Mar 2 2005
Study links tears of anterior cruciate ligament to increased risk and severity of disease even among patients with no recall of significant knee injury.
As many professional athletes know, tears of the cruciate ligaments – the two ligaments that in the knee that keep it stable– can lead to short-term as well as long-term problems, including severe osteoarthritis (OA) of the knee. Rupture of the front or anterior cruciate ligament is, in fact, known to provoke premature knee OA. However, much about the relationship between knee OA and cruciate ligament damage is still unknown, especially its impact in ordinary individuals with OA as opposed to athletes or people with known knee injuries.
Recently, a team of researchers set out to investigate the prevalence of anterior and posterior cruciate ligament tears among middle-aged and elderly patients with symptomatic OA, as well as the effect of such tears on disease progression and pain. Their findings, published in the March 2005 issue of Arthritis & Rheumatism, indicate anterior cruciate ligament (ACL) rupture as a widely under-recognized and under-treated factor in knee OA.
The study focused on 360 patients with advanced, painful knee OA, recruited through the cooperation of Boston University Medical Center and the Boston Veterans Affairs Healthcare System. Just over 66 percent were male, and the mean age was 67 years. An additional 73 patients, similar in age and sex, were recruited to serve as controls. Of the controls, 48 had knee OA, confirmed by radiographs, but no pain, and the remaining 25 had no OA symptoms or knee discomfort. Overall, the case group tended to have a slightly higher body mass index (BMI) than the control groups.
Researchers used magnetic resonance imaging (MRI) to assess the prevalence of cruciate ligament tears in all groups. Rupture of the posterior cruciate ligament (PCL) was extremely rare, found in less than one percent of the case group and none of the controls. Complete ACL tears, however, were present in nearly one-quarter of the case subjects, compared with less than 3 percent of the controls. Furthermore, knee OA was assessed as more severe, according to radiographic evidence and joint space narrowing, among patients with ruptures than those with intact ACLs. Yet, patients with ACL tears, whether partial or complete, did not suffer more pain than their counterparts. Patients who reported knee pain were also asked about their history of serious knee injury requiring the use of crutches or a cane. Interestingly, fewer than half of the patients with complete ACL tears – about 48 percent – reported a previous knee injury. "Due to the cross- sectional nature of this study, we could not ascertain when the ACL ruptures occurred," notes one of the study's authors, Catherine L. Hill. "The interval between ACL injury and significant knee symptoms may be as long as 30 years, providing one explanation for the low recall of significant knee injury in our study."
On the strength of their common occurrence among older people with advanced OA of the knee, this study suggests that complete ACL tears play a major, under-reported role in the development of this debilitating disease. Yet, as Hill reports, the benefits of surgical intervention for OA patients with ACL ruptures is still open to debate and investigation. "Arthroscopic reconstruction of early ACL rupture has recently been shown to lessen episodes of rotational instability compared with knees that remain ACL deficient, leading to the speculation that reconstructive surgery may reduce future degenerative damage," Hill notes. "However, in patients with complete ACL rupture who have already developed some degenerative changes, the role of ACL reconstruction to reduce progression of knee OA has not been addressed."
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