The meniscal "pseudocyst." A clinical sign of a torn meniscus.

We report a study of 636 patients requiring knee surgery, all of whom underwent detailed preoperative assessment. Fifty-eight patients had a clinical sign of a lump on the joint line when the knee was examined at 45 degrees of flexion, which has been thought to indicate a meniscal cyst. Of these 58 patients, however, only 30 patients had a meniscal cyst demonstrated at surgery. The remaining 28 patients had a meniscal tear without a cyst. In these 28 cases, the clinical sign of a lump protruding from the joint line was termed a "pseudocyst." This new clinical sign is important because of its frequency of occurrence and the complete correlation with meniscal tears requiring surgical intervention.

Molecular evolution of the F glycoprotein of human parainfluenza virus type 1.

Human parainfluenza virus type 1 (hPIV1) is a major cause of upper and lower respiratory tract infections among children. Immunity is mediated at least in part by antibody to the fusion (F) surface glycoprotein. Thus, genetic variation in the F gene could influence host range, virulence, and immunity. To examine the genetic diversity among hPIV1 isolates, the F genes of hPIV1 isolates from a single geographic location were sequenced and compared with the F gene of a strain isolated in 1957. Genetic variation was 2.2%-3.4%, averaging 0.8 amino acid changes per year. Changes were progressive over time, and virus evolution was dominated by a single lineage. Three of 7 isolates tested did not induce syncytium formation in tissue culture. This phenotype could not be ascribed to a single unique mutation in the F gene, but these 3 isolates had mutations in the transmembrane region of the HN gene. It is unlikely that the limited genetic evolution of the F gene will be an obstacle to vaccine development.

Human parainfluenza virus type 1 evolution combines cocirculation of strains and development of geographically restricted lineages.

The hemagglutinin neuraminidase (HN) glycoprotein of human parainfluenza virus type 1 (HPIV-1) mediates attachment to the host cell and is the target of protective antibody. Since the efficacy of a potential vaccine depends on antigenic constancy, the antigenic and genetic stability of the HPIV-1 HN glycoprotein was examined for 13 isolates obtained between 1981 and 1989. Antigenic analysis with a panel of 11 monoclonal antibodies demonstrated a single change among 3 isolates from 1989 that distinguished them from all other isolates. The HN genes from all 13 isolates and 13 previously published HN gene sequences shared > 95% homology. Evolutionary analysis demonstrated cocirculation of strains, without a dominant lineage. The 1989 isolates and the previously proposed subtype A isolates occupied distinct evolutionary branches, indicating geographically limited evolution. The slow rate of evolution and HN homogeneity may allow development of a single vaccine formulation for the prevention of disease.

Cysts and "pseudocysts" of the menisci of the knee joint.

A series of 636 consecutive knee arthrotomies was subjected to a prospective study, including the incidence, clinical presentation, and operative findings of meniscal cysts and associated pathological conditions. The clinical differential diagnosis was studied in detail, and from this, the importance of a specific clinical sign indicating a torn lateral meniscus was realized. This sign was termed a "pseudocyst". It was concluded that meniscectomy was the operation of choice and not simple cyst removal, and that the high incidence of associated meniscal tears and other less frequent joint pathological conditions justified a standardized approach designed to assess the meniscus and other intraarticular structures, rather than a simple incision over the joint-line swelling.