Knee Osteoarthritis: Causes, Symptoms, and Treatment
Also known as: gonarthrosis, knee arthritis, osteoarthritis of the knee, degenerative knee disease
Overview
Knee osteoarthritis, also called gonarthrosis, is a degenerative joint disease marked by the progressive breakdown of the cartilage that cushions the bone surfaces of the knee. It is the most common form of osteoarthritis in the United States. According to the CDC, roughly 45% of people may develop symptomatic knee osteoarthritis by age 85. It is a leading cause of chronic pain and functional disability in adults, with a real impact on quality of life and independence.
Causes and risk factors
Several factors contribute to knee osteoarthritis. Joint aging is the main driver, but other elements speed up cartilage breakdown:
- Obesity, which increases mechanical strain on the knee
- A history of joint injuries (fractures, severe sprains, meniscus tears)
- Lower-limb alignment problems (bowed legs, knock knees)
- Genetic predisposition and metabolic conditions such as diabetes and gout
- Jobs that involve heavy lifting or prolonged squatting
Symptoms
Knee osteoarthritis develops gradually, with characteristic signs:
- Mechanical knee pain that worsens with activity and eases with rest, the hallmark symptom
- Brief morning stiffness (usually less than 30 minutes), especially on waking or after sitting still
- Joint cracking (crepitus) when the knee moves
- Knee swelling from fluid buildup during inflammatory flare-ups
- Progressive joint deformity and limited range of motion
- Instability and difficulty with stairs in advanced cases
Diagnosis
Diagnosis is mainly clinical, based on your history and a physical exam of the knee. The doctor looks for mechanical pain, stiffness, and joint crepitus. A weight-bearing knee X-ray is the standard test: it shows narrowing of the joint space, bone spur formation, and thickening of the bone beneath the cartilage. An MRI may be ordered to evaluate soft tissue such as the meniscus and ligaments when the diagnosis is unclear.
Treatments
Care is multi-pronged and tailored to how severe the symptoms are:
- Pain relievers and anti-inflammatories: acetaminophen first, then NSAIDs (ibuprofen, naproxen) during painful flare-ups, under medical supervision
- Physical therapy: a program to strengthen the quadriceps and hamstrings, which helps stabilize the joint and reduce pain
- Corticosteroid injections: helpful for inflammatory flare-ups with fluid buildup
- Viscosupplementation (hyaluronic acid injections): to improve joint lubrication
- Braces and orthotic inserts: to correct alignment problems and ease joint strain
- Surgery (total knee replacement): reserved for severe cases that do not respond to conservative treatment
Prevention
Several steps can delay the onset or slow the progression of knee osteoarthritis:
- Weight management: every pound lost takes about four pounds of pressure off the lower-body joints, so losing 10 to 12 pounds (about 5 kg) can meaningfully reduce strain on the knee
- Regular, appropriate exercise: swimming, cycling, and walking on flat ground are gentler choices than high-impact sports
- Strengthening the leg muscles to protect the joint
- Avoiding prolonged bent-knee postures and excessive heavy lifting
- Wearing supportive shoes with good cushioning
- Seeing a doctor promptly after any knee injury
When should you see a doctor?
See a doctor promptly for knee pain that lasts more than a few weeks, or for significant swelling, redness, or local warmth that could point to infection or a severe inflammatory flare-up. Sudden instability, a locked knee, or rapidly worsening symptoms also call for urgent evaluation.
Sources
- American Academy of Orthopaedic Surgeons (AAOS), OrthoInfo, osteoarthritis as the most common knee arthritis, X-ray and MRI diagnosis, over-the-counter pain relievers as first choice, corticosteroid injections, bracing, and total knee replacement
- Arthritis Foundation, the four-pounds-of-pressure-per-pound-lost weight relationship and osteoarthritis symptom patterns
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), osteoarthritis as the most common form of arthritis and morning stiffness usually lasting less than 30 minutes
- MedlinePlus, U.S. National Library of Medicine overview of symptoms, imaging-based diagnosis, and treatment
- Hsu H, Siwiec RM. Knee Osteoarthritis. StatPearls, NCBI Bookshelf, knee osteoarthritis as the most common type of arthritis, weight-bearing radiographs as the standard imaging with joint-space narrowing, osteophytes, and subchondral sclerosis, plus physical therapy, injections, and hyaluronic acid viscosupplementation
- Murphy L, Schwartz TA, Helmick CG, et al. Lifetime risk of symptomatic knee osteoarthritis. Arthritis Rheum. 2008 (PMC), CDC-authored Johnston County Osteoarthritis Project estimate of a 44.7% lifetime risk of symptomatic knee osteoarthritis by age 85