The rupture of the cranial cruciate ligament is the most common cause of hind limb lameness in dogs. The multifactorial etiopathogenesis is discussed in this manuscript. The causes include immunological and inflammatory factors, genetic components and the plastic deformation of the tibia – the latter resulting in altered biomechanics of the stifle. Many therapeutic options have been developed depending on the suspected cause. Tibia osteotomies represent the newest therapeutic approach to restore the physiological biomechanics of the stifle. The best known techniques are certainly the tibial tuberosity advancement (TTA) and the tibial plateau levelling osteotomy (TPLO). While the TTA results in a broader tibia, the TPLO results in a reduced tibia plateau angle. In our study we examined the proximal tibia of 100 dogs with intact cranial cruciate ligament (group I) and 100 dogs with ruptured cranial cruciate ligament (group R). Tibia width and the tibial plateau angle (+/- standard deviation) were measured. The tibia width was 39.43 +/- 9.13mm in group I, and 40.83 +/- 8.98mm in group R. The tibia plateau angle of dogs in group I was 27.20 +/- 3.39°, in group R 28.58 +/- 3.76° respectivley. Logisitc regresssion analysis indicated that the odds for a rupture of the cruciate ligament increases by 34% per millimeter decrease of the tibia width and about 15% per degree increase of the tibia plateau angle. Therefore our study confirms that the odds for a rupture increases with a small tibia width and a steep tibia plateau angle. This explains the good outcome of both surgical techniques. Inadequate breeding is the suspected cause for the plastic deformation of the proximal tibia.