, mostly in the major joints of the lower limb, frequently bilaterally. The hip joint is commonly affected in a population with western living habits, while the knee is involved more commonly in a population with Asian living habits i.e., the habit of squatting and sitting cross-legged. Pain is the earliest symptom. It occurs intermittently in the beginning but becomes constant over months or years. Initially, it is dull pain and comes on staing an activity after a period of rest; but later it becomes worse and cramp-like, and comes after activity. Other symptoms are A coarse crepitus, Swelling, Stiffness, a feeling of &;instability&; of the joint, and &;locking&; resulting from loose bodies and frayed menisci. REF:Maheswari 9TH ED pg: 296