Knee osteoarthritis (OA) is one of the common diseases which causes pain and disability with increasing age. In developed countries, it is said to be one of the ten diseases which decreases functionality most.

Knee osteoarthritis (OA) is one of the common diseases which causes pain and disability with increasing age. In developed countries, it is said to be one of the ten diseases which decreases functionality most. With a prevalence between 22% - 39%, 7% of which are patients who are over 65 years old, and when examined world-wide, it is stated that knee OA is seen 18% of women and 9,6% of men. Knee OA is characterized by pain, and; functional loss and progressive mobility where motions are required a physical activity of lower extremity. The disease causes 80% of restriction of motions and 25% of restriction of daily life activities. Additionally, along with the loss of proprioception, it can be seen defects of static and dynamic postural stability and the loss of balance. The factors of disease cause reduced muscle strength, defects of functionality of muscles and reduced workout capacity. According to the radiographic classification of Kellgren and Lawrence, quadriceps muscle weakness is frequently seen without atrophy and pain in early phases of knee OA of which degree is 0 or 1. If the symptoms are accompanied by a knee pain, the weakness of muscles will show an increase more and cause dysfunction and progression of disease. An increase of force in the muscles of quadriceps and hamstring plays a positive role for stability and mobility of joints and pain tolerance.

In the literature, studies with intra-articular HA injection in the treatment of knee OA are frequently seen, but the number of studies about the co-injection of HA, CS and GA is scarcely any. At the same time, studies investigating the effect of intra-articular viscosupplementation injection on isokinetic muscle strength was not observed. Therefore, the investigators aimed at investigating the effects of HA, CS and GA injection on isokinetic quadriceps and hamstring muscle strengths in our study.

Inclusion Criteria:

• being between 40-65 years of age,
• being diagnosed with Stage 3 and 4 knee OA according to the Kellgren-Lawrence classification

Exclusion Criteria:

• any lower extremity deformity (knee flexion contracture, knee hyperextension, varus and valgus deformities),
• septic arthritis, rheumatoid arthritis,
• major dysplasia,
• congenital anomalies, acromegaly, primary osteochondromatosis,
• Ehler-Danlos syndrome,
• neuropathic arthropathy,
• hyperparathyroidism, hypothyroidism,
• diabetes mellitus,
• active synovitis,
• severe knee traumas,
• previous surgery and in the last year,
• knee arthroscopy, injections and fracture history and pregnancy