Introduction The reports in the literature on the appearance of the patellar tendon after harvesting its central third are contradictory. Nixon et al. [14] reported that the histo- logical appearance is indistinguishable from that of normal tendon in biopsies taken from two humans approximately 2 years after harvesting the central third of the patellar tendon. Using a goat model, Proctor et al. [15] reported that the donor site, despite looking normal while using magnetic resonance imaging (MRI), revealed abnormal tissue composition when the biopsies were evaluated both histologically and with transmission electron microscopy. In a study involving humans, Kartus et al. [9] reported abnormal tissue composition in both the central and peripheral parts of the patellar tendon after harvesting its central third. However, the follow-up period was only 2 years. Similar findings in a Michael Svensson Ju¨ri Kartus Lars Rostga˚rd Christensen Tomas Movin Nikos Papadogiannakis Jon Karlsson A long-term serial histological evaluation of the patellar tendon in humans after harvesting its central third Received: 24 May 2004 Accepted: 5 October 2004 Published online: 1 February 2005 Ó Springer-Verlag 2005 Abstract It is previously known that the patellar tendon does not nor- malise histologically in the short term after harvesting its central third. The aim of the study was to obtain long-term serial biopsies from the central and peripheral parts of the patellar tendon after the har- vesting procedure. Our hypothesis was that in the long term after har- vesting its central third, the patellar tendon does not regain normal his- tological appearance. Seventeen consecutive patients, who had undergone anterior cruciate liga- ment reconstruction using patellar tendon autografts, were included. Percutaneous biopsies were obtained under ultrasonographic guidance 27 (24–29) months and 71 (68– 73) months after the index proce- dure, respectively. The sections were stained with haematoxylin and eo- sin. The biopsies were evaluated using light microscope. Both at 27 months and 71 months, the fibre structure was deteriorated and the vascularity and cellularity were increased compared with normal tendon. This was seen in both the central and peripheral parts of the tendon. In conclusion, nearly 6 years after harvesting its central third, the patellar tendon had still not norma- lised histologically, neither in the central nor peripheral parts of the tendon. Keywords Anterior cruciate ligament Æ Patellar ligament Æ Surgery Æ Serial biopsies Æ Histology DOI 10.1007/s00167-004-0590-9 Knee Surg Sports Traumatol Arthrosc (2005) 13: 398–404 KNEE M. Svensson Æ J. Kartus Department of Orthopaedics, Norra A ¨ lvsborg/Uddevalla Hospital, 461 85 Trollha¨ttan, Sweden L. R. Christensen Department of Diagnostic Radiology, Norra A ¨ lvsborg, Trollha¨ttan, Sweden T. Movin Department of Orthopaedics, Karolinska University Hospital, Karolinska Institutet, Huddinge, Stockholm, Sweden N. Papadogiannakis Department of Pathology, Karolinska University Hospital, Karolinska Institutet, Huddinge, Stockholm, Sweden J. Kartus (&) Fyrbodal Research Institute, Uddevalla, Sweden E-mail: juri.kartus@vgregion.se Fax: +46-520-91701 J. Karlsson Department of Orthopaedics, Sahlgrenska University Hospital, Go¨teborg, Sweden