Vascular volume determination of articular tissues in normal and anterior cruciate ligament-deficient rabbit knees

The vasculature of diarthroidal joints has been well documented; however, the volume of vessels supplying different articular tissues is unknown. Angiogenesis, the formation of new vessels from preexisting ones, is difficult to quantify in joints due to the unavailability of a suitable technique. Although angiogenesis is known to occur in rheumatoid arthritis, the development of new vessels following joint injury has not been ascertained. A vascular casting technique was developed using carmine red dye to measure the vascular volume of the medial collateral ligament (MCL), lateral collateral ligament (LCL), menisci, medial capsule, and infrapatellar fat pad of the rabbit knee joint. Vascular volume determinations were repeated at 4 weeks in a group of anterior cruciate ligament (ACL)-transected animals and in a sham-operated control group. The volume of vessels supplying the MCL was estimated to be 0.22 +/- 0.07 microliter (mean +/- S.E.M.), the LCL volume was 0.25 +/- 0.05 microliter, the medial meniscus volume was 0.19 +/- 0.03 microliter, the lateral meniscus volume was 0.40 +/- 0.08 microliter, the medial capsule volume was 0.14 +/- 0.05 microliter, and the infrapatellar fat pad volume was 1.90 +/- 0.62 microliters. Following ACL transection, angiogenesis was found to occur in the MCL only. All other tissue vascularities were not significantly different from sham-operated controls. A quantifiable method for measuring vascular volume of knee joint tissues has been described. Joint instability stimulates angiogenesis in the ipsilateral MCL; however, the absence of angiogenic activity in other articular tissues might help explain the lack of posttraumatic healing associated with these joints.