Abstract
A brief overview of mechanical and inflammatory joint conditions.
Key Concepts ( Fig. 15.1 )
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A healthy articular joint such as the hip or knee is composed of two bony surfaces lined with hyaline cartilage that are surrounded by a joint capsule. The capsule is lined with a thin synovial membrane that is no more than a few cell layers thick.
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Articular joints move freely and painlessly with a low coefficient of friction due to the smooth surfaces of articular cartilage and the lubricating properties of synovial fluid.
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Joint pain due to arthritis arises from damage to articular surfaces and tension on the joint capsule from effusions. Joint damage can occur from several different processes including mechanical stresses over time, trauma, crystal deposition, primary joint inflammation, and primary joint infection.
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The hallmarks of inflammatory joint pain include stiffness and pain that are most pronounced in the morning. These symptoms improve with activity and return after periods of rest. Prolonged stiffness is a key historical feature of inflammatory joint pain. Morning stiffness typically lasts more than 1 hour in individuals with inflammatory joint disease.
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In contrast to inflammatory joint pain, mechanical joint pain is typically worse with activity and improves with rest. Morning stiffness may be present, though it tends to improve within 30 minutes of activity.
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Additional features are important to consider as they may help narrow the differential diagnosis. Important features of arthritis include the duration of symptoms, the number of joint involved, the size of joints involved, symmetry of joint involvement, pattern of onset (episodic, additive, migratory, etc.), and axial involvement (SI joints and spine; Boxes 15.1 to 15.3 ).
Box 15.1
Causes of Acute Arthritis
Acute Monoarthritis
Septic arthritis
Gonococcal
Nongonococcal
Acute crystalline arthritis
Gout
Pseudogout (acute CPPD)
Trauma
Acute Oligoarthritis
Septic arthritis
Gonococcal— often migratory
Nongonococcal— up to 25% of cases involve >1 joint
Lyme Arthritis
Postinfectious arthritis
Rheumatic fever
Reactive arthritis
Acute sarcoid—Lofgren syndrome
Acute Polyarthritis
Viral infections
Parvovirus B19
Acute hepatitis B
Hepatitis C
HIV
Acute sarcoid—Lofgren syndrome
Atypical manifestations of systemic autoimmune disease
Rheumatoid arthritis
Psoriatic arthritis
Systemic lupus
Box 15.2
Causes of Chronic Noninflammatory Arthritis
Osteoarthritis
Internal and periarticular derangements
Meniscal
Ligament
Tendon
Labrum
Osteochondrosis dissecans
Osteonecrosis
Neuropathic arthritis (Charcot joint)
Box 15.3
Causes of Chronic Inflammatory Arthritis
Chronic Monoarthritis
Infection
Gonococcal
Nongonococcal
Lyme arthritis
Fungal arthritis
Mycobacterial arthritis
Syphilis
Tophaceous gout
Chronic Oligoarthritis
Tophaceous gout
Spondyloarthropathy
Psoriatic arthritis
Reactive arthritis
Ankylosing spondylitis
IBD related arthropathy
Rheumatoid arthritis
Systemic lupus erythematosus
Infection
Lyme
Chronic Polyarthritis
Rheumatoid arthritis
Systemic lupus and related conditions
Spondyloarthropathy
Drug induced
Lupus (hydralazine and others)
Periostitis (voriconazole)
Tophaceous gout
Adult-onset Still’s
Systemic vasculitis
Paraneoplastic
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Acute (<2 weeks) joint pain and swelling requires a rapid workup and must include synovial fluid analysis including gram stain and cultures to evaluate for a bacterial infection suggestive of septic arthritis. Septic arthritis may lead to rapid joint damage and can be life threatening if left untreated.
Osteoarthritis
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Osteoarthritis (OA) arises due to degeneration of joint surfaces from mechanical stress over time or from prior trauma. Articular cartilage loss exposes underlying bone, ultimately resulting in the downstream activation of pain/sensory nerve endings in the subchondral bone.
History
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The hips, knees, and the first metatarsophalangeal joint (MTP) of the foot are the most common lower extremity joints affected. The first carpometacarpal joint (CMC), distal interphalangeal joints (DIPs), and proximal interphalangeal joints (PIPs) of the hands are the most commonly affected joints in the upper extremity. In the absence of trauma or other conditions, osteoarthritis is uncommon in the wrist, shoulder, and ankle.
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Pain related to osteoarthritis is worse with use of the involved joint and improves with rest.
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Stiffness typically resolves within 30 minutes of activity.
Physical Examination
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Vital signs
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Usually normal
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Gait
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Often antalgic with lower extremity joint involvement
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Joints
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Joint effusions may be present
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Bony swelling may be observed due to osteophyte formation.
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Joints affected by osteoarthritis are rarely warm to touch. Joint temperature should be assessed by comparing the temperature of the joint to a neighboring large muscle group. Normal joints are cooler than the area over normal muscle bellies.
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Joint range of motion may be limited, with pain at the endpoints of motion. On hip examination, internal rotation will often elicit pain when hip OA is present
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Joint lines may be tender to palpation
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Joint crepitations may be present.
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Ligament stability is usually unaffected in early disease but may occur in late disease.
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Imaging
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Radiographic hallmarks of osteoarthritis include joint space narrowing (which may be asymmetric in weight bearing joints), osteophytes, joint line sclerosis, and subchondral cysts ( Fig. 15.2 ).
Fig 15.2
Osteoarthritis of the medial compartment of the knee.
Classic radiographic features seen here include asymmetric joint space narrowing, osteophyte formation, and joint line sclerosis.
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Magnetic resonance imaging is more sensitive than plain films at detecting osteoarthritis and may show chondral defects and subchondral bone edema.
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Bone scans have no utility in the workup of osteoarthritis
Additional Tests
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Synovial fluid analysis will demonstrate either normal or noninflammatory joint fluid with <2000 white blood cells (WBCs; Table 15.1 ).
TABLE 15.1Related posts:
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