X-Ray of both hands in a 48 year old male patient. Erosive arthropathy involving both hands. Multiple erosions can be seen in the metacarpophalangeal and the proximal interphalangeal joints bilaterally, (the first and second finger joints on both hands). The radiocarpal joint (joining the radius to the carpal bones of the hand) shows secondary degenerative changes and joint space reduction. Conclusion: Psoriatic Arthritis.
Radiography and Psoriatic Arthritis
Two classic signs of Psoriatic Arthritis on X-Ray are bony proliferations and erosion as clearly seen in Image 1. Erosions (or osteolysis) are typified by the destruction of bone tissue and can be seen on imaging to have ‘fuzzy margins’ or outlines. There can also be loss of joint space as demonstrated in both radiocarpal joints in the above image. Another common sign of Psoriatic Arthritis on X-Ray is known as the ‘pencil in cup’ deformity and happens when the tip or distal head of a bone becomes pointed (like a sharpened pencil), and the neighbouring surface becomes rounded or ‘saucerised’ due to erosion (See Image 2 below).
X-Ray of phalanges demonstrating a common sign of erosive changes
in Psoriatic Arthritis, the classic ‘pencil-in-cup’ deformity.
Psoriatic Arthritis most commonly starts at the outer proximities of the body and will often affect the hands first followed by the feet. It can also affect the sacroiliac joints. There can sometimes be spinal involvement characterised by stiffness of the neck and spine, if this occurs it is known as Spondylitis. Less frequently involved are the knees, elbows, ankles and shoulders(1). One of the hallmark features of Psoriatic arthritis is a condition called enthesitis; enthuses are the sites where tendons or ligaments join the bones and when inflammation occurs at these sites, pain and tenderness usually follow. Common sites of pain are the back of the heel (tendinitis in the Achilles tendon) and the sole of the foot (plantar fascitis) and around the elbows. Dactylitis is another inflammatory problem associated with Psoriatic Arthritis; this is a swelling of the tendon that runs along the length of the finger or toe and makes the digit appear swollen or ‘sausage-like’. Ultrasound examinations of an affected digit demonstrate underlying synovitis (inflammation of the synovial membrane) and tenosynovitis (inflammation of the tendon)(2).
Photograph shows severe Dactylitis. The fingers appear sausage-like; shaping and definition of the fingers have been lost due to the severe inflammation. Findings: Arthritis Mutilans – This is the rarest and most destructive form of Psoriatic Arthritis occuring in less than 1% of all cases(3).
Psoriasis is the most prevalent autoimmune disease in the United States and in total 125 million people worldwide, around 2–3 % of the total population, have psoriasis(4). Psoriasis is a chronic skin disease characterised by itchy, red scaly patches, little spots and plaques. The definitive cause of psoriasis is not known but it is characterised by an inflammatory reaction thought to be triggered by a dysfunction in the normal immune response. Psoriatic arthritis is an inflammatory disease of the joints and will develop in up to 30 % of patients diagnosed with psoriasis(5).
Psoriatic arthritis can be asymmetrical whereby the disease does not affect the same joints on both sides of the body equally. The asymmetrical form is the most common and usually mild, involving 3 or less joints in the body and affects around 70 % of patients. The symmetrical type affects around 25 % of patients and affects joints on both sides of the body to equal degrees. This type tends to be more severe and disabling.
1. ‘Psoriatic Arthritis’. The Johns Hopkins University School of Medicine and the Johns Hopkins Arthritis Center. Retrieved 2011-05-04.4.
2. Olivieri I, Padula A, Scarano E et-al. Dactylitis or “sausage-shaped” digit. J. Rheumatol. 2007;34 (6): 1217-22. Rheumatol. (pdf) – Pubmed citation.
3. Fuller KS. Pathology: Implications for the Physical Therapist. Third Edition. St.Louis: Saunders Elsevier; 2009.
4. World Psoriasis Day consortium. National Psoriasis Foundation: Statistics.
5. ‘About psoriatic arthritis’.. National Psoriasis Foundation. Retrieved 2008-08-31.