The stifle joint is the equivalent of the human knee joint. The main joint is between the femur and tibia, but there is also a joint between the femur and patella.
Conditions of the stifle joint are common in dogs and cats. Common conditions include cranial cruciate ligament rupture, patellar luxation and meniscal injury. We have further information on these conditions here:

Publications from Publications from Movement Vets surgeons on stifle problems
Innes, JF, Morton MA, and Lascelles BDX. 2023. ‘Minimal clinically-important differences for the ‘Liverpool Osteoarthritis in Dogs’ (LOAD) and the ‘Canine Orthopedic Index’ (COI) client-reported outcomes measures’, Plos One, 18.
Innes JF, Barr AR. Clinical natural history of the postsurgical cruciate deficient canine stifle joint: year 1. J Small Anim Pract. 1998 Jul;39(7):325-32. doi: 10.1111/j.1748-5827.1998.tb03723.x. PMID: 9693418.
Innes JF, Costello M, Barr FJ, Rudorf H, Barr AR. Radiographic progression of osteoarthritis of the canine stifle joint: a prospective study. Vet Radiol Ultrasound. 2004 Mar-Apr;45(2):143-8. doi: 10.1111/j.1740-8261.2004.04024.x. PMID: 15072147.
Innes JF, Bacon D, Lynch C, Pollard A. Long-term outcome of surgery for dogs with cranial cruciate ligament deficiency. Vet Rec. 2000 Sep 16;147(12):325-8. doi: 10.1136/vr.147.12.325. PMID: 11058021.
Baird, AEG, Carter, SD, Innes, JF, Ollier, WE, Short, AD (2014). Genetic basis of cranial cruciate ligament rupture (CCLR) in dogs. Connective tissue research, 55(4), 275-281. https://doi.org/10.3109/03008207.2014.910199