Painful knees? New injection halves pain for many patients, but there's a catch

Walking up the stairs, getting out of a chair, or taking a short trip to the grocery store can become painful when you have knee arthritis. Now, two major clinical trials have found promising results with an experimental weight-loss injection.

In the studies, involving more than 1,000 adults with painful knee osteoarthritis and excess weight, roughly two-thirds of patients receiving the drug saw their knee pain reduced by at least half. But there's an important catch.

Fortunately, doctors say there are ways to help painful knees that don't require a new medication.

What researchers discovered about the new injection

The research, published on November 8, 2026, in the New England Journal of Medicine, examined an experimental drug called retatrutide.

Participants receiving the highest doses lost roughly a quarter of their body weight on average. A pooled analysis found that approximately two in three patients taking retatrutide experienced at least a 50% reduction in knee pain.

Interestingly, 38% of participants receiving a placebo also reported at least a 50% reduction.

The results are encouraging, but researchers still don't know whether the medication actually slows joint damage or prevents knee replacement surgery.

The drug was developed by Eli Lilly, which funded the trials. Serious adverse events were more common with retatrutide than with placebo, and digestive problems were the most common side effects. The injection remains experimental and has not received regulatory approval.

Why losing a little weight may already help your knees

You don't have to lose 25% of your body weight to potentially notice a difference.

According to the American College of Rheumatology's osteoarthritis guidelines, losing as little as 5% of your body weight can improve symptoms in people who are overweight.

For someone weighing 200 pounds, that's just 10 pounds.

Losing weight reduces the load on your knees during everyday activities. Combining gradual weight loss with regular exercise may provide even greater benefits.

A balanced diet and manageable physical activity are good starting points. There's no special diet that cures osteoarthritis.

Start with just five or ten minutes of movement

When your knees hurt, avoiding movement can seem sensible. But staying inactive may weaken the muscles that support your joints.

The NHS recommends regular exercise as a core treatment for osteoarthritis.

Walking, cycling, and swimming are useful options because they can improve fitness without placing excessive stress on painful knees.

If 30 minutes feels impossible, begin with five or ten minutes. You can gradually increase the time as your knees become stronger.

Some additional stiffness or mild discomfort can occur when you start. However, worsening pain is a reason to reduce the intensity and seek advice.

Three simple exercises you can try at home

The Royal Orthopaedic Hospital and other NHS hospitals recommend several strengthening exercises that require little or no equipment.

• Chair stands: Sit in a sturdy chair, stand up slowly, then sit back down. Work toward 10 repetitions, using support if necessary.
• Thigh tightening: Sit or lie with your leg straight. Tighten your thigh muscles, pressing your knee downward. Hold for 10 seconds and repeat up to 10 times.
• Straight-leg raises: Lie down, tighten your thigh, and slowly lift your straight leg a few inches. Hold briefly before lowering.

Start with a comfortable number of repetitions and build gradually. Aim for strengthening activity at least twice weekly, allowing recovery between sessions.

When should you see your doctor?

If knee pain continues to interfere with walking, sleeping, or everyday activities, speak with your doctor.

A physical therapist can help you develop a suitable exercise program. Pain-relieving medication or a corticosteroid injection may also be considered when needed.

Seek urgent medical advice if your knee becomes suddenly very swollen, hot, or red, particularly with a fever, or if you cannot bear weight or straighten it.

The new injection research offers hope for future treatment. But for people living with knee arthritis today, regular movement, stronger leg muscles, and modest weight loss remain among the most useful places to start.

Medical disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Retatrutide is an experimental medication and not approved for public use. If you have knee osteoarthritis or persistent knee pain, consult your doctor before starting a new exercise program, weight-loss treatment, or medication. Not every exercise or treatment is suitable for everyone, and results may vary.