- Discussion:
    - it is important that the foot gets flat on the floor as quickly as possible after heel strike;
    - if plantar flexion bumper provides too much resistance at heel strike, the knee may buckle;
         - SACH foot with a firm heel cushion may cause this;
    - at midstance, knee stability is enhanced when the ankle is solid;
    - if foot is allowed to dorsiflex because of a soft dorsiflexion bumper or poor alignment, the knee may buckle;
    - hyperextension of knee joint on prosthetics side may be caused by too soft a heel cushion because it allows excessive compressibility of
         heel cushion as the effect of allowing ground reaction force to pass anterior to the knee access between heel strike and mid stance;
         - this causes hyperextension of the knee joint