Which activity will be difficult to perform for a patient with an anterior cruciate deficient knee joint?

Ans. is 'a' i.e. Walk downhill I could not get a satisfactory answer to this question in any of the book, not even from residents and consultants of orthopedics. The only clue is derived from these lines of Turek- "The type of injury that most frequently damage the anterior cruciate ligament are those that cause excessive external rotation and valgus of the flexed knee or forcible hyper extension of the knee while the tibia is in internal rotation. The knee may immediately collapse and become extremely painful; at the other extreme, it may not give way and the initial discomfort may be so trivial that person is misled into continuing his activity. Later, the knee may give way to sudden change of direction, squatting, walking on uneven ground, or descending stairs."