Progressive chronic osteoarthritis in femorotibial joints of partial medial meniscectomized guinea pigs.

The sequential histopathologic alterations in femorotibial joints of partial meniscectomized male and female guinea pigs were evaluated at 1, 2, 3, 6, and 12 weeks post-surgery. Foci of moderate to severe cartilage degeneration were present in the medial tibial plateau and femoral condyle of the operated leg by 1 week post-surgery. At 2 weeks post-surgery, the cartilage degeneration in the operated legs was more extensive and there was evidence of early chondrophyte formation on the medial side of either the femur or tibia in three animals. Changes were progressively more severe at 3,6, and 12 weeks. Focal areas of minimal to mild cartilage degeneration were in the medial tibial plateau of the contralateral nonoperated leg in some animals at 3 weeks post-surgery and in all animals at 12 weeks post-surgery. Changes in the contralateral leg of meniscectomized guinea pigs have not been described previously. Since cartilage degeneration was often severe by 1 week post- surgery, the model has limited utility for testing agents designed to modify the degenerative process in the operated leg. Milder, more slowly progressive lesions in the contralateral leg may be amenable to therapeutic intervention. Osteoarthritis (OA) is a common affliction of aged human and some domestic animal specie^.^-^ Sponta- neous and experimental animal models of OA allow investigation of pathogenesis and effects of chemo- therapeutic agents on disease progression. Experimental degenerative joint disease has been in- duced by a variety of different procedures in various animal species. Surgical models of OA using collateral ligament transection, partial or complete meniscecto- my, cruciate ligament transection, or various combi- nations thereof have been described in the dog, rabbit, and guinea pig. The guinea pig is smaller and requires less space for housing. Also, less compound would be required than if dogs or rabbits were te~ted.~-~.~~J~ In guinea pigs, medial collateral ligament and anterior cruciate transection with partial medial meniscectomy resulted in severe lesions at 14 weeks post-surgery.13 Minimal arthritic changes were present at 2 1 weeks in guinea pigs in which only the anterior cruciate and collateral ligaments were transected. Lesions were not described in the contralateral nonoperated knees of animals in either group, nor was any information given about the progression of the disease (i.e., whether the lesions were slowly progressive to the ultimate severity described or whether the cartilage degeneration was rapid following surgical intervention). Since osteoar- thritis is generally thought to be a slowly progressive disease, knowledge of the rapidity of disease progres- sion in animal models is important in determining the suitability of models for study of the degradative pro- cesses which occur. In order to better characterize the development of OA in the guinea pig and to determine the suitability of this model of OA for the screening of potential che- motherapeutic agents, the present study was designed to determine the sequential histopathologic alterations in the operated and contralateral nonoperated femo- rotibial joints of partially meniscectomized male and female guinea pigs at 1, 2, 3, 6, and 12 weeks post- surgery.