Nuclear magnetic resonance imaging (MRI) was used to study the normal knee. As well as revealing bone quality, MRI provided useful information on intra-articular and extra-articular soft tissues. Midsagittal views gave clear images of the cruciate ligaments, and of the patellar and quadriceps tendons. Parasagittal views were the best for delineating the menisci which, like ligaments and tendons, are of low intensity; the semimembranosus tendon and its insertion to the proximal tibia were also seen clearly in these views. The cruciate ligaments and menisci, though visible in the coronal view also, were better seen in the sagittal view. Axial views provided information on the structure of the patella, its cartilage, the patellofemoral joint and posterior soft-tissue structures.

The soft tissue response to carbon fibre was studied histologically one and a half years after being used to reconstruct the lateral collateral ligament of the human knee. A remarkably consistent pattern was seen in the induced ligament. The basic pattern was a "composite unit", consisting of a core of carbon fibre enveloped in a concentric manner by coherent layers of fibroblasts and collagen fibres. This new structure seemed to have been induced by continuous irritation caused by the physical structure of the carbon fibres; it is unlikely ever to acquire the structure of a natural ligament. However, it is biologically compatible and is biomechanically sufficient as long as the entire tow of carbon fibres is preserved.