Background:  Knee osteoarthritis (KOA) is a common joint disorder leading to considerable pain and locomotor disability in lower limb function. Locomotor disability, which is difficulty in activities of daily living related to lower limb function, can be the consequence of KOA, so early diagnosis and management may improve quality of life.

Objective: To assess the contribution of radiological osteoarthritis of the knees to disability in the activities of daily living related to lower limb function.

 Methods: One hundred twenty Iraqi KOA patients (104 females and 16 males) who were attending to Rheumatology Unit, Full history was taken and complete clinical examination was done for all patients. Wight-bearing X-rays of both knees (anteroposterior and lateral view) were taken for patients and were graded according to Kellgren and Lawrence scale.

Results: The frequency of locomotor disability, was 62.50% for men and 72.11% for women (p=0.431). The frequency of radiological osteoarthritis of the knee was 50% for men and 40.37% for women (p=0.651). There was significant statistical differences between; locomotor disability, and increased age, morning stiffness, muscle wasting & BMI (p=0.000, p=0.003, p=0.002 and p=0.028 respectively). There was no statistical significant association between; KOA radiological grading, and gender, morning stiffness, BMI & lower limb locomotor functions disability (p=0.651, p=0.357 and p=0.972 respectively).

Conclusion:  Radiological osteoarthritis of the knee is only weak independent predictors of locomotor disability. Patient's age, pain of the knees, muscle wasting, morning stiffness and obesity seem to be the most important independent determinants of locomotor disability.