Arthroscopy: The Journal of Arthroscopic and Related Surgery 7(2):148-150 Published by Raven Press, Ltd. 8 1991 Arthroscopy Association of North America
Congenital Hypoplasia of the Medial Meniscus: A Report of Two Cases Roy S. Twyman,
F.R.C.S.
and Barry D. Ferris, M.S., F.R.C.S.
Summary: Congenital abnormalities of the medial meniscus are extremely rare. We present two cases of hypoplasia and demonstrate the arthroscopic and radiological features. Key Words: Hypoplasia, congenital-KneeMeniscus.
Case 2 A 34-year-old Afro-Caribbean man presented, having had a twisting injury to his right knee on two occasions. The second of these was followed by immediate swelling and pain on the medial aspect of the knee. At presentation he complained of slight instability. Apart from a small effusion, examination was unremarkable. An arthrogram showed the medial meniscus to be short throughout its length, especially in its middle one-third (Fig. 2). An arthroscopy revealed a small medial meniscus with no tear. There was a bucket-handle tear of the lateral meniscus and an old tear of the anterior cruciate ligament. The bucket-handle fragment was removed arthroscopically and the patient has resumed sports. In both of these cases the morphology of the abnormal medial meniscus was the same. The posterior horn was normal but on coming forward it rapidly faded to a narrow rim that barely covered any of the tibia1 surface. The base of its peripheral attachment was of normal height, but instead of fanning out into the joint to a narrow point, its free edge was short and blunt. Anteriorly the meniscus remained narrow and hypoplastic all the way to its tibia1 attachment. The articular surfaces of the femur and tibia were normal.
Congenital abnormalities of the medial meniscus of the knee are rare. There have been several case reports of discoid medial menisci, but hypoplasia is virtually unknown. We were only able to find two case reports, without illustrations. We will present the arthroscopic and radiological features of two cases, both of which were incidental findings in patients with other problems. CASE REPORTS Case 1 A lZyear-old girl of mixed race was referred with a fixed flexion deformity of the left knee that was present since birth. She had a number of other features: short stature, short neck, hypoplasia of the atlas with fusions of the first three cervical vertebrae, obesity, coarse hair, and clawing of the fingers. No definite diagnosis was made. There was no history of injury to the knee. The knee presented with quadriceps wasting and 20” of fixed flexion. A marked “clunk” was present on extending the knee to 90”. Plain radiographs were normal. Arthroscopic examination revealed a hypoplastic but stable medial meniscus (Fig. 1) and a normal anterior cruciate ligament. The lateral meniscus was hypermobile and the posterior rim could be dislocated into the joint. It was sutured to the capsule arthroscopically.
DISCUSSION From the Westminster Hospital, London, England. Address correspondence and reprint requests to Mr. R. S. Twyman at 122 Astonville Street, Southfields, London, SW18 SAG, England.
Hypoplastic congenital abnormalities in the medial meniscus are virtually unknown. Clark and Og148
CONGENITAL
HYPOPLASIA
OF MEDIAL
MENISCUS
FIG. 1. Arthroscopic appearances of the hypoplastic medial meniscus in case 1. Note that the diameter of the tip of the hook is -2 mm.
den (1) studied the natural development of the menisci in the normal knee. They found that the knee joint was fully formed with menisci by the 8th week in utero. During development they found there was considerable variation in the size of the lateral meniscus but not the medial one. In the two cases we are presenting, there was clearly hypoplasia of the medial meniscus, The first case almost certainly had a congenital abnormality of the lateral meniscus, but interestingly the lateral meniscal tear in the second case was through an otherwise normal lateral meniscus and was caused by a twisting injury. We could only find two other reports of congenital hypoplasia of the medial meniscus. Pfeil (2) described an otherwise normal man who presented with spontaneous locking of the knee. At arthrotomy a hypermobile hypoplastic meniscus was found and removed. The author believed that this was necessary to prevent early degeneration of the knee. The only report of complete absence of the medial meniscus was described by To10 in a child with thrombocytopenia with absent radius syndrome (3). A boy with unstable knees had absence of the anterior cruciate ligament and both menisci (4). In addition, this child had abnormalities on plain radiographs of the knee joints, a point of distinction from our two cases. Tolo stated that the presence of menisci might be an important determinant of the growth of the femoral and tibia1 condyles (3). The
FIG. 2. Arthrogram of the medial meniscus in case 2. Frame 1 is anterior, 2 and 3 are middle, and 4 is posterior. The posterior part of the meniscus appears normal, but the anterior and middle portions are markedly hypoplastic.
two cases that we describe suggest that this might not be so. In contrast to the previous cases, we are able to demonstrate the arthroscopic and radiological features. The hypoplastic medial meniscus in both instances were not the cause of the patients’ symptoms, suggesting that this is a benign and rare condition. Arthroscopy,
Vol. 7. No. 2. 1991
150
R. S. TWYMAN
Acknowledgment: We thank Mr. P. M. Aichroth, consultant orthopaedic surgeon, and Mr. J. E. Scott, consultant orthopaedic surgeon, for permission to report these cases. REFERENCES 1. Clark CR, Ogden JA. Development of the menisci of the human knee joint. Morphological changes and their potential
Arthroscopy, Vol. 7, No. 2, 1991
AND B. D. FERRIS role in childhood meniscal injury. J Bone Joint Surg [Am] 1983;65:538-47. 2. Pfeil G. Der hypoplastische, hypermobile Meniskus. Beitr Orthop Traumatol 1%7;14:3-5. 3. Tolo VT. Congenital absence
of the menisci and cruciate ligaments of the knee. A case report. J Bone Joint Surg [Am] 1981;63:1022-4. 4. Hall JG, Levin J, Kuhn JP, Ottenheimer EJ, Von Berkum KAP, McKusick VA. Thrombocytopenia with absent radius (TAR). Medicine (Baltimore) 1%9;48:411-39.
Congenital Hypoplasia of the Medial Meniscus: A Report of Two Cases Roy S. Twyman,
F.R.C.S.
and Barry D. Ferris, M.S., F.R.C.S.
Summary: Congenital abnormalities of the medial meniscus are extremely rare. We present two cases of hypoplasia and demonstrate the arthroscopic and radiological features. Key Words: Hypoplasia, congenital-KneeMeniscus.
Case 2 A 34-year-old Afro-Caribbean man presented, having had a twisting injury to his right knee on two occasions. The second of these was followed by immediate swelling and pain on the medial aspect of the knee. At presentation he complained of slight instability. Apart from a small effusion, examination was unremarkable. An arthrogram showed the medial meniscus to be short throughout its length, especially in its middle one-third (Fig. 2). An arthroscopy revealed a small medial meniscus with no tear. There was a bucket-handle tear of the lateral meniscus and an old tear of the anterior cruciate ligament. The bucket-handle fragment was removed arthroscopically and the patient has resumed sports. In both of these cases the morphology of the abnormal medial meniscus was the same. The posterior horn was normal but on coming forward it rapidly faded to a narrow rim that barely covered any of the tibia1 surface. The base of its peripheral attachment was of normal height, but instead of fanning out into the joint to a narrow point, its free edge was short and blunt. Anteriorly the meniscus remained narrow and hypoplastic all the way to its tibia1 attachment. The articular surfaces of the femur and tibia were normal.
Congenital abnormalities of the medial meniscus of the knee are rare. There have been several case reports of discoid medial menisci, but hypoplasia is virtually unknown. We were only able to find two case reports, without illustrations. We will present the arthroscopic and radiological features of two cases, both of which were incidental findings in patients with other problems. CASE REPORTS Case 1 A lZyear-old girl of mixed race was referred with a fixed flexion deformity of the left knee that was present since birth. She had a number of other features: short stature, short neck, hypoplasia of the atlas with fusions of the first three cervical vertebrae, obesity, coarse hair, and clawing of the fingers. No definite diagnosis was made. There was no history of injury to the knee. The knee presented with quadriceps wasting and 20” of fixed flexion. A marked “clunk” was present on extending the knee to 90”. Plain radiographs were normal. Arthroscopic examination revealed a hypoplastic but stable medial meniscus (Fig. 1) and a normal anterior cruciate ligament. The lateral meniscus was hypermobile and the posterior rim could be dislocated into the joint. It was sutured to the capsule arthroscopically.
DISCUSSION From the Westminster Hospital, London, England. Address correspondence and reprint requests to Mr. R. S. Twyman at 122 Astonville Street, Southfields, London, SW18 SAG, England.
Hypoplastic congenital abnormalities in the medial meniscus are virtually unknown. Clark and Og148
CONGENITAL
HYPOPLASIA
OF MEDIAL
MENISCUS
FIG. 1. Arthroscopic appearances of the hypoplastic medial meniscus in case 1. Note that the diameter of the tip of the hook is -2 mm.
den (1) studied the natural development of the menisci in the normal knee. They found that the knee joint was fully formed with menisci by the 8th week in utero. During development they found there was considerable variation in the size of the lateral meniscus but not the medial one. In the two cases we are presenting, there was clearly hypoplasia of the medial meniscus, The first case almost certainly had a congenital abnormality of the lateral meniscus, but interestingly the lateral meniscal tear in the second case was through an otherwise normal lateral meniscus and was caused by a twisting injury. We could only find two other reports of congenital hypoplasia of the medial meniscus. Pfeil (2) described an otherwise normal man who presented with spontaneous locking of the knee. At arthrotomy a hypermobile hypoplastic meniscus was found and removed. The author believed that this was necessary to prevent early degeneration of the knee. The only report of complete absence of the medial meniscus was described by To10 in a child with thrombocytopenia with absent radius syndrome (3). A boy with unstable knees had absence of the anterior cruciate ligament and both menisci (4). In addition, this child had abnormalities on plain radiographs of the knee joints, a point of distinction from our two cases. Tolo stated that the presence of menisci might be an important determinant of the growth of the femoral and tibia1 condyles (3). The
FIG. 2. Arthrogram of the medial meniscus in case 2. Frame 1 is anterior, 2 and 3 are middle, and 4 is posterior. The posterior part of the meniscus appears normal, but the anterior and middle portions are markedly hypoplastic.
two cases that we describe suggest that this might not be so. In contrast to the previous cases, we are able to demonstrate the arthroscopic and radiological features. The hypoplastic medial meniscus in both instances were not the cause of the patients’ symptoms, suggesting that this is a benign and rare condition. Arthroscopy,
Vol. 7. No. 2. 1991
150
R. S. TWYMAN
Acknowledgment: We thank Mr. P. M. Aichroth, consultant orthopaedic surgeon, and Mr. J. E. Scott, consultant orthopaedic surgeon, for permission to report these cases. REFERENCES 1. Clark CR, Ogden JA. Development of the menisci of the human knee joint. Morphological changes and their potential
Arthroscopy, Vol. 7, No. 2, 1991
AND B. D. FERRIS role in childhood meniscal injury. J Bone Joint Surg [Am] 1983;65:538-47. 2. Pfeil G. Der hypoplastische, hypermobile Meniskus. Beitr Orthop Traumatol 1%7;14:3-5. 3. Tolo VT. Congenital absence
of the menisci and cruciate ligaments of the knee. A case report. J Bone Joint Surg [Am] 1981;63:1022-4. 4. Hall JG, Levin J, Kuhn JP, Ottenheimer EJ, Von Berkum KAP, McKusick VA. Thrombocytopenia with absent radius (TAR). Medicine (Baltimore) 1%9;48:411-39.
