Biochemical properties of collagen from ligaments and periarticular tendons of the human knee.

The biochemical properties of collagens from the periarticular connective tissues of the human knee (ligaments, semitendinosus and gracilis tendons, and the iliotibial band) were investigated in subjects ranging from 20 to 70 years of age. Although the total collagen content of most tissues was more than 90% of the dry weight, the anterior cruciate ligament and the iliotibial band had relatively low collagen contents. There were no significant changes in the tissue collagen content with aging. However, the anterior cruciate ligament and the patellar tendon of the 20-year-old subject had a higher content of soluble collagen than the other ligaments and tendons. The iliotibial band of the 20-year-old subject contained more collagen that was soluble by a combination of salt, sodium citrate extractions and pepsin digestion. Dihydroxylysinonorleucine was the major reducible cross-link of collagen from all the ligaments. The amount of dihydroxylysinonorleucine in the anterior cruciate ligament of the 20-year-old subject was much higher than that in the other ligaments. In contrast, the tendons and the iliotibial band contained a large amount of histidino-hydroxymerodesmosine and hydroxylysinonorleucine, while the patellar tendon was the only tendon with a significant content of dihydroxylysinonorleucine. Hydroxypyridinium non-reducible cross-links were more abundant in collagens from ligaments than in collagens from the other tissues. The cross-link study and the analysis of collagen solubility showed that patellar tendon collagen more closely resembled the collagen from the anterior cruciate ligament than that from periarticular tendons. It was also shown that the anterior cruciate ligament contains relatively immature collagen compared with the other ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)