Knee osteoarthritis


Knee osteoarthritis is a degenerative disease of the knee joint. It is more common in people older than 40 years. Women are more likely to be affected.[1]




  • 1 Signs and symptoms
  • 2 Causes
  • 3 Pathophysiology
  • 4 Diagnosis
  • 5 Treatment
    • 5.1 Surgery
  • 6 Epidemiology
  • 7 References


Signs and symptoms

Some of the signs and symptoms associated with knee osteoarthritis include:

  • Pain
  • Stiffness
  • Decreasing range of motion
  • Muscle weakness and atrophy (particularly of quadriceps femoris, muscle on front of thigh) due to inactivity or stiffness
  • Crepitus
  • Effusion-increase in quantity of synovial fluid leading to swelling
  • Deformity[2]
  • Baker's cyst (a harmless but sometimes painful collection of joint fluid behind the knee)


Osteoarthritis of the knee is predominately considered a "wear and tear" process, where there is gradual degradation of the hyaline cartilage that covers the articulating surfaces of the bones in the knee joint. The medial compartment of the knee (the half closest to the other knee) is affected almost 5 times as frequently as the lateral compartment.[3] and it is is estimated that in a normal knee the moving load on the medial side is two and half times greater than on the lateral side.[4]

In most people, the disease is either post-traumatic or hereditary.

Causes or contributing factors may include:

  • Trauma
  • Elements injury of the knee joint
    • Tear of meniscus
    • Partial menisectomy via arthroscopy
  • Recurrent patellar dislocation and patella fracture
  • Interarticular fractures of the knee and knee dislocations
  • Other forms of arthritis
  • Weak front thigh muscles ("weak quads")[5] and associated gait (quad avoidance gait typically combines keeping knee fully extended throughout stance with excessive forward lean of the trunk)[6]
  • Deformities of the knee joint that include:
    • Genu varum ("bow-legs", especially for medial compartment knee OA)
    • Genu recurvatum (Knee hyperextension)
    • Knee flexion deformity
  • Ligamentous instability
    • Anterior cruciate ligament
    • Posterior cruciate ligament
    • Medial collateral ligament
    • Lateral collateral ligament
  • Obesity
  • Genetics factors
  • Osteochondritis dissecans disease
  • Meniscal cyst
  • Discoid meniscus


The most important characteristic of knee osteoarthritis is degeneration of the articular cartilage in the knee joint. Osteoarthritis of the knee can involve one, two, or all three compartments of the knee:

  • Medial or lateral compartments of the tibiofemoral joint (between the femur and the tibia)
  • Patellofemoral joint (between the femur and patella)


  • Joint space narrowing
  • Osteophyte formation at the joint margins
  • Subchondral Sclerosis (new subchondral bone formation in response to stress on the bone)
  • Subchondral Cyst formation (joint fluid under pressure gets into cracks in the cartilage)


  • Pharmacologic therapy (acetaminophen; NSAIDS such as ibuprofen; glucosamine/chondroitin)
  • Intra-articular injection of hyaluronic acid preparations is not of significant benefit and can result in potential harm.[7]
  • Weight loss, especially prior the disease becoming advanced (the widely cited Framingham Study found that a loss of 5 kg reduced the risk of symptoms by more than 50% in overweight women following a diagnosis of radiographic knee OA)[8]
  • Low Impact Aerobic Exercise (walking, bike or stationary bike, swimming or water aerobics) and lifestyle changes including: never attempting to ski when joints are painful, walking only on level, even terrain, cycling instead of running, avoiding stairs when possible and using handrails when not possible, avoiding the carrying of heavy objects or being on one's feet more than one hour at a time, stretching legs when seated, avoiding low seats or having to kneel)[9]
  • Assistive devices (walker, cane in the hand opposite the affected knee, custom fit "unloader brace" which laterally transfers loading off of the affected knee compartment)
  • Physical therapy. Aims of physical therapy include:
    • Pain and spasm relief
    • Reducing stiffness
    • Muscles strengthening (stronger quads in particular can help minimize the destabilization that occurs as ligaments lose their tightness following cartilage loss)
    • Increasing range of motion
    • Increasing flexibility
    • Gait training
    • Balance improvement
    • Patient education
    • Prescribing Orthotics to fix genu valgum or varum
    • Increasing functional activities
  • Hydrotherapy
  • AposTherapy
  • Surgical treatment (when nonsurgical management fails to provide relief)


Surgical operations can include the following:

  • Total or partial knee replacement (Arthroplasty of the knee)
  • Femoral osteotomy
  • Tibial osteotomy
  • Arthroscopic debridement (so-called "clean out"). Debridement may be done for these knee problems:
    • Damaged cartilage
    • Damaged meniscus
    • The presence of loose bodies in knee joint
    • Osteophytes of the joint
    • Synovial hypertrophy (by synovectomy)
  • Osteochondral allograft (bulk or mosaic)
  • Arthrodesis (Fusion)


  1. ^ "Mayo Clinic Examines Why Knee Osteoarthritis Afflicts More Women Than Men". 3 August 2011. Retrieved 13 January 2012.
  2. ^ Graham Appley and Louis Solomon: "System o Orthopaedics and Fractures", editions Churchille Livingstone, London, Paris, New York, 1993
  3. ^ Crenshaw SJ, Pollo FE, Calton EF. Effects of lateral-wedged insoles on kinetics at the knee] Clin Orthop Relat Res 2000;(375):185-192
  4. ^ Schipplein OD, Andriacchi TP. Interaction between active and passive knee stabilizers during level walking. J Orthop Res 1991;9(1):113-119
  5. ^ Slemenda C, Heilman DK, Brandt KD, et al. Reduced quadriceps strength relative to body weight: a risk factor for knee osteoarthritis in women? Arthritis Rheum 1998;41(11):1951-1959.
  6. ^ Mikesky AE, Meyer A, Thompson KL. Relationship between quadriceps strength and rate of loading during gait in women. J Orthop Res 2000;18(2):171-175.
  7. ^ Viscosupplementation for Osteoarthritis of the Knee A Systematic Review and Meta-analysis
  8. ^ Felson DT, Zhang Y, Anthony JM, et al. Weight loss reduces the risk for symptomatic knee osteoarthritis in women. The Framingham Study. Ann Intern Med 1992;116(7):535-539
  9. ^ Practical Tips for Osteoarthritis of the Knee American Arthritis SocietyAccessed: February 2013
  10. ^ Vos, T (2012 Dec 15). "Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010.". Lancet 380 (9859): 2163–96. PMID 23245607.
  • John Crawford Adams and David L.Hamblen. Outline of Orthopaedics. Twelfth Edition. ISBN 0-443-05149-6
  • Darlene Hertling and Randolph M.Kessler. Management of Common Musculoskeletal Disorders. Third Edition. ISBN 0-397-55150-9

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