Knee Osteoarthritis

Also known as: Degenerative knee disease, Knee OA, Arthritic knee, Wear and tear arthritis of knee, Gonarthrosis, Knee joint degeneration

Last updated: December 18, 2024

Knee osteoarthritis involves gradual breakdown and thinning of the knee’s articular cartilage, along with changes in bone and other joint tissues. Symptoms often develop over time and may fluctuate, commonly including pain, stiffness, swelling or a feeling of fullness, and reduced function. Exercise therapy and physical therapy can improve strength, mobility, and function and may reduce pain. Symptoms may have periods of improvement and flare-ups.

Key Facts

•Knee osteoarthritis involves gradual breakdown and thinning of the knee’s articular cartilage, with related changes in bone and other joint tissues
•Knee pain occur during or after activity and progress to pain with less activity over time
•Diagnosed through history, physical exam, and imaging
•First-line treatment includes exercise, weight management, and activity modification

What It Is

Knee osteoarthritis generally involves gradual breakdown and thinning of the knee’s articular cartilage, with related changes in bone and other joint tissues. Symptoms often can develop over time and may fluctuate, with pain, stiffness, and reduced function commonly reported.

Affected Anatomy

This condition affects several structures in and around the joint:

•Articular cartilage of the tibiofemoral and patellofemoral joints
•Subchondral bone (including osteophyte formation)
•Synovium (synovial lining)
•Menisci
•Joint capsule
•Supporting ligaments and periarticular muscles

Common Symptoms

Symptoms can vary in intensity and may change over time. Common experiences include:

•Knee pain may occur during or after activity and can progress to pain with less activity over time
•Stiffness often can be more noticeable after rest or in the morning
•Swelling or a feeling of fullness may occur due to inflammation or joint effusion
•Reduced range of motion can develop gradually
•Crepitus (grinding, clicking, or crackling sensation) may be noticed with movement
•Tenderness around the joint line can occur
•Instability or a sensation of the knee “giving way” may occur
•Functional limitations typically can include difficulty with stairs, walking longer distances, or rising from a chair

Causes and Risk Factors

Multiple factors can contribute to the development of this condition:

Causes

•Age-related joint tissue degeneration can contribute to cartilage wear over time
•Prior knee injury (such as meniscal tear or ligament injury) can increase the likelihood of degenerative changes
•Repetitive mechanical stress or overuse can contribute to joint cartilage breakdown
•Abnormal joint mechanics or malalignment can increase focal cartilage loading
•Genetic predisposition can contribute to susceptibility in some individuals
•Inflammatory or metabolic contributors can coexist and may affect symptom severity

Risk Factors

•Older age can increase risk
•Higher body weight can increase mechanical load across the knee and may increase risk
•Previous knee injury or surgery can increase risk
•Occupations or activities involving frequent kneeling, squatting, heavy lifting, or repetitive impact may increase risk
•Family history can increase risk in some individuals
•Female sex can be associated with higher risk, particularly with increasing age
•Knee malalignment (varus or valgus) can increase risk of compartment-specific degeneration
•Muscle weakness or reduced neuromuscular control around the knee can be associated with symptoms and functional limitation

How It's Diagnosed

Diagnosis typically involves a combination of clinical assessment and imaging studies:

•Medical history and symptom review can help characterize pain pattern, stiffness, and functional impact
•Physical examination often can evaluate tenderness, range of motion, crepitus, alignment, stability, and gait
•Weight-bearing knee X-rays typically can show joint space narrowing, osteophytes, and subchondral changes
•MRI may be used when soft-tissue injury or alternative diagnoses are being considered
•Laboratory tests may be used to help evaluate for inflammatory arthritis or other causes when clinical features suggest alternatives to osteoarthritis

Treatment Options

Treatment approaches range from conservative measures to surgical interventions, often starting with the least invasive options:

Self-Care and Activity Modification

•Weight management can reduce knee joint loading and may lessen symptoms in some individuals
•Activity modification and pacing can help manage symptom flares
•Assistive devices (such as a cane) can reduce joint load and may improve walking tolerance
•Bracing or orthotics may help some individuals, particularly with malalignment-related symptoms

Physical Therapy and Exercise

•Exercise therapy and physical therapy can improve strength, mobility, and function and may reduce pain
•Heat or cold modalities can help with symptom relief for some individuals

Medications

•Topical NSAIDs can reduce pain for some individuals
•Oral NSAIDs can reduce pain and inflammation for some individuals, with risk considerations
•Acetaminophen may reduce pain for some individuals

Injections and Office-Based Procedures

•Intra-articular corticosteroid injections can provide short-term symptom relief for some individuals
•Intra-articular hyaluronic acid injections may provide symptom relief for some individuals, with variable response

Surgery

•Surgical options (such as total knee arthroplasty, unicompartmental arthroplasty, or osteotomy) can be considered for advanced disease with significant symptoms and functional limitation; arthroscopy typically may have limited benefit for degenerative osteoarthritis without specific mechanical pathology

Prognosis and Recovery

The course of this condition varies between individuals:

•Symptoms often can fluctuate over time, with periods of relative improvement and flare-ups
•Structural changes generally can progress gradually, although the rate of progression may vary
•Pain and function can respond to non-surgical strategies for many individuals, with variable magnitude of benefit
•Advanced disease may be associated with persistent pain and reduced mobility, and surgical treatment can improve pain and function for selected individuals

Total Knee Arthroplasty (Total Knee Replacement)(Procedure)
Partial Knee Replacement (Unicompartmental Knee Arthroplasty)(Procedure)
Hip Osteoarthritis(Condition)
Meniscus Tear(Condition)

Frequently Asked Questions

Common symptoms include: Knee pain may occur during or after activity and can progress to pain with less activity over time; Stiffness often can be more noticeable after rest or in the morning; Swelling or a feeling of fullness may occur due to inflammation or joint effusion; Reduced range of motion can develop gradually; Crepitus (grinding, clicking, or crackling sensation) may be noticed with movement.

Diagnosis typically involves: Medical history and symptom review can help characterize pain pattern, stiffness, and functional impact; Physical examination often can evaluate tenderness, range of motion, crepitus, alignment, stability, and gait; Weight-bearing knee X-rays typically can show joint space narrowing, osteophytes, and subchondral changes; MRI may be used when soft-tissue injury or alternative diagnoses are being considered.

Treatment options range from conservative measures to surgical interventions, including: Exercise therapy and physical therapy can improve strength, mobility, and function and may reduce pain; Weight management can reduce knee joint loading and may lessen symptoms in some individuals; Activity modification and pacing can help manage symptom flares; Assistive devices (such as a cane) can reduce joint load and may improve walking tolerance; Bracing or orthotics may help some individuals, particularly with malalignment-related symptoms.