As you may be aware, knee injuries are a strong clinical interest of mine. To increase my understanding of this very important joint, I sat down with Orthopedic Surgeon Dr Chris Raynor to find out more information on the menisci (AKA the “shock absorbers” of the knee).

For those who don’t know Chris, Chris is an orthopaedic surgeon specializing in sports medicine. He is staff at the Cornwall Community Hospital, and runs clinics at the University of Ottawa, and at his brand-new integrated healthcare facility in Ottawa’s southeast end – Human 2.0.

He completed his residency in orthopaedic surgery at the University of Ottawa, and he did a fellowship in sports medicine and arthroscopy at the University of Western Ontario’s renowned Fowler/Kennedy Clinic. Dr. Raynor’s patients have included amateur and competitive athletes from a variety of sports, CIS varsity athletes, MMA fighters, rodeo athletes, and professional CFL players. He believes that movement is medicine, and he wants to help people inject as much physical activity into their lives as possible.

So without further ado, here’s our discussion on meniscus injuries. I hope you enjoy our chat and learn something new!

Mick: Thanks for your time today Chris! Can I start off with this one - What are the menisci in the knee, and what is their function?

Chris: No problems at all Mick. Within the knee there are two menisci – one medial and one lateral, and they have three primary functions. Number one, their role is to act as a shock absorber. Number two, they provide a force distribution mechanism within the knee so that there are not any areas where force in the knee can be loaded in one particular area. And lastly, they serve to help maintain some form of stability within the knee outside of the knee ligaments. Much in the same way a chock block would function if you were trying to stop a car from rolling downhill and you put a wedge behind the back wheels. The menisci function in that same way, so that when the knee is moving into flexion, they prevent the femoral condyles rolling off the back of the tibial surface.

Mick: Interesting to hear they are more than just a “shock absorber”. How would you injure your menisci and what could happen as a result in the short and long terms?

Chris: There are a number of ways in which you can injure the menisci, either individually or in pairs, and typically you're going to have one of two mechanisms. Firstly, you can have direct loading of the meniscus so that the femoral condyle is basically loaded directly onto the tibial surface and compresses the meniscus. Think compression injury from landing on a stiff straight knee. The more common mechanism however is going to be when the meniscus is exposed to a shear force. In this case, the femoral condyle is sliding across the surface of the tibia with the meniscus in between. And what happens is that as the bone slides across the meniscus, the meniscus gets pulled one way by the femoral condyle and another way by the tibia. This would be common in pivoting or change of direction movement.

Now in the short term, you're likely to have pain in the knee, and you're going to have the development of fluid and swelling in the knee, which will basically stretch the capsule of the knee until it is taut adding to the pain state. Then you're likely to have short term stiffness in the knee and a loss of range of motion - an inability to straighten or bend the knee. Depending on the pain, swelling and loss of range of movement, you may also have decreased ability to walk.

In the long term, however, this is where you can sometimes see the real detrimental effects of an injured meniscus. Because of their role in force distribution and force absorption at the knee, the loss of a functioning menisci results in degenerative changes to the knee.

Mick: Not all meniscus injuries are created equally are they Chris? Can you take us through the different types of meniscus injuries that one could sustain?

Chris: Sure. So there are a number of different types of meniscal injury. Some may be more severe than others. First you can have meniscal tears that are only partial, as opposed to complete or full meniscal tears. And what we mean by that is that the tear does not extend all the way through from top to bottom. So that's the broad headings.

But then when you look at the specific types of meniscus tears, you can have something that we call a horizontal meniscus tear, which is usually a simple tear that follows the circumferential fibres of the meniscus. It usually does not involve a significant part of the meniscus, and it is usually close to the edge, the inside edge. It only extends over a very short distance and is the most benign or the simplest meniscus tear that you could have.

Then if you allow that to progress and one end of that breaks off, you can have what we call a radial tear that runs perpendicular to the circumferential fibres of the meniscus. Sometimes, these may progress to become a “parrot-beak” tear, which is basically a radial tear that has extended further across, and then into, the meniscus body. These types of tears are considered full-thickness tears, as they've gone into the substance of the meniscus.

Next you can have what we call a bucket handle tear, which is a full thickness tear that follows the curvature of the meniscus. It’s called a bucket handle because if you kind of look at it from the side, the large portion of the meniscus looks like a bucket, and when the inner part flips onto itself into the notch, it looks like the handle of a bucket. With a bucket handle tear, it is considered a more severe tear, and often cause the knee to “lock”.

Finally, you can have something that we call a complex tear, which is a tear that has several different planes to it. It may have a horizontal component, but it may also have a vertical component or a parrot-beak component or a radial component.

Aside from the specific types of tears, the other thing that we need to consider is the location of these tears. If you were to look at the meniscus from the top down, the meniscus is divided into three zones based on the vascularity of the meniscal segment. The outermost edge of the meniscus, the portion of the meniscus that's closest to the capsule, is called the “red-red” zone. And this is the zone of the most abundant vascularity (blood supply), and is the part of the meniscus which is most likely to heal. Conversely, the innermost edge is what's called the “white-white” zone, which is the least vascular part of the meniscus, and this is the part that is unlikely. Then In between the two zones, we have the “red-white” zone. And this is intermediate vascularity. And so as long as we provide an ideal milieu for healing meniscal tears in that zone could possibly heal themselves if appropriately stabilized and we give them the appropriate time to do so. Location of tears can also be defined by where the tear occurs in relation to the meniscus itself. Locations of tears may include the body of the meniscus, the anterior horn, the posterior horn, the anterior root, or the posterior root.

Mick: Very good. You mentioned before that a person may experience “locking” sensations when they injure their meniscus. The “locking” sensations that people describe; are they a consistent “locking” or can it be transient?

Chris: The “locking” is typically related to a specific knee position or angle, and it can certainly be transient in nature. Usually patients will say to me that they were doing a particular movement when locking occurred. They pivoted or they were in deep knee flexion, and they were able to get into that position, but then suddenly when they tried to get out of that position and then tried to straighten the leg, it would “lock”. And usually that would be at about 10 to 15 degrees of extension, and they were unable to get it straight for all that they tried to do. But then over the next day or so, after they were relaxed, they would feel a little click or a clunk or something move. And then all of a sudden, they'd be able to straighten their leg again. So it's something that is transient, and in some cases unpredictable.

Sometimes people, when they describe “locking”, they will say, "Oh yeah, my knee locks," but the knee actually doesn’t lock. They'll mean that they heard a click, or that it was painful, so they didn't want to extend it, but that extension was still possible. So I'll specifically say to them, "When you bend your knee, are you able to bend it freely?”. I also ask “When you go to straighten your knee, is there something mechanically stopping you from fully extending it?". I specifically use those words just so that there's clarity. I don't say locking. I just ask them if there's a mechanical block, because from a surgical perspective, that's what we surgeons think of as “locking”.

Image: Arthroscopic image of a meniscus repair

Mick: So it seems that not all meniscus require surgery? And if so, which ones would be indicated for surgery?

Chris: During my orthopedic training and residency, we learned of a rule pertaining to meniscal injuries, and it was a general rule of thumb. These aren't hard and fast numbers, but basically we used to say that meniscal injuries follow the rule of thirds. What we meant by that, is that roughly one third of meniscal injuries will get better on their own and will not require any type of operative treatment. Another third will continue to be symptomatic intermittently, but the symptoms will not progress either in frequency, intensity, or severity. And then finally, another third will progress over time to become more frequent, more debilitating, more painful, and more severe.

So if we consider the first third, and once we have determined that meniscus injury is in fact the diagnosis, I will send those people off for physiotherapy so that we have their range of motion and strength addressed. I'll then follow those patients up, usually in about six weeks-time, and we'll see how they're doing. If they have improved with physical therapy and they are continuing to make progress, then I will send them off and I'll see them again in another six weeks, so I'll see them at six and twelve weeks. Generally speaking, I'm expecting that we're going to see a full resolution or their symptoms within that three month timeframe.

Then there's the second third that don’t necessarily get better, and the last third that get worse. So I'll see those patients back at 6 and 12 weeks after they have undergone a course of physiotherapy. If they remain unchanged after the physical therapy then we'll consider operative management, or if they have worsened during that time period, we'll consider operative management if they're an appropriate candidate. And the decision to do either a meniscus repair, partial menisectomy or a full menisectomy will include a number of factors, including their age, their occupation, their ability to comply, what their overall health status, and so forth.

In saying all that however, there is one group of patients who I will consider right from the outset for immediate surgery; and those are patients who have a true locked knee which does not resolve on its own. From our point of view, that's basically an orthopaedic surgical emergency. It's not a life or limb threatening emergency in that sense, but certainly from the viewpoint of the cartilage and from the meniscus itself, we consider that a surgical emergency.

Mick: So with those that end up having a meniscus repair or a meniscectomy, are there any limitations on their rehabilitation?

Chris: Absolutely. With menisectomy patients, I'm going to have less restrictions postoperatively than with the meniscal repair as we don’t have to worry about in the short term any “repair work”. I'm a firm believer that people need to be moving right away, and they need to start physical therapy immediately after surgery. If people are comfortable enough to start the next day, then I will have them do that. I'll allow my patients to weight-bear as tolerated right from day one, and they will start out with crutches. I'm a huge proponent of restoring full extension of the knee as the first step in rehabilitation of the knee. Once they have restored full extension, then we work on flexion. Then we work on strength, then we work on balance and proprioception thereafter.

For my meniscus repair patients however, I'm going to be a little bit more conservative, although not as conservative as some. With a meniscal repair, the intensity of rehabilitation varies on the the type of tear, and the type and location of the repair. If it is any kind of very minor repair (one stitch and/or in the “red-red” zone), then I'll pretty much let them go and do most of the things that I would allow them to do with the partial meniscectomy, except that I wouldn't allow them to flex beyond 90 degrees for six weeks.

For anything else that's more complex that requires more than one suture, or is either in the combination of the “red-white” zone, or extends from the “red-red” to the “red-white” zone, then I'm going to be a little bit more conservative. For those patients I still am going to allow those patients to weight-bear as tolerated right from day one, unless it's a monstrous bucket-handle tear. Then I'll protect or partial weight-bear for about two weeks and then allow them to weight-bear as tolerated. But for most of the tears, they'll be able to weight-bear as tolerated right from day one with crutches with a range of motion brace which allows them to range between full extension and 90 degrees as tolerated for six weeks. They can do all of the regular range of motion stuff with their physical therapist, but I won't allow them to squat with weight for the first six weeks, and I won't allow the therapist to do passive range of motion in flexion for the first six weeks.

After six weeks then I will increase the range of motion in the brace by 10 degrees per week until full range of movement has been achieved by about 10-12 weeks post-op. From a rehabilitation perspective, once full range of motion has been achieved, I will allow meniscal repair patients to start loading their knee with resistance, but I will limit them to 90 degrees again. I will repeat the process of progressing from 90 degrees flexion with resistance, to their maximum knee flexion with resistance at a rate of 10 degrees per week, until maximum resisted knee flexion is obtained. From this point, the process is the same as with a partial menisectomy.

The general principles are to work to obtain full extension, and then full flexion. Strengthen the lower extremity until baseline strength has been restored. I prefer closed chain strengthening first and then progress to open chain as an advanced option. Add balance and proprioception training concomitantly, and then direction change activities/drills as an advanced exercise. This process usually takes between 4-6 months before the patient has completed rehabilitation and is ready to return to regular activities.

Mick: Nice insight Chris! For ACL reconstructions there is emerging literature that a return to sport following ACL reconstruction should be criteria-driven, and not time based. Is there anything that you’re aware of in the meniscus literature in regards to returning to sport following meniscus injury or meniscus surgery?

Chris: I haven't seen anything in particular for that, but just as I am a fan of the Melbourne ACL Rehabilitation Guide for ACLs, I do think that it is worthwhile to follow a similar approach for meniscal tears.

Like ACL injury, many meniscus injuries are non-contact injuries. If you ever look at the film of these injuries as they happen, you see that people put themselves in a compromised position because they don't have the ability to decelerate or change direction appropriately. Even though they're athletes, and some of these athletes are phenomenal athletes, it's like someone's given them the keys to a Porsche, and they have never been taught how to drive. These patients and athletes don't actually have really good body awareness. They don't have an understanding of landing mechanics, change of direction mechanics, pivoting mechanism, none of that. I really think the Melbourne ACL Rehabilitation Guide – and I know it is designed for the ACL - but quite frankly, I think that any injury to do with the knee, a return to sport like how you have mapped out in the Melbourne ACL Rehabilitation Guide is appropriate for meniscus injury because it hits all of the things that are important. Range of motion, strength, proprioceptive ability and knowing where you are in space and then your ability to change direction with control. That's what we want.

Mick: Thank you for your support! I agree, I think the principles in the Melbourne ACL Rehabilitation Guide can be generalised to a wider knee population. My last question - someone's got a suspected meniscus injury, what would be your advice to them?

Chris: First of all, if somebody thinks that they have injured their meniscus, we need to get confirmation of that diagnosis. You need to find a health professional who can properly assess the knee. Once you have the diagnosis, then you're going to want to control the swelling in the knee and restore the full range of motion, and your ability to walk properly at a normal gait. You'll want to do all of this with a physical therapist or physiotherapist.

Then you'll want to revisit the knee to see whether your symptoms have improved or not. You may want to get imaging, if you haven’t already done so, and you may also need to see a sports medicine physician or an orthopedic surgeon if things aren’t getting better to see what else can be done to help your symptoms.

Mick: Very good Chris. As always, I learn a lot from these talks that I have with experts in their field and tonight was no exception mate. So I appreciate your time, and your expertise on this conversation we've had tonight.