Researchers at Michigan State University have developed a promising new method for detecting early bone changes after anterior cruciate ligament (ACL) surgery, using ultrasound instead of costly MRIs. The tool could help doctors identify patients at greater risk for re-injury or long-term joint problems like osteoarthritis.
In a March 2025 study published in Osteoarthritis Imaging, Assistant Professor Matt Harkey and Kinesiology Ph.D. student Arjun Parmar validated an innovative bone measure using ultrasound called the “B-score.” This score offers a simple, one-number summary of subtle shape characteristics in the femur, the thigh bone, following anterior cruciate ligament reconstruction (ACLR).
“The accessibility is what excites me most,” Parmar said. “With ultrasound, clinicians and researchers can make these assessments using equipment that’s much more affordable and widely available.”
A common injury with long-term consequences
ACL tears are among the most common sports injuries, especially for teens and young adults. Even after surgery, many go on to develop osteoarthritis within a decade. According to the study, about 36% of people who undergo ACLR develop knee osteoarthritis within 10 years, with the rate climbing even higher in both knees over time.
Harkey and Parmar focused on a part of the femur called the femoral trochlea, a groove where the kneecap sits and glides during movement. Though often overlooked in traditional assessments, the researchers say this region could play a key role in the early development of joint disease.
“It’s an emerging area of research, and it’s easy to visualize with ultrasound,” Parmar explained. “We already had a large inventory of cartilage images from previous work, so it made sense to focus here.”
Their model analyzed ultrasound images from 48 participants, 20 with prior ACL surgeries and 28 without, to build a statistical shape model of the femoral trochlea. The B-score measures how much a person’s bone shape resembles that of someone who has undergone ACLR. A higher score could indicate a higher risk of reinjury or joint degeneration.
The B-score proved highly accurate, correctly identifying patients with prior ACL surgery 92% of the time. Even more promising, this study is the first to generate such a score using ultrasound, which is faster, cheaper and more accessible than MRI scans.
“This could eventually be a screening tool used in sports physicals or follow-up appointments to help determine who needs further imaging or intervention,” said Harkey.
The researchers say that while ultrasound only captures a small 2D cross-section of the knee, it still provides a detailed and clinically relevant snapshot of bone shape in a critical area.
Their study focused primarily on college-aged females, an age and demographic with high ACL injury rates, but future work will expand the model’s applicability. Parmar is currently refining the B-score using a broader dataset that includes adolescent patients as young as 15 and adults up to age 35.
“There’s still a lot to learn,” Harkey said. “But we’re hopeful that with continued validation, this approach can help identify patients at risk sooner and help prevent the onset of osteoarthritis.”
As the first study to apply B-score modeling with ultrasound, the work opens the door to more accessible, preventative care for athletes and others recovering from ACL surgery.
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