Soft tissue rheumatism
Soft tissue rheumatism refers to a group of musculoskeletal pain syndromes that result from the pathology of extraarticular and extraosseous periarticular structures. These “soft tissue” structures include bursae, tendons and their synovial sheaths, entheses, muscles, and fasciae. A major point conceptually is that pain from soft tissue rheumatism is not caused by pathology of structures within the true joint (i.e., arthritis).
Soft tissue rheumatism may manifest as well-defined pathology of a single periarticular site or a regional myofascial pain syndrome. Although FMS is considered a form of soft tissue rheumatism in that patients experience soft tissue pain in the absence of articular disease, the underlying pathology is probably within the central nervous system (CNS).
Examples of involvement of single periarticular sites include bursitis, tendinitis, tenosynovitis, and enthesitis or enthesopathy (e.g., plantar fasciitis). Although diffuse connective tissue disorders, such as rheumatoid arthritis (RA) and seronegative spondyloarthropathy, may involve these soft tissue structures, involvement of a single or few periarticular sites in the absence of articular disease suggests the syndrome is attributable to chronic low-grade repetitive trauma or acute overexertion (e.g., the weekend warrior).