Bilateral discoid medial menisci.

SUMMARY: This article adds 2 more cases of bilateral discoid medial menisci to the previously reported 9 cases. The radiographs of the first case revealed bilateral cupping of the medial tibial plateaus and a small lytic lesion of the left distal medial femoral metaphysis. Beside the posteriorly unstable incomplete type discoid medial meniscus, the left knee had several associated arthroscopic findings: depression of the medial tibial plateau with exposed subchondral bone, anomalous insertion of the anterior horn of the discoid meniscus to the anterior cruciate ligament, a pathological medial plica, and longitudinal deep fissures in the trochlea. The second case was a complete type with peripheral horizontal cleavage tears. Following arthroscopic surgery, magnetic resonance imaging (MRI) scans of the contralateral knees were obtained in both cases to search for bilaterality. MRI revealed discoid medial menisci in the unoperated knees as well. The short-term results of arthroscopic meniscectomy may not be as satisfactory as those reported for normal menisci.

Dislocating anterior horn of the medial meniscus.

Dislocating anterior horn of the medial meniscus was found in 15 knees of 13 patients during arthroscopic examinations done between 1992 and 1995. All of them were available for follow-up evaluation (4 by telephone). There were 11 men and 2 women (average age, 28 years; range, 17 to 49 years). Nine knees had a history of trauma. Only 1 knee had had trauma in two bilateral cases. Duration of symptoms was an average of 3.3 years (range, 3 months to 10 years). The knees were stable clinically. Arthroscopy revealed associated lesions in 13 knees; hypertrophic medial plicae, meniscal, chondral and anterior cruciate ligament (ACL) lesions predominated. Three knees had unusually hypertrophic ligamentum mucosum. Eleven of 13 knees had more than one associated lesions. Only 2 knees (2 patients) had isolated dislocating anterior horn of the medial meniscus. Only the associated lesions were treated (except for ACL lesions) and dislocating anterior horns of the medial menisci were left alone. Follow-up averaged 21 months (7 to 40 months). At follow-up, 11 knees were graded as excellent, 3 as good, and 1 as fair according to the Lysholm scale. Eight knees had minor symptoms and 6 were asymptomatic; no improvement was noted in 1 knee. Overall, 12 patients (14 knees) were satisfied with their treatment. Dislocating anterior horn of the medial meniscus is a normal anatomic variant with little or no clinical significance. When seen during arthroscopy, a significant lesion should be looked for. It is an incidental finding and should be left alone.

Intra-articular hemangioma of the knee with meniscal and bony attachment.

A hemangioma in the knee joint of a 37-year-old woman was diagnosed by magnetic resonance imaging. The case presented with pain and a tender localized swelling lateral to the patellar tendon. Arthroscopy verified the diagnosis but did not allow visualization of the full extent of the tumor. After arthroscopic subtotal excision of the associated hypertrophic medial plica, a miniarthrotomy was done. The tumor was attached to the periphery of the anterior horn of the lateral meniscus, to the anterior tibial plateau, and to the fat pad. It seemed to take its origin from the venous plexus just below the anterior lip of the central tibial plateau. The patient was asymptomatic 9 months after surgery. In hemangiomas not amenable to arthroscopic surgery, open excision through miniarthrotomy ensures complete removal without prolonging recovery.

Intraarticular fibroma of the tendon sheath of the knee.

Fibroma of the tendon sheath is an uncommon soft-tissue tumor. Intraarticular localization has not been previously reported. The patient presented with unexplained recurrent swelling of the knee not associated with recent trauma. The soft-tissue tumor was identified by magnetic resonance imaging. Arthroscopy confirmed the diagnosis. Arthrotomy was performed because of the large size of the lesion.

Kinematic and dynamic axial computerized tomography of the normal patellofemoral joint.

Fourteen normal volunteers with no history suggesting previous or current knee pathology underwent axial computed tomographic examination of the patellofemoral joint. There were 11 men and 3 women, whose ages ranged from 10 to 46 years (average 25 years). Axial images were obtained at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 60 degrees flexion both with and without contraction of the thigh muscles. Thus, 12 images were obtained for each individual. The CT scanner was focused at the midpatellar level prior to each image. Three measurements were made on 24 knees for each individual: congruence angle (CA), patellar tilt angle (PTA), and sulcus angle (SA). PTA increased slightly from 0 degrees to 20 degrees, and decreased slightly with more flexion (not significant, NS). The lower limit of PTA was usually 9 degrees-10 degrees; it was not lower than 7 degrees in any knee position. Muscle contraction increased PTA slightly at each degree of flexion (NS). Mean CA was +18.3 degrees (SD 20.8 degrees) at 0 degrees, which means that normal individuals may have CAs as high as +39 degrees at full extension. There was a gradual decrease in CAs with knee flexion. The mean values became negative between 20 degrees and 60 degrees flexion. Contraction of the thigh muscles caused lateralisation of the patella except at 30 degrees and 40 degrees flexion. This lateral pull was statistically significant at full extension (P < 0.01) and at 10 degrees flexion (P < 0.05). The SA decreased gradually as the flexion of the knee increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinematic and dynamic axial computed tomography of the patello-femoral joint in patients with anterior knee pain.

Thirty-eight knees of 26 patients with anterior knee pain (12 bilateral) were included in the study. There were 22 women and 4 men, and their average age was 29 years. Axial computed tomography (CT) examination of both knees were done at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees and 60 degrees of flexion with and without muscle contraction. Images were always taken at the mid-patellar level. Patellar tilt angle (PTA), congruence angle (CA) and sulcus angle (SA) were measured at each knee position. Normal values were also obtained from 14 healthy volunteers (28 knees). Thus, the types of patello-femoral incongruence were determined at each knee position: 1, tilt + lateralisation (TL: 12 knees); 2, lateralisation (L: 4 knees); 3, medialisation (M: 5 knees); 4, lateral to medial instability (LM: 1 knee); 5, tilt (T: 1 knee). Fifteen knees were classified as normal. When the groups were analysed separately, in the TL group the T or L component would have been missed in nine cases if the images were taken only at 30 degrees or only in the first 30 degrees of flexion. In the L group two patellae were reduced at 30 degrees. In three knees in the M group, medialisation began at 10 degrees, 20 degrees and 30 degrees. One patella was reduced at 40 degrees. In the LM case, the patella was lateralised at 0 degrees, 10 degrees, 20 degrees and medialised at 30 degrees and 40 degrees. In the T case, the patella was tilted only at 20 degrees, 40 degrees and 60 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)