ACL Tears-That Terrible Pop You Felt in Your Knee

We hear it all the time, "I felt this pop in my knee."  It may occur skiing, playing basketball, soccer, or even while at work.  Rest assured that when you feel it, you will know something happened in your knee.  The "pop" sensation is often followed by swelling, instability, and a trip to see me!

So what is the ACL (Anterior Cruciate Ligament)?  The ACL is one of two ligaments that sit the in center of our knee in a crossing pattern. (The name "cruciate" comes from the Latin cruci or crux meaning cross.)  The ACL is responsible for what is called anterior/posterior stability or you knee shifting forwards and backwards, as well as some rotational movements.  Often individuals tear the ligament with a non-contact injury like twisting their knee, pivoting, or shifting with their leg planted.  All of these movements cause the femur bone and tibia bone, where the ACL attaches, to shift and put stress on the ligament.  If the stress becomes too great the ligament will give resulting in an ACL tear.

Usually after the tear, one will experience a period of reduced range of motion, swelling, and instability.  This is often when the patient is seen for their first in office appointment. X-ray studies are almost always negative in ACL tears. Physical exam findings will show swelling and positive testing for laxity or looseness in the knee. Often, patients are sent for MRI scans which will confirm the diagnosis of an ACL tear, and rule out an other injury to the meniscus or other ligaments.

Most patients will begin a short course of physical therapy to regain range of motion. It is always recommended that patients have a return of their range of motion and a reduction of their swelling before under going ACL reconstructive surgery.  Motion before surgery always dictates motion after surgery, so it is much easier to rehab a knee if the motion was full before surgery.   At this point a lot of individuals are feeling significantly better, their swelling is down and motion is back; they are thinking--"Why am I having surgery?"  Which is not  a terrible question.  So let me answer it.

The ACL stabilizes the knee from shifting whether that be big noticeable shifts or small more micro-shifting. Each time the knee shifts there is potential for injury or tearing to the meniscus, and damage to the articular cartilage on the ends of the bones.  The more times the knee shifts the more damage or at least risk for damage a patient accumulates.

Ok, now you have decided to have surgery right?  Well the first decision you have to make is what type of tissue to use to reconstruct the ACL.  This is a bit of a hot topic but I will break it down for you with the speech I usually give patients.  Autograft (your own tissue) vs Allograft (cadaver) has been debated and honestly if you ever have a chance to use your own tissue you probably should.  There are always disease transmission risks with any cadaver tissue--they are very small! However if you are that 1 in Million person you will not care what the odds were.  Also there are multiple studies that show there is an increased risk of graft failure in allografts compared with autografts.  Here are a few example studies:  1.  Autograft vs Allograft ACL Reconstructions: A Prospective, Randomized Clinical Study with Minimum 10 Year Follow-up         2.  Prospective Comparative Study of ACL Reconstruction Between Using Hamstring Autograft and Soft Tissue Allograft

There are 3 types of autografts most surgeons choose from: patella tendon, hamstring, and quadriceps.  All have pros and cons and in a good surgeon's hands would be fine choices for your graft.  I will just give you a run down of each.  Patella tendon, also know as a BTB graft has been around the longest and is considered the gold standard we compare everything else too.  It takes a small portion of the patella tendon from the front of the knee and usually also a piece of bone from both the patella and the tibia "(shin bone) to form the graft.  This is a strong graft similar to a native ACL however some patients especially those older than teens tend to get some knee cap pain from this graft.  Hamstring tendon grafts have also been around a long time and  take a small piece of the hamstring from the back of the thigh from it's attachment on the shin bone.  This does not involve removing any bone, but does not act as much like a native ACL and some think it can stretch a bit.  A quadriceps tendon graft removes a small portion of the central quadriceps tendon with or without a small piece of the patella bone.  The quad graft is a newer graft and fewer surgeons are using it on a regular basis, it does have similar properties to a native ACL.

Courtesy of Arthrex Inc

Surgery involves removing the old torn ACL and drilling bone tunnels in the tibia and femur.  These
tunnels will allow for the graft to be pulled into the knee and secured with metal buttons or screws that come in a variety or materials.  Rehab protocols will vary by surgeon, some will place patients in post operative braces and on crutches, some will begin physical therapy with in days or weeks.  The most important thing to remember when it comes to rehabilitation is that it will take 9-12 months for the graft to mature and heal.  That means a slow return to activities!  I cannot stress that enough.  I could do a whole separate blog on ACL rehab. If you take nothing else from this remember that everyone will heal at a different rate and it is important to listen to your body and doctor.  Often a return to full athletic sport may take up to one year depending on the sport and athlete.  

    

Total Knee Replacements--Why so Spooky?

This topic is brought to you by popular demand!  I've had great deal of requests for a topic on total knee replacements or as we call them in the ortho world TKAs (Total Knee Arthroplasty).  TKAs can seem overwhelming and downright SPOOKY if you are faced with the possibility of surgery.  Let's see if we can dust some cobwebs off the common myths about TKAs and reveal the truth hidden underneath!

I have a conversation about the compartments of the knee with patients on a weekly basis, so this may sound familiar to some of you.  The knee is separated into three compartments, the inside of the knee (Medial compartment) outside of the joint (Lateral compartment) and the knee cap joint (Patellofemoral compartment).   The knee may wear in one, two, or all three of those compartments and the amount of wear determines what surgery is recommended.

There are two types of cartilage within the knee. The Meniscus the large shock absorber between the bones and Articular cartilage which covers the ends of the bones.  Articular cartilage acts in a similar way to enamel on our teeth, it in itself does not feel pain, but when it is worn away the bone beneath feels pain.  This is considered arthritis (just like a cavity in your tooth) and can be very painful.

When you have this break down in cartilage in one of the compartments in the knee that one area of the knee can be replaced.  This is called a Unicompartmental Arthroplasty or "Half Knee."   I personally think we should call them "1/3 knee replacements" but my opinion doesn't seem to count for much!  The problem is when individuals begin to develop damage in two sometimes all three compartments of the knee.  This is global or total knee arthritis, and is when surgeons recommend a TKA to replace the entire knee.

By the time a patient needs a total knee replacement it is usually easy to see on xray studies.  As you can see on my background images for the blog the patients' knees are pretty healthy with good space between the thigh bone (femur) and shin bone (tibia).  He did not need a TKA he was actually a young healthy teenager.  In contrast, this knee shown below, has no joint space at all in the medial compartment, or "bone on bone" arthritis.  The patient also has bone spurs that have formed at the ends of the femur and tibia at the joint line.  The body will try to put down bone in areas where cartilage has been worn away.  It is a protective mechanism in the body but unfortunately backfires and causes us to lose range of motion.     

Total knee arthroplasties as we know them were developed in the early 1970s.  The surgery continues to be tweaked and modified on a regular basis but many of the concepts are the same.  We still replace the end of the femur and the tibia with metal components and a plastic spacer replaces the meniscus.  There are many companies on the market today and most will tell you their knee components are the best around.  I compare this to care manufactures.  Many are built on similar constructs with different bells and whistles, but all will drive you from one place to another.  I  think the most important concept is that your surgeon is comfortable working with the implant.  Most joint surgeons have a preferred brand or two that they feel works best for their patients and has had the best outcomes in their hands.


There are two major distinctions when it comes to total knee replacement implants--cemented vs press fit components.  The type of component a surgeon uses often is related to where he/she was trained.   A "press-fit" component get its name because it is actually impacted or pressed onto the ends of the bones.  The idea is that the patient's own bone will actually adhere or grow into the metal components forming a stable construct.  This is good for younger patients who may need a second replacement procedure early in their lifetime because revising these implants is a little easier.  A cemented implant requires gluing or cementing the metal onto the bone.  This also forms a stable construct, and maybe good for older patients or patients with poor quality bone.  The cement allows for a secondary fixation when poor quality bone may not be quite enough.

TKAs are a fascinating topic and relevant to so many people.  I hope this provides a background on the procedure and need for a replacement.  As I began writing this article it became clear that it would be too large for one post.  We have so much more to discuss!! Hospital stays, rehabilitation, risks vs benefits of surgery.   I will have to post a TKA Part Two in the near future.  Feel free to ask questions if you would like them included in that article.

Next post in two weeks is a surprise...     

   

For more info on TKAs check out the AAOS webpage here





Sources
Ranawat, C. (2002). History of Total Knee Replacement. J South Orthopedics Assoc, 11(4), 218-26. Retrieved September 22, 2015, from http://www.ncbi.nlm.nih.gov/pubmed/12597066