When one talks of the knee 'giving way' it means that the knee suddenly and unexpectedly is unable to support the person, and the leg just buckles, leading to stumbling or falling.
Causes of giving way, giving out or buckling of the knee
There may be a number of reasons for the knee suddenly giving out:
- a loose body in the joint
- a piece of torn meniscus catching in the joint
- a piece of loose joint cartilage catching in the joint
The impact of knee instability with and without buckling on balance confidence, fear of falling and physical function: the Multicenter Osteoarthritis Study. Nguyen U-SDT, Felson DT, Niu J, White DK, Segal NA, Lewis CE, Rasmussen M and Nevitt MC. Osteoarthritis Cartilage. 2014 Apr; 22(4): 527–534.
The association between antagonist hamstring coactivation and episodes of knee joint shifting and buckling. Segal NA, Nevitt MC, Welborn RD, Nguyen SDT, Niu J, Lewis CE, Felson DT and Frey-Law L., Osteoarthritis Cartilage. 2015 Jul; 23(7): 1112–1121.