Gonarthrosis is the medical term for osteoarthritis of the knee, a condition where the cartilage that cushions the knee joint gradually breaks down and wears away. It affected roughly 375 million people worldwide in 2021, making it one of the most common joint disorders. The term comes from the Greek words “gony” (knee) and “arthrosis” (joint disease), and while it sounds unfamiliar, it describes something many people eventually experience: a knee that becomes painful, stiff, and harder to move over time.
What Happens Inside the Knee
Healthy knee cartilage is a smooth, rubbery tissue that lets your thighbone and shinbone glide against each other without friction. In gonarthrosis, the cells responsible for maintaining this cartilage (called chondrocytes) initially try to repair the damage by ramping up production of collagen and other structural proteins. But over time, the destruction outpaces the repair. The cartilage thins, develops cracks, and eventually wears down to the point where bone meets bone.
This isn’t just a cartilage problem. The bone underneath the cartilage hardens and thickens, a process called sclerosis. Small bony growths called osteophytes form around the edges of the joint. The membrane lining the joint becomes inflamed, and the joint fluid that normally lubricates the knee changes in quality and quantity. All of these changes together produce the pain, swelling, and loss of movement that characterize gonarthrosis.
Who Is Most at Risk
Age is the strongest predictor. Prevalence climbs steeply after age 50 and peaks in the 80s, when roughly one in four adults shows signs of the condition. Women face nearly twice the risk of men, with about 231 million women affected globally compared to 145 million men in 2021.
Beyond age and sex, several factors significantly raise the odds:
- Previous knee injury: A prior knee trauma increases the risk by nearly 4 times.
- Obesity: Carrying excess weight raises risk by about 2.6 times. This is partly mechanical, since every pound of body weight translates to roughly 4 pounds of force on the knee with each step.
- Meniscal surgery: Having surgery on a torn meniscus increases future risk by 2.6 times.
- Repetitive strain: Jobs or activities involving frequent squatting and kneeling are among the strongest occupational risk factors.
- Vitamin D deficiency: Low vitamin D levels are associated with a 2.6-fold increase in risk.
- Muscle weakness and joint laxity: Weak thigh muscles and loose ligaments leave the knee less supported and more vulnerable to damage.
Genetics also play a role. If your parents had knee osteoarthritis, your likelihood of developing it is higher, though no single gene is responsible.
How Gonarthrosis Feels
The hallmark symptoms are pain and stiffness. Early on, you might notice your knee aches after a long walk or a day on your feet, then feels better after rest. As the condition progresses, even mild activity can trigger pain, and rest may bring only partial relief.
Morning stiffness is common but tends to be relatively brief. In most cases it lasts 30 minutes or less, which helps distinguish gonarthrosis from inflammatory types of arthritis like rheumatoid arthritis, where stiffness often persists for an hour or more. If inflammation flares up in the joint, the stiffness can stretch beyond 30 minutes, but it typically improves once you start moving and the joint “warms up.”
Over time, you may notice the knee becomes harder to fully bend or straighten. Some people hear or feel a grinding sensation during movement. In more advanced stages, the joint can visibly enlarge from bone spur formation, and the leg may begin to bow inward or outward as cartilage loss becomes uneven across the joint.
How It Is Diagnosed
Doctors typically diagnose gonarthrosis through a combination of physical examination and X-rays. On an X-ray, the key signs are narrowing of the space between bones (indicating cartilage loss), the presence of bone spurs, and hardening of the bone beneath the cartilage.
The most widely used system for grading severity is the Kellgren-Lawrence scale, which runs from 0 to 4:
- Grade 0: Normal knee, no visible changes.
- Grade 1: Questionable. Possible slight narrowing and tiny bone spurs. Often considered a “maybe.”
- Grade 2: Mild. Clear bone spurs are visible, and the joint space may be starting to narrow.
- Grade 3: Moderate. Multiple bone spurs, definite narrowing, some bone hardening, and possible early deformity.
- Grade 4: Severe. Large bone spurs, significant joint space loss, pronounced bone hardening, and visible deformity of the joint.
Not everyone with X-ray changes has symptoms, and not everyone with knee pain shows clear changes on X-rays, especially in the early stages. Your doctor will consider both the imaging and your symptoms together.
Treatment Without Surgery
Exercise is one of the most effective tools for managing gonarthrosis, even though it can feel counterintuitive to move a painful joint. Resistance training, where you strengthen the muscles around the knee, consistently reduces pain across dozens of clinical trials. Higher-intensity strength programs show larger pain improvements than lower-intensity ones, and benefits appear within the first 12 weeks. Programs lasting longer than 12 weeks still help, though the effect on pain is somewhat smaller, likely because the biggest gains come early.
Tai chi has also shown meaningful pain reduction, particularly in programs lasting 8 to 20 weeks. It combines gentle movement with balance training, which can be especially helpful for older adults concerned about falls. Aquatic exercise, while popular because the water reduces joint loading, has shown less consistent results for pain relief in clinical studies, though many people find it easier to tolerate than land-based exercise. Home exercise programs that you do on your own also reduce pain compared to doing nothing.
Weight loss delivers a disproportionately large benefit. Research from Wake Forest University found that every pound of weight lost reduces the force on your knee by about 4 pounds per step. Over the course of a day, thousands of steps add up to a dramatic reduction in cumulative joint stress. For someone who is overweight, losing even 10 to 15 pounds can meaningfully change how the knee feels during daily activities.
Medications and Injections
Anti-inflammatory pain relievers are the most commonly used medications for gonarthrosis. They reduce both pain and swelling and are often combined with a stomach-protecting medication to reduce the risk of digestive side effects from long-term use. Stronger pain medications like opioid-based drugs have been shown to be less effective than anti-inflammatories for knee osteoarthritis pain, and they carry significantly higher risks, including a 2 to 4 times greater rate of fractures, hospitalizations, and death compared to standard anti-inflammatory use.
For flare-ups where the knee becomes acutely swollen and inflamed, corticosteroid injections directly into the joint can provide short-term relief. Hyaluronic acid injections, which aim to supplement the knee’s natural lubricating fluid, are another option, though evidence on their effectiveness is mixed. Some people experience notable improvement while others see little difference.
When Surgery Becomes an Option
Knee replacement surgery is generally considered when gonarthrosis reaches an advanced stage, typically Grade 3 or 4, and non-surgical treatments no longer provide adequate relief. The decision isn’t based on X-ray findings alone. It hinges on how much pain and functional limitation you experience in daily life: difficulty walking, climbing stairs, sleeping through the night, or doing activities that matter to you.
Total knee replacement involves resurfacing the damaged ends of the bones with metal and plastic components. Most people experience significant pain relief and improved mobility, with the artificial joint lasting 15 to 20 years or longer. Recovery takes several months of physical therapy, with most people returning to normal daily activities within 3 to 6 months, though continued improvement can occur for up to a year.