General Introduction to Rheumatic Diseases

Rheumatic diseases are among the oldest diseases recognized, and more than 100 diverse disorders affect the muscles, bony joints, and supporting structures of the musculoskeletal system (Table 36-1). The classification of rheumatic diseases is often difficult because of their unknown etiology and heterogeneity in their clinical presentation. Some of them are relatively more common, whereas many other conditions are rare (e.g., connective tissue diseases and disorders of collagen metabolism). This chapter focuses on the rheumatic diseases most likely to be seen by a physiatrist, in particular osteoarthritis (OA) and rheumatoid arthritis (RA). Both conditions are variable in manifestation, chronic in status, widespread in nature, and often take a progressive course. Other disorders, such as fibromyalgia, complex regional pain syndrome, and osteoporosis, are described in other chapters in this textbook.

Table 36-1 The Main Types of Rheumatic Diseases

Disease Group	Description	Examples
Degenerative and overuse syndromes	Diseases in which the predominant feature is repetitive trauma and/or “wear and tear” of cartilage or periarticular tissues, with minor secondary inflammation	Osteoarthritis Tendonitis Bursitis
Inflammatory arthropathies	Diseases characterized by chronic or recurrent joint inflammation of unknown cause; classified according to the pattern of joint involvement and associated features	Rheumatoid arthritis Psoriatic arthritis Spondyloarthropathies
Extraarticular rheumatism	Poorly understood disorders characterized by chronic or recurrent pain with no evidence of inflammation; primary pathology might be in the perception of pain rather than in the soft tissues	Fibromyalgia Nonspecific neck pain Nonspecific back pain
Connective tissue diseases	Autoimmune diseases of unknown etiology characterized by multisystem inflammation and damage	Systemic lupus erythematosus Polymyositis or dermatomyositis Scleroderma Vasculitis
Inherited disorders of connective tissue	Rare diseases caused by genetic abnormalities affecting the synthesis of structural molecules of the bone and connective tissues	Collagenopathies Mucopolysaccharidoses Osteogenesis imperfecta Ehlers-Danlos syndrome
Crystal-associated arthropathies	Diseases characterized by acute or recurrent inflammation caused by deposition of crystals in or around the joints	Gout Calcium pyrophosphate crystals Hydroxyapatite crystals
Infectious arthropathies	Diseases caused by invasion of joint tissues by microorganisms	Viral Bacterial Tuberculosis and fungi
Postinfectious arthropathies	Diseases triggered by previous exposure to infectious agents	Poststreptococcal Postchlamydial Postviral

OA and RA are the two most common rheumatic diseases and account for a large proportion of disability worldwide. Impairment to the musculoskeletal organ systems as a result of rheumatic conditions is the primary cause of functional limitations in the adult population. OA has been estimated to be the eighth leading cause of disability in the world and accounts for 2.8% of the total number of years of living with a disability. RA affects up to 1% of the adult population in developed countries, with 10% of these patients having severe disability. The prevalence of overall disability has been estimated at 20% of the adult and aging population.

The physical impairments, functional decline or lack of ability, decreased quality of life, lost productivity, and staggering costs of health care for rheumatic diseases such as OA and RA affect both the individual and society. The economic and social burden of these diseases can be overwhelming. This overall impact can be expected to increase with the incremental pace of aging of our world’s population.

One of the many challenges in studying rheumatic diseases is deriving epidemiologic data that can be used to better understand the factors that contribute to the initiation and progression of these diseases. With these data, significant progress can be made in the clinical diagnosis, medical management, surgical interventions, and rehabilitative care of patients.

The goal of this chapter is to describe the fundamental concepts and basic principles that a physiatrist needs to know to effectively address the impairments and disability that are associated with rheumatic diseases. We recommend that the rehabilitation-centered approach to these chronic and progressive illnesses include the following: (1) patient-defined problems are identified along with clinical and functional problems diagnosed by clinicians; (2) patients and providers focus on a specific problem, set realistic objectives, and develop an action plan for attaining these objectives in the context of patient preferences and readiness; (3) patients have access to educational services that teach the skills needed to carry out medical regimens, guide health behavior changes, and provide emotional and psychologic support; and (4) patients are contacted at specified intervals to monitor health status, identify potential complications, and check and reinforce progress in implementing the care plan. The rehabilitation of patients with rheumatic diseases demands an appropriately reasonable, systematically organized, and comprehensively coordinated approach that is both multidisciplinary and collaborative.

Kinesiology: The Structure and Function of Joints

Kinesiology is a significant part of the foundation for the practice of physical medicine and rehabilitation. It involves knowledge from anatomy, biomechanics, and physiology. The human body is composed of more than 200 joints, each with different shapes and functions. Joints are links between bones in the human body that control the movement of bony segments and provide stability. The knee joint, for example, joins the femur and tibia and allows the lower leg to swing freely. It also allows it to be stable during the stance phase of gait. Some joints provide the body with stability, whereas others provide with mobility. Most joints provide both mobility and stability. All the joints in the human body can be affected by rheumatic diseases. For this chapter, we will divide joints into three classifications: diarthrosis, amphiarthrosis, and synarthrosis.

A diarthrosis joint, also known as a synovial joint, consists of two reciprocally shaped bony articular surfaces and is a freely movable joint. The knee joint is an example of a diarthrosis joint. The ends of the adjoining bones are covered with a thin cartilaginous sheet, and the bones are linked by a ligament lined with synovial membrane. The synovial membrane secretes synovial fluid. Synovial fluid lubricates and smoothes the tendon movement.

The amphiarthrosis joint, sometimes called a fibrocartilaginous joint, is a junction between bones that is formed primarily by a fibrocartilage or hyaline cartilage. The interbody joint in the spine is an example. The amphiarthrosis joint is only slightly movable, allowing relatively restrained movements. It can also transmit and disperse forces between the bones separated by the fibrocartilage or hyaline cartilage.

The synarthrosis, or synarthodial, joint functions primarily to allow forces to be dispersed across a relatively large area of contact, thereby reducing the possibility of injury. The interosseous membrane of the radial–ulnar and tibial–fibular joints is a good example.

OA is a rheumatic disease that can affect one or multiple joints in the human body. OA is commonly seen in diarthrosis and amphiarthrosis joints, such as the hand, hip, knee, shoulder, and spine. The predominant feature of OA is the causal relationship between repetitive trauma, the “wear and tear” of the cartilage and periarticular tissues, with minor secondary inflammation.

RA is usually seen in multiple joints and presents symmetrically. RA is one of the rheumatic diseases that are characterized by chronic or recurrent joint inflammation of unknown cause. Similar to OA, RA is seen in all types of joints.

Joints of the human body can be affected by injury, increased demand, immobilization, or long-term bed rest. Diseases such as OA and RA also affect joints. Injury can occur if a large stress or load is placed on a joint. Constant excessive loading, repetitive over time, can also change the joint structure, leading to breakdown. Immobilization or long-term bed rest causes muscles around the joints to atrophy and weaken. It is just as important to understand that joints and articular surfaces need some load, such as gravity, to maintain proper integrity. If a load is not present, over time articular surfaces will progressively weaken and degenerate because of a lack of stimulus. Inflammatory disease processes can also disrupt the integrity of the joint. The above problems can affect and impair joint structure and eventually disrupt functions such as standing and walking. Severely advanced or progressive joint degradation can lead to disability.

An Overview of Common Rheumatic Diseases

Osteoarthritis

OA is the most common form of arthritis and affects nearly 21 million people in the United States. OA is the leading cause of chronic disability. The number of people diagnosed with OA is increasing steadily. The aging of the population, the increase in obesity, and the sports-related injuries of active baby boomers can be attributed to this increase. OA is a disease that involves degeneration in various structures of the joint, including cartilage, bone, synovium, muscles, and ligaments. This can result in stiffness, loss of mobility, swelling, and pain. In contrast to RA, OA is primarily a noninflammatory disorder, but inflammation eventually occurs and is progressive. OA generally occurs in weight-bearing joints, such as hips, knees, and the lower back. It also commonly occurs in the neck, the fingers, the base of the thumb, and the great toe. It rarely occurs elsewhere in the absence of stress or injury.

No single known cause of OA exists. Factors that might contribute to a diagnosis of OA include genetic disposition, age, injury, weight, stress on the joint, and previous surgery involving the joint. Age is the most commonly identified risk factor for OA of all joints. The prevalence of OA increases sharply for women after age 40 years and after age 50 for men. OA of the hand is more prevalent in women, whereas men are slightly more likely to have hip OA. Genetics is likely to contribute to the development of primary OA. Inhibited bone abnormalities or inherited traits (e.g., dysplasia, malalignment) that subject the joint to unusual stress increase the likelihood of its development.

No standard definition of OA is used by researchers and clinicians. A review of the literature showed the validity of the various definitions of hip OA has been barely investigated. Despite precise and extensive development, the American College of Rheumatology (ACR) criteria showed poor reliability and cross-validity in a primary care setting. No agreed criteria exist for knee OA in population studies. The radiographic scoring system of Kellgren and Lawrence ¹⁵ (Table 36-2) has been most used in the past. Although other methods have been developed, comparisons have not been performed. Data suggest that the presence or absence of a definite osteophyte read on a weight-bearing radiograph is the best method of defining knee OA for epidemiologic studies. Assessment of joint space narrowing might be better used in evaluating the disease severity.

Table 36-2 Kellgren-Lawrence Radiographic Grading Scale for Osteoarthritis of the Tibiofemoral Joint

Grade of Osteoarthritis	Description
0	No radiographic findings of osteoarthritis
1	Minute osteophytes of doubtful clinical significance
2	Definite osteophytes with unimpaired joint space
3	Definite osteophytes with moderate joint space narrowing
4	Definite osteophytes with severe joint space narrowing and subchondral sclerosis

The typical progression of OA involves the following events: (1) loss of cartilage matrix, which makes the joint more susceptible to further injury; (2) alterations to underlying bone associated with wear on the cartilage, with the development of osteophytes at the periphery of the affected joint; (3) release of debris of cartilage or bone fragments into the joint; (4) cartilage breakdown associated with synovial inflammation, which can lead to release of cytokines and enzymes that exacerbate the cartilage damage. Some examples of OA in different joints can be seen in Figure 36-1.

FIGURE 36-1 Typical deformities and x-ray findings in osteoarthritis of the spine (A), hands (B), hip (C), and knee (D).

Goals of OA therapy are to decrease pain, increase function in activities of daily living (ADL) and mobility, prevent and correct deformity, and slow disease progression. The treatment approach varies because of lack of inflammation and the influence of degeneration in joint integrity. Many pharmacologic options can be used for the treatment of OA. Conditioning muscles around joints with physical therapy and weight loss have been shown to improve symptoms and ADL. Application of heat and cold therapy and use of assistive devices have specific benefits. If OA progresses where conservative measures are not successful, joint replacement surgery is an option.

Box 36-1 lists the criteria for classification of OA of the hand, hip, and knee.

BOX 36-1 The American College of Rheumatology Criteria for the Classification of Osteoarthritis of the Hand, Hip, and Knee

Classification criteria for idiopathic osteoarthritis of the knee

Clinical and radiographic

Knee pain plus at least one of the following (91% sensitive, 86% specific):

• Age >50 yr

• Stiffness <30 min

• Crepitus plus osteophytes

Rheumatoid Arthritis

RA is defined as an autoimmune disease in which the joint lining and occasionally other tissues become inflamed as a result of overactivity of the body’s immune system.^5,⁷ RA is a chronic, systemic, inflammatory disorder of unknown etiology that primarily involves the joints. RA begins insidiously with generalized weakness, anorexia, fatigue, and vague musculoskeletal symptoms before the appearance of synovitis. RA affects about 1% of the adult population but causes more than 250,000 hospitalizations annually. RA is one of the most serious and disabling types of arthritic diseases and affects women 2 to 3 times more often than men. Like OA, RA encompasses a combination of events or a pattern of reactions that can result in joint injury.²⁶

Although RA is universal and found in all populations, prevalence and incidence rates vary in different ethnic groups. A low prevalence is found among African blacks, and a high prevalence is seen in rural Germany. Prevalence rates are influenced according to which set of criteria is used to diagnose RA and whether the RA is definite or probable. Genetic studies of RA show that there is a limited concordance of the disease in twins. No specific pattern of inheritance exists, although there is a twofold increase among first-degree relatives of patients with RA. Some examples of its effects on the hands and feet are shown in Figure 36-2.

FIGURE 36-2 Typical deformities and x-ray findings in rheumatoid arthritis of the hands and feet: swan-neck deformities (A), boutonnière deformities (B), ulnar deviations (C), and foot deformities (D).

Review of the literature presents various quantitative measures to assess RA in research trials and clinical care. No single “gold standard” is used to assess and monitor the status of patients with RA. Different measures have been used in research and clinical care, including laboratory tests, radiographic scores, formal joint counts, physical measures of functional status, global measures, and patient self-report questionnaires. These measures or assessment tools can address the activity of the disease, damage to the joint, both activity and damage, or long-term outcomes. Measures of disease activity (e.g., joint swelling) are reversible and can be improved over time, whereas measures of joint damage (e.g., radiographic scores) indicate disease progression.^22,²³

In evaluating new therapies for RA, randomized controlled trials provide the optimal method by comparing a therapy with a placebo or another therapy without selecting patients for specific therapies. Randomized trials in chronic diseases have important limitations. Examples of these limitations include relatively short observation, patient selection for inclusion and exclusion criteria, inflexible dosage schedules, influence of the design on results despite a control group, emphasis on group data instead of individual variations in treatment responses, and nonstandardized interpretation of adverse effects. Clinical trials in RA must be supplemented by long-term observational studies to assess the results of therapy in regard to long-term outcomes. Long-term outcomes include work disability, joint replacement surgery, and premature mortality. The patient self-report questionnaire is the most simple and effective method of collecting important long-term data from patients in routine clinical care.

Goals of RA therapy are to prevent or control joint damage, prevent loss of function, and decrease pain. Treatment measures are aimed at ameliorating inflammation after identifying active disease. Treatment is not considered curative, only palliative, aiming to relieve signs and symptoms of the disease. Management initially includes patient education, disease-modifying antirheumatic drugs (DMARDs) within 3 months, nonsteroidal antiinflammatory drugs (NSAIDs), low-dose systemic steroids, and physical and occupational therapy. Disease activity must be reassessed, and if the response to drugs is inadequate, then methotrexate or a biologic response modifier (BRM) should be considered. Surgery might be an option if drug failure is evident, the patient is more symptomatic, and structural joint damage occurs.

Box 36-2 lists the criteria for classification of RA.

BOX 36-2 American College of Rheumatology Criteria for the Classification of Rheumatoid Arthritis

From Arnett FC, Edworthy SM, Bloch DA, et al: The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis, Arthritis Rheum 31:315-324, 1988.

1. Morning stiffness: Morning stiffness in and around the joints, lasting at least 1 hour, before maximal improvement.

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