Bony Erosion with Mucoid Degeneration of the Anterior Cruciate Ligament
Yusuke Ueda, Kazuo Saita, Takehiko Yamaguchi, Hitoshi Sekiya, Toru Akiyama
The Journal of Knee Surgery Reports
The first reported case of mucoid degeneration of the anterior cruciate ligament (MDACL) was provided by Kumar et al in 1999. 1 The pathogenesis is still unclear, but this condition is thought to be secondary to ACL degeneration. A 2004 study reported the prevalence of MDACL as 0.043%, 2 but a 2008 study found a prevalence of 5.3%. 3 Although MDACL is not as rare as previously thought, it is not still well known by physicians and is probably underdiagnosed or misdiagnosed as an ACL tear. More
... curate data on MDACL are needed. MDACL with erosion of adjacent bone is extremely rare; only a few cases have been reported to date. 1,4,5 We treated two patients with MDACL, one with an eroded lesion in the lateral femoral condyle and one with tibial insertion of the ACL. We report these two cases and discuss their clinical features with reference to previous MDACL reports, focusing on bone erosion. Patients and Methods The two patients were male, aged 38 and 34 years. Their presenting complaints were knee pain, inability to flex beyond 125 and 140 degrees, respectively, and difficulty climbing up and down stairs or walking short distances (less than 500 m). The knee pain was not limited to specific points, spreading out to the whole knee in both the cases. Both patients' preoperative Keywords ► knee ► anterior cruciate ligament ► mucoid degeneration ► bone erosion Abstract Mucoid degeneration of the anterior cruciate ligament (MDACL) is a comparatively rare pathological finding in clinical practice. Its pathophysiology is still unclear. MDACL can be suspected in patients with knee pain associated with a thickened ACL. Treatment involving arthroscopic resection of the yellow mucoid substance is efficient for relieving the symptoms. Only few reports had mentioned about the association with the erosion of adjacent bone. Here, we describe the cases of our two MDACL patients with osseous erosion. Both the patients had suffered from posterior knee pain for several months. Magnetic resonance imaging (MRI) indicated a thickened ACL with increased signal with bone erosion on T2-weighted images. On arthroscopy, the ACLs were found to be grossly hypertrophied, and the region of the posterolateral bundle was impinged in both the patients. No bony pathological findings were observed by arthroscopy. The yellowish degenerated portion of the ACL was resected to resolve the pathological situation in each case. Postoperatively, both the patients had a full range of painless motion with no impediments to the quick resumption of daily living. Follow-up MRIs showed reduced volumes of bone erosion. Thus, bone erosion was not the main cause of the knee pain, but rather was a lesion associated with MDACL.