Cervical spine damage is common in psoriatic arthritis especially in older forms and it is rarely initiated by symptomatic atloid-axoid instability. Spinal involvement is frequently associated with sacroiliac dysfunction, the cervical spine involvement is observed in 35%-75% of cases with two types of radiological lesion. Upper cervical spine localization often manifests as C1-C2 arthritis, lower cervical spine involvement is manifested by syndesmophytes, ossification of the anterior longitudinal ligament and posterior inter apophyseal osteoarthritis. Our case is about a late onset upper cervical spine instability in a 45-year-old patient who has been treated for 20 years for rheumatism and has checked for paraesthesia's of the four limbs and gait difficulty that have been evolving over the last 3 months and the outcome of this case is that a C1-C2 instability must be systematically checked for in view of the appearance of deficient signs.