The posterior cruciate is one of the two cruciate ligaments which are important in stabilising the knee.
The torn posterior cruciate ligament
Injuries to the posterior cruciate ligament are less frequent than those of the anterior cruciate, because it requires a greater force to tear the ligament or pull it from the bone.
Symptoms of a tear include pain at the time of injury, which is not always severe, swelling of the knee which again is sometimes tense but not always so, and instability with a limp and feelings of 'giving way'.
Anatomical study of the posterior cruciate ligament with the knee flexed at 90°. Cho DK, Rosa SP, Prestes GB, da Cunha LAM, de Moura MFA and Filho ES. Rev Bras Ortop. 2014 Sep-Oct; 49(5): 494–498.
Posterior Cruciate Ligament: Current Concepts Review. Pache S, Aman ZS, Kennedy M, Nakama GY, Moatshe G, Ziegler C and LaPrade RF. Arch Bone Jt Surg. 2018 Jan; 6(1): 8–18.