New research has revealed that noisy knees following an anterior cruciate ligament (ACL) injury do not necessarily indicate future arthritis. The study, conducted by researchers at La Trobe University, provides important insights for patients and clinicians, helping to distinguish between existing joint damage and potential long-term risks.
The investigation focused on the phenomenon known as knee crepitus, which includes the sounds of grinding, cracking, and popping often experienced after a knee injury. Previous studies linked these noises to osteoarthritis (OA) in older adults, raising concerns among younger individuals who might experience similar symptoms after a traumatic knee injury.
Jamon Couch, a graduate researcher and physiotherapist, led the study to explore the relationship between knee crepitus and OA in young adults. The findings suggest that while knee crepitus indicates existing cartilage damage, it does not predict worsening conditions over time.
In this study, researchers evaluated 112 young adults with a median age of 28 years who had undergone surgical reconstruction of their ACL. They assessed participants one year post-surgery and again after five years. As part of their evaluation, participants answered questions regarding the presence of noise in their knees, categorized within the Knee Injury and Osteoarthritis Outcome Score (KOOS). Those who answered “often” or “always” were classified as having knee crepitus.
MRI scans were utilized to examine cartilage damage, bone spurs, and lesions in the bone marrow. In addition to the KOOS, participants reported their pain levels and overall knee function using validated questionnaires. The researchers adjusted their statistical models for factors such as age, sex, and body mass index (BMI) to ensure accurate comparisons.
The study revealed that, one year after surgery, individuals with knee crepitus were over two and a half times more likely to have full-thickness cartilage defects in the patellofemoral joint, located behind the kneecap. Furthermore, these individuals reported greater pain, lower knee-related quality of life, and poorer functional outcomes compared to those without crepitus.
Despite these initial findings, the long-term follow-up indicated no significant increase in joint damage between one to five years post-surgery. Participants with knee crepitus did not exhibit a greater risk of deteriorating OA features on MRI scans during this period. Interestingly, those who experienced crepitus reported greater improvements in pain and function over time, primarily because they began with more severe symptoms.
The researchers acknowledged limitations in the study, including the small sample size and the low prevalence of crepitus, with around 21% of participants reporting the condition. Approximately 30% of participants returned for the five-year follow-up, which may also affect the strength of the observed associations.
Overall, the findings underscore that while knee crepitus signals existing joint damage, it does not serve as a definitive indicator of future deterioration in young individuals following ACL injuries. This research can provide reassurance to both patients and healthcare providers, as noisy knees after ACL reconstruction should not be viewed as a harbinger of inevitable arthritis.
As a result of this study, clinicians can encourage ongoing physical activity and rehabilitation for those experiencing knee crepitus, countering misconceptions that these noises equate to long-term joint issues. The research was published in the journal Arthritis Care & Research, contributing valuable information to the field of sports medicine and rehabilitation.
