Systemic lupus erythematosus (musculoskeletal manifestations)

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Musculoskeletal manifestations in patients with systemic lupus erythematosus are common and often symptomatic. Characteristic manifestations are seen in approximately 80% of patients, but many less characteristic manifestations are important to be aware of. Multiple different presenting complaints are possible.

For a general discussion, and for links to other system specific manifestations, please refer to the article on systemic lupus erythematosus.

Clinical picture

Symmetric polyarthritis

Seen in 75-90% of patients with varying degrees of severity, it represents the most common presenting complaint clinically, usually worse in the morning. Areas of involvement most commonly include the small joints of the hand, knees, wrists, and shoulders.

Deforming non-erosive arthropathy

When articular abnormalities are present, approximately 5-40% will develop a deforming non-erosive arthropathy due to ligamentous laxity (not articular destruction) and muscle contracture. This is more common in those with long-standing disease. In the hands, this can be classically seen on Nørgaard views but absent on PA views and are termed as reducible deformities. The presence of deformities without erosions can diffrentaite from rheumatoid arthritis.

Due to their frequently reducible nature, deformities are seldom disabling.

Myositis

Clinically observed in 30-50% of patients, true myositis occurs in approximately only 4% of patients. Elevated serum levels of muscle enzymes may or may not be observed. Fibromyalgia may be associated and contribute to the overall fatigue.

Radiographic features

Plain radiograph

Plain radiographs demonstrate soft tissue swelling of the involved joints, periarticular osteoporosis, and normal joint spaces. Carpal instability may be seen in 15% of patients .

Hands and feet

Symmetric involvement of interphalangeal joints is most common, showing swan neck and boutonniere deformities, subluxation with ulnar deviation at MCP joints, subluxation of the 1 metacarpophalangeal joint, a widened forefoot, and hallux valgus.

Joint space narrowing is uncommon, and when present is likely due to disuse atrophy or pressure from an adjacent subluxed bone. Altered stresses across the joint may also cause a "hook erosion" at the metacarpal heads due to capsular stress, mimicking findings of rheumatoid arthritis. This is more often observed on the radial side.

Spine

Spinal manifestations are uncommon and nonspecific, but a higher incidence of spinal findings is seen in those with deforming arthropathy. Up to 10% may have atlantoaxial subluxation/dislocation.

Osteonecrosis

The most common location of osteonecrosis is the femoral head, but nearly any site may be affected. This is more commonly seen in younger patients and those with Raynaud phenomenon and other signs of vasculitis. This may also be seen as a complication of steroid therapy.

Calcifications

Linear or nodular calcification in the subcutaneous and deep soft tissues may be seen, especially around the small joint of extremities. Associations with diuretic therapy and vitamin D supplementation has been documented.

Insufficiency fracture

Those with systemic lupus erythematosus are at increased risk for insufficiency fracture, possibly due to disuse demineralization or osteopenia secondary to steroid therapy, or both.

Osteomyelitis and septic arthritis

Lupus patients are at increased risk of bacterial and mycotic infections, in large part due to steroid administration and renal disease. Osteomyelitis and septic arthritis involvement are less common than infection elsewhere.

Ultrasound

Most symptomatic patients have ultrasound features of inflammation (i.e. tenosynovitis) . Bone erosions can also be noted and tend to be mild and monoarticular.

Tendinopathies

Tendon pathologies include tenosynovitis, bursitis, spontaneous tendon weakening and eventually rupture, more affecting weight-bearing joints as a complication of steroid therapy. Imaging features also include capsular swelling, edematous and proliferative tenosynovitis and synovial hypertrophy .

Subcutaneous nodules

They can be present, particularly over the flexor tendons of the hand.