Effects of compression and recovery on bovine articular cartilage: Appearance on MR images

PURPOSE: To determine the influence of compression and decompression on bovine articular cartilage as it appears on magnetic resonance (MR) images. MATERIALS AND METHODS: Consecutive spin-echo MR images (repetition time msec/echo time msec = 800/33) of normal bovine cartilage were obtained with increasing increments of pressure, to a maximum of 4.14 MPa (600 psi); this was followed by consecutive MR imaging after release of the pressure. RESULTS: Before compression, cartilage showed a laminated appearance. After incremental pressure, cartilage thickness progressively decreased; a short T2, low-signal-intensity lamina became thicker and more distinct at the articular surface; signal intensity of the deep cartilage zone initially was high and then gradually decreased; and at maximum pressure, the cartilage showed uniform low signal intensity. After release of pressure, signal intensity changes in the cartilage were sequentially reversed from those observed with compression. Image resolution and echo time influenced the appearance of these findings, particularly the low-signal-intensity line at the cartilage interface. CONCLUSION: The varying appearance and signal intensity characteristics of cartilage under pressure are hypothesized to result from a combination of net water loss and alteration in collagen orientational structure.