Inflammatory Arthritis - General Tips and Tricks

Question 1

What do the terms ‘loose-pack’ position, ‘tight-pack position’ and ‘universal stress pain’ refer to in the context of synovitis.

Answer 1

A joint with increased intra-articular pressure is most comfortable in the position that minimises the pressure. This position, generally mild to mid-flexion, is termed the ‘loose-pack’ position, in which the capsule is at its loosest and can accommodate an increase in fluid and soft tissue. Conversely, the positions in which the capsule is naturally tight—the ‘tight-pack’ positions at the extremes of range of movement—are the positions that are the first to be painful when synovitis is developing and are the first movements to become restricted. For example, gleno-humeral synovitis is most comfortable with the arm adducted and internally rotated as if in a sling and the patient will naturally adopt this attitude at rest. Conversely, the opposite movements, abduction, and external rotation, are the earliest affected and most uncomfortable since these maximise intra-articular pressure. This uneven distribution of pain, maximal in all tight-pack positions, is called ‘universal stress pain’—the most sensitive sign of synovitis, occurring even before there is visible swelling or restricted movement (figure 5).

Joint damage is associated with a more even spread of pain throughout the range of movement.

Question 2

What is the characterisation of arthritis? How is it described?

Answer 2

Question 3

What is the most common cause of acute inflammatory arthritis?

Answer 3

Crystal synovitis (although septic arthritis should always be considered).

Question 4

What are the main causes of chronic inflammatory monoarthritis?

Answer 4

1. Infection (Brucella, mycobacterium, borreliosis, others)
2. Monoarticular presentation of oligo- or polyarthritis (JIA, reactive arthritis, seronegative spondyloarthropathy)
3. Foreign body (e.g., plant thorns)
4. OA
5. Recurrent hydrarthrosis
6. Osteonecrosis
7. Chronic regional pain syndrome
8. Neuropathic (Charcot’s) joints
9. Tumours, including pigmented villonodular synovitis (PVNS)

The aetiological diagnosis of chronic monoarthritis usually requires a synovial biopsy with pathological and bacteriological examination and in selected cases PCR technique. In many cases, no specific cause can be identified.

Question 5

What are some differentials for chronic polyarthritis?

Answer 5

1. RA
2. PsA (tends to be asymmetrical and can involve DIPs and/or the SIJ)
3. JIA
4. CTD
   
   • SLE
   • Primary Sjogren’s syndrome
   • MCTD
5. Chronic sarcoid arthropathy may evolve with polyarthritis, but also oligoarthritis - the inflammed joint tends to show a nodular asymmetric aspect as opposed to the spindle shape of psoriatic synovitis.
6. OA with CPPD
7. Chronic polyarticular gout
8. Viral arthritis associated with parvovirus B19, HIV and hepatitis (may present as polyarthritis, but tends to have a more acute onset than RA or the connective tissue diseases).
9. Still’s disease (in adults or children) is characterised
10. Autoinflammatory disorder (recurrent episodes of polyarthritis – but also mono- and oligoarthritis - with fever point to the diagnosis of rare hereditary disorders with a common phenotype of lifelong, recurrent inflammatory episodes, characterised by inflammatory symptoms such as fever, abdominal pain, diarrhoea, rash, or arthralgia. Between the fever episodes, patients with most of these syndromes generally feel healthy and function normally. These syndromes include familial Mediterranean fever, cryopyrin-associated periodic syndrome and others.)