Strengthening this part of your body could be the secret to long-term knee health, according to a new study.

New research suggests that compared to the hamstrings, Stronger thigh muscles may be more important and could significantly lower the odds of total knee replacement.

Enhanced strength in the quadriceps, in comparison to the hamstrings, could reduce the risk of needing total knee replacement.

This is a key finding from research presented at the Radiological Society of North America’s (RSNA) annual meeting.

The study highlights how this insight could shape strength-training regimens for individuals with severe knee arthritis.

Globally, severe knee osteoarthritis is a leading cause of pain and disability.

In the United States, about 14 million adults are affected by symptomatic knee osteoarthritis. Of those diagnosed, it’s estimated that more than half might eventually require total knee replacement surgery.

It’s commonly understood that stronger muscles generally correlate with a decreased necessity for knee replacement. However, the specific importance of different muscle groups has not been conclusively established. The focus of this research is on the dynamics between the knee’s extensor and hamstring muscles.

The extensors, located at the front of the thigh and known as the quadriceps, are the body’s most powerful muscle group. They play a vital role in walking, other activities, and overall biomechanics. The hamstrings, situated at the back of the thigh, are crucial for hip extension and knee flexion, and are vital for physical activity.

“The two muscle groups act as counter forces, and the balance between them enables a wide range of activities while protecting the knee joint,” explained lead researcher Upasana Upadhyay Bharadwaj, M.D., from the University of California, San Francisco (UCSF). “An imbalance, in addition to other factors, leads to a change in the biomechanics resulting in the progression of osteoarthritis.”

Dr. Upadhyay Bharadwaj’s team analyzed thigh muscle size in 134 participants from the Osteoarthritis Initiative, an extensive study funded by the National Institutes of Health. The study contrasted 67 patients who had a total knee replacement in one knee with 67 control subjects who did not have the surgery, ensuring they were matched for age and gender.

The team used advanced 3T MRI scans of the thigh taken during the time of knee replacement surgery, as well as reviewing scans from two and four years prior. To measure the thigh muscles’ volumes—a task that is complex to perform manually—they employed a deep-learning algorithm that had been trained for this purpose.

The comparison revealed that those who had undergone total knee replacement had a significantly lower ratio of quadriceps to hamstring volume compared to the control group. Moreover, individuals with larger hamstring and gracilis muscles—the slender muscle running along the inner thigh—were less likely to require knee replacement surgery.

Dr. Upadhyay Bharadwaj summarized, “Our study shows that in addition to strong muscles individually, larger extensor muscle groups—relative to hamstring muscle groups—are significantly associated with lower odds of total knee replacement surgery in two to four years.”

The implications of this study extend to both diagnostic imaging interpretations and the clinical approach to patient care. The evidence suggests that exercise regimens which emphasize strengthening the quadriceps over the hamstrings could offer protective benefits.

“Although we presume that overall muscle volume is important as a surrogate marker for muscle strength, the ratio, hence the balance, between extensor and hamstring muscles may be more important and significantly associated with lower odds of total knee replacement,” explained Dr. Upadhyay Bharadwaj.

While the research was arthritis-centric, its conclusions have broader applications, potentially guiding fitness strategies for the general populace.

“While these results are essential for targeted therapy in a population at risk for osteoarthritis, even the general public can benefit from our results to preventively incorporate appropriate strengthening exercises,” noted Dr. Upadhyay Bharadwaj.

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