Forty six patients with knee osteoarthritis will be randomly allocated into two groups: water-based exercises and land-based exercises. Both of them will receive a strengthening exercise protocol for lower limb muscles. A blind investigator will assess the patients before and immediately after, 3 months and 6 months following the interventions. The main outcomes will be pain, function and strength.

Forty six patients with knee osteoarthritis will be randomly allocated into two groups: water-based exercises and land-based exercises. Both of them will receive a strengthening exercise protocol for lower limb muscles. A blind investigator will assess the patients before and immediately after, 3 months and 6 months following the interventions. The main outcomes will be pain, function, physical performance and strength.

Inclusion Criteria:

• Moderate knee osteoarthritis (grade 2 or 3 using the Kellgren-Lawrence radiograph classification), diagnosed based on clinical and radiological criteria of the American College of Rheumatology
• No other lower limb and spine musculoskeletal disorders
• Independent gait
• Body mass index below 32
• Minimum of 4 points in the pain numeric rating scale during climb and descend stairs activities

Exclusion Criteria:

• Cognitive or psychological disorders
• Neurological disorders
• History of post-traumatic knee osteoarthritis
• Knee pain at least 12 months
• Prior surgery of the lower limbs or spine
• Fibromyalgia
• Rheumatoid arthritis
• Cardiovascular disease
• Participating in exercise programs and received treatment for the knee at least 3 months