Clinical Implications of Bone Bruise Patterns Accompanying Anterior Cruciate Ligament Tears

Abstract

Background:

Anterior cruciate ligament (ACL) tears are common injuries; they are often associated with concomitant injuries to other structures in the knee, including bone bruises. While there is limited evidence that bone bruises are associated with slightly worse clinical outcomes, the implications of bone bruises for the articular cartilage and the risk of developing osteoarthritis (OA) in the knee are less clear. Recent studies suggest that the bone bruise pattern may be helpful in predicting the presence of meniscal ramp lesions.

Evidence Acquisition:

A literature review was performed in EMBASE using the keyword search phrase (acl OR (anterior AND cruciate AND ligament)) AND ((bone AND bruise) OR (bone AND contusion) OR (bone AND marrow AND edema) OR (bone AND marrow AND lesion) OR (subchondral AND edema)).

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

The literature search returned 93 articles of which 25 were ultimately included in this review. Most studies identified a high prevalence of bone bruises in the setting of acute ACL injury. Individual studies have found relationships between bone bruise volume and functional outcomes; however, these results were not supported by systematic review. Similarly, the literature has contradictory findings on the relationship between bone bruises and the progression of OA after ACL reconstruction. Investigations into concomitant injury found anterolateral ligament and meniscal ramp lesions to be associated with bone bruise presence on magnetic resonance imaging.

Conclusion:

Despite the ample literature identifying the prevalence of bone bruises in association with ACL injury, there is little evidence to correlate bone bruises to functional outcomes or progression of OA. Bone bruises may best be used as a marker for concomitant injury such as medial meniscal ramp lesions that are not always well visualized on magnetic resonance imaging. Further research is required to establish the longitudinal effects of bone bruises on ACL tear recovery.

Strength of Recommendation Taxonomy:

2.

Tears of the anterior cruciate ligament (ACL) are one of the most common sports injuries with more than 250,000 ACL reconstructions performed annually. ²⁴ Within the general population, the overall incidence of ACL tears is 68.6 per 100,000 person-years with a higher incidence in men than women (81.7 vs 55.3 per 100,000). ⁴² Many of these injuries occur in young athletes between the ages of 15 and 25 years.^6,17,18,23 Incidence peaks in women between the ages of 14 and 18 years versus in men between the ages of 19 and 25 years, possibly reflecting a greater male participation in sporting activities throughout collegiate years. ⁴²

ACL tears are associated with a significant risk of long-term health effects, including knee instability and inhibited function, chronic pain, and osteoarthritis (OA). ¹⁷ The risk of developing OA is 4 times higher in the injured knee than the noninjured knee and 6 times higher than the non-injured population. ²⁹ Progression to total knee arthroplasty is 7 times greater after ACL injury. ²⁹ The objective of ACL reconstruction is to restore its functional properties, namely to limit anterior tibial translation and rotation, such that the knee stability is restored and so the patient is able to return to previous activity. ¹⁰

A concomitant injury first identified in 1988, ⁵¹ the pathological condition referred to as bone bruise refers to the traumatic origin of trabecular microfractures, edema, and hemorrhage within subchondral bone. ⁴⁹ Their association with ACL injuries are well described with recent studies reporting a prevalence of 78%. ¹⁴ However, the clinical significance of bone bruises is less clear, despite extensive study.^{4,5,7,13,15,16,37-41,50,52} The purpose of this study is to review the current understanding of how bone bruise presence/absence, location, and size related to clinical outcomes and the risk for developing OA after ACL injury.

Search Criteria

A literature search was performed in EMBASE on July 7, 2020, using keyword search phrase (acl OR (anterior AND cruciate AND ligament)) AND ((bone AND bruise) OR (bone AND contusion) OR (bone AND marrow AND edema) OR (bone AND marrow AND lesion) OR (subchondral AND edema)). Search results were limited to studies in the English language and published between 2017, the submission year of the most recent systematic review, and 2020. Exclusion criteria included biomechanical studies, radiographic studies, case reports, poster presentations, commentaries, and abstracts only. Based on the titles and abstracts, we assessed 34 articles from the initial 93 search results and selected 25 studies to include in this literature review. Review of references did not yield additional articles for inclusion.

Mechanisms of Bone Bruises

Traumatic bone bruises are the result of direct injury that disrupts the trabeculae of subcortical bone with subsequent accumulation of interstitial fluid and hemorrhage in the extracellular space. ³⁸ Bone bruises are diagnosed using MRI and are identified by subcortical hypointense signals in T1-weighted images or hyperintense signals in T2-weighted images, reflecting the localized increase in water content. ⁴⁹ Bone bruises in ACL injury are related to physical impact on the bone; therefore, the pattern of the bone bruises can be used to ascertain the kinematics of joint injury.

Recent studies into the distribution of bone bruises within the knee found a wide range: between 48.3% and 91.7% of ACL tears had a bruise of the lateral femoral condyle (LFC) (Figure 1),^{1,5,7,8,12,26,27,31,35,44,46} between 49.4% and 97.6% of the lateral tibial plateau (LTP) (Figure 1),^{1,5,7,8,12,26,27,31,35,44,46} between 12.5% and 53% of the medial femoral condyle (MFC) (Figure 2),^{1,7,8,12,26,27,44,46} and between 12.4% and 83.5% of the medial tibial plateau (MTP) (Figure 3).^{1,7,8,12,26,27,31,44,46}

Figure 1.

Bone bruises of the lateral femoral condyle and lateral tibial plateau.

Figure 2.

Bone bruises of the medial femoral condyle.

Figure 3.

Bone bruises of the medial tibial plateau.

Consistently, lateral contusions are more prevalent than medial contusions, and tibial contusions are more prevalent than femoral contusions. Shi et al ⁴⁴ and Bordoni et al ⁷ identified bone bruise locations in the sagittal plane and found bone bruises primarily in the posterior compartment of the tibia and the central or anterior compartments of the femur. Shi et al ⁴⁵ and Owusu-Akyaw et al ³⁹ found these patterns imply a knee in a flexed position with valgus, anterior tibial translation. A systematic review by Zhang et al ⁵² demonstrated that the primary injury mechanism was anterior tibial translation and that knee valgus occurred after sufficient translation to damage the ACL. Knee hyperextension is also a possible mechanism for noncontact injury.

Bone Bruise Resolution

Investigations into bone bruise progression show a wide range in the time frame for resolution, from complete resolution at 2 months to persistence at 1 year, due in part to heterogeneity in imaging modalities and improved sensitivity over time. ¹⁴ A recent study by Kroker et al ²⁸ using dual-energy radiograph absorptiometry and high-resolution peripheral quantitative computed tomography found that 19 of 21 bone bruises had healed by 2 months and all 21 had resolved by 8 months. However, subchondral bone loss continued up until 10 months, even after bone bruises were no longer visible on imaging. This is of potential clinical interest since subchondral bone turnover has been linked to OA progression. ²⁵

Associated Injuries

Because of the positional displacements and high forces required for ACL rupture, there are often additional injuries to the knee. Recent literature has investigated whether the presence of bone bruises is predictive of the presence of concomitant injury. This may serve as a valuable tool particularly for injuries to the anterolateral ligament (ALL), which has high nonvisualization indices. ²⁰ Helito et al ²⁰ found only 1 of 66 instances of ALL injury was not accompanied by a bone bruise and that an ALL injury was present 46.5% of the time when there were both LFC and LTP bone bruises. A separate study showed 33/88 (37.5%) of acute ACL tears with LFC and LTP bone bruises were accompanied by ALL injury. ¹⁹ Similarly, Lintin et al ³⁴ found that 68 of 75 cases of ALL injury had an associated bone bruise. Their results were supported by 2 studies by Lee et al that found increased risk of ALL injury with bone bruise presence ³² and increased severity of ALL injury with bone bruise presence. ³¹ Marot et al, ³⁵ however, did not find a correlation between ALL injury and bone bruise volume. Li et al ³³ found an odds ratio (OR) of 53.5 for ALL injury when lateral bone bruises were present.

Meniscal injuries are a common occurrence in ACL tears. Numerous studies^1,5,32,33 have found relationships between lateral bone bruises and tears of the lateral meniscus. No definitive consensus exists as Bordoni et al ⁷ and Novaretti et al ³⁷ did not find a relationship between bone bruises and any meniscal lesion. Of practical consideration, these 2 studies were performed in pediatric populations. Bone bruise volume, however, does not appear to be related to meniscal injury. ⁴ In adult populations, Chan et al ⁹ failed to find a relationship between bone bruises and lateral meniscus tears. Studies returned contradictory results on tears of the medial meniscus as well. Bernholt et al ⁵ found an association between LFC and LTP bone bruises with medial meniscal ramp lesions. Balazs et al, ² DePhillipo et al, ¹¹ and Kim et al ²⁷ found significant associations of MTP bone bruises and medial meniscal ramp lesions while Calvo-Gurry et al ⁸ found an association between MTP bone bruises and posterior medial meniscus tears. Aravindh et al ¹ and Chan et al ⁹ found no association between bone bruises and meniscal lesions. However, neither study investigated an association with ramp lesions individually. Considering the low reported sensitivity of MRI for detecting medial meniscal ramp lesions (48%), ¹¹ clinicians should have heightened awareness for these injuries when MTP bone bruises are present.

The current body of literature consistently demonstrates an association between bone bruises and ALL injury. There is less consensus regarding meniscal lesions, but studies investigating specifically medial meniscal ramp lesions are more uniform in their identification of a relationship. Table 1 summarizes the studies investigating bone bruises and their association with ALL and medial meniscal ramp injuries.

Table 1.

Summary of relationship between bone bruises and associated injuries

Study	Study Design	Results
Helito et al 20	Prospective cohort	65 of 66 (98%) of ALL injuries were accompanied by a bone bruise 53 of 114 (46.5%) cases with LFC and LTP bone bruises had ALL injury
Helito et al 19	Case series	33 of 88 (37.5%) cases with LFC and LTP bone bruises had ALL injury
Lintin et al 34	Retrospective cross-section	68 of 75 (91%) of ALL injuries had associated bone bruise
Lee et al 32	Cross-sectional study	ALL injury associated with LFC and LTP bone bruises Severity of ALL injury correlated with degree of bone bruise
Lee et al 31	Case-control	MTP and LTP bone bruises associated with more severe ALL injuries MTP bone bruise is a risk factor for poor ALL healing
Marot et al 35	Prospective diagnostic	No correlation between ALL injury and bone bruise volume
Li et al 33	Case-control	Lateral bone bruises associated with ALL injury (OR, 53.5)
Bernholt et al 5	Case series	Medial meniscal ramp lesions associated with LFC bone bruise (OR, 2.0)
Balaz et al 2	Case series	Medial meniscal ramp lesions associated with MTP bone bruise (OR, 2.3)
DePhillipo et al 11	Case series	PMT bone bruise identified in 36 of 50 (72%) of medial meniscal ramp lesions
Kim et al 27	Cross-sectional study	Medial meniscal ramp lesions associated with MTP bone bruise (OR, 4.2) MTP bone bruise identified in 48 of 95 (51%) of medial meniscal ramp lesions

ALL, anterolateral ligament; LFC, lateral femoral condyle; LTP, lateral tibial plateau; MTP, medial tibial plateau; OR, odds ratio; PMT, posteromedial tibial.

A systematic review performed by Filardo et al ¹⁴ found 11 of 13 studies investigating bone bruises and cartilage defects found an association between the two. Li et al ³³ have since found medial and lateral bone bruises to be associated with cartilage injury, while Aravindh et al, ¹ Chan et al, ⁹ and Bordoni et al ⁷ failed to identify a relationship. Considering the conflicting evidence to date, the question of whether bone bruises are associated with cartilage defects has yet to be answered definitively.

Clinical Outcomes

The aforementioned systematic review by Filardo et al ¹⁴ identified 19 studies investigating the influence of bone bruises on clinical outcomes. Two of 5 studies showed that bone bruises are correlated with higher pain and joint laxity, 4 demonstrated a longer time to restore normal range of motion (ROM), and 1 of 10 was able to identify a lower rate of return to sport at midterm follow-up. Gage et al ¹⁶ later found that LFC bone bruises were a predictor of delayed time to achieve full knee extension preoperatively. Preoperative ROM deficits are associated with higher rates of arthrofibrosis ³⁶ and lower subjective scores. ⁴³ Driban et al ¹² also found that increased bone bruise volume is associated with lower Knee injury and Osteoarthritis Outcome Score (KOOS) pain scores in the absence of a depression fracture. When depression fractures were present, this relationship was nonexistent. A systematic review by Walczak et al ⁵⁰ failed to identify the relationship between the presence of bone bruises and subjective score outcomes. Similarly, a review by Papalia et al ⁴¹ found no relationship between bone bruises and functional outcomes.

The individual study results for patient-reported outcomes (PROs) and clinical measures after ACL reconstruction are presented in Table 2. Bone bruises are a poor prognosticator for clinical outcomes as most studies did not show a relationship between bone bruises and PROs.

Table 2.

Summary of relationship between bone bruises and postreconstruction outcomes

Study	Study Design	Evaluation Methods	Results
Filardo et al 14	Systematic review	KOOS, Tegner, IKDC, SF-36, ADL, Lysholm, Noyes, VAS, ROM, clinical examination, gait analysis	2 of 5 studies showed bone bruise presence correlated with pain and joint laxity 1 of 10 studies showed presence correlated with lower rate of return to sport
Driban et al 12	Cross-sectional analysis of RCT	KOOS	Bone bruise volume associated with increased pain when no associated depression fracture (P = 0.02)
Walczak et al 50	Systematic review	Marx Activity, KOOS, SF-36, IKDC	3 of 3 studies demonstrated no correlation between bone bruise presence and PRO

ADL, activities of daily living; IKDC, International Knee Documentation Committee; KOOS, Knee Injury and Osteoarthritis Outcome Score; PRO, patient-reported outcome; RCT, randomized controlled trial; ROM, range of motion; SF-36, Short Form–36 health questionnaire; VAS, visual analogie scale.

These findings are not surprising considering the evidence that bone bruise volume is not associated with other factors that predict clinical outcomes such as inflammation and pain. ⁴ Jacobs et al ²¹ found no difference in bone bruise volume between patients with dysregulated inflammation compared with patients with low inflammation. This would suggest that bone bruise volume does not affect patient outcomes via this mechanism since elevated inflammatory cytokines have been shown to have an unfavorable effect on KOOS and International Knee Documentation Committee scores. ³⁰ Increased pain at the time of reconstruction is predictive of a more difficult rehabilitation, prolonged recovery, and increased postoperative pain. ¹³ Panwani et al ⁴⁰ failed to identify a relationship between bone bruises and preoperative pain.

Biomechanical Impacts

One concern after ACL and bone bruise injury is modification of gait to unload the lateral femoral compartment and relieve pain. ²² These altered gait mechanics could increase medial tibiofemoral loading, a mechanism for OA development. ³ External knee-adduction moment is often used as a measure of medial tibiofemoral loading. Thomas et al ⁴⁷ did not find an increase in knee-adduction moment in ACL-deficient patients with bone bruises relative to those without. Nonetheless, patients with bone bruises do take longer to recover a nonantalgic gait after an acute ACL tear. ²²

Cartilage Degeneration and OA Progression

Rates of OA development have been reported between 10% and 90% in mid- and long-term follow-up studies on ACL injury. ⁴¹ The literature has contradictory findings with regard to the influence of bone bruises and OA progression. Filardo et al ¹⁴ identified 8 studies investigating the impact of bone bruises on joint damage over time, with 4 showing a correlation with progressive damage to the articular surface, concerning for early development of OA. The limited ROM caused by bone bruises ¹⁶ may be a mechanism leading to accelerated OA since limited preoperative ROM ⁴³ is associated with increased rates of OA progression. Tsoukas et al, ⁴⁸ however, did not find the presence of bone bruises to be an independent factor associated with OA progression at a mean follow-up of 10 years.

Nevertheless, the association between bone bruises and cartilage lesions at the time of injury may play a role in OA progression. ¹⁴ Cartilage lesions are associated with increased chance of progression of OA, even after ACL reconstruction. ¹⁵ Furthermore, the continued presence of bone loss after bone bruise resolution may lead to further chondral degeneration. ²⁸ Kia et al ²⁶ investigated the relationship between bone bruise volume and chondral degeneration at a mean follow-up of 5.1 years. They found increased bone bruise volume to be predictive of higher Outerbridge scores with the absence of a bone bruise the greatest predictor of a grade 0 score. An LFC bone bruise that encompassed 100% of the lateral femoral compartment had a 74% likelihood of progressing to a grade 3 or 4 score. While mechanistic evidence exists to support the theory that bone bruises could have a deleterious effect on OA progression after ACL reconstruction, clinical evidence is currently inconsistent, and more studies are required to determine the true magnitude of their significance. The clinical results of OA progression are summarized in Table 3.

Table 3.

Summary of relationship between bone bruises and osteoarthritis progression

Study	Study Design	Results
Filardo et al 14	Systematic review	4 of 8 studies demonstrated bone bruise presence correlated with progressive damage to articular surface
Tsoukas et al 48	Randomized controlled trial	No relation between bone bruises and osteoarthritis progression at 10-year mean follow-up
Kia et al 26	Retrospective cohort	Bone bruise presence correlated with higher Outerbridge score. Large bone bruises correlated with risk of grade 3 or 4 chondral lesions (P < 0.001)

Conclusion

The most important finding of this study is that the functional impact of bone bruises on recovery and long-term risk for OA after ACL injury is yet to be determined, despite ample literature documenting the prevalence of bone bruises in acute ACL injury. Individual studies have provided support for theoretical pathways for bone bruise presence, size, and location to affect outcomes via inflammatory, pain interference, or mobility-restricting mechanisms. However, direct evidence of the effect of these pathways on clinical outcomes is lacking. Based on current evidence, the best clinical utility of bone bruise presence in patients with ACL tears may be as a marker for concomitant injury such as medial meniscal ramp lesions that are not always well visualized on MRI.