Background: Knee osteoarthritis is the most common joint disease and a major cause of functional limitation and pain in adults. The aim of this literature review is to review the existing evidence regarding the impact of exercise in people with knee osteoarthritis concerning physical and functional outcomes. The secondary aim is to provide both healthcare professionals and patients with updated and high-quality recommendations for the management of this condition. Methods: A systematic search was performed at Pubmed, Scopus and Web of Science databases, limiting the studies to English, French and Portuguese language, from 2010 to May 2020. Eligible studies were randomized control trials or clinical control trials that compared an intervention consisting of an exercise programme in adult participants with knee osteoarthritis against no intervention. Results: A total of 4499 studies were retrieved and 19 articles met the inclusion criteria. Beneficial effects of exercise were found on pain and strength. Regarding function, functional performance and quality of life, evidence is controversial. Both strengthening and aerobic exercise showed positive effects and both aquatic and land-based programmes presented improvement of pain, physical function and quality of life. Relatively to stretching, plyometric and proprioception training, no concrete conclusions can be taken. Conclusion: Exercise programmes appear to be safe and effective in knee osteoarthritis patients, mainly regarding pain and strength improvement. Pilates, aerobic and strengthening exercise programmes performed for 8-12 weeks, 3-5 sessions per week; each session lasting 1 h appear to be effective. Both aquatic and land-based programmes show comparable and positive effects.