Knee osteoarthritis is a degenerative disease of the knee joint. It is more common in people older than 40 years. Women have greater chance to be affected.

Signs and symptoms

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

• Pain
• Stiffness
• Decreasing range of motion
• Muscle weakness and atrophy due to inactivity or stiffness
• Crepitus
• Effusion
• Deformity
• Baker's cyst
  Baker's cyst
  A Baker's cyst, also known as a popliteal cyst, is a benign swelling of the semimembranous or more rarely some other synovial bursa found behind the knee joint. It is named after the surgeon who first described it, William Morrant Baker...
  
   (a harmless but sometimes painful collection of joint fluid behind the knee)

Causes

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

Other causes or contributing factors may include:

• Trauma

• Elements injury of the knee joint
  • Tear of meniscus
    Tear of meniscus
    In sports and orthopedics, a tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meniscus at the top of one of the tibiae. Menisci...
    
    
  • Partial menisectomy via arthroscopy

• Recurrent patellar dislocation and patella fracture
  Patella fracture
  A patella fracture is a fracture of the kneecap, which is one of the most common knee injuries. It is usually the result of a hard blow to the front of the knee...
  
  

• Interarticular fractures of the knee and knee dislocations

• Arthritis
  Arthritis
  Arthritis is a form of joint disorder that involves inflammation of one or more joints....
  
   (such as rheumatoid arthritis, infectious arthritis, etc.)

• Deformities of the knee joint that include:
  • Genu varum
  • Genu valgum
    Genu valgum
    Genu valgum, commonly called "knock-knee", is a condition where the knees angle in and touch one another when the legs are straightened. Women have a wider pelvis than men and a relatively shorter length of the thigh bone, and as a result, have a greater static genu valgum than men...
    
    
  • Genu recurvatum
    Genu recurvatum
    Genu recurvatum is a deformity in the knee joint, so that the knee bends backwards. In this deformity, excessive extension occurs in the tibiofemoral joint. Genu recurvatum is also called knee hyperextension and back knee. This deformity is more common in women and people with familial ligamentous...
    
     (Knee hyperextension)
  • Knee flexion deformity

• Ligamentous instability
  • Anterior cruciate ligament
    Anterior cruciate ligament
    The anterior cruciate ligament is a cruciate ligament which is one of the four major ligaments of the human knee. In the quadruped stifle , based on its anatomical position, it is referred to as the cranial cruciate ligament.The ACL originates from deep within the notch of the distal femur...
    
    
  • Posterior cruciate ligament
    Posterior cruciate ligament
    The posterior cruciate ligament is one of the four major ligaments of the knee. It connects the posterior intercondylar area of the tibia to the medial condyle of the femur...
    
    
  • Medial collateral ligament
    Medial collateral ligament
    The medial collateral ligament of the knee is one of the four major ligaments of the knee. It is on the medial side of the knee joint in humans and other primates. It is also known as the tibial collateral ligament, or abbreviated as the MCL.- Structure :It is a broad, flat, membranous band,...
    
    
  • Lateral collateral ligament
• Obesity
• Genetics
  Genetics
  Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
  
   factors
• Osteochondritis dissecans
  Osteochondritis dissecans
  Osteochondritis dissecans , often abbreviated to OCD or OD, is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone. OCD is caused by blood deprivation in the subchondral bone. This loss of blood flow causes the subchondral bone to die in a process...
  
   disease
• Meniscal cyst
• Discoid meniscus
  Discoid meniscus
  Discoid meniscus is a rare human anatomic variant that usually affects the lateral meniscus of the knee. Usually a person with this anomaly has no complaints, however, it may present as pain, swelling, or a snapping sound heard from the affected knee...
  
  

Pathophysiology

The most important characteristic of knee osteoarthritis

Osteoarthritis

Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...

 is degeneration of the articular cartilage

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 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
  Femur
  The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
  
   and the tibia
  Tibia
  The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
  
  )
• Patellofemoral joint (between the femur and patella)

Diagnosis

• 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)

Treatment

• Pharmacologic therapy (Tylenol; NSAIDS such as ibuprofen, naprosyn, etc.; glucosamine/chondroitin)

• Intra-articular injection (steroid or hyaluronic acid
  Sodium hyaluronate
  Sodium hyaluronate is the sodium salt of hyaluronan. The name hyaluronic acid is derived from the Greek word ύαλος meaning vitreous, and uronic acid as it was first isolated from the vitreous humour in the eye and possesses a high uronic acid content. The term hyaluronate also refers to the...
  
   preparations such as Synvisc or Supartz)

• Weight loss (if obesity or overweight)

• Vibration therapy for non-pharmacological pain relief

• Low Impact Aerobic Exercise (walking, treadmill, elliptical, bike or stationary bike, swimming or water aerobics)

• Physical therapy
  Physical therapy
  Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
  
  . Aims of physical therapy include:
  • Pain and spasm relief
  • Reducing stiffness
    Joint stiffness
    Joint stiffness may be either the symptom of pain on moving a joint, the symptom of loss of range of motion or the physical sign of reduced range of motion. Doctors prefer the latter two uses but patients often use the first meaning....
    
    
  • Muscles strengthening
  • Increasing range of motion
  • Increasing flexibility
    Flexibility (anatomy)
    Flexibility or limberness refers to the absolute range of movement in a joint or series of joints, and length in muscles that cross the joints. Flexibility is variable between individuals, particularly in terms of differences in muscle length of multi-joint muscles...
    
    
  • Gait training
    Gait training
    In its most general form, Gait training is the act of learning how to walk. However, the term is more often used in reference to a person learning how to walk again after injury or with a disability...
    
    
  • Balance improvement
  • Patient education
  • Increasing functional activities

• Hydrotherapy
  Hydrotherapy
  Hydrotherapy, formerly called hydropathy, involves the use of water for pain-relief and treating illness. The term hydrotherapy itself is synonymous with the term water cure as it was originally marketed by practitioners and promoters in the 19th century...
  
  

• Assistive devices (cane, walker)

• Surgical treatment (when nonsurgical management fails to provide relief)

Surgery

Surgical operations can include the following:

• Total or partial knee replacement
  Knee replacement
  Knee replacement, or knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve the pain and disability of osteoarthritis. It may be performed for other knee diseases such as rheumatoid arthritis and psoriatic arthritis...
  
   (Arthroplasty
  Arthroplasty
  Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...
  
   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
  Arthrodesis
  Arthrodesis, also known as artificial ankylosis or syndesis, is the artificial induction of joint ossification between two bones via surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, splints, or other normally-indicated treatments. The typical...
  
  (Fusion)