Introduction: Osteoarthritis (OA) is a common joint disorder, with the knee being one of the most frequently involved sites. Knee OA causes pain and stiffness and can lead to considerable disability and consequently to impaired quality of life.

Aim of the work: Clinical evaluation of participant with painful knee OA to detect the possible causes of pain knee OA.

Patients and Methods: Our study included 50 knee OA patients, attending to Sohag university hospitals rheumatology and rehabilitation outpatient clinic. They were divided according to pain into 2 groups. Group 1 with painful OA and group 2 with painless OA. Both groups were age and sex-matched.

Results: Our study showed that the group 1 participants had more varus deformities, more and significant effusion and Baker cyst. Among painful OA patients, all factors showed non-significant relation to the degree of VAS.

Conclusion: Our study found that knee effusion and Baker cyst were the main possible causes of pain in knee OA.