Effect of combined traumatic impact and radial transection of medial meniscus on knee articular cartilage in a rabbit in vivo model

Purpose: The purpose of this study was to test the hypothesis that combined meniscectomy and traumatic impact accelerate early degeneration of articular cartilage in the knee versus meniscectomy alone. Methods: A previously published in vivo rabbit cartilage impact model was used combined with radial transection of the medial meniscus posterior horn versus meniscal transection alone. Rabbits were killed 3 months after surgery. Quantitative histologic analysis of the articular cartilage proteoglycan depth and glycosaminoglycan (GAG) fraction was performed at the site of impact on the posterior femoral condyle (PFC) and at the distal femoral condyle (DFC) overlying the meniscectomy in the surgical knee and the contralateral control knee. Results: The articular cartilage in the knees that underwent isolated meniscectomy did not differ significantly from the contralateral control knees for any measured value. The knees with a combined insult had a lower GAG fraction (P =.03) at the PFC and a greater depth of proteoglycan loss at both the PFC (P =.02) and the DFC (P =.04) versus contralateral controls. Compared with meniscectomy alone, the combined-insult knees had a greater depth of proteoglycan loss at the DFC (P =.005). Conclusions: On the basis of early results using GAG fraction and proteoglycan depth, combined traumatic impact and meniscectomy are more damaging to articular cartilage than meniscectomy alone. Clinical Relevance: A knee with a combination of meniscal injury and articular cartilage impact may be at particularly high risk for early joint degeneration.