Stronger thigh muscles may prevent knee replacement surgery, an increasingly common procedure for knee osteoarthritis, according to a new study.
Having stronger quadriceps than hamstrings may reduce the risk of knee arthroplasty, according to a study presented today at the annual meeting of the Radiological Society of North America (RSNA). The researchers say these findings could inform strength training programs for people with advanced knee arthritis.
Advanced knee osteoarthritis is one of the most common causes of pain and disability worldwide. In the USA alone, 14 million adults suffer from symptomatic knee osteoarthritis and in Spain it is 14% of the population. More than half of those diagnosed are expected to undergo knee replacement surgery.
Although it is generally believed that stronger muscle groups are associated with lower rates of total knee replacement, their relative importance is not clearly established. What is particularly interesting is the relationship between the extensors and the hamstrings, the two most important muscle groups of the knee.
The extensors, the muscles at the front of the thigh commonly referred to as the quadriceps, are the strongest muscle group in the body and have a significant impact on walking, other activities, and biomechanics. The muscles at the back of the thigh, called the hamstrings, are responsible for hip extension and knee flexion and are therefore equally important for physical activity.
More muscles in the thighs
“The two muscle groups act as opposing forces, and the balance between them allows for a wide range of activities while protecting the knee joint,” said the study’s lead author, Dr. Upasana Upadhyay Bharadwaj from the University of California, San Francisco (UCSF). “An imbalance leads, among other factors, to a change in biomechanics that leads to the progression of osteoarthritis.”
Dr. Upadhyay Bharadwaj and colleagues examined hamstring volume in 134 participants in the Osteoarthritis Initiative, a national study sponsored by the National Institutes of Health. They compared 67 patients who underwent single knee arthroplasty with 67 control participants who did not undergo knee arthroplasty. Cases and controls were matched based on variables such as age and gender.
Knee joint of a patient with (A) severe cartilage defects and (B) intact knee joint. CREDIT
RSNA
Researchers obtained 3T MRI images of the thigh at the time of the procedure. They also evaluated MRI results two and four years before the procedure. They used a pre-trained deep learning model to segment and calculate thigh muscle volume, measurements that are laborious to calculate manually.
When comparing patients who underwent total knee arthroplasty with the control group, a higher quadriceps to hamstring volume ratio was significantly associated with a lower likelihood of total knee arthroplasty. Larger volumes of the hamstring muscles and the gracilis, a long, thin muscle on the inside of the thigh, were also associated with a lower likelihood of total knee replacement.
“Our study shows that in addition to individually strong muscles, larger extensor muscle groups – compared to thigh muscle groups – are significantly associated with lower chances of a total knee replacement within two to four years,” said Dr. Upadhyay Bharadwaj.
The study’s conclusions have implications for both the interpretation of imaging tests and clinical management. The results suggest that exercise programs that strengthen the quadriceps relative to the hamstrings may be beneficial.
“Although we assume that total muscle volume is important as a surrogate indicator of muscle strength, the ratio and therefore balance between the extensor and hamstring muscles may be more important and be significantly associated with a lower likelihood of complete muscle replacement. Knee,” said Dr. Upadhyay Bharadwaj.
Although the study focused on people with arthritis, the results could also help bring strength training to a broader portion of the population.
“While these results are crucial for targeted treatment of a group at risk of osteoarthritis, the general public can also benefit from our results to carry out appropriate strengthening exercises as a preventive measure,” said Dr. Upadhyay Bharadwaj.
REFERENCE
RSNA 2023 109th Scientific Assembly and Annual Meeting