Osteoarthritis – Knee

General Information

 


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Description:

  • degenerative joint disorder characterized by articular cartilage loss, bone remodeling, and periarticular muscle weakness resulting in joint pain and instability


Also called:

  • degenerative arthritis
  • osteoarthritis
  • osteoarthrosis


Organs involved:

  • knee joint – including synovium, cartilage, bone, periarticular muscles, ligaments


Who is most affected:

  • older persons or those with previous significant trauma or repetitive stress
  • women > men
    • very common, 88/100,000 person-years in one health management organization (HMO) study
      • based on approximately 130,000 HMO members
      • 461 had new onset knee joint osteoarthritis (age and sex standardized incidence rate 240/100,000 person-years)
      • 195 had new onset hand osteoarthritis (age and sex standardized incidence rate 100/100,000 person-years)
      • 173 had new onset hip joint osteoarthritis (age and sex standardized incidence rate 88/100,000 person-years)
      • all types of osteoarthritis increased with age up to 80 years, and were higher in women (especially after age 50 years)
      • Reference – Arthritis Rheum 1995 Aug;38(8):1134
    • 12.2% overall prevalence in elderly persons in United States with higher rate in women
      • based on of 7,577 persons aged 60-90 years responding to survey in Spain
      • estimated prevalence of knee osteoarthritis
        • 12.2% overall
        • 14.9% in women
        • 8.7% in men
        • tended to increase with age
      • estimated appropriateness rate for knee replacement 11.8% in men and 17.9% in women
      • Reference – Arch Intern Med 2008 Jul 28;168(14):1576
    • knee pain common among United States older adults
      • based on NHANES III study of 6,596 adults > 60 years old
        • 18.1% men and 23.5% women reported knee pain on most days of preceding 6 weeks
        • trend for increased knee pain with female sex and older age
        • Reference – J Am Geriatr Soc 1999 Dec;47(12):1435
      • based on Framingham Osteoarthritis (FOA) cohort study
        • 671 adults ≥ 70 years old were asked about knee pain and had bilateral weight-bearing anteroposterior knee radiography to define radiographic knee osteoarthritis from 2002-2005
        • age- and body mass index-adjusted prevalence of knee pain was 27.7% in men and 32.9% in women
        • Reference – Ann Intern Med 2011 Dec 6;155(11):725
    • 12.5% estimated prevalence of knee osteoarthritis in general population > 45 years old in North Staffordshire (Fam Pract 2005 Feb;22(1):103)


    Causes and Risk Factors

    Causes:

    • causes of degenerative joint disease of knee include
      • trauma
      • Charcot joint (neuropathic arthropathy)
      • inflammatory arthritis (such as crystal arthropathy [calcium pyrophosphate dihydrate deposition disease, gout], rheumatoid arthritis (RA), septic arthritis)
      • congenital or development cause
    • additional causes of degenerative joint disease include
      • endocrine disorders (acromegaly, hyperparathyroidism, diabetes)
      • metabolic disorders (ochronosis, hemosiderosis, Wilson’s disease)
      • neuropathic disorders (diabetes, syphilis)
      • avascular necrosis
      • Paget disease


    Pathogenesis:

    • knee cartilage defects have variable natural history
      • 325 subjects (mean age 45 years) had magnetic resonance imaging (MRI) at baseline and mean 2.3 years later
      • 33% had worsening of cartilage defect score in any knee compartment
      • 37% had improvement of cartilage defect score in any knee compartment
      • Reference – Arch Intern Med 2006 Mar 27;166(6):651
    • knee alignment affects progression of knee osteoarthritis (OA)
      • 237 persons with primary knee osteoarthritis defined by presence of definite tibiofemoral osteophytes and at least some difficulty with knee-requiring activity were followed for 18 months
      • varus knee alignment associated with medial progression (joint space narrowing)
      • valgus alignment associated with lateral progression
      • bilateral knee alignment > 5 degrees associated with greater functional decline than bilateral knee alignment < 5 degrees
      • Reference – JAMA 2001 Jul 11;286(2):188, correction can be found in JAMA 2001 Aug 15;286(7):792
    • bone marrow lesions might cause pain in OA
      • MRI study of 401 adults with knee arthritis on radiography
      • comparing 351 who reported pain vs. 50 without pain
        • 78% vs. 30% had discrete areas of increased signal adjacent to subcortical bone in either femur or tibia (consistent with fluid)
        • 36% vs. 2% had large lesions
      • Reference – Ann Intern Med 2001 Apr 3;134(7):541 in J Watch 2001 Jun 1;21(11):88, editorial can be found in Ann Intern Med 2001 Apr 3;134(7):591
      • resolution of pain coincided with disappearance of MRI lesions, presumed to be edema with localized bone contusions (Hosp Pract 2001 Jul;36(7):26)


    Likely risk factors:

    • risk factors strongly associated with knee osteoarthritis
      • age > 50 years old
      • female sex
      • increasing body mass index (BMI)
      • previous knee injury or misalignment
      • joint laxity
      • occupational or recreational use
      • family history
      • presence of Heberden’s nodes
    • previous knee trauma or surgery
    • history of joint injury
      • joint injury associated with increased risk for osteoarthritis (OA); 1,321 medical students (mean age 26) followed for median 36 years; comparing 11%-16% subjects with trauma to hip or knee to subjects without joint injury, cumulative incidence by age 65 per 1,000 person-years was 7.5 vs. 1.2 for knee OA and 3.2 vs. 0.7 for hip OA (Ann Intern Med 2000 Sep 5;133(5):321 in J Watch 2000 Oct 15;20(20):159)
      • knee osteoarthritis may be common following ACL injury; study of 103 Swedish female soccer players (mean age 31 years) with history of ACL injury 12 years earlier; 67 patients had weight-bearing knee radiography, 82% of injured knees (vs. 37% contralateral knees) had radiographic changes, 51% of injured knees had radiographic knee arthritis; 84 patients completed questionnaires, 75% reported symptoms affecting knee-related quality of life (Arthritis Rheum 2004 Oct;50(10):3145 in J Musculoskel Med 2004 Dec;21(12):650)
    • leg length inequality associated with increased risk of knee OA
      • based on cohort of 3,026 adults aged 50-79 years with or at high risk of knee OA who were followed for 30 months
      • all patients had radiographic leg length measurement
      • comparing leg length inequality ≥ 1 cm vs. < 1 cm
        • symptomatic knee OA in shorter leg at baseline in 30% vs. 17% (odds ratio [OR] 2, 95% CI 1.6-2.6)
        • incident symptomatic knee OA in shorter leg 15% vs. 9% (OR 1.7, 95% CI 1.2-2.4)
        • incident symptomatic knee OA in longer leg 13% vs. 9% (OR 1.5, 95% CI 1-2.1)
      • Reference – Ann Intern Med 2010 Mar 2;152(5):287
    • excess body weight
      • multiple measures of overweight associated with increased incidence knee OA
        • based on cohort study
        • 27,960 men and women from general population, mean age 58.3 years had baseline measures of BMI, waist circumference, waist-hip ratio (WHR), weight and body fat percentage
        • mean follow-up 11 years
        • 1.7% participants developed knee OA
        • risk of knee OA associated with higher (p < 0.05 for all)
          • BMI
          • waist circumference
          • WHR
          • weight
          • percent body fat
        • Reference – Ann Rheum Dis 2009 Apr;68(4):490
      • obesity and overweight associated with increased risk of knee OA
        • based on systematic review of 47 observational studies with 446,219 persons with knee OA
        • compared to persons of normal weight, increased risk of knee OA associated with
          • overweight (OR 2.02, 95% CI 1.84-2.22)
          • obesity (OR 3.91, 95% CI 3.32-4.56)
        • Reference – Arthritis Care Res (Hoboken) 2011 Jul;63(7):982
      • body mass index > 27 kg/m2 associated with increased risk for knee osteoarthritis
        • based on retrospective cohort study
        • 3,585 persons > 55 years old in Rotterdam Study in the Netherlands followed for mean 6.6 years
        • high BMI (> 27 kg/m2) at baseline associated with incident knee osteoarthritis (odds ratio 3.3)

     

    • occupational bending or lifting
      • heavy physical activity such as mowing with nonpower mower, shoveling, digging, chopping wood, brisk cycling; in study of 5,000 persons, heavy physical activity > 4 hours/day associated with > 6 times increased risk for radiographic knee OA, symptomatic knee OA also associated with heavy physical activity, obese individuals at disproportionately higher risk; no association of knee OA with light or moderate physical activity, daily amount of walking, or number of stairs climbed (Am J Med 1999 Feb;106(2):151)
      • physical education teachers had 3 times higher risk for OA of knee in cohort study of 571 physical education teachers and 512 controls, increased risk similar for both men and women (Occup Environ Med 2000 Oct;57(10):673 in BMJ 2000 Mar 18;320(7237):774)


    Possible risk factors:

    • osteoarthritis of hands predicts future osteoarthritis (OA) of hip or knee
      • cohort of 1,235 subjects without OA of hip or knee at baseline who had x-rays of hands at baseline and x-rays of hips and knees at baseline and 6.6 years later
      • 12.1% subjects developed hip or knee OA, 19.7% with vs. 10% without OA of hands at baseline
      • OA of hands increased risk of future hip OA (OR 3) with further increase if family history of OA
      • OA of hands increased risk of future knee OA (OR 1.6) with further increase if overweight
      • Reference – Arthritis Rheum 2005 Nov;52(11):3520
    • high heels may increase risk, high heels increased force across patellofemoral joint and compressive force on medial knee compared with barefoot walking in study of 20 healthy women (Lancet 1998 May 9;351(9113):1399)
    • genetic predisposition
      • family history of parent with total knee replacement for severe knee OA associated with higher annual knee cartilage loss in longitudinal study of 163 matched pairs with and without such family history (Arthritis Res Ther 2006;8(1):R8)
      • genetics may have significant role in hip OA but not knee OA
        • study of siblings of 635 probands undergoing total hip replacement, siblings of 486 probands undergoing total knee replacement and siblings of 787 spouses
        • familial aggregation observed for hip arthroplasty but not knee arthroplasty
        • Reference – Arthritis Res Ther 2006;8(1):R25
      • chromosome 7q22 rs4730250 appears to be susceptibility locus for knee OA
        • based on meta-analysis of 4 case-control studies of 6,709 cases of knee OA and 44,439 controls in Caucasian population
        • Reference – Ann Rheum Dis 2011 Feb;70(2):349
      • 5 genome-wide significant loci associated with osteoarthritis
        • based on genetic analysis of 7,410 unrelated patients of European descent with severe hip or knee osteoarthritis (80% with total joint replacement) and 11,009 unrelated controls
        • loci replicated in independent cohort of up to 7,473 cases and 42,938 controls
        • genome-wide significant loci associated with osteoarthritis
          • chromosome 3 with rs6976
          • chromosome 9 close to ASTN2
          • chromosome 6 between FILIP1 and SENP6
          • chromosome 12 close to KLHDC5 and PTHLH
          • chromosome 12 close to CHST11
        • all variants were common and had small effects
    • low intake and low serum levels of vitamin D (Ann Intern Med 1996 Sep 1;125(5):353), but epidemiologic studies have failed to consistently find association between vitamin D levels and OA (Alternative Medicine Alert 2008 Aug;11(8):85)


    Factors not associated with increased risk:

    • conflicting evidence regarding meniscal damage and knee osteoarthritis (OA)
      • meniscal damage may be associated with radiographic OA in knees without previous surgery
        • based on nested prospective case-control study
        • 121 patients aged 50-79 years at high risk of knee OA who developed tibiofemoral OA over 30 months were compared with 294 controls
        • no patients had previous knee surgery
        • meniscal damage at baseline in 54% cases vs. 18% controls (p < 0.001)
      • meniscal damage not associated with development of knee OA
        • based on nested case-control study of patients at high risk of knee OA
        • 110 patients with frequent pain, aching, or stiffness were compared to 220 controls who showed no symptoms after 15 months
        • meniscal damage at baseline observed in 38% of patients who developed symptoms compared with 29% of patients with no symptoms (not significant)


    Complications:

    • malalignment – when severe in medial or lateral compartment, varus or valgus deformity