Abnormal joint mechanics and the proteoglycan composition of normal and healing rabbit medial collateral ligament.

OBJECTIVE

This study investigated the influence that abnormal joint mechanics may have upon the biochemical composition of the joint's own soft tissue holding elements.

DESIGN

The investigation used an animal model of ligament injury, the rabbit medial collateral ligament (MCL). The proteoglycan component of the ligament extracellular matrix was extracted, purified and characterized.

INTERVENTIONS

The experimental groups consisted of: a) a control group consisting of the MCL from both right and left knees of six animals that had not undergone surgery; b) a group (healing gap injury) of six MCL from right knees in which a segment of tissue had been excised from the anterior cruciate and the MCL of the right knee 3 wk prior to sacrifice; and c) a third group (contralateral gap injury) comprised of the MCL from the six left knees of the same gap injury animals.

OUTCOME MEASURES

The MCL water content, total proteoglycan content, hexose and hexuronate-containing proteoglycan and proteoglycan electrophoretic mobility were determined for each group studied.

RESULTS

The healing gap injury MCL was found to have a higher water content, a higher total proteoglycan content and a higher proportion of aggregating proteoglycan than MCL from control animals. The nonaggregating proteoglycan fraction from the contralateral MCL (group 3) had a greater electrophoretic mobility and probably, therefore, a smaller molecular weight than that found in the MCL from the same knee of control animals.

CONCLUSIONS

Since MCL healing took place in an abnormal mechanical environment, these results suggest that joint biomechanics may be an important factor in mediating connective tissue proteoglycan composition.