Anterior cruciate ligament (ACL) pathology is the third most common knee injury (accounting for 25.4%) in high school athletes.1 The total number of ACL ruptures is estimated at nearly 250,000 per year2 and a subsequent surgical reconstruction is performed in nearly 125,000 patients.3 ACL injuries and the following surgical/rehabilitative principles have received ample attention in the literature over the years; however, one factor is often overlooked.
Chondral damage often accompanies ACL ruptures
Articular cartilage defects, although less common than meniscal pathology, were found in 30% of knees that recently underwent ACL reconstruction, according to a recent systematic review by Flanigan et al.4 Similarly, in an arthroscopic evaluation of 378 knees following acute ACL rupture, 163 patients (43%) had evidence of a concomitant full-thickness articular cartilage lesion.5
In another study, 146 of 663 (19.1%) patients showed evidence of at least one chondral lesion with the majority (41%) localized to the medial femoral condyle.6 Among patients with a chondral lesion, 80% had a meniscal lesion and the primary ACL rupture in the same compartment. Moreover, the odds of having a serious chondral lesion (grade III/IV) were 2.7 times higher at 2 to 5 years post-injury and 12.6 times higher at > 5 years.
A concomitant chondral lesion was present in 36% of ACL ruptures documented in a retrospective analysis of over 25,000 knee arthroscopies.7 A much smaller retrospective analysis of 1,000 knee arthroscopies found an associated ACL rupture in 26% of chondral defects.8
ACL-R may be aggravating articular cartilage damage
Although ACL reconstruction failure and revisions are typically rare – only 2-6% of all surgeries9 – the revisions may be causing additional articular cartilage damage.
Borchers et al evaluated cartilage defects during primary and revision ACL reconstruction.10 They found a higher odds ratio of grade III and IV chondral lesions in revision compared with primary ACL reconstruction in the lateral and patellar-trochlear compartments.
Based on this data, chondral injuries occur more often in individuals who have undergone ACL reconstruction, especially a revision.
Does chondral damage affect patient outcomes and return to sport?
Although limited research was dedicated to this question, substantial preliminary evidence suggests that chondral damage does lead to inferior patient outcomes – especially in cases of full-thickness cartilage lesions.
Defect size matters
Røtterud et al evaluated the varying patient-reported outcomes following ACL reconstruction between patients with no additional defects and those with concomitant full-thickness chondral defects or meniscal pathology.11
A total of 3,674 patients were assessed on 5 subscales of Knee Injury and Osteoarthritis Outcome Score (KOOS):
- Other symptoms
- Function in daily living
- Function in sport and recreation
- Knee related Quality of life.12
At the 2-year follow-up, patients with full-thickness cartilage lesions reported lower crude mean values for all of the KOOS subscales compared with those without cartilage lesions.
Patients with lesions ≥ 2 cm2 in diameter also reported poorer outcomes, but the differences were below statistical significance.
Somewhat surprisingly, patient-perceived outcomes remained at the same level in patients with meniscal pathology and smaller chondral lesions (grades I/II) and those without any intra-articular lesions.
Based on these findings, patients with full-thickness cartilage damage reported more pain and symptoms, impaired function in activities of daily living, sports, recreation, and reduced knee-related quality of life compared to those without concomitant chondral damage.
Focal cartilage damage can be worse than ACL-deficiency
In a cross-sectional study, Heir et al further identified the extreme patient-perceived deficits in individuals with focal cartilage damage.13 The patient complaints were worse than with ACL-deficiency and the quality of life was affected as much as in patients scheduled for total knee replacement.
So even though full-thickness chondral lesions are not nearly as common as meniscal pathology, we should still consider them in patients recovering from ACL reconstruction because they can hurt the patient-perceived outcomes.
MRI underestimates chondral defects
Two studies suggest significant chondral defects may be underestimated or missed altogether due to unreliable pre-operative imaging.
In his study, Campbell et al tried to determine how accurately radiologists can estimate the size of chondral defects in the knee via pre-operative MRI evaluation.14 In the 92 cartilage defects imaged, radiologists underestimated lesions by about 1.04 cm2 in diameter compared to intra-operative findings.
Imaging of medial femoral condyle and femoral trochlea was particularly unreliable, underestimating defects by 92.0% and 82.8%, respectively. This raises serious concerns since most chondral defects associated with ACL-R occur at the medial femoral condyle (see above).
When all compartments were averaged together, MRI imaging underestimated chondral defects by 70%… And this is in high-grade defects.
This leads us to believe that significant chondral defects are potentially underestimated or missed altogether due to unreliable pre-operative imaging. While this study was not focused primarily on patients undergoing treatment for ACL pathology, it does give us information on the underestimation of cartilage defects.
MRI has only 45% specificity in chondral lesions
To further support the potential for underrated chondral lesions, Figueroa et al reported specificity of only 45% when MRI had was used to rule in a chondral lesion.15
This data should raise red flags for therapists and orthopedic surgeons alike. Just because imaging is negative, does not mean we can definitively rule out a chondral lesion as a differential diagnosis or contributory factor.
Return to sport after ACL-R and chondral changes
The above findings indicate that we should consider the potential cartilage damage when planning a patient’s return to sport.
Poorer chondral resiliency after ACL-R
Van Ginckel et al evaluated 15 patients treated with isolated ACL reconstruction compared with 15 matched controls.16 Each patient received a 3-T MRI cartilage evaluation (3-D volume/thickness documented), biochemical composition (T2/T2* mapping), and functional assessment. Patient function was determined by recording in vivo deformation (including recovery) after a 30-minute run. Patients recovering from an isolated ACL reconstruction demonstrated diminished quality and in vivo cartilaginous resiliency compared with controls.
Post-injury chondral thickness changes
In a similar study, Frobell et al performed diagnostic 1.5-T MRI evaluation at baseline, three, six, twelve, and twenty-four months post-injury.17 At twenty-four months, cartilage in the femoral trochlea became significantly thinner compared to the thickening of the central medial aspect of the femur.
Consider morphological changes during the return to sport
The morphological changes to the articular cartilage described above show that we need to understand the biomechanical and neurophysiological changes associated with return to sport following ACL reconstruction. We should keep both short-term (6 months) and long-term (24 months) changes in the back of our minds and pay special attention to the short-term cartilaginous thinning seen in these patients despite the lack of radiological and/or arthroscopic evidence of chondral lesions. We must handle return to sport delicately to avoid the potential osteoarthritic changes down the road despite the continual pressures from the athlete and coaching staff.
Most importantly, we don’t know if what we do in rehabilitation can positively OR negatively impact this process. It may be that the “dye” is cast with the initial injury OR we may be able to alter the progression – time will tell.
- Swenson D, Collins C, Best T, Flanigan D, Fields S, Comstock R. Epidemiology of knee injuries among U.S. high school athletes, 2005/2006-2010/2011. Medicine and science in sports and exercise. 2012;3(45).http://www.ncbi.nlm.nih.gov/pubmed/23059869.
- Griffin L, Albohm M, Arendt E, et al. Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005. The American journal of sports medicine. 2006;9(34).http://www.ncbi.nlm.nih.gov/pubmed/16905673.
- Kim S, Bosque J, Meehan J, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: a comparison of National Surveys of Ambulatory Surgery, 1996 and 2006. The Journal of bone and joint surgery American volume. 2011;11(93). http://www.ncbi.nlm.nih.gov/pubmed/21531866.
- Flanigan D, Harris J, Trinh T, Siston R, Brophy R. Prevalence of chondral defects in athletes’ knees: a systematic review. Medicine and science in sports and exercise. 2010;10(42).http://www.ncbi.nlm.nih.gov/pubmed/20216470.
- Maffulli N, Binfield P, King J. Articular cartilage lesions in the symptomatic anterior cruciate ligament-deficient knee.Arthroscopy: the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association. 2003;7(19).http://www.ncbi.nlm.nih.gov/pubmed/12966374.
- Tandogan R, Taşer O, Kayaalp A, et al. Analysis of meniscal and chondral lesions accompanying anterior cruciate ligament tears: relationship with age, time from injury, and level of sport. Knee surgery, sports traumatology, arthroscopy: official journal of the ESSKA. 2003;4(12). http://www.ncbi.nlm.nih.gov/pubmed/14504718.
- Widuchowski W, Widuchowski J, Trzaska T. Articular cartilage defects: study of 25,124 knee arthroscopies. The Knee. 2007;3(14). http://www.ncbi.nlm.nih.gov/pubmed/17428666.
- Hjelle K, Solheim E, Strand T, Muri R, Brittberg M. Articular cartilage defects in 1,000 knee arthroscopies.Arthroscopy: the journal of arthroscopic & related surgery: official publication of the Arthroscopy Association of North America and the International Arthroscopy Association. 2002;7(18).http://www.ncbi.nlm.nih.gov/pubmed/12209430.
- Spindler K, Kuhn J, Freedman K, Matthews C, Dittus R, Harrell FJ. Anterior cruciate ligament reconstruction autograft choice: bone-tendon-bone versus hamstring: does it really matter? A systematic review. The American journal of sports medicine. 2004;8(32). http://www.ncbi.nlm.nih.gov/pubmed/15572332.
- Borchers J, Kaeding C, Pedroza A, et al. Intra-articular findings in primary and revision anterior cruciate ligament reconstruction surgery: a comparison of the MOON and MARS study groups. The American journal of sports medicine. 2011;9(39). http://www.ncbi.nlm.nih.gov/pubmed/21646434.
- Røtterud J, Sivertsen E, Forssblad M, Engebretsen L, Arøen A. Effect of meniscal and focal cartilage lesions on patient-reported outcome after anterior cruciate ligament reconstruction: a nationwide cohort study from Norway and Sweden of 8476 patients with 2-year follow-up. The American journal of sports medicine. 2013;3(41).http://www.ncbi.nlm.nih.gov/pubmed/23371474.
- Knee injury and Osteoarthritis Outcome Score, Ewa Roos. http://www.koos.nu/.
- Heir S, Nerhus T, Røtterud J, et al. Focal cartilage defects in the knee impair quality of life as much as severe osteoarthritis: a comparison of knee injury and osteoarthritis outcome score in 4 patient categories scheduled for knee surgery. The American journal of sports medicine. 2010;2(38).http://www.ncbi.nlm.nih.gov/pubmed/20042546.
- Campbell A, Knopp M, Kolovich G, et al. Preoperative MRI underestimates articular cartilage defect size compared with findings at arthroscopic knee surgery. The American journal of sports medicine. 2013;3(41).http://www.ncbi.nlm.nih.gov/pubmed/23324431.
- Figueroa D, Calvo R, Vaisman A, Carrasco M, Moraga C, Delgado I. Knee chondral lesions: incidence and correlation between arthroscopic and magnetic resonance findings. Arthroscopy: the journal of arthroscopic & related surgery: official publication of the Arthroscopy Association of North America and the International Arthroscopy Association. 2007;3(23). http://www.ncbi.nlm.nih.gov/pubmed/17349476.
- Van Ginckel A, Verdonk P, Victor J, Witvrouw E. Cartilage Status in Relation to Return to Sports After Anterior Cruciate Ligament Reconstruction. The American Journal of Sports Medicine. 2013;41(3):550-559. doi:10.1177/0363546512473568. http://ajs.sagepub.com/content/41/3/550.abstract
- Frobell R. Change in cartilage thickness, posttraumatic bone marrow lesions, and joint fluid volumes after acute ACL disruption: a two-year prospective MRI study of sixty-one subjects. The Journal of bone and joint surgery American volume. 2011;12(93). http://www.ncbi.nlm.nih.gov/pubmed/21776546.