Psoriatic arthritis is a very important topic for any orthopaedic exam! Seronegative spondyloarthropathies affect approximately 10% of patients with psoriasis (Figure 1).
If the spine is affected, the human leukocyte antigen B27 (HLA-B27) is positive in more than 50% of cases. The clinical presentation of psoriasis in the cervical spine in similar to rheumatoid arthritis, but in general, it is different than ankylosing spondylitis (debatable and controversial) (Figure 2).
Psoriatic arthritis will have negative rheumatoid factor and negative antinuclear antibody (ANA) tests. Psoriatic arthritis presents itself with patchy plaques and scales that can be red or silver-like in color (Figure 3). It usually occurs before the arthritis andis commonly found on the patient’s elbows or knees; generally observed at the extensor surface of the extremity. The physician should always check the elbows!
In about 20% of the cases, the arthritis occurs before the scales and the plaques. This will make the patient wonder, “why is the knee not getting better?” “Why is the swelling not going away?” (Figure 4)
Psoriatic arthritis most commonly affects the hands, feet, spine and sacroiliac (SI) joints (Figure 5).
The hand can reveal very important information for clinical practice and for exams. In the hand you will find dactylitis, also referred to as sausage digits. The physical will also find a pencil-in-cup deformity, where the DIP is involved (Figure 6). Some believe this deformity is an x-linked recessive trait.
Nail pitting, fragmentation, and discoloration are common, as well as onycholysis, the lifting of the nail plate that starts distally. The patient may similarly develop arthritis mutilans, uveitis (Figure 7), Achilles tendonitis, plantar fasciitis, and conditions that are similar to Reiter’s syndrome (reactive arthritis).
The treatment of arthritis is largely pharmaceutical including nonsteroidal; methotrexate or TNF-alpha inhibitors Occasionally surgery will be performed, however there is a high infection rate with surgery and the surgeon should try to avoid skin incisions through the active psoriatic lesions (there is a high colonization rate with bacteria). The surgeon should do preoperative treatment of such lesions.
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