"Spiking", "sharpening" or "peaking" of the tubercles of the intercondylar eminence of the tibial plateau has been described as an early sign of osteoarthritis of the knee joint, but there are no reports confirming this association. The radiographs of 55 patients with established osteoarthritis of the knee joint and 36 controls were reviewed. Measurements were made of the angulation of the tips of the medial and lateral tubercles, and the ratio of the tubercle height to the width of the tibial plateau was calculated. There was a significant difference in both these parameters between the two groups, confirming that lengthening and sharpening of the angles of the tubercles are features of osteoarthritis of the knee joint.