General
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• Also called osteoarthritis (OA) (inaccurate since not due to inflammation)
• Nonneoplastic disorder of progressive erosion of articular cartilage associated with aging, trauma, occupational injury

Sites
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• Men-hips, women-knees and hands; also first metatarsophalangeal joint, lumbar spine; usually one joint or same joint bilaterally, at least initially
• Also common in small joints of hands and wrist, particularly first carpometacarpal joint

Clinical features
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• Either no prior arthritis (primary or idiopathic OA) or due to severe arthritis (secondary OA)
• Usually age 50+ years (present in 80% at age 65 years)
• Symptoms: pain worse with use of joint, crepitus, limited range of motion, nerve root compression; Heberden nodes in fingers of women only (osteophytes at DIP joints)
• Secondary degenerative joint disease: younger patients with predisposing condition (trauma, congenital, diabetes, obesity, ochronosis, hemochromatosis); includes knees of basketball players
• Chondromalaciae patellae: softening, fibrillation, fissuring and erosion of articular cartilage of patella (Wikipedia)
• Charcot joint (neuropathic arthropathy): progressive (slow or rapid), destructive variant with large amounts of dead bone and cartilage particles embedded in synovium; severe subluxation or dislocation of joint with extreme deformity; also fibroblastic proliferation, reactive new bone formation; may be due to peripheral neuropathy associated with diabetes or syringomyelia
• Mseleni joint disease: familial disorder of South Africa, causes severe precocious, progressive degenerative osteoarthropathy; occurs in femoral head, degenerative and regenerative changes are present, but only mild osteomalacia and ebernation (Hum Pathol 1985;16:117); characterized by two distinct abnormalities, protrusio acetabuli that mainly affects females and increases in frequency with age, and hip dysplasia that is more frequent with age (Joint Bone Spine 2010;77:399)
• Loose bodies: may form if portion of articular cartilage breaks off; has the tide mark of articular cartilage, has evidence of prior structure; normally loose body is nourished by synovium and continues to grow, has a tree ring appearance; no clumped atypical chondrocytes; no unevenly distributed chondrocytes

Radiology
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• Deformity of joint with loss of bone substance and cartilage, loss of joint space, migration of joint, osteophyte formation, sclerosis of subchondral bone, subchondral bone cysts

Case reports
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• 55 year old diabetic man with Charcot joint (J La State Med Soc 2002;154:246)
• 61 year old woman with chronic pain and stiffness in multiple joints (Am Fam Physician 2011;83:1203)
• 66 year old man with rapidly destructive osteoarthritis of the hip (Reumatol Clin 2011;7:56)
• Case with mucinous synovial transformation (Hum Pathol 1982;13:946)

Treatment
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• Medication for pain
• May have sinus histiocytosis of pelvic lymph nodes after hip replacement due to metal microparticles of implants (Am J Surg Pathol 1994;18:83)

Clinical images
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Swelling around distal interphalangeal joints

 

Charcot joints

Joint mice-loose body

Gross description
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• Early changes are even degeneration of hyaline cartilage of articular surface, with fibrillation of cartilaginous matrix and possible cartilage fragmentation
• Later thinning of cartilage and overgrowth of apposing joint surface
• At time of resection, articular surface is often soft and granular with altered shape, sloughing of cartilage, bone eburnation (friction smoothes and burnishes the exposed bone to resemble ivory), joint mice (dislodged pieces of cartilage and subchondral bone), cysts (synovial fluid forced into fractures via ball valve-like mechanism), osteophytes (bony outgrowths at margins of articular surface), pannus (fibrous synovium that covers periphery of articular surface)
• Rarely secondary infarcts / osteonecrosis (Hum Pathol 1984;15:79)

Gross images
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Advanced osteoarthritis of hip

Micro description
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• Ghost chondrocytes (no nuclei) or necrotic chondrocytes, marked irregularity of tidemark
• Irregular thinning, fragmentation and fibrillation of thinned cartilage
• Subchondral cysts with mucoid fluid surrounded by sclerotic bone
• Usually no significant inflammatory component although advanced cases have synovial hyperplasia with lymphoid follicles
• May have associated sterile acute subchondral inflammation (Am J Surg Pathol 1999;23:192)

Micro images
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Reactive changes with increased cellularity and multilayering of synovial cells

Areas of uninjured bone tissue (A), necrotic bone tissue (B) and cartilage (C)

Synovial area with granulation tissue and chronic inflammation

   

Microscopic changes

Virtual slides
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Degenerative joint disease

Molecular / cytogenetics description
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• Clonal aberrations in HMGIC gene at 12q13-15 in synovia of 5% of patients (Mod Pathol 2001;14:311)

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