Monday, May 4, 2009

What the H_LL is the ACL

OK, things got out of hand at work and I slipped back into an old pattern and I haven't posted for a while. I guess that when I decided to write about cruciate ligament injury in the dog, I found the topic so overwhelming that I just avoided the entire project. So, I'm going to divide it up into several smaller posts and the task will be easier for me to tackle. This post will deal with the ligament itself, and an explanation of some of the anatomy of the knee.

The knee is a pretty remarkable joint. The photo shows a model looking at the knee from the front. The joint, is a hinge, designed to flex and extend in one plain of motion similar to the way a door hinge opens and closes. It also has some very amazing shock absorbing principles, that allow us to run and jump. The joint runs into real problems when we ask it to do things it isn't designed to do like rotate, or hyper extend beyond it's normal range of motion.

There are extra articular structures (outside of the joint) that keep the knee stable. The muscles of the thigh that cross the joint and several collateral ligaments that do the same. You can see these collateral ligaments on the outside of the model.

Inside the knee, there are two cushions of cartilage, called the menisci. The medial meniscus on the inside and the lateral meniscus on the outside. They are labeled in the photo above. Finally, making a cross in the center of the knee are the two cruciate (cross) ligaments. The anterior (ACL) and caudal (CCL) cruciate ligaments. These guys keep the knee from sliding forward and backward. In fact the instability caused by injury to the ACL is called anterior drawer sign because when the muscles are relaxed you can actually pull the tibia (shin bone) forward like a drawer in a desk.
So now we all know where everything is. Next post I'll talk about what can happen to these structures. Then finally, we'll get around to explaining how they can be fixed.
Until next time, check us out at: where you can search our library for free information


Anonymous said...

Interesting post!

(I am following you on Twitter).

As for my myself, I relly like cats, look forward to bring one in my home.

Little animals also require care and attention.

Keith Niesenbaum, VMD said...

Well I've repaired ruptured ACL's in cats as well. They do very well post op, proving your point that the are easy to care for.