- Email: [email protected]
Symptomatic Anomalous Insertion of the Medial Meniscus
Case Report
Symptomatic Anomalous Insertion of the Medial Meniscus Tetsuo Nakajima, M.D., Yuji Nabeshima, M.D., Hideo Fujii, M.D., Akihiro Ozaki, M.D., Hirotsugu Muratsu, M.D., and Shinichi Yoshiya, M.D.
Abstract: We report a case of a young athlete with a symptomatic anomaly of the medial meniscus. An anomalous portion in conjunction with the anterior horn of the medial meniscus extended to the intercondylar notch of the femur through the surface of the anterior cruciate ligament. This anomalous band was arthroscopically resected and the symptoms completely disappeared. Histologic examination showed fibrocartilaginous tissue compatible with meniscus. Key Words: Medial meniscus—Anomaly—Surgical treatment.
T
he introduction and development of magnetic resonance imaging (MRI) has led to significant improvements in the diagnostic accuracy and treatment of meniscal abnormalities. However, for some patients with prolonged knee pain, no positive findings are revealed by MRI, which makes treatment somewhat difficult. In particular, anomalies of the medial meniscus have been reported to be difficult to detect before arthroscopic intervention. Moreover the clinical significance of this anomaly is still unknown. We present a rare case of anomalous insertion of the anterior horn of the medial meniscus extending to the intercondylar notch of the femur, which was incidentally found during arthroscopy. Arthroscopic resection of this anomalous insertion was successful.
From the Department of Orthopaedic Surgery, Himeji St. Mary’s Hospital, Himeji, Japan. Address correspondence and reprint requests to Yuji Nabeshima, M.D., Department of Orthopaedic Surgery, Himeji St. Mary’s Hospital, 650 Nibuno Himeji, Hyogo 670-0801, Japan. E-mail: [email protected] © 2005 by the Arthroscopy Association of North America Cite this article as: Nakajima T, Nabeshima Y, Fujii H, Ozaki A, Muratsu H, Yoshiya S. Symptomatic anomalous insertion of the medial meniscus. Arthroscopy 2005;21:629.e1-629.e4 [doi: 10.1016/j.arthro.2005.02.002]. 0749-8063/05/2105-4270$30.00/0 doi:10.1016/j.arthro.2005.02.002
CASE REPORT A 13-year-old female sprinter felt left anterior knee pain on landing during long jump activities. She visited our hospital 1 month later because of unrelieved pain and catching. Examination revealed tenderness over the anteromedial joint line and the McMurray’s test result was positive on the medial side. She complained of anterior knee pain on the hyperextension test although she had full range of motion. Plain radiographs showed no abnormalities. Although MRI scans showed no meniscal tear, the initial diagnosis was medial meniscal tear. Diagnostic arthroscopy was performed and it revealed an anomalous band, in conjunction with the anterior horn of the medial meniscus, extending to the intercondylar notch of the femur through the surface of the anterior cruciate ligament (ACL) (Fig 1A). This white-colored band was relatively thin and had a lustrous structure without substantial adhesion to the ACL (Fig 1B). Impingement between the band and roof of the intercondylar notch was observed when the knee was fully extended (Fig 1C). The ACL was normal and no tear was found in the medial meniscus. The transverse ligament was absent and the normal semilunar-shaped lateral meniscus was seen. No therapeutic procedure was conducted.
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 5 (May), 2005: pp 629.e1-629.e4
629.e1
629.e2
T. NAKAJIMA ET AL.
FIGURE 1. (A) Arthroscopic examination showing an anomalous band, in conjunction with the anterior horn of the medial meniscus, extending to the intercondylar notch of the femur through the surface of the ACL. (B) The white-colored band was relatively thin and had a lustrous structure without substantial adhesion to the ACL. (C) The impingement between the band and roof of the intercondylar notch is observed when the knee is fully extended.
However, the patient’s knee pain did not resolve after arthroscopic intervention, leading us to conclude that the impingement of the abnormal inser-
tion of the medial meniscus was the cause of the pain. Three months after the first surgery, the anomalous insertion was arthroscopically resected and
FIGURE 2. (A) The anomalous insertion is arthroscopically resected and trimmed to the shape of a normal meniscus. (B) The impingement is no longer observed after the procedure.
SYMPTOMATIC ANOMALY OF THE MEDIAL MENISCUS
629.e3
trimmed to the shape of a normal meniscus (Fig 2A). As a result, impingement was no longer observed (Fig 2B) and the stable anterior horn of the medial meniscus was confirmed by a probe. Histologic examination of the anomalous band showed fibrocartilaginous tissue compatible with meniscus (Fig 3). A follow-up evaluation 1 year after surgery showed complete resolution of symptoms and the patient had returned to athletic activities. DISCUSSION Anomalies of the medial meniscus are rare compared with those of the lateral meniscus. Most anomalous variations of the medial meniscus other than those of discoid type are seen in the anterior horn. In the normal knee, the anterior horn of the medial meniscus is attached to the tibial plateau in the area of the anterior intercondylar fossa in front of the ACL. The posterior fibers of the anterior horn attachment merge with the transverse ligament, which connects the anterior horns of the medial and lateral menisci.1 Several reports have documented the anomalous insertion of the anterior horn directly to the ACL or to the intercondylar notch. Ohkoshi et al.2 analyzed the relatively wide variations of the anterior insertion of the medial meniscus in a report that included an anomaly identical to the present case. There are 2 clinical problems to be solved in treating this anatomic variation: the diagnostic challenge and the necessity for surgical intervention. The only method to date of diagnosing this anomalous insertion, except for arthroscopy, is MRI, although challenges remain in detecting this anomaly using only this method. Arjun et al.3 documented the appearance of a lesion on prearthroscopic MRI and diagnosed it as an anomalous meniscus. Soejima et al.4 showed the cord-like object running from the anterior horn of the medial meniscus alongside of the ACL on MRI without clear recognition of clinical significance. Other reports have only described it as an incidental finding during arthroscopy, which was also the case in the present report. However, a subsequent review of the MRIs in the present case showed a thin, low-signal band just anterior to the ACL on a T2-weighted sagittal image, which was considered to be consistent with the anomalous portion (Fig 4A). This low-signal band was not imaged in the follow-up study (Fig 4B). Previous reports have stated 2 distinct directions
FIGURE 3. Histologic examination of the anomalous band showed fibrocartilaginous tissue compatible with meniscus.
for the treatment of this lesion. Santi and Richardson5 described a case in which the symptoms fully disappeared by resection of the anomalous insertion. Shea et al.6 reported a case of anomalous insertion of the medial meniscus with lateral subluxation of the patella. They speculated that there was a possible relationship between symptoms and the anomaly because resection of the anomalous portion resulted in a resolution of the pain over the medial joint line. Recently, Rainio et al.7 reported on 11 cases with anomalous insertion of the anterior horn of the medial meniscus. They concluded that the symptoms of 3 of the 11 patients were caused by this anomaly and considered that simple resection of the anomalous portion relieved the pain. On the other hand, Kim et al.8 reported cases of a similar anomaly with lateral discoid meniscus in which they concluded that this anomaly had no clinical significance because they were able to relieve the symptoms by simply trimming the lateral discoid meniscus. Arjun et al.3 reported the successful treatment of a medial meniscal tear associated with the present anomaly by only partial medial meniscectomy with no treatment for the anomalous portion. In the present case, pain at hyperextension and catching disappeared completely following resection of the anomalous insertion of the medial meniscus. Therefore, we concluded that this anomaly was the definitive symptomatic lesion.
Acknowledgment: The authors thank Ms. Janina Tubby for her help in preparing the manuscript.
629.e4
T. NAKAJIMA ET AL.
FIGURE 4. (A) Preoperative MRI showing a thin, low-signal band just anterior to the ACL on the T2-weighted sagittal image. (B) The low-signal band was not visible on postoperative MRI.
REFERENCES 1. Arnoczky SP. Meniscus. In: Fu FH, Harner CD, Vince KG, eds. Knee surgery. Baltimore: Williams & Wilkins, 1994;131-140. 2. Ohkoshi Y, Takeuchi T, Inoue C, Hashimoto T, Shigenobu K, Yamane S. Arthroscopic studies of the anterior horn of the medial meniscus. Arthroscopy 1997;13:725-730. 3. Arjun S, Takahashi S, Tang Y, Nakane N, Yonemitsu H. MR appearance of anomalous insertion of the medial meniscus. Acta Radiologica 1998;39:554-556. 4. Soejima T, Murakami H, Tanaka N, Nagata K. Anteromedial meniscofemoral ligament. Arthroscopy 2003;19:90-95.
5. Santi MD, Richardson AB. Bilaterally painful anomalous insertion of the medial meniscus in a volleyball player with Marfanoid features. Arthroscopy 1993;9:217-219. 6. Shea KG, Westin C, West J. Anomalous insertion of the medial meniscus of the knee. J Bone Joint Surg Am 1995;77:18941896. 7. Rainio P, Sarimo J, Rantanen J, Alanen J, Orava S. Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament. Arthroscopy 2002;18:1-6. 8. Kim S-J, Kim D-W, Min B-H. Discoid lateral meniscus associated with anomalous insertion of the medial meniscus. Clin Orthop 1995;315:234-237.
Symptomatic Anomalous Insertion of the Medial Meniscus Tetsuo Nakajima, M.D., Yuji Nabeshima, M.D., Hideo Fujii, M.D., Akihiro Ozaki, M.D., Hirotsugu Muratsu, M.D., and Shinichi Yoshiya, M.D.
Abstract: We report a case of a young athlete with a symptomatic anomaly of the medial meniscus. An anomalous portion in conjunction with the anterior horn of the medial meniscus extended to the intercondylar notch of the femur through the surface of the anterior cruciate ligament. This anomalous band was arthroscopically resected and the symptoms completely disappeared. Histologic examination showed fibrocartilaginous tissue compatible with meniscus. Key Words: Medial meniscus—Anomaly—Surgical treatment.
T
he introduction and development of magnetic resonance imaging (MRI) has led to significant improvements in the diagnostic accuracy and treatment of meniscal abnormalities. However, for some patients with prolonged knee pain, no positive findings are revealed by MRI, which makes treatment somewhat difficult. In particular, anomalies of the medial meniscus have been reported to be difficult to detect before arthroscopic intervention. Moreover the clinical significance of this anomaly is still unknown. We present a rare case of anomalous insertion of the anterior horn of the medial meniscus extending to the intercondylar notch of the femur, which was incidentally found during arthroscopy. Arthroscopic resection of this anomalous insertion was successful.
From the Department of Orthopaedic Surgery, Himeji St. Mary’s Hospital, Himeji, Japan. Address correspondence and reprint requests to Yuji Nabeshima, M.D., Department of Orthopaedic Surgery, Himeji St. Mary’s Hospital, 650 Nibuno Himeji, Hyogo 670-0801, Japan. E-mail: [email protected] © 2005 by the Arthroscopy Association of North America Cite this article as: Nakajima T, Nabeshima Y, Fujii H, Ozaki A, Muratsu H, Yoshiya S. Symptomatic anomalous insertion of the medial meniscus. Arthroscopy 2005;21:629.e1-629.e4 [doi: 10.1016/j.arthro.2005.02.002]. 0749-8063/05/2105-4270$30.00/0 doi:10.1016/j.arthro.2005.02.002
CASE REPORT A 13-year-old female sprinter felt left anterior knee pain on landing during long jump activities. She visited our hospital 1 month later because of unrelieved pain and catching. Examination revealed tenderness over the anteromedial joint line and the McMurray’s test result was positive on the medial side. She complained of anterior knee pain on the hyperextension test although she had full range of motion. Plain radiographs showed no abnormalities. Although MRI scans showed no meniscal tear, the initial diagnosis was medial meniscal tear. Diagnostic arthroscopy was performed and it revealed an anomalous band, in conjunction with the anterior horn of the medial meniscus, extending to the intercondylar notch of the femur through the surface of the anterior cruciate ligament (ACL) (Fig 1A). This white-colored band was relatively thin and had a lustrous structure without substantial adhesion to the ACL (Fig 1B). Impingement between the band and roof of the intercondylar notch was observed when the knee was fully extended (Fig 1C). The ACL was normal and no tear was found in the medial meniscus. The transverse ligament was absent and the normal semilunar-shaped lateral meniscus was seen. No therapeutic procedure was conducted.
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 21, No 5 (May), 2005: pp 629.e1-629.e4
629.e1
629.e2
T. NAKAJIMA ET AL.
FIGURE 1. (A) Arthroscopic examination showing an anomalous band, in conjunction with the anterior horn of the medial meniscus, extending to the intercondylar notch of the femur through the surface of the ACL. (B) The white-colored band was relatively thin and had a lustrous structure without substantial adhesion to the ACL. (C) The impingement between the band and roof of the intercondylar notch is observed when the knee is fully extended.
However, the patient’s knee pain did not resolve after arthroscopic intervention, leading us to conclude that the impingement of the abnormal inser-
tion of the medial meniscus was the cause of the pain. Three months after the first surgery, the anomalous insertion was arthroscopically resected and
FIGURE 2. (A) The anomalous insertion is arthroscopically resected and trimmed to the shape of a normal meniscus. (B) The impingement is no longer observed after the procedure.
SYMPTOMATIC ANOMALY OF THE MEDIAL MENISCUS
629.e3
trimmed to the shape of a normal meniscus (Fig 2A). As a result, impingement was no longer observed (Fig 2B) and the stable anterior horn of the medial meniscus was confirmed by a probe. Histologic examination of the anomalous band showed fibrocartilaginous tissue compatible with meniscus (Fig 3). A follow-up evaluation 1 year after surgery showed complete resolution of symptoms and the patient had returned to athletic activities. DISCUSSION Anomalies of the medial meniscus are rare compared with those of the lateral meniscus. Most anomalous variations of the medial meniscus other than those of discoid type are seen in the anterior horn. In the normal knee, the anterior horn of the medial meniscus is attached to the tibial plateau in the area of the anterior intercondylar fossa in front of the ACL. The posterior fibers of the anterior horn attachment merge with the transverse ligament, which connects the anterior horns of the medial and lateral menisci.1 Several reports have documented the anomalous insertion of the anterior horn directly to the ACL or to the intercondylar notch. Ohkoshi et al.2 analyzed the relatively wide variations of the anterior insertion of the medial meniscus in a report that included an anomaly identical to the present case. There are 2 clinical problems to be solved in treating this anatomic variation: the diagnostic challenge and the necessity for surgical intervention. The only method to date of diagnosing this anomalous insertion, except for arthroscopy, is MRI, although challenges remain in detecting this anomaly using only this method. Arjun et al.3 documented the appearance of a lesion on prearthroscopic MRI and diagnosed it as an anomalous meniscus. Soejima et al.4 showed the cord-like object running from the anterior horn of the medial meniscus alongside of the ACL on MRI without clear recognition of clinical significance. Other reports have only described it as an incidental finding during arthroscopy, which was also the case in the present report. However, a subsequent review of the MRIs in the present case showed a thin, low-signal band just anterior to the ACL on a T2-weighted sagittal image, which was considered to be consistent with the anomalous portion (Fig 4A). This low-signal band was not imaged in the follow-up study (Fig 4B). Previous reports have stated 2 distinct directions
FIGURE 3. Histologic examination of the anomalous band showed fibrocartilaginous tissue compatible with meniscus.
for the treatment of this lesion. Santi and Richardson5 described a case in which the symptoms fully disappeared by resection of the anomalous insertion. Shea et al.6 reported a case of anomalous insertion of the medial meniscus with lateral subluxation of the patella. They speculated that there was a possible relationship between symptoms and the anomaly because resection of the anomalous portion resulted in a resolution of the pain over the medial joint line. Recently, Rainio et al.7 reported on 11 cases with anomalous insertion of the anterior horn of the medial meniscus. They concluded that the symptoms of 3 of the 11 patients were caused by this anomaly and considered that simple resection of the anomalous portion relieved the pain. On the other hand, Kim et al.8 reported cases of a similar anomaly with lateral discoid meniscus in which they concluded that this anomaly had no clinical significance because they were able to relieve the symptoms by simply trimming the lateral discoid meniscus. Arjun et al.3 reported the successful treatment of a medial meniscal tear associated with the present anomaly by only partial medial meniscectomy with no treatment for the anomalous portion. In the present case, pain at hyperextension and catching disappeared completely following resection of the anomalous insertion of the medial meniscus. Therefore, we concluded that this anomaly was the definitive symptomatic lesion.
Acknowledgment: The authors thank Ms. Janina Tubby for her help in preparing the manuscript.
629.e4
T. NAKAJIMA ET AL.
FIGURE 4. (A) Preoperative MRI showing a thin, low-signal band just anterior to the ACL on the T2-weighted sagittal image. (B) The low-signal band was not visible on postoperative MRI.
REFERENCES 1. Arnoczky SP. Meniscus. In: Fu FH, Harner CD, Vince KG, eds. Knee surgery. Baltimore: Williams & Wilkins, 1994;131-140. 2. Ohkoshi Y, Takeuchi T, Inoue C, Hashimoto T, Shigenobu K, Yamane S. Arthroscopic studies of the anterior horn of the medial meniscus. Arthroscopy 1997;13:725-730. 3. Arjun S, Takahashi S, Tang Y, Nakane N, Yonemitsu H. MR appearance of anomalous insertion of the medial meniscus. Acta Radiologica 1998;39:554-556. 4. Soejima T, Murakami H, Tanaka N, Nagata K. Anteromedial meniscofemoral ligament. Arthroscopy 2003;19:90-95.
5. Santi MD, Richardson AB. Bilaterally painful anomalous insertion of the medial meniscus in a volleyball player with Marfanoid features. Arthroscopy 1993;9:217-219. 6. Shea KG, Westin C, West J. Anomalous insertion of the medial meniscus of the knee. J Bone Joint Surg Am 1995;77:18941896. 7. Rainio P, Sarimo J, Rantanen J, Alanen J, Orava S. Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament. Arthroscopy 2002;18:1-6. 8. Kim S-J, Kim D-W, Min B-H. Discoid lateral meniscus associated with anomalous insertion of the medial meniscus. Clin Orthop 1995;315:234-237.