Insidious Onset

RA has an insidious, slow onset over weeks to months in 55% to 65% of cases.¹⁴ The initial symptoms may be systemic or articular. In some people, fatigue, malaise, swollen hands, and diffuse musculoskeletal pain may be the first nonspecific symptoms, with joints becoming involved later. Involvement of tendon sheaths early in the process can focus attention on periarticular structures. In retrospect, the patient often can identify one joint that was involved first, quickly followed by the others. Asymmetric initial presentations (often with increased symmetry developing later in the course of disease) are common. The reason for the symmetry of joint involvement compared with other forms of arthritis, such as the seronegative spondyloarthropathies, is unknown.

Morning stiffness is a cardinal sign of inflammatory arthritis that can appear even before pain and may be related to the accumulation of edema fluid within inflamed tissues during sleep. Morning stiffness dissipates as edema and products of inflammation are absorbed by lymphatics and venules and returned to the circulation by motion accompanying the use of muscles and joints. To be specific for joint inflammation, morning stiffness (e.g., “difficulty moving around”) should persist for at least 30 to 45 minutes before disappearing. A similar “gel” phenomenon can occur if a person is inactive during the day.

It is rare for symptoms to remit completely in one set of joints while developing in another. This quality of arthritis sets RA apart from rheumatic fever or palindromic rheumatism, in which a true migratory pattern of arthritis is common. A subtle, early change in RA is the development of muscle atrophy around affected joints. Muscle efficiency and strength become diminished. As a result, weakness develops that can be out of proportion to pain. Opening doors, climbing stairs, and doing repetitive work rapidly become more demanding. A low-grade fever without chills is rarely present. Depression and anxiety can accentuate symptoms. A small but significant weight loss is common and reflects the catabolic effects of cytokines and associated anorexia.

Acute or Intermediate Onset

Among patients with RA, 8% to 15% have an acute onset of symptoms that peak within a few days. Rarely, a patient can pinpoint the onset of symptoms to a specific time or activity. Symptoms mount, with pain developing in other joints, often in a less symmetric pattern than in patients who have an insidious onset. Acute-onset RA is difficult to diagnose, and sepsis or vasculitis should be ruled out. Fever, suggesting an infectious process, can rarely be a prominent sign. An intermediate type of onset, in which symptoms develop over days or weeks, occurs in 15% to 20% of patients. Systemic complaints are more noticeable than in the insidious type of onset.

Joint Involvement

The joints most commonly involved first in RA are the metacarpophalangeal (MCP) joints, the proximal interphalangeal (PIP) joints, the metatarsophalangeal joints, and the wrists (Table 70-1).¹⁵ Larger joints generally become symptomatic after small joints. Synovitis in large joints is likely to remain asymptomatic for a longer time than in smaller ones, and a biopsy specimen of an asymptomatic knee often shows histologic evidence of synovitis.¹⁶ One anatomic study correlated the area, in square centimeters, of synovial membrane with that of hyaline cartilage in each joint. Joints with the highest ratio of synovium to articular cartilage correlated positively with those most frequently involved in the disease (see Table 70-1).¹⁷

Table 70-1 Distribution of Joints Involved in Attacks Based on Cumulative Experience with 227 Patients

Palindromic Pattern

Palindromic rheumatism was described by Hench and Rosenberg in 1942. Pain usually begins with pain in one joint or in periarticular tissues; symptoms worsen for several hours to a few days and are associated with swelling and erythema. Then, in reverse sequence, symptoms resolve, leaving no residua. Table 70-2 lists joints involved in a series of 227 patients. An intercritical period, similar to that of gout, is asymptomatic. Half of patients with palindromic rheumatism go on to develop RA, particularly those with HLA-DR4. In a compilation of patients from nine series, only 15% became asymptomatic after at least 5 years with a palindromic syndrome (see Table 70-2).²⁴ In the remainder, multiple joints became involved, swelling did not subside completely between attacks, and tests for RF became positive. Neither the characteristics of joint fluid nor the pathologic findings of synovial biopsy specimens allow the prediction that RA will evolve from palindromic rheumatism,²⁵ although it may be worthwhile to measure ACPAs in these people.²⁶ Those who do not develop RA rarely have constitutional symptoms, and involved joints show no erosion because the synovitis does not become chronic. A more recent study of long-term outcomes in 60 patients diagnosed with palindromic rheumatism revealed that two-thirds of patients developed chronic arthritis, and the risk for chronic arthritis remained for longer than 10 years.²⁷ Of 51 patients with palindromic rheumatism, 41 experienced marked improvement in frequency and duration of attacks during treatment with antimalarials.²⁸ The use of antimalarials might reduce the risk of progression to RA.

Table 70-2 Evolution of Patients with Palindromic Rheumatism in Nine Series*

Insidious Onset in Older Individuals

Older individuals (≥65 years old) who develop RA often present with stiffness, limb girdle pain, and diffuse swelling of the hands, wrists, and forearms. Clinical onset that mimics polymyalgia rheumatica or remitting seronegative synovitis with pitting edema (RS3PE) also can occur in the elderly. Individuals with onset at age 60 years or older are less likely to have subcutaneous nodules or RF at the onset of disease, despite the high prevalence of RF in the general population in this age group. Generally, elderly individuals who develop RA tend to have a more benign course than younger people; the frequency of positive tests for RF is lower, but a strong association with HLA-DR4 has been noted. Onset is slow, but stiffness is often incapacitating.

In a study of patients with RA of less than 15 months’ duration, older patients had higher scores for joint space narrowing and osteophytes at baseline than patients younger than 55 years. However, no evidence suggested that older patients had more rapid progression of damage, indicating that osteoarthritis was responsible for a significant portion of the damage noted at the onset of disease.²⁹

Arthritis Robustus

Arthritis robustus is not so much an unusual presentation of disease as an unusual reaction of patients to the disease.³⁰ Most patients are men whose disease is characterized by proliferative synovitis, often with deformity, which seems to cause little pain and even less disability. Patients are athletic and invariably keep working (often at physical labor). Periarticular osteopenia is unusual, whereas new bone proliferation at joint margins near significant erosions of bone and cartilage is common. Bulky subcutaneous nodules develop. Subchondral cysts also develop, presumably from excessive pressure caused by synovial fluid within a thick joint capsule during muscular effort.

Rheumatoid Nodulosis

Whether rheumatoid nodulosis is a variant subset of RA or a different entity has not been clarified. The clinical picture includes recurrent pain and swelling in different joints, radiologic subchondral bone cysts, and subcutaneous rheumatoid nodules. In one series of 16 patients followed over 12 years, 6 had an aggressive course indistinguishable from classic erosive polyarticular RA. In 7 patients, cholesterol crystals were found in fluid from the olecranon bursae. Second-line drugs helped articular disease but did not help other components of the process.³¹

Hands and Wrists

The hand and the wrist should be considered together because they form a functional unit. Data have linked disease of the wrist to ulnar deviation of the MCP joints.³² The hypothesis is that weakening of the extensor carpi ulnaris muscle leads to radial deviation of the wrist as the carpal bones rotate (the proximal row in an ulnar direction and the distal ones in a radial direction). In response to this, ulnar deviation of the fingers (a “zigzag” deformity) keeps the tendons to the phalanges in a normal line with the radius. Other factors, including the tendency for a power grasp to pull the fingers into an ulnar attitude and inappropriate intrinsic muscle action, are also involved (Figure 70-1). Erosion of bone or articular cartilage is not essential for the development of ulnar deviation (Figure 70-2). Significant but reducible ulnar deviation can result from repeated synovitis or muscle weakness in the hands (e.g., in systemic lupus erythematosus, in Parkinson’s disease).

Figure 70-1 A, Polyarticular arthritis, especially with fusiform swelling of the proximal interphalangeal joints. Note deformity of wrists with radial deviation. B, Complete subluxation with marked ulnar deviation at the metacarpophalangeal joints in a patient with rheumatoid arthritis. The heads of the metacarpals are now in direct contact with the joint capsule instead of the proximal phalanges.

(Courtesy Iain McInnes, MD.)

Figure 70-2 Ulnar deviation and subluxation. The hands show typical manifestations of end-stage erosive changes around the metacarpophalangeal joints, with volar dislocation and ulnar drift of the fingers.

(Copyright A.L. Ladd.)

Dorsal swelling on the wrist within the tendon sheaths of the extensor muscles is one of the earliest signs of disease. Typically, the extensor carpi ulnaris and extensor digitorum communis sheaths are involved. Rarely, cystic structures resembling ganglia are early findings of RA.

As synovial proliferation develops within the wrist, pressure increases within the relatively nondistensible joint spaces. Proliferative synovium develops enzymatic machinery sufficient to destroy ligaments, tendons, and the articular disk distal to the ulnar head. Pressure and enzymes combine to produce communications among radiocarpal, radioulnar, and midcarpal joints. The integrity of the distal radioulnar joint is lost. The ulnar collateral ligament, stretched by the proliferative synovium of the radioulnar joint, finally ruptures or is destroyed, and the ulnar head springs up into dorsal prominence, where it “floats” and is easily depressed by the examiner’s fingers (piano key styloid).

On the volar side of the wrist, synovial protrusion cysts develop; they can be palpated, and their origins can be confirmed by arthrography. The thick transverse carpal ligament provides significant resistance to decompression, however, and the hyperplastic synovium can compress the median nerve, causing carpal tunnel syndrome, often bilaterally.

Progression of disease in the wrist may be characterized by radiographic loss of joint space and bone or by ankylosis (Figure 70-3A). Ultrasound of the wrist correlates with function and classic signs of inflammation and is a complementary tool in the evaluation of wrist arthritis in RA (Figure 70-3B). Early detection of carpal bone involvement by RA is also possible with magnetic resonance imaging (MRI), which reveals early synovial proliferation and carpal bone erosions. Bony ankylosis is associated with increased duration and severity of the disease and is found in joints that have been immobilized by pain, inflammation, treatment, or all of these.

Figure 70-3 A, Typical sites of osseous erosion shown on radiographs of a rheumatoid wrist include triquetrum, pisiform, scaphoid, and radius. Erosions are also seen at the ulnar aspect of the distal radius and the distal ulnar styloid process secondary to involvement of the inferior radioulnar compartment. Diffuse cartilage loss is evident in the radiocarpal compartment. B, Ultrasound of the rheumatoid wrist dorsal longitudinal view shows synovial proliferation (*), tenosynovial thickening (white arrows), synovitis, and synovial hyperemia (yellow arrows). Upper panel, grayscale; lower panel, power Doppler mode.

(A, Courtesy Dr. Barbara Weissman. B, Courtesy Dr. Arnoldas Ceponis.)

The hand may have many joints involved in RA. A sensitive index of hand involvement is grip strength, which simulatneously stresses multiple hand joints. Muscular contraction causes ligamentous tightening around joints, compressing inflamed synovium. The immediate result is weakness, with or without pain; the reflex inhibition of muscular contraction due to pain may be a primary factor in this weakness. Quantitative radiographic scores for joint space narrowing, erosion, and malalignment correlate well with loss of motion but do not correlate with joint count tenderness scores³³; these data support the concept that inflammatory synovitis and the erosive-destructive potential of proliferative synovitis in RA are not one and the same, but rather reflect different aspects of the same disease.

The swan neck deformity is one of flexion of the distal interphalangeal (DIP) and MCP joints with hyperextension of the PIP joint. The lesion probably begins with shortening of the interosseous muscles and tendons. Shortening of the intrinsic muscles exerts tension on the dorsal tendon sheath, leading to hyperextension of the PIP joint (Figure 70-4A).³⁴ Deep tendon contracture or, rarely, DIP joint involvement with RA leads to the DIP joint flexion. Marginal erosive changes in DIP joints occur more often in patients with RA who have coexisting osteoarthritis.³⁵

Figure 70-4 A, Swan neck deformity. This common deformity leads to hyperextension of the proximal interphalangeal joints and flexion of the distal interphalangeal joints. B, Boutonnière deformity. This deformity, which is the opposite of swan neck deformity, is marked by flexion of the proximal interphalangeal joints and extension of the distal interphalangeal joints.

(Courtesy Iain McInnes, MD.)

If, during chronic inflammation of a PIP joint, the extensor hood stretches or is avulsed, the joint may pop up in flexion, producing a boutonnière deformity (Figure 70-4B). The DIP joint remains in hyperextension.

The most serious result of rheumatoid involvement of the hand is severe resorption of bone that begins at the articular cartilage and spreads along the diaphysis of involved phalanges. Digits appear shortened, excess skin folds are present, and phalanges can be retracted (telescoped) into one another and then pulled out into abnormally long extension, often without pain. With the availability of more effective therapy for RA, this complication has become rare.

Three types of deformity have been described for the thumb:

One of the most common manifestations of RA in the hands is tenosynovitis in flexor tendon sheaths; this can be a major cause of hand weakness.³⁶ Tenosynovitis manifests on the volar surfaces of the phalanges as diffuse swelling between joints or as a palpable grating within flexor tendon sheaths in the palm and may occur in half of RA patients.

It is particularly important to diagnose de Quervain’s tenosynovitis of the extensors of the thumb because this condition causes severe discomfort and yet is easily treated. Pain originating from these sheaths can be shown by Finkelstein’s test, that is, ulnar flexion at the wrist after the thumb is maximally flexed and adducted.

Frequently, rheumatoid nodules develop within tendon sheaths and may “lock” the finger painfully into fixed flexion or cause “trigger” fingers. When they are chronic or recurrent, it may be necessary to inject the tendon sheath or, if that fails, to remove it surgically.

Elbows

RA rarely manifests with severe pain in the elbow, perhaps because the elbow is a stable hinge joint. Nevertheless, involvement of the elbow is common, and if lateral stability at the elbow is lost as the disease progresses, disability can be severe.

The frequency of elbow involvement varies from 20% to 65%, depending on the severity of disease in the patient populations studied. One of the earliest findings, often unnoticed by the patient, is loss of full extension. Because the elbow is principally a connecting joint between the hand and the trunk, the shoulder and the wrists can compensate partially for the loss of elbow motion.

Shoulders

RA of the shoulder not only affects synovium within the glenohumeral joint but also involves the distal third of the clavicle, various bursae and the rotator cuff, and multiple muscles around the neck and chest wall. Severe shoulder pain is often bilateral and can lead to sleep disorders because of difficulty finding a comfortable position. Involvement of the rotator cuff in RA also has been recognized as a principal cause of morbidity. The function of the rotator cuff is to stabilize the humeral head in the glenoid. Weakness of the cuff results in superior subluxation. Rotator cuff tears or insufficiency from other causes can be shown by shoulder arthrography or MRI. In a series of 200 consecutive patients with RA studied by arthrography, 21% had rotator cuff tears, and an additional 24% had evidence of frayed tendons.³⁷ One likely mechanism behind tears is that the rotator cuff tendon insertion into the greater tuberosity is vulnerable to erosion by the proliferative synovitis that develops there. Previous injury and aging may predispose to the development of tears. Sudden tears may be accompanied by pain and inflammation so great as to suggest infection.

Standard radiographic examinations of the shoulder in RA reveal erosions and superior subluxation (Figure 70-5). Arthrograms, in addition to showing tears of the rotator cuff, can show diffuse nodular filling defects, irregular capsular attachment, bursal filling defects, adhesive capsulitis, and dilation of the biceps tendon sheath (perhaps unique to RA).³⁸ High-resolution computed tomography (CT) or MRI may provide much of this information without the need for invasive techniques.

Figure 70-5 Abnormalities of the shoulder in rheumatoid arthritis. The Grashey posterior oblique view of a shoulder shows severe glenohumeral joint space narrowing with marginal erosion and cystic changes of the humeral head adjacent to the greater tuberosity (lower arrow). Elevation of the humeral head with respect to the glenoid indicates chronic rotator cuff tear. Tapering of the distal end of the clavicle is seen, along with widening of the acromioclavicular joint (upper arrow).

(Courtesy Dr. Barbara Weissman.)

Marked soft tissue swelling of the anterolateral aspect of the shoulders in RA may be caused by chronic subacromial bursitis rather than by glenohumeral joint effusions. In contrast to rotator cuff tears, bursal swelling is not associated with decreased range of motion or pain. Synovial proliferation within the subdeltoid bursa might explain the resorption of the undersurface of the distal clavicle seen in this disease. Rarely, the shoulder joint may rupture, with symptoms resembling those of obstruction of venous return from the arm.

Temporomandibular Joints

The temporomandibular joint is commonly involved in RA. Histories reveal that 55% of patients have jaw symptoms at some time during the course of their disease. Radiographic examination reveals structural alterations in 78% of the joints examined. An overbite can develop as the mandibular condyle and the corresponding surface of the temporal bone, the eminentia articularis, are eroded. Physical examination of the rheumatoid patient should include palpation of the temporomandibular joint for tenderness and auscultation for crepitus. Occasionally, patients have acute pain and an inability to close the mouth, necessitating intra-articular glucocorticoid therapy to suppress the acute process.

Temporomandibular joint abnormalities are common in nonrheumatoid populations. The only specific findings for RA in the temporomandibular joint are erosions and cysts of the mandibular condyle detected by CT or MRI. No correlation has been noted between clinical and CT findings of the temporomandibular joint in RA.³⁹

Cricoarytenoid Joints

The cricoarytenoid joints are small diarthrodial joints with an important function: They rotate with the vocal cords as the vocal cords abduct and adduct to vary the pitch and tone of the voice. Careful histories may reveal hoarseness in 30% of rheumatoid patients. This hoarseness is not disabling in itself, but the cricoarytenoid joints may become inflamed and immobilized, with the vocal cords adducted to the midline, causing inspiratory stridor. Autopsy examinations have shown cricoarytenoid arthritis in almost half of patients with RA, suggesting that much significant disease of the larynx may be asymptomatic. Although CT scans detected laryngeal abnormalities in 54% of patients with moderately severe RA, no symptoms suggested that these abnormalities would be found.⁴⁰ In contrast, findings on indirect laryngoscopy, which detected mucosal and gross functional abnormalities (including rheumatoid nodules), were abnormal in 32% of the same patients and correlated with symptoms of sore throat and difficult inspiration. It follows that the latter examination should be performed in symptomatic rheumatoid patients. Asymptomatic cricoarytenoid synovitis occasionally may lead to aspiration of pharyngeal contents, particularly at night.

Sternoclavicular and Manubriosternal Joints

Sternoclavicular and manubriosternal joints, both possessing synovium and a cartilaginous disk, are often involved in RA. Because of their relative immobility, few symptoms are reported. Patients occasionally describe pain in the sternoclavicular joints, however, while lying on their sides in bed. When symptoms do occur, the physician must be concerned about superimposed sepsis. CT or MRI is useful for careful delineation of the sternoclavicular joint. Manubriosternal involvement is almost never clinically important, although by tomographic criteria, it is common in RA.

Cervical Spine

In contrast to other nonsynovial joints, such as the manubriosternal joint or the symphysis pubis, diskovertebral joints in the cervical spine often manifest osteochondral destruction in RA and on lateral radiographs may be found to be narrowed (Figure 70-6). Significant pain is reported, but passive range of motion in the absence of muscle spasm may be normal. At least two possible mechanisms have been put forth for this process: (1) extension of the inflammatory process from adjacent neurocentral joints (the joints of Luschka), which are lined by synovium, into the discovertebral area, and (2) chronic cervical instability initiated by apophyseal joint destruction leading to vertebral malalignment or subluxation. This process may produce microfractures of the vertebral end plates, disk herniation, and degeneration of disk cartilage. The atlantoaxial joint is prone to subluxation in several directions and is summarized later.

Figure 70-6 Rheumatoid arthritis of the cervical spine. A, Lateral radiograph in flexion shows severe anterior atlantoaxial subluxation with a wide anterior atlantodental interval (asterisks) and a decreased posterior atlantodental interval (arrow). B, Almost complete reduction of subluxation is noted on the lateral view in extension. Subaxial subluxation is evident at the level of C4-C5 (arrowheads) with erosive changes in various facet joints. O, odontoid.

(Courtesy Dr. Barbara Weissman.)

The earliest and most common symptom of cervical subluxation is pain radiating up into the occiput. Two other serious, but less common, clinical patterns include slowly progressive spastic quadriparesis with painless sensory loss in the hands and transient episodes of medullary dysfunction associated with vertical penetration of the dens and probable vertebral artery compression. In the latter, paresthesias may occur in the shoulders or arms during movement of the head.

Physical findings suggestive of atlantoaxial subluxation include loss of occipitocervical lordosis, resistance to passive spine motion, and abnormal protrusion of the axial arch felt by the examining finger on the posterior pharyngeal wall. Radiographic views (lateral, with the neck in flexion) reveal more than 3 mm of separation between the odontoid peg and the axial arch. In symptomatic patients, films in flexion should be taken only after radiographs (including an open-mouth posteroanterior view) have ruled out an odontoid fracture or severe atlantoaxial subluxation. Studies have indicated that CT is useful for showing spinal cord compression by loss of posterior subarachnoid space in patients with C1 to C2 subluxation. MRI has proved particularly valuable in determining pathologic anatomy in this syndrome (Figure 70-7).

Figure 70-7 Rheumatoid arthritis of the cervical spine. T2-weighted sagittal image shows low signal periodontoid pannus (P). Odontoid process appears irregular secondary to erosion (arrow). The atlantodental distance shows mild widening (solid line). Vertical subluxation can also be seen without signs of cord compression. The anterior subarachnoid space is compromised by disk protrusions at multiple levels. Erosions (arrowheads) are seen at the vertebral end plates at the C6-C7 level.

(Courtesy Dr. Barbara Weissman.)

Neurologic symptoms often have little relationship to the degree of subluxation and may be related to individual variations in the diameter of the spinal canal. Symptoms of spinal cord compression that demand intervention include altered consciousness, syncope, and loss of sphincter control. Dysphagia, vertigo, convulsions, hemiplegia, dysarthria, nystagmus, and peripheral paresthesias are additional symptoms that require immediate attention.

Some of these symptoms may be related to compression of the vertebral arteries, which must wind through foramina in the transverse processes of C1 and C2, rather than to compression of the spinal cord.

The progression of peripheral joint erosions parallels cervical spine disease in RA. The two coincide in severity and timing; cervical subluxation is more likely to develop in patients with erosion of the hands and feet. In a series of patients with RA referred for hip or knee arthroplasty, 61% had radiographic evidence of cervical spine instability.⁴¹

Is mortality increased in patients with atlantoaxial subluxation? Neurologic signs do not inevitably develop in patients with large subluxations. When signs of cervical cord compression do appear, however, myelopathy progresses rapidly, and 50% of patients die within 1 year.⁴² These patients are at risk for these complications if they sustain small falls, whiplash injuries, and general anesthesia with intubation. Cervical collars can be prescribed for symptomatic relief. Operative stabilization may be considered if symptoms are progressive.

Some data support the hypothesis that early C1-to-C2 fusion for atlantoaxial subluxation before the development of superior migration of the odontoid decreases the risk for further progression of cervical spine instability.⁴³ The incidence of sustained neurologic deterioration related to surgery may be 6%; this emphasizes the importance of a skilled surgical team and of careful assessment of each patient. In many cases, surgical intervention in asymptomatic patients is riskier than conservative management despite the dire appearance of imaging studies.

Vertical atlantoaxial subluxation is important and may follow anterior or posterior subluxation. Symptoms associated with this collapse of the lateral support system of the atlas occur in patients with severe erosive disease. Neurologic findings include decreased sensation in the distribution of cranial nerve V, sensory loss in the C2 area, nystagmus, and pyramidal lesions.

Thoracic, Lumbar, and Sacral Spine

The thoracic, lumbar, and sacral portions of the spine are usually spared in RA. Exceptions include the apophyseal joints; rarely, synovial cysts at the apophyseal joint can impinge as an epidural mass on the spinal cord, causing pain, neurologic deficits, or both.

Hips

The hip is less frequently involved in early RA than in juvenile RA. Hip joint involvement must be ascertained by careful clinical examination; symptoms of hip synovitis include pain in the lower buttock or, more commonly, the groin. Pain on the lateral aspect of the hip is often a manifestation of trochanteric bursitis rather than true hip joint synovitis.

About half of patients with well-established RA have radiographic evidence of hip disease. In contrast to osteoarthritis, in which the femoral head usually migrates superiorly, symmetric thinning of the cartilage in RA leads to axial migration. The femoral head may collapse and be reabsorbed, and the acetabulum is remodeled and pushed medially, leading to protrusio acetabuli (Figure 70-8). Significant protrusion occurs in about 5% of all patients with RA.⁴⁴ Loss of internal rotation on physical examination correlates best with radiographic findings. Similar to the situation in other weight-bearing joints, the femoral head may develop cystic lesions that communicate with the joint space.

Figure 70-8 Bilateral protrusio acetabuli in rheumatoid arthritis. The medial acetabular margins protrude into the pelvis. Severe accompanying cartilage loss is evident.

(Courtesy Dr. Barbara Weissman.)

Knees

In contrast to the hips, synovial inflammation and proliferation in the knees are readily shown on physical examination. Early in knee disease, often within 1 week after the onset of symptoms, noticeable quadriceps atrophy leads to the application of more force than usual through the patella to the femoral surface. Another early manifestation of knee disease in RA is loss of full extension—a functional loss that can become a fixed flexion contracture unless corrective measures are undertaken.

Flexion of a knee with a moderate to large effusion markedly increases intra-articular pressure. The increased intra-articular pressure may cause an outpouching of posterior components of the joint, producing a popliteal or Baker’s cyst. This can generate pressures so high in the popliteal space that it may rupture down or dissect into the calf or, less often, superiorly into the posterior thigh. Rupture occurs posteriorly between the medial head of the gastrocnemius and the tendinous insertion of the biceps. Clinically, popliteal cysts and their complications have several manifestations. An intact popliteal cyst may compress superficial venous flow from the lower leg, producing dilation of superficial veins, edema, or both.⁴⁵ Rupture of the joint posteriorly with extravasation of joint fluid into the calf may resemble acute thrombophlebitis with swelling and tenderness and may produce systemic signs of fever with leukocytosis. One helpful sign in identifying cyst rupture may be the appearance of a crescentic hematoma beneath one of the malleoli of the ankle.⁴⁶ Although arthrography clearly defines the abnormal anatomy of a Baker’s cyst, this invasive procedure has been replaced by ultrasonography and, when necessary, MRI (Figure 70-9).

Figure 70-9 Magnetic resonance imaging (MRI) of the knee in rheumatoid arthritis. Sagittal fast spin echo T2-weighted fat-suppressed image allows excellent contrast. Synovial fluid is shown in white as a posterior fluid collection.

(Courtesy Dr. Barbara Weissman.)

Ankles and Feet

Ankle involvement is usually mild in RA, but damage can occur in severe progressive forms of the disease. Clinical evidence for ankle involvement consists of cystic swelling anterior and posterior to the malleoli. Much of the stability of the ankle depends on the integrity of the ligaments holding the fibula to the tibia and these two bones to the talus. In RA, inflammatory and proliferative disease may loosen these connections by stretching and eroding the collagenous ligaments, causing erosions (Figure 70-10). The result is incongruity, which progresses to pronation deformities and eversion of the foot.

Figure 70-10 Rheumatoid arthritis of the ankle. Diffuse loss of cartilage space can be seen with erosion of the fibula (arrows). Scalloping along the medial border of the distal fibula is designated the fibular notch sign and is a characteristic finding in rheumatoid arthritis. The hindfoot is in valgus alignment.

The Achilles tendon is a major structural component and kinetic force in the foot and ankle. Rheumatoid nodules develop in this collagenous structure, and spontaneous rupture of the tendon has been reported when diffuse granulomatous inflammation is present.⁴⁷ The subtalar joint controls eversion and inversion of the foot on the talus; patients with RA invariably have more pain while walking on uneven ground; this is related to the relatively common subtalar joint involvement in RA. Progressive eversion at the subtalar joint, combined with foot pain, leads to a lateral subluxation beginning in the midfoot and the development of a rocker-bottom deformity. Midfoot disease leads to collapse of the arch, which contributes to difficulty walking because of pain.

More than one-third of patients with RA have significant disease in the feet (Figure 70-11). Metatarsophalangeal (MTP) joints are often involved, and gait is altered as pain develops during push-off in striding. Studies have shown that MTPs are the initial site of erosion in many patients. Downward subluxation of the metatarsal heads occurs soon after the MTP joints become involved, producing “cock-up” toe deformities of the PIP joints. Hallux valgus and bunion or callus formation occur if disease continues. Cystic collections representing outpouchings of flexor tendon sheaths often develop under the MTP joints.⁴⁸ Patients with subluxation of metatarsal heads can develop pressure necrosis of the plantar surfaces. Alternatively, those who have subluxation of MTP joints often develop ulceration over the PIP joints that protrude dorsally (hammer toes). The net result is increased pressure on the MTP joints with a sensation described as “walking on marbles” by many patients. Changes caused by the progress of disease and destruction in the foot include intermetatarsal joint ligament stretching in response to inflammation, spreading of the forefoot, anterior migration of the plantar fat pad, and dorsal subluxation of toes followed by plantar subluxation of the metatarsal heads.⁴⁹ Concurrently, hallux valgus results in progressive overlap of the second and third toes on top of the great toe.

Figure 70-11 Valgus of ankle, pes planus, and forefoot varus deformity of the left foot related to painful synovitis of the ankle, forefoot, and metatarsophalangeal joint in a 24-year-old man with severe rheumatoid arthritis.

DIP joints of the foot are rarely affected in RA, but a functional rigid hallux caused by muscle spasm of the great toe intrinsic muscles in an effort to relieve pressure on the lesser metatarsal heads can be extremely painful and may require surgical intervention. Another cause of foot pain in rheumatoid patients is the tarsal tunnel syndrome. In a group of 30 patients with RA, erosions in the feet visible on radiographs and foot pain (4 patients; 13%) were shown by electrodiagnostic techniques to produce slowing of medial or lateral plantar nerve latency, or both.