We finish the Knee Pain and Mobility Impairments: Meniscal and Articular Cartilage Lesions CPG (2018 revision) with this episode focused on articular cartilage lesions and surgeries. Additionally, we include an overview of the 5-stage decision tree model this CPG recommends and how the OCS exam might use information like this on the exam.
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Thanks for joining us again as we wrap up the knee pain and mobility impairments: meniscal and articular cartilage lesions revision 2018 CPG. We’ve already covered the meniscus portion of this CPG, so now we’re going to talk through the articular cartilage lesion portion. As I mentioned in the introduction to the meniscal lesion episode, we think this is a pretty confusing CPG to study. This is partially because it’s covering two different injuries at the same time, and partially because articular cartilage lesions are so tricky to diagnose, and our research on them is so sparse. So as I go through the CPG today, I’m going to try to organize the material in a more natural format than the CPG, which I hope will help us all absorb the material a bit better. First we will talk about the portions of the CPG that describe articular cartilage injuries. Then we will talk about the portions describing articular cartilage surgeries, outcomes, and treatment recommendations.
Starting with the incidence section of the CPG, we see that articular cartilage injuries are pretty common. Knee arthroscopy studies show that the prevalence of articular cartilage pathologies is between 60-70%. However, most injuries are smaller than 1 cm, and many are asymptomatic. We have a less clear picture of how common articular cartilage lesions are in athletes: estimates range range from 17-59%, and again, many of these may be asymptomatic. Many of these injuries—somewhere between 32 and 58%—are the result of a traumatic, non-contact mechanism of injury. This can be a single acute trauma or repetitive minor trauma. I don’t think you’ll need to know where these injuries are most common, but just in case you’re curious: articular lesions are most common on the medial femoral condyle and the patellar surface.
It’s common for articular cartilage injuries to occur concomitantly with other knee injuries; in fact, only 30% of articular cartilage injuries are isolated injuries. Most commonly, articular cartilage injuries occur with medial meniscus tears or with ACL ruptures. And it’s twice as common to see them after a second ACL injury compared to after an initial ACL injury.
And that segues us into risk factors for articular cartilage injuries. The CPG notes that, following an ACL injury, increased patient age and presence of a medial meniscus tear increase the odds of the patient having a chondral lesion. Additionally, there are two factors that are predictive for severity of chondral lesions: increased patient age and longer time since initial ACL injury. Increased number of chondral lesions is associated with increased time since initial ACL injury. So to recap these risk factors: increase your suspicion of articular cartilage injuries with increased age, increased time since the ACL injury, and with the presence of a medial meniscus injury.
Let’s move on into evaluation. It is difficult to diagnose articular cartilage lesions with a physical assessment. The CPG notes that we can determine meniscus injuries with a “fair” level of certainty, but we can only diagnose articular cartilage injuries with a “low” level of certainty. Still, here’s what we’re looking for to rule in this diagnosis. For most cartilage injuries, we’re looking for insidious onset aggravated by repetitive impact, intermittent pain and swelling, history of “catching” or “locking,” and joint line tenderness. In the case of an osteochondral fracture, we will see acute trauma with hemarthrosis, which will present as swelling 0-2 hours after injury. You can see that the insidious onset type of cartilage injury looks a lot like a meniscus injury: there can be swelling, a history of “catching” or “locking,” and joint line tenderness. A couple features might help you distinguish between the two: although meniscus injuries can appear insidiously in older individuals, a twisting injury should make you suspect meniscus more than articular cartilage. Additionally, you’ll notice that intermittent swelling is associated with cartilage injuries; meniscus injuries are associated with delayed effusion 6-24 hours after injury, but not necessarily intermittent swelling. I would also recommend this general rule: if it looks like a meniscus injury at first, but your meniscus tests and clusters are negative and you’ve ruled out ligament injury, you should suspect articular cartilage injury next.
You can also see how the acute trauma osteochondral fracture might look like an ACL injury with hemarthrosis occurring 0-2 hours after injury. Again, I would recommend suspecting a ligament injury first, and after you’ve ruled out the cruciate and collateral ligaments, consider osteochondral fracture next.
Before we move on into articular cartilage surgeries, there is one more recommendation that deals specifically with articular cartilage injuries. We have a B-level recommendation to use the IKDC 2000 or the KOOS as self-reported outcome measures in patients who have articular cartilage lesions. I want to point out that, unlike with meniscus injuries, the CPG does give us an MCID for the KOOS when it’s being used for those with chondral lesions. Well…it sort of gives us an MCID. It gives us an estimated range: the MCID is somewhere between 7.4 and 12.1. As we’ve emphasized before, we think you should really only focus on the MCIDs for the biggest and the most well-studied outcomes. I suspect you won’t need to know the MCID for the KOOS, but if you want to remember it, I would split the middle between those values and estimate that the MCID is about 10—just like with the ODI and the NDI. See? MCIDs aren’t too hard to remember when we can estimate that many of them are about 10.
Now the rest of the CPG’s recommendations involve articular cartilage surgeries or postoperative guidelines. According to the guidelines, the four most widely used surgeries for managing articular cartilage lesions are arthroscopic lavage and debridement, microfracture, autologous chondrocyte implantation (ACI), and osteochondral autograft transplantation (OAT). After this, the CPG really only focuses on the latter three: microfracture, where holes are drilled in the cartilage defect to stimulate bleeding and subsequent healing; autologous chondrocyte implantation (or ACI), which is a two-stage surgery where cartilage is harvested, chondrocytes are isolated and multiplied, and then several weeks later the chondrocytes are injected into the defect to encourage cartilage growth; and osteochondral autograft transplantation (OAT), which is where a flap or plug of cartilage is removed from a nonweightbearing part of the knee and placed over the defect. Sometimes you will also see the abbreviation “OCT,” which stands for osteochondral transfer, and as far as I can find, this is just a broader category that the OAT procedure falls under. So for the purposes of this CPG and the exam, the OAT procedure and OCT procedure can be used interchangeably.
Let’s talk about when each procedure is recommended. Microfracture is best for treating small lesions in those with low-load demands. Younger patients do better with micro fracture than older patients. Those who attempted to return to higher demand activities had increased failure rates. So younger patients with small defects who want to return to low-load activities are ideal for micro fracture.
Return to activity after ACI is good, even for those with higher level demands, but the timeline for return to activity is much longer and the failure rate is much higher compared to the OAT procedure.
The OAT procedure is best for athletes wanting to return to higher demand activities. Athletes who have the OAT procedure have a higher rate of self-reported knee function, return to sports, and maintenance of level of activity compared to athletes who had ACI or microfracture procedures.
To drive this home, here’s a summary of a meta-analysis by Mithoefer et al. comparing these three procedures. The return to sport rate was 66% after microfracture, 67% after ACI, and 91% after OAT. Time to return to sport was 8 months after micro fracture, 18 months after ACI, and 7 months after OAT. So if the patient has low-load demands, micro fracture is ideal. If the patient is an athlete with higher level demands, we recommend the OAT procedure.
We also have data on risk factors that increase the chances of these surgeries failing: female sex, older age, higher BMI, longer symptom duration, previous procedures and surgeries, and lower self-reported knee function are associated with higher failures after surgery. Most of these, like age, BMI, symptom duration, previous surgeries, and lower function, all make intuitive sense.
Let’s move on to physical therapy evaluation and treatment following surgery. Following surgery, the CPG recommends very similar measures to what it recommended for post-operative meniscus lesion management. In the early rehab phase, they recommend the 30-second chair-stand test, the stair-climb test, the timed up-and-go test, and the 6-minute walk test as physical performance measures. During the return to sport phase, they recommend single leg hop testing. For physical impairment measures, they recommend the modified stroke test for effusion, knee AROM measurement, quadriceps strength testing, and joint line tenderness.
And now we’ll move into post-operative treatment recommendations. The CPG gives a B-level recommendation for progressive active and passive knee motion following articular cartilage surgery. Currently we have mixed evidence on whether active or passive ROM is better in this group, so the recommendation is for both. Additionally, a systematic review found that continuous passive motion did not improve histological outcomes, so a CPM machine isn’t going to hurt anything, but it also doesn’t seem particularly helpful long term.
The CPG also gives a B-level recommendation to accelerated progressive weight bearing. Three randomized controlled trials compared a standard, slower weight bearing group to an accelerated weight bearing group after an ACI procedure. The accelerated group gradually increased their weight bearing status until they were full weight bearing at either 6 or 8 weeks. In all the trials, the accelerated group had better KOOS scores than the standard group. This was true in the short, medium, and long term. So at least after ACI procedures, we want early progressive weight bearing to a full weight bearing status in 6-8 weeks after surgery.
The CPG gives an E-level recommendation—which means we just have theoretical or foundational evidence—that clinicians may need to delay return to activity depending on the type of articular cartilage surgery. We’ve already mentioned that return to sport is typically about 8 months for micro fracture, 18 months for ACI, and 7 months for OAT procedure.
The CPG gives a B-level recommendation for therapeutic exercise, saying, “Clinicians should provide supervised, progressive range-of-motion exercises, progressive strength training of the knee and hip muscles, and neuromuscular training to patients with knee meniscus tears and articular cartilage lesions and after meniscus or articular cartilage surgery.” Notice this is the only recommendation that also applies to nonsurgical articular cartilage management.
You’ll notice that the meniscus portion of this CPG also recommends supervised rehab instead of just an HEP and neuromuscular electrical stimulation or biofeedback for post-operative meniscus rehabilitation, but we have no data to apply these recommendations to cartilage lesions.
So to recap: we have B-level recommendations for active and passive ROM after surgery, accelerated progressive weight bearing after surgery, and therapeutic exercise for either conservative or post-operative management. We have a single E-level recommendation for delaying the return-to-activity timeline depending on the type of surgery.
And that covers the articular cartilage lesion content. There’s one more section in this CPG that I want to mention, and it applies to both meniscus lesions and articular cartilage lesions. This CPG recommends a 5-stage decision tree model for addressing knee injuries. I don’t think you need to memorize this whole decision tree. However, this sort of content might show up on the 10% of the exam that is classified as “orthopedic physical therapy and practice.” My understanding is that this section of the exam is a bit of a catch-all for miscellaneous information regarding orthopedic PT practice. In it, the exam may ask questions about order of examination or interventions or types of verbal cues to use with your patients—all sorts of things that don’t fit well into other categories. And in this decision tree, I think there’s some information that the exam writers could use as question material.
This tree follows a chronological process of evaluating and treating a patient with one of these knee injuries. There are five components: first, medical screening; second, classifying the condition through evaluation; third, determining the irritability of the condition; fourth, determining the appropriate outcome measures; and fifth, determining the most appropriate post-surgical interventions.
Medical screening involves screening for fracture with the Ottawa knee rules, but it also includes screening for psychosocial factors, like fear of reinjury, low internal health locus of control, lower self-efficacy, depressive symptoms, decreased motivation, and any relevant cognitive-behavioral tendencies. All of this fits into the first stage.
The second stage involves classifying the condition through evaluation. We already talked about how to evaluate these conditions, so we won’t rehash that here.
The third stage is irritability, which is how we attempt to determine the amount of physical stress the tissue can handle. Irritability can be assessed using our traditional pain-related measures, but the CPG also recommends that patient-reported disability and activity avoidance be considered here. All of this is meant to inform dosing of treatment.
Fourth, we pick our outcome measures, which is going to be influenced by all of the previous steps: a high-irritability, fearful patient should not be doing triple hop testing. The timed up-and-go would be much better.
And fifth, we intervene using the recommendations in this guideline.
Let’s run through a few practice questions to tie this whole CPG together.
An active 24-year-old presents with knee pain that started after a very physical basketball game about a month ago. He remembers landing hard when trying to get a competitive rebound, but he’s not sure if that’s what caused the injury. The next day, he noticed some swelling in his knee, and since then he has noticed his knee occasionally “catches.” He has tried to play basketball several times since then, but when he does, his knee hurts and sometimes swells again. He reports feeling frustrated and that he doesn’t know who to go to in order to get his knee fixed. Physical examination reveals the following:
During the initial evaluation, which of the following assessments should be performed first?
A. AROM of the unaffected extremity
B. Palpation for joint line tenderness
C. Screening for health-related locus of control
D. Timed up-and-go
Of course, we just went through these five stages, so you should recognize that screening for health-related locus of control is part of the first stage—medical screening. So the correct answer is C. This is something we should screen and watch out for in general, but you’ll notice that this patient has indicated he wants someone else to fix his knee for him, which suggests an external locus of control.
Question 2: Which of the following diagnoses is most likely:
A. Degenerative tear of the medial meniscus
B. Grade I ACL sprain
C. Rheumatoid arthritis
D. Articular cartilage lesion
We might have given away the answer since this is the articular cartilage lesion episode, but think about how you should come to that decision: the delayed swelling, joint line tenderness, and report of catching all fit a meniscus tear. However, if you’re using your meniscal pathology composite score, you’ll notice he only has 2/5 positives: the joint line tenderness and history of catching. So now we’ve decreased our suspicion of meniscus tear and increased our suspicion of articular cartilage lesion.
Question 3: Based not he available information, which procedure would likely be most appropriate for this patient?
A. ACI procedure
C. OAT procedure
D. Levage and debridement
You will recall that OAT procedure is most highly recommended for athletes with higher functional demands. There may be other factors that influence a surgeon to choose a different route, but if you’re going to refer him to a surgeon, you’re going to be looking for one who does the OAT procedure.
Okay, I think that covers the most important portions of this CPG. As always, we appreciate you all and wish you good luck in your studies.