Lateral knee compartment osseous pseudoligamentous instability

Five occurrences of intra-articular lateral knee compartment osseous pseudoligamentous instability associated with three cases of fractures of the posterior lateral femoral condyle are reported. The instability being located within the knee joint region was termed false in that it was due to fracture instability rather than the usual ligamentous, or true, instability. The main clinical diagnostic guide to this type of instability was a positive manual straight-knee adduction snap-click test that consisted of an initial snap followed in sequence by a click on release of adduction. The positive adduction snap-click test is an adjunct to the roentgenographic recognition of lateral knee compartment osseous pseudoligamentous instability.