Meniscal Lesions CPG

Today we cover the meniscus portion of the CPG also known as the Knee Pain and Mobility Impairments: Meniscal and Cartilage Lesions Revision 2018. Additionally, we pull in a CPG from the British Journal of Sports Medicine and some extra material to explain the CPG's recommendations.

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Transcript

Welcome back to OCS Field Guide. Today we’re going to start to tackle the 2018 update of the Knee Pain and Mobility Impairments: Meniscal and Articular Cartilage Lesions CPG. In general, we find this to be one of the more confusing CPGs, and in particular we think it’s confusing how the CPG handles both meniscus injuries and articular cartilage injuries side-by-side, so we’re going to break this down into two episodes. First, we’re going to cover meniscus injuries. In the next episode, we’ll cover cartilage injuries.

Since 10% of the OCS exam is anatomy and physiology, I’m going to start today by reviewing some knee anatomy. You recall from your basic anatomy classes that the menisci are wedge-shaped, semicircular cartilaginous discs that can bear up to 70% of the load on the knee during weight bearing activities. You will also recall that the outer third of both menisci is well vascularized and is referred to as the red zone. Injuries here can heal well conservatively. Injuries in the middle third, or the red-white zone, might heal conservatively. And the inner third, or the white zone, is avascular, so injuries here are unlikely to heal on their own. The exception to this general rule is the posterior lateral corner of the lateral meniscus, which is separated from the capsule by the popliteus tendon. This region is fairly avascular even in the outer third, so even the outer third may not heal. You may be able to remember that this area is less likely to heal because it sits in the posterolateral corner, and  posterolateral corner injuries are particularly unpleasant and difficult knee injuries.

Regarding medial and lateral differences, the lateral meniscus is larger, more circular, and more mobile than the medial meniscus—which is a good thing, because it requires more mobility during the screw home mechanism. It is connected to the popliteus, and contractions of the popliteus can cause small movements in the lateral meniscus. The medial meniscus is smaller, more C-shaped, and less mobile than the lateral meniscus, which is thought to be one reason that the medial meniscus is injuries more frequently. This lack of mobility is due in part to the medial meniscus having more attachments to the joint capsule, and in part because the MCL attaches to the medial meniscus. (In contrast, the lateral meniscus is not attached to the LCL.) The semimembranosus also attaches to both the MCL and the medial meniscus, so contractions of the semimembranosus can cause small movements in the medial meniscus as well. To recall the highlights here, remember: the Lateral is Larger and attaches to the popLiteus. The Medial attaches to the semiMembranosus, and it’s more commonly injured because it’s less mobile. It’s less mobile, because it’s attached to the MCL.

Let’s move on into the CPG and talk about meniscus tears. There are two major categories of meniscus tears: traumatic tears and degenerative tears. Traumatic tears are more likely to be sustained by young individuals, and the mechanism of injury is usually a closed chain, non-contact twisting injury. Degenerative tears are more likely to occur in older individuals; in fact, 91% of people with symptomatic OA have a meniscus tear. When we compare medial and lateral meniscus injuries, we’ve already said that the medial is the one that is injured most often; however, when lateral tears occur, they tend to occur in the younger population. Let’s talk about risk factors. The CPG reads, “Cutting and pivoting sports are risk factors for acute meniscus tears. Increased age and delayed ACL reconstruction are risk factors for future medial and lateral meniscus tears. Female sex, older age, higher body mass index, lower physical activity, and delayed ACL reconstruction are risk factors for medial meniscus tears.” So, to put that all together one more time the risk factors for medial or lateral meniscus tears are: cutting and pivoting sports, increased age, or delayed ACL reconstruction. The risk factors that are specific to medial meniscus tears are female sex, higher BMI, and lower physical activity.

When it comes to diagnosis, the CPG recommends a combination of the following factors: knee pain with a history of a twisting mechanism of injury, history of “catching” or “locking,” delayed onset of effusion, and a Meniscal Pathology Composite Score greater than 3 positive findings. The Meniscal Pathology Composite Score is a clinical prediction rule with five parts: first, a history of “catching” or “locking;” second, pain with forced hyperextension; third, pain with maximal knee flexion; fourth, joint line tenderness; and fifth, pain or audible click with McMurray’s maneuver. This is not the most sensitive prediction rule, but it is 90% specific if there are greater than 3 positives. So at least 3 positives in the Meniscal Pathology Composite Score combined with a twisting mechanism of injury and delayed joint effusion should be plenty of information to diagnose a meniscus tear. One note about the joint effusion before we move on. Effusion due to a meniscus injury should occur 6-24 hours after injury. This distinguishes a meniscus injury from an osteochondral fracture, where hemarthrosis is expected 0-2 hours after injury, and from an ACL, PCL, or MCL tear, where hemarthrosis is expected 0-12 hours after injury. In fact, when hemarthrosis is present 0-2 hours following a knee injury, the injury is most often an ACL injury. So if you get a case on the OCS where hemarthrosis occurs within the first 2 hours after injury, suspect ACL first, then PCL, MCL, or osteochondral fracture. If effusion takes 6-24 hours to occur, suspect meniscus tear.

Next we’ll talk about surgery. On average, whether patients chose surgery or conservative management, those who have torn a meniscus will report lower knee function compared to the general population. Again, on average, the CPG says, “those who chose nonoperative management…have similar to better outcomes in terms of strength and perceived knee function in the short and intermediate term compared to those who had [an arthroscopic partial meniscectomy].”

This is especially true for degenerative meniscus tears. In 2018, the British Journal of Sports Medicine published a clinical practice guideline that made a strong recommendation against arthroscopic surgery and in favor of conservative management when dealing with degenerative meniscus tears. Their recommendation reads, “We make a strong recommendation against the use of arthroscopy in nearly all patients with degenerative knee disease, based on linked systematic reviews; further research is unlikely to alter this recommendation. This recommendation applies to patients with or without imaging evidence of osteoarthritis, mechanical symptoms, or sudden symptom onset.” This is recommendation is partially based on a 2016 randomized controlled trial by Kise et al. in the British Journal of Sports Medicine, which examined 140 adults with a mean age of 49.5 years with degenerative meniscus tears. 96% of them had no evidence of knee OA. Over 2 years, the only difference noted between the surgical group and the nonsurgical group was better thigh muscle strength in the nonsurgical group at the 3-month follow up. I mention all of this to drive into your head: we should not be recommending MRIs and surgery to those with likely degenerative meniscus tears. In real life and on the OCS exam, if your patient has a degenerative tear, do not choose to recommend arthroscopic surgery.

All of this does stand in contrast to young patients, who seem to do better with meniscus repair—at least compared to partial meniscectomy. The CPG reads, “Young patients who have meniscus repair have similar to better perceived knee function, less activity loss, and higher rates of return to activity compared to those who have [arthroscopic partial meniscectomy].” Although there’s not a hard-and-fast rule on who is a “young” patient, 30-years-old is a fairly common cutoff.

Regarding return to sport timelines following partial meniscectomy, the CPG reads, “Elite and competitive athletes or athletes younger than 30 years are likely to return to sport less than 2 months after APM, and athletes older than 30 years are likely to return by 3 months after APM.” 

Since a portion of the OCS exam is prognosis, I will summarize what I think you could be asked about once more before we move on: on average, those who have torn a meniscus have lower reported knee function years following the injury whether or not they get a partial meniscectomy. On average, those who have a meniscus tear should chose nonoperative management, since the outcomes with conservative care are the same or better than partial meniscectomy. This is especially true for those with degenerative tears. Young patients have better outcomes with meniscus repair compared to partial meniscectomy, so if surgery is ever recommended following a meniscus tear, it should be in a young patient where a repair rather than a partial meniscectomy is possible. And if your patient does get a partial meniscectomy, the return-to-sport timeline is 2 months for elite athletes, competitive athletes, or athletes under 30, and it’s 3 months for everyone else.

That’s enough about surgery outcomes. Let’s move on to outcome measures. This CPG recommends the same self-report measures as the knee ligament sprain CPG: the IKDC 2000 and the KOOS. Again, there are no cutoffs or MCIDs mentioned for individuals with meniscus injuries, so we would recommend that you just remember that on both the IKDC 2000 and on the KOOS a higher score is better and a lower score is worse.

For physical outcome measures, the CPG recommends the 30-second chair-stand test, the stair-climb test, the timed up-and-go test, and the 6-minute walk test for the early rehab period and single-leg hop testing for return to activity or sports.

For physical impairment measures, their recommendations follow your normal clinical instincts: active range of motion, quadriceps strength, forced hyperextension, maximum passive knee flexion, McMurray’s, joint-line tenderness, and the modified stroke test for effusion. The one you might be less familiar with is the modified stroke test. In this test, the patient is supine with an extended knee. Starting at the medial joint line, the examiner strokes the knee upward 2 to 3 times toward the suprapatellar pouch in an attempt to move the swelling from the joint capsule to the suprapatellar pouch. Then the examiner strokes downward on the distal lateral thigh toward the joint line. What you’re watching for is a wave of fluid on the medial side of the knee. The measure is graded “zero” if there is no wave produced with the downstroke, or it’s graded “trace” if there’s a small wave. If the downstroke produces a large bulge, it’s scored a 1+. If the effusion returns spontaneously without a downstroke, it’s a 2+. And if there is so much fluid that the upstrokes cannot move the effusion out of the medial knee, it’s a 3+. I think that grading system is confusing, so one more time: this test can be graded zero, trace, 1+ for a large bulge with downstroke, 2+ if no downstroke is necessary, and 3+ if the upstroke doesn’t work.

Finally, let’s get into interventions. The only recommendation that is made about nonoperative meniscus tear management is a B-level recommendation in favor of supervised, progressive range-of-motion exercises, progressive strength training of the knee and hip muscles, and neuromuscular training. This recommendation also applies to postoperative management.

All the other recommendations are specific to postoperative management. There is a B-level recommendation for early progressive active and passive knee motion after arthroscopic surgery.

There is also a B-level recommendation for providing in-clinic supervised rehab with a home exercise program compared to providing a home exercise program alone. Notably, it seems that studies comparing in-clinic programs versus at-home programs show no differences in patient-reported outcomes, but functional measures like vertical jump and hop testing favor in-clinic rehabilitation.

There is a B-level recommendation for neuromuscular electrical stimulation following meniscus procedures for improving quadriceps strength, functional performance, and knee function.

The only C-level recommendations both concern postoperative management of meniscus repairs. There are C-level recommendations for clinicians to consider early progressive weight bearing and early progressive return to activity in patients with meniscal repairs. This recommendation comes from three studies: one is described in the 2018 CPG, and the other two were described in the 2010 version. In the two studies from the 2010 CPG, “early progressive weight bearing and return to activity” meant absolutely no ROM restrictions and full weight bearing as tolerated immediately after the surgery. In the third study, the “early mobility” group had a 2-week period of toe touch weight bearing and restricted ROM followed by unrestricted ROM and activity. In each of these studies, there was no significant increase in failure rate in the early mobility group, and in one study, the early mobility group achieved higher quadriceps strength and faster return to full activity.

And that covers the meniscus portion fo the knee pain and mobility impairments CPG. As we wrap up, here are a few practice questions to reinforce some of the material:

A 17-year-old male basketball player jumps up for a rebound and lands awkwardly. He immediately goes to the ground and requires help off the court. Within the next hour, his knee becomes notably swollen. What injury has he most likely sustained?

A. Medial meniscus tear
B. ACL tear
C. MCL tear
D. PCL tear

In most of our practice questions—and on most of the OCS questions—you get a ton of information and have to sort through it all to find what is relevant. Sometimes, like in this question, you’re almost not given enough information. Even if we had just mentioned how he landed, you could probably pick your answer with 100% confidence. Here, meniscus tear is ruled out because the swelling happens too rapidly. ACL, PCL, and MCL tears all might present with early effusion, so they are all technically possible. Here you have to know that, when effusion is present within 2 hours of the injury, it is most often an ACL injury. So based on the statistics of what is most common, you should pick B. ACL tear.

Next question: A patient presents for initial evaluation following an arthroscopic partial meniscectomy. His affected knee shows some edema. The therapist strokes the medial side of the knee upward twice and strokes the lateral side downward once. A small wave of swelling is noted on the medial side of the knee during the downward stroke. How would this be graded on the modified stroke test for knee effusion?

A. Zero
B. Trace
C. 1+
D. 2+

Recall that to score a 1+ or 2+, there needs to be at least a large bulge. So here the correct answer is B. trace.

Last question: A 22-year-old female patient presents to an outpatient clinic 2 days after an isolated meniscus repair. She presents with bilateral axillary crutches and no brace. The surgeon told the patient that the physical therapist would establish her weight bearing restrictions and progression. Based on the available evidence and current practice recommendations, which of the following is the most appropriate recommendation for this patient at this stage?

A. Non-weight bearing for the next week, followed by 2 weeks of toe touch weight bearing
B. Toe-touch weight bearing for the next week, followed by 50% weightbearing for 2 weeks
C. Toe touch weight bearing for the next 4 weeks, followed by WBAT
D. WBAT immediately following surgery

Now, there may be some clinical reasons to recommend a slower progression—especially if you note some yellow flags, or if the repair was particularly complex. However, based on the limited information you are given, the correct answer is D. Weight-bearing as tolerated immediately following surgery. This follows two of the three studies that informed the CPG’s recommendation for early progression of weight bearing following meniscus repair.

Okay, that wraps up this episode on the meniscus portion of the knee pain and mobility impairments CPG. We’ll be back soon to cover the cartilage portion. Until then, happy studying!