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

It has been explained that ACL is taut in extension, and prevent anterior gliding of tibia an femur. When one walks downhill, he tries to keep the knee in extension to maintain the balance and In extension, ACL is required to prevent anterior gliding of tibia. Therefore a person with ACL deficient knee will have difficulty in going downhill. Opposite is true for PCL. When one climbs upstairs, he keeps the knee in flexion most of the time. PCL is taut in flexion and prevent posterior gliding of tibia. Therefore PCL deficient knee will have difficulty in climbing upstairs.