iarjimphIARJIMPHIARJIMPH2709-331Xhttps://doi.org/10.47310/iarjimph.2022.v03i02.025Idiopathic Primary Osteoarthritis of the Knee and Difficulties in DiagnosisOthmanFarhanTheyabAdilkhudhairMizeel50 Patients with presumably primary knee osteoarthritis were evaluated for involvement of other joints. The osteoarthritic group was compared with 50 age matched control group, suffering from low back pain. It was found that 56% of osteoarthritis cases have other joint involvement, compared to 6% of control group if the shoulder joint involvement is excluded (p-value < 0.05). The frequency of joint involvement (articular and or periarticular) in the osteoarthritic group was shoulders (50%), elbows (40%), Wrist (55%), metacarpophalangeal joints (34%), ankles (56%) and metatarsophalangeal joints (34%). On the other side the frequency of joint involvement in the control group (articular and or periarticular) was shoulders (40%), elbows (2%), wrists (6%), metacapophalangeal joints (6%), ankles (16%) and metatarsophalangeal joints (1%). The frequency of symptoms and signs outside the Knee in the Osteoarthritis group can be explained by either an underlying low grade inflammatory joint disease or by a degenerative process which is “Multifocal”. These possibilities will be explained later in the discussion. We conclude that careful clinical and laboratory evaluation, as well as long term follow up is necessary before a firm diagnosis of primary osteoarthritis is to be made. Further studies are needed to uncover the spectrum of what is considered a primary Knee Osteoarthritis and whether many of the causes could be not primary.