Does Anterior Cruciate Ligament Reconstruction Protect the Meniscus and Its Repair? A Systematic Review

More knee reinjuries after ACL reconstruction compared to nonsurgical treatment of the ACL. A 2-year follow-up of the NACOX prospective cohort study

PURPOSE

To describe knee reinjuries and surgeries within 2 years after an acute anterior cruciate ligament (ACL) injury, in patients treated with or without ACL reconstruction (ACLR).

METHODS

Two years follow-up of 275 patients (52% females, mean age 25.2 [SD 7.0] years) about knee reinjuries and surgeries were analysed from the prospective NACOX cohort study, aiming to describe recovery after an acute ACL injury treated according to clinical routine. Knee reinjury was defined as increase or new symptoms due to new trauma. At 2 years after injury, 169 (61%) had undergone an ACLR. Results are presented with descriptive statistics and risk ratios (RR).

RESULTS

Thirty-two patients sustained reinjuries within 2 years; 6 in the non-ACLR group, and 26 in the ACLR group (7 before and 19 after ACLR). Twelve patients in the ACLR group sustained a graft rupture and three did an ACL revision. Patients with non-ACLR, aged 21-25 years, had a 5.9-fold higher risk for reinjury than those aged 15-20 years (RR 5.9 [1.3-26.9]; p = 0.012). Twenty-four patients had surgery in the non-ACLR group and 36 patients in the ACLR group (excluding primary ACLR), where six were before ACLR and 30 were after ACLR.

CONCLUSION

Twelve percent sustained a knee reinjury and 21% underwent knee surgery within 2 years after the index ACL injury. There was a higher reinjury incidence in the ACLR group, but no difference in incidence of surgeries. Thus, ACLR did not reduce the risk of traumatic reinjuries or surgeries, which is important for treatment decision considerations.

LEVEL OF EVIDENCE

Level I.

Accuracy assessment of ChatGPT responses to frequently asked questions regarding anterior cruciate ligament surgery

BACKGROUND

The emergence of artificial intelligence (AI) has allowed users to have access to large sources of information in a chat-like manner. Thereby, we sought to evaluate ChatGPT-4 response's accuracy to the 10 patient most frequently asked questions (FAQs) regarding anterior cruciate ligament (ACL) surgery.

METHODS

A list of the top 10 FAQs pertaining to ACL surgery was created after conducting a search through all Sports Medicine Fellowship Institutions listed on the Arthroscopy Association of North America (AANA) and American Orthopaedic Society of Sports Medicine (AOSSM) websites. A Likert scale was used to grade response accuracy by two sports medicine fellowship-trained surgeons. Cohen's kappa was used to assess inter-rater agreement. Reproducibility of the responses over time was also assessed.

RESULTS

Five of the 10 responses received a 'completely accurate' grade by two-fellowship trained surgeons with three additional replies receiving a 'completely accurate' status by at least one. Moreover, inter-rater reliability accuracy assessment revealed a moderate agreement between fellowship-trained attending physicians (weighted kappa = 0.57, 95% confidence interval 0.15-0.99). Additionally, 80% of the responses were reproducible over time.

CONCLUSION

ChatGPT can be considered an accurate additional tool to answer general patient questions regarding ACL surgery. None the less, patient-surgeon interaction should not be deferred and must continue to be the driving force for information retrieval. Thus, the general recommendation is to address any questions in the presence of a qualified specialist.

MCL pie crusting for concomitant medial meniscal surgery does not appear to adversely influence primary ACL reconstruction functional outcomes

OBJECTIVES

Medial collateral ligament "pie-crusting" (MCLPC), selective release of the superficial MCL, has been shown to improve the arthroscopic access to the posterior horn of the medial meniscus without adversely affecting the outcomes of isolated meniscal surgery. However, whether MCL PC, to address concomitant meniscal lesions during anterior cruciate ligament reconstruction (ACLR) surgery, adversely affects ACLR outcomes is unknown. The aim of this study was to assess whether patients who had undergone MCLPC at the time of ACLR had similar post outcomes to patients undergoing isolated ACLR.

METHODS

55 consecutive patients (33 male and 22 female), with minimum 2-year follow-up, who had undergone MCLPC with concomitant primary ACLR (PC group) were retrospectively matched on the basis of age, sex and follow-up with 55 patients who underwent isolated primary ACLR. Post-operative outcome measures (PROMs) included the Knee injury and Osteoarthritis Outcome Score, the International Knee Documentation Committee score, Tegner activity score, the EuroQol five-dimension health questionnaire and EuroQol visual analogue scale.

RESULTS

The two groups' median postoperative EQ 5D-VAS, EQ 5D-index and Tegner scores were similar. The difference between pre-operative and post-operative KOOS scores was similar for the two group for all subscales except the ADL subscale which was higher in the MCLPC group (24, IQR ​= ​6-32) than in the isolated ACLR group (5, IQR ​= ​0-9.74). The median post op IKDC score was 84 in the MCLPC group and compared with 90 in the isolated ACLR group. However, the difference between pre-operative and post-operative IKDC scores was higher in patients in the MCLPC group (40, IQR ​= ​25-49) than in the isolated ACLR group (32, IQR ​= ​19.6-46.8).

CONCLUSIONS

MCLPC, performed at the time of ACLR does not appear to adversely affect the functional post-operative outcomes.

LEVEL OF EVIDENCE

IV.

Meniscal allograft transplantation (MAT) combined with revision ACL reconstruction and lateral extra-articular tenodesis results in significantly improved outcomes, but patient-reported knee function is inferior compared to an isolated MAT

PURPOSE

Meniscal allograft transplantation (MAT) is a valuable option for postmeniscectomy syndrome in young and active patients, which can successfully improve symptoms, function and quality of life. This study aimed to report outcomes and complications in patients treated with isolated MAT or MAT combined with revision anterior cruciate ligament reconstruction (ACLR) and lateral extra-articular tenodesis (LET).

METHODS

In total, 18 patients who were treated with MAT using a soft tissue fixation technique were retrospectively analysed. Patients were allocated into two groups, the isolated MAT group and the MAT plus revision ACLR + LET group (MAT+ group). Both groups were assessed using the following Patient-Reported Outcome Measures (PROMs): Knee Injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC), Tegner Activity Scale, Lysholm score, EuroQol 5-Dimension 5-level (EQ-5D-5L) questionnaire and a patient acceptable symptom state (PASS) statement.

RESULTS

The mean follow-up was 3.2 years and the mean age of patients was 29 (±7.6) years. Ten patients were treated with isolated MAT and eight patients were treated with MAT combined with revision ACLR and LET. No complications and no reoperations were reported. In both groups, all PROMs significantly improved postoperatively (p < 0.05), except for the Tegner score in the MAT+ group, which did not reach statistical significance (not significant [n.s.]). No significant difference was found postoperatively in PROMs between the MAT and the MAT+ group; however, differences in the KOOS Symptoms, Sports and Quality-of-life subscales reached the minimal clinically important threshold. Mean values were: IKDC 61.2 (±13.9) versus 64.7 (±23.2), KOOS Total 72.8 (±14.9) versus 68.0 (±16.7), Lysholm score 83.2 (±11) versus 84.2 (±8.7) and EQ-5D-5L 71.8 (±14.9) versus 72.2 (±22.4). Median values for the Tegner Activity Scale were 4 versus 3. PASS statement was negative in 37.5% of the MAT+ group in comparison to 20% of the MAT group (n.s.).

CONCLUSION

In terms of patient-reported outcomes, MAT is an effective and safe procedure, even when combined with revision ACLR + LET. Compared to the preoperative assessment, a significant improvement of the postoperative PROMs can be expected either when MAT is performed isolated or in combination with ACLR + LET. However, clinically important differences between the two groups can be noted in favour of the isolated MAT procedure, especially regarding symptoms and sporting activity.

LEVEL OF EVIDENCE

Level III.

Meniscus Tears in Elite Athletes: Treatment Considerations, Clinical Outcomes, and Return to Play

PURPOSE OF REVIEW

Management of meniscal injuries in the elite athlete is a difficult problem secondary to the high demands of athletic competition, the need for a timely return to sport, and the desire to maximize performance over time. The purpose of this review is to provide an up-to-date summary on the current literature and trends regarding the management of meniscus injuries with a special consideration for elite athletes.

RECENT FINDINGS

Historically, partial meniscectomy has been the primary treatment option for meniscus injuries. However, in recent years there has been an increased emphasis on meniscus preservation due to the increased risk of cartilage degeneration over time. Moreover, while partial meniscectomy still provides a quicker return to sport (RTS), recent literature has demonstrated similar rates of RTS and return to pre-injury levels between partial meniscectomy and meniscus repair. In the setting of symptomatic meniscal deficiency, meniscus allograft transplantation has become an increasingly utilized salvage procedure with promising yet variable outcomes on the ability to withstand elite competition. Currently, there is no uniform approach to treating meniscal injuries in elite athletes. Therefore, an individualized approach is required with consideration of the meniscus tear type, location, concomitant injuries, athlete expectations, rehabilitation timeline, and desire to prevent or delay knee osteoarthritis. In athletes with anatomically repairable tears, meniscus repair should be performed given the ability to restore native anatomy, provide high rates of RTS, and mitigate long-term chondral damage. However, partial meniscectomy can be indicated for unrepairable tears.

Good mid- to long-term outcomes after meniscus bucket-handle tear repair: A comparative analysis with and without anterior cruciate ligament reconstruction

Purpose

To evaluate mid- to long-term clinical outcomes after arthroscopic bucket-handle meniscal tear (BHMT) repair and to assess the impact of concurrent anterior cruciate ligament reconstruction (ACLR).

Methods

A comparative retrospective case series with blinded outcome assessment was conducted. All consecutive patients treated with arthroscopic BHMT repair with or without concurrent ACLR between 2001 and 2021 were eligible for inclusion. Fifty-five patients with an average follow-up of 7.3 ± 3.4 years were included in the analysis. Outcome measures comprised post-operative IKDC Subjective Knee Form, Lysholm Score, Tegner Activity Scale, KOOS, and visual analogue scale (VAS) for satisfaction. Additionally, failure and reoperation rates were assessed.

Results

The failure rate was 9%. Medial BHMT repair showed superior post-operative IKDC scores compared to lateral meniscus repair (p = 0.038). Concurrent ACLR did not demonstrate any impact on post-operative KOOS, IKDC, Tegner or patient satisfaction. The mean IKDC score at final follow-up across both groups was 80.4 ± 17.8. The mean Lysholm score was 86.9 ± 16.7. Mean KOOS scores were (i) symptoms: 83.6 ± 18.3, (ii) pain: 90.2 ± 14.4, (iii) activities of daily living: 93.6 ± 15.1, (iv) sports: 78.3 ± 26.0 and (v) quality of life: 70.5 ± 24.5. Mean patient satisfaction (VAS) was 7.9 ± 2.5. The mean Tegner score was 4.9 ± 1.9. A consistent positive correlation between the number of sutures used and post-operative outcome measures was observed but did not reach statistical significance for most items.

Conclusion

Arthroscopic BHMT repair achieved good clinical outcomes and an acceptable failure rate of 9% at a mean follow-up of 7 years, supporting the clinical value of meniscal repair, including large BHMTs. Concurrent ACLR showed no impact on clinical outcomes.

Level of Evidence

Level IV (retrospective case series).

The Impact of Bone Marrow Venting Augmentation on Knee Functions in the Repair of Vertical/Longitudinal Meniscus Tears: A Triple Comparison

Objective

Preserving and restoring meniscus function is crucial for maintaining knee biomechanics and overall functionality. To enhance the healing process after meniscus repair, various biological techniques have been introduced. In this study, three treatment approaches examined were bone marrow venting with stem cells (BMVP), anterior cruciate ligament reconstruction (ACLR) with meniscus repair, and isolated meniscus repair.

Materials and Methods

From 2015 to 2019, we retrospectively analyzed data from 83 patients who presented with complaints of knee pain or pain in addition to instability, were diagnosed with vertical/longitudinal meniscus tears, and underwent arthroscopic repair (30 with isolated repair, 28 with ACLR repair, and 25 with BMVP) at our University Hospital. Among the 28 patients with anterior cruciate ligament rupture, pain and instability were the predominant complaints, whereas 55 patients with meniscus tear primarily complained pain. Clinical and functional conditions were assessed using Lysholm, WOMAC, IKDC, and VAS scores before and 18 months after surgery. Surgical success was evaluated based on Barrett's criteria. Causes of failure were analyzed considering demographic data, smoking status, injury time, tear location, shape, zone, and suture type and number.

Results

Of the participants, 58 were male, 25 were female, 61 had medial meniscus lesions, and 22 had lateral meniscus lesions. The tear types included 51 simple longitudinal tears, 18 bucket handle tears, and 14 complex tears. A significant improvement was observed in the postoperative 18 month Lysholm, WOMAC, and IKDC values in all three groups (p: 0.001). At the 18 month mark, clinical and functional outcomes were comparable between BMVP and ACLR repair groups (Lysholm p: 0.951, WOMAC p: 0.241, IKDC p: 0.984). Both of these procedures yielded better results compared to isolated meniscus repair (Lysholm p: 0.001, WOMAC p: 0.027, IKDC p: 0.001).

Conclusion

The superior clinical and functional outcomes observed after meniscus repair with BMVP and ACLR, compared to isolated meniscus repair, indicate positive effects of bone marrow stem cells, blood components, and tissue healing factors on meniscus repair and knee function.

Segond fracture: an indicator for increased risk of lateral meniscus injury in patients with acute anterior cruciate ligament ruptures

PURPOSE

The purpose of this study was to investigate the incidence and anatomic distribution of meniscus injury in patients who have sustained acute ACL injuries with and without concomitant Segond fracture. We hypothesized that patients who have sustained a torn ACL with a concomitant Segond fracture would have a higher incidence of lateral meniscal injuries than patients with an isolated ACL injury.

METHODS

Patients who underwent ACL reconstruction from 2012 to 2022 were retrospectively reviewed. Segond fractures were identified on knee radiographs. Inclusion criteria were age 18-40, injury during sports activity, and reconstruction within 90 days of injury. Sports activity, anatomic location of meniscus injury, and meniscus treatment were documented. Multivariable regression was used to identify predictors of meniscus injury/treatment.

RESULTS

There were 25 of 603 (4.1%) patients who had an ACL tear with concomitant Segond fracture. The incidence of lateral meniscus injury in the Segond group (72%) was significantly higher than in the non-Segond cohort (49%; p = 0.024). A significantly smaller proportion of medial meniscus injuries among patients with Segond fractures were repaired (23.1%) compared to the non-Segond group (54.2%; p = 0.043). Multivariate analysis found patients with Segond fractures to have increased odds of lateral meniscus injury (OR 2.68; [1.09, 6.60], p = 0.032) and were less likely to have medial meniscus injuries repaired (OR 0.35; [0.15, 0.81], p = 0.014). Additionally, males had increased odds of lateral meniscus injury (OR 1.54; [1.08 - 2.91], p = 0.017), which were more likely to require repair (OR 1.48; [1.02, 2.14], p = 0.038).

CONCLUSIONS

Among acute ACL injuries, the incidence of lateral meniscus injury is greater among patients with Segond fractures. Patients with Segond fracture were less likely to undergo repair of medial meniscal injuries.

Incidence of Osteoarthritis Diagnosis Within 5 Years of Surgery Was Greater Following Partial Meniscectomy Than Meniscus Repair and/or Anterior Cruciate Ligament Reconstruction

Purpose

To compare knee osteoarthritis (OA) incidence within 5 years of surgery between 5 common sports medicine procedures: isolated anterior cruciate ligament (ACL) reconstruction, isolated meniscus repair (MR), isolated arthroscopic partial meniscectomy (APM), ACL reconstruction with MR (ACL + MR), and ACL reconstruction with APM (ACL + APM).

Methods

The PearlDiver Mariner M157Ortho database was searched. Five cohorts were identified using Current Procedural Terminology (CPT) codes and included those 16 to 60 years old who underwent isolated ACL reconstruction, isolated MR, ACL + MR, isolated APM, or ACL + APM repair. Groups were matched by age, sex, and presence of diagnosis codes for obesity. The incidence of knee OA diagnosis within 5 years of the index procedure was determined for each group, and odds ratios (ORs) were calculated and compared against isolated ACL reconstruction.

Results

Each group consisted of 7,672 patients (3,450 females, 4,222 males). A significantly greater proportion of the APM group was diagnosed with knee OA within 5 years of surgery compared to isolated ACL reconstruction (APM = 1,032/7,672 [13.5%] vs ACL = 745/7,672 [9.7%]; P ≤ .001; OR, 1.45; 95% confidence interval [CI], 1.31-1.60). Similarly, a greater proportion of the MR group was diagnosed with OA compared to isolated ACL reconstruction (MR = 826/7,672 [10.7%]; P = .030; OR, 1.12; 95% CI, 1.01-1.25). No differences in OA incidence were noted between the ACL + APM group when compared to isolated ACL reconstruction (P = .81). Patients undergoing ACL + MR demonstrated the lowest OA incidence with reduced odds when compared to isolated ACL reconstruction (ACL + MR = 575/7,672 [7.5%]; P < .001; OR, 0.75; 95% CI, 0.67-0.84).

Conclusions

In this analysis using CPT codes, APM was associated with the highest knee OA incidence, and ACL + MR was associated with the lowest OA incidence within 5 years of surgery.

Level of Evidence

Level III, retrospective cohort study.

Study on the use of 3D printed guides in the individualized reconstruction of the anterior cruciate ligament

OBJECTIVE

Evaluation of the accuracy and effectiveness of 3D printed guides to assist femoral tunnel preparation in individualised reconstruction of the anterior cruciate ligament.

METHODS

Sixty patients who attended the Affiliated Hospital of Binzhou Medical College for autologous hamstring single bundle reconstruction of the anterior cruciate ligament from October 2018 to October 2020 were selected and randomly divided into two groups, including 31 cases in the 3D printing group (14 males and 17 females, mean age 41.94 ± 10.15 years) and 29 cases in the control group (13 males and 16 females, mean age 37.76 ± 10.34 years). Patients in both groups were assessed for intraoperative femoral tunnel accuracy, the number of intraoperative positioning and the time taken to prepare the femoral tunnel, the length of the anteromedial approach incision, the pre-planned bone tunnel length and intraoperative bone tunnel length in the 3D printed group, IKDC score and Lysholm score preoperatively and at 3, 6 and 12 months postoperatively, the Lachman、pivot-shift test preoperatively and at 6 months postoperatively, gait analysis to assess internal and external rotation in flexion of the knee at 12 months postoperatively and postoperative complications in both groups.

RESULTS

There was no statistical difference in functional knee scores and anteromedial approach incision length between the 3D printed and control groups (p > 0.05), while there was a statistical difference in the accuracy of tunnel positioning, the time taken to prepare the femoral bone tunnel and the degree of external rotation of the knee in flexion between the two groups (p < 0.05). There was no statistical difference between the preoperative planning of the bone tunnel length and the intraoperative bone tunnel length (p > 0.05).

COMPLICATIONS

One case in the 3D printing group developed intermuscular vein thrombosis in the affected lower limb after surgery, which disappeared after treatment, while three cases in the control group developed intermuscular vein thrombosis in the affected lower limb. No complications such as bone tunnel rupture, deep vein thrombosis in the lower limb and infection occurred in either group.

CONCLUSION

3D printed guides assisted with individualized ACL reconstruction may improve the accuracy of femoral tunnel positioning, which is safe and effective, while reducing the operative time and the number of intraoperative positioning, without increasing the length of incision, and may obtain higher functional scores and rotational stability of the knee joint, which is in line with the concept of individualized ACL reconstruction.

Graft failure within 2 years of isolated anterior cruciate ligament reconstruction is associated with increased risk of secondary meniscus tears

PURPOSE

A debilitating complication following anterior cruciate ligament reconstruction is a secondary meniscus tear. Currently, the literature is mixed regarding the risk factors associated with the incidence of secondary meniscus tears. The aim of this study was to investigate risk factors associated with meniscus tears following an isolated primary anterior cruciate ligament reconstruction. ACL graft failure was hypothesized to be the strongest risk factor for secondary meniscal injury occurrence.

METHODS

A retrospective cohort analysis was performed using the PearlDiver Database. Patients with a primary anterior cruciate ligament reconstruction were identified in the database. Patients with concomitant knee ligament injury or meniscus injury present at the time the index procedure were excluded. Patients were grouped to those who had a secondary meniscus tear within 2 years following anterior cruciate ligament reconstruction and those who did not. Univariate analysis and multivariable regression analysis was conducted to identify significant risk factors for a secondary meniscus tear.

RESULTS

There were 25,622 patients meeting criteria for inclusion in this study. Within 2 years from the primary anterior cruciate ligament reconstruction, there were 1,781 patients (7.0%) that experienced a meniscus tear. Graft failure had the highest odds of having a postoperative meniscus tear within 2 years (OR: 4.1; CI 3.5-4.8; p < 0.002). Additional significant risk factors included tobacco use (OR: 2.0; CI 1.0-3.1; p < 0.001), increased Charlson Comorbidity Index (OR: 1.2; CI 1.1-1.4), male gender (OR: 1.1; CI 1.1-1.2; p < 0.001), obesity (OR: 1.1; CI 1.1-1.2; p < 0.001), delayed surgery (OR:1.1; CI 1.1-1.2; p < 0.002), and patients age 30 and older (OR: 1.0; CI 1.0-1.0; p < 0.001).

CONCLUSIONS

This study found that anterior cruciate ligament graft failure is the strongest predictor of post-operative meniscus tears. Other risk factors, including tobacco use, increased CCI, male gender, obesity, delayed surgery, and age 30 and older, were established, with several being modifiable. Therefore, targeted preoperative optimization of modifiable risk factors and postoperative protocols may reduce the risk of secondary meniscus tears.

LEVEL OF EVIDENCE

Level III, prognostic trial.

Meniscal injuries in skeletally immature children with tibial eminence fractures. Systematic review of literature

PURPOSE

Although the mechanisms of injury are similar to ACL rupture in adults, publications dealing with meniscal lesions resulting from fractures of the intercondylar eminence in children are much rarer. The main objective was to measure the frequency of meniscal lesions associated with tibial eminence fractures in children. The second question was to determine whether there is any available evidence on association between meniscal tears diagnostic method, and frequencies of total lesions, total meniscal lesions, and total entrapments.

METHODS

A comprehensive literature search was performed using PubMed and Scopus. Articles were eligible for inclusion if they reported data on intercondylar tibial fracture, or tibial spine fracture, or tibial eminence fracture, or intercondylar eminence fracture. Article selection was performed in accordance with the PRISMA guidelines.

RESULTS

In total, 789 studies were identified by the literature search. At the end of the process, 26 studies were included in the final review. This systematic review identified 18.1% rate of meniscal tears and 20.1% rate of meniscal or IML entrapments during intercondylar eminence fractures. Proportion of total entrapments was significantly different between groups (17.8% in the arthroscopy group vs. 6.2% in the MRI group; p < .0001). Also, we found 20.9% of total associated lesions in the arthroscopy group vs. 26.1% in the MRI group (p = .06).

CONCLUSION

Although incidence of meniscal injuries in children tibial eminence fractures is lower than that in adults ACL rupture, pediatric meniscal tears and entrapments need to be systematically searched. MRI does not appear to provide additional information about the entrapment risk if arthroscopy treatment is performed. However, pretreatment MRI provides important informations about concomitant injuries, such as meniscal tears, and should be mandatory if orthopaedic treatment is retained. MRI modalities have yet to be specified to improve the diagnosis of soft tissues entrapments.

STUDY DESIGN

Systematic review of the literature REGISTRATION: PROSPERO N° CRD42021258384.

Anterior cruciate ligament reconstruction with a biocomposite interference screw maintains graft fixation survival and improves clinical outcomes at 1 year: A multicenter prospective case series

A biocomposite interference screw with an open architecture was developed to provide a greater available surface area for bone ingrowth compared with conventional solid interference screws. We herein describe a prospective, single-cohort study conducted using this interference screw in anterior cruciate ligament (ACL) reconstruction. Sixty subjects (mean age, 34.9 years; standard deviation, 10.6) undergoing ACL repair using the biocomposite interference screw were enrolled at 3 sites in the United States. Subjects were followed preoperatively (baseline) and postoperatively at 6 months and 1 year. The primary endpoint was graft fixation survival rate at 6 months and 1 year. Secondary endpoints included graft survival (failure defined as that occurring for any reason); International Knee Documentation Committee (IKDC) score (exam and subjective forms); Tegner Activity form; Lysholm score; and EQ (EuroQuol)-5D-5L index score and visual analogue scale. There was a 100 % rate of graft fixation survival at 6 months (54/54; 95 % confidence interval [CI]: 100-100) and 1 year (50/50; 95 % CI: 100-100). One patient experienced a complete tear of the ACL 5 months following index surgery, resulting in graft survival rates of 98.1 % (53/54; 95 % CI: 94.6-100) at 6 months at 98.0 % (49/50; 95 % CI: 94.1-100) at 1 year. Significant improvements (p < .0001) were obtained between baseline and 6 months for the majority of patient-reported outcomes, and were maintained out to 1-year follow up. There was no significant difference over baseline in the IKDC sub-scale of symptoms. Nine patients (15.0 %) experienced serious adverse events during the course of the study; three of these patients' adverse events were considered possibly or definitely related to the procedure device (ACL tear, pulmonary embolism/deep vein thrombosis, and a patellar fracture). In conclusion, this biocomposite interference screw has a favorable safety and efficacy profile at 1 year, with no failures of graft fixation, noted during that time.

Surgeon anterior cruciate ligament reconstruction volume and rates of concomitant meniscus repair

PURPOSE

The purpose of this study was to assess the effect of surgeon anterior cruciate ligament reconstruction (ACLR) volume on rates of ACLR with concomitant meniscus repair versus meniscectomy and subsequent meniscus surgeries.

METHODS

A retrospective review was conducted from a database of all ACLR performed between 2015 and 2020 at a large integrated health care system. Surgeon volume was categorized as < 35 ACLR per year (low-volume), and ≥ 35 ACLR per year (high-volume). Rates of concomitant meniscus repair and meniscectomy were compared between low-volume and high-volume surgeons. Subgroup analyses compared the rates of subsequent meniscus surgery and procedure time based on surgeon volume and meniscus procedure type.

RESULTS

A total of 3,911 patients undergoing ACLR were included. High-volume surgeons performed concomitant meniscus repair statistically significantly more often than low-volume surgeons (32.0% vs 10.7%, p < 0.001). Binary logistic regression indicated 4.15 times higher odds of meniscus repair among high-volume surgeons. Subsequent meniscus surgery occurred more commonly following ACLR with meniscus repair among low-volume surgeons (6.7% vs 3.4%, p = 0.047), but not high-volume surgeons (7.0% vs 4.3%, p = 0.079). Low-volume surgeons also had longer procedure times for concomitant meniscus repair (129.9 vs 118.3 min, p = 0.003) and meniscectomy (100.6 vs 95.9 min, p = 0.003).

CONCLUSIONS

Data from this study shows that surgeons with lower volume of ACLR select meniscus resection statistically significantly more often than higher-volume surgeons. However, an abundance of literature is available to show that meniscus loss negatively affects the development of post-traumatic osteoarthritis in patients Therefore, as demonstrated in this study by high-volume surgeons, the meniscus should be repaired and protected whenever possible.

LEVEL OF EVIDENCE

III.

Management after acute rupture of the anterior cruciate ligament (ACL). Part 1: ACL reconstruction has a protective effect on secondary meniscus and cartilage lesions

PURPOSE

The aim of this consensus project was to validate which endogenous and exogenous factors contribute to the development of post-traumatic osteoarthritis and to what extent ACL (anterior cruciate ligament) reconstruction can prevent secondary damage to the knee joint. Based on these findings, an algorithm for the management after ACL rupture should be established.

METHODS

The consensus project was initiated by the Ligament Injuries Committee of the German Knee Society (Deutsche Kniegesellschaft, DKG). A modified Delphi process was used to answer scientific questions. This process was based on key topic complexes previously formed during an initial face-to-face meeting of the steering group with the expert group. For each key topic, a comprehensive review of available literature was performed by the steering group. The results of the literature review were sent to the rating group with the option to give anonymous comments until a final consensus voting was performed. Consensus was defined a-priori as eighty percent agreement.

RESULTS

Of the 17 final statements, 15 achieved consensus, and 2 have not reached consensus. Results of the consensus were summarized in an algorithm for the management after ACL rupture (infographic/Fig. 2).

CONCLUSION

This consensus process has shown that the development of post-traumatic osteoarthritis is a complex multifactorial process. Exogenous (primary and secondary meniscus lesions) and endogenous factors (varus deformity) play a decisive role. Due to the complex interplay of these factors, an ACL reconstruction cannot always halt post-traumatic osteoarthritis of the knee. However, there is evidence that ACL reconstruction can prevent secondary joint damage such as meniscus lesions and that the success of meniscus repair is higher with simultaneous ACL reconstruction. Therefore, we recommend ACL reconstruction in case of a combined injury of the ACL and a meniscus lesion which is suitable for repair.

LEVEL OF EVIDENCE

Level V.

Acute Iliotibial Band ACL Reconstruction at Time of Tibial Plateau Fracture Fixation: A Case Report

Introduction

Tibial plateau fractures are frequently associated with associated soft-tissue injuries. Typical treatment algorithms prioritize bony stabilization followed by delayed soft-tissue reconstruction. However, when the soft-tissue injury needs urgent intervention to optimize patient outcome, early soft-tissue reconstruction may be indicated.

Case Report

This case report features a high-energy tibia plateau fracture-dislocation with associated anterior cruciate ligament (ACL) and bucket-handle lateral meniscus tear sustained after a fall. The treatment of both bony and soft-tissue injury took place during a single anesthetic event by utilizing a novel application of a previously described technique for ACL reconstruction with iliotibial band (ITB) autograft.

Conclusion

The ITB ACL reconstruction technique can be used in adults with concomitant ACL rupture and tibial plateau fracture. This allows patients to undergo a single anesthetic event for treatment of both bony and soft-tissue injuries.

Management after acute injury of the anterior cruciate ligament (ACL), part 2: management of the ACL-injured patient

PURPOSE

The aim of this consensus project was to create a treatment algorithm for the management of the ACL-injured patient which can serve as an aid in a shared decision-making process.

METHODS

For this consensus process, a steering and a rating group were formed. In an initial face-to-face meeting, the steering group, together with the expert group, formed various key topic complexes for which various questions were formulated. For each key topic, a structured literature search was performed by the steering group. The results of the literature review were sent to the rating group with the option to give anonymous comments until a final consensus voting was performed. Sufficient consensus was defined as 80% agreement.

RESULTS

During this consensus process, 15 key questions were identified. The literature search for each key question resulted in 24 final statements. Of these 24 final statements, all achieved consensus.

CONCLUSIONS

This consensus process has shown that ACL rupture is a complex injury, and the outcome depends to a large extent on the frequently concomitant injuries (meniscus and/or cartilage damage). These additional injuries as well as various patient-specific factors should play a role in the treatment decision. The present treatment algorithm represents a decision aid within the framework of a shared decision-making process for the ACL-injured patient.

LEVEL OF EVIDENCE

Level V.

Early ACLR and Risk and Timing of Secondary Meniscal Injury Compared With Delayed ACLR or Nonoperative Treatment: A Time-to-Event Analysis Using Machine Learning

BACKGROUND

Surgical and nonoperative management of anterior cruciate ligament (ACL) injuries seek to mitigate the risk of knee instability and secondary meniscal injury. However, the associated risk and timing of secondary meniscal tears have not been completely elucidated.

PURPOSE

To compare risk and timing of secondary meniscal injury between patients receiving nonoperative management, delayed ACL reconstruction (ACLR), and early ACLR using a machine learning survival analysis.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A geographic database was used to identify and review records of patients with a diagnosis of ACL rupture between 1990 and 2016 with minimum 2-year follow-up. Patients undergoing ACLR were matched 1:1 with nonoperatively treated controls. Rate and time to secondary meniscal tear were compared using random survival forest algorithms; independent models were developed and internally validated for predicting injury-free duration in both cohorts. Performance was measured using out-of-bag c-statistic, calibration, and Brier score. Model interpretability was enhanced using global variable importance and partial dependence curves.

RESULTS

The study included 1369 patients who underwent ACLR and 294 patients who had nonoperative treatment. After matching, no significant differences in rates of secondary meniscal tear were found (P = .09); subgroup analysis revealed the shortest periods of meniscal survival in patients undergoing delayed ACLR. The random survival forest algorithm achieved excellent predictive performance for the ACLR cohort, with an out-of-bag c-statistic of 0.80 and a Brier score of 0.11. Significant variables for risk of meniscal tear for the ACLR cohort included time to return to sports or activity ≤350 days, time to surgery ≥50 days, age at injury ≤40 years, and high-impact or rotational landing sports, whereas those in the nonoperative cohort model included time to RTS ≤200 days, visual analog scale pain score >3 at consultation, hypermobility, and noncontact sports.

CONCLUSION

Delayed ACLR demonstrated the greatest long-term risk of meniscal injury compared with nonoperative treatment or early ACLR. Risk factors for decreased meniscal survival after ACLR included increased time to surgery, shorter time to return to sports or activity, older age at injury, and involvement in high-impact or rotational landing sports. Pending careful external validation, these models may be deployed in the clinical space to provide real-time insights and enhance decision making.

Patient's subjective knee function 3-5 years following partial meniscectomy or meniscus repair compared to a normal population: a retrospective cohort study

Purpose

Evaluate patient-reported knee function after arthroscopic partial meniscectomy (APM) and meniscus suture repair in two different age cohorts compared with a normal population.

Method

Arthroscopic meniscus surgery was performed on 421 patients at Skåne University Hospital from 2010 to 2014, with a mean (SD) follow-up of 4.2 (1.4) years. Patients and controls were divided into two age cohorts; 18-34 years (younger) and 35-54 years (middle-aged) as well as according to surgery performed; either solely meniscus surgery or with concurrent anterior cruciate ligament reconstruction (ACLR). The outcome is measured with the five subscales of the Knee and Osteoarthritis Outcome Score (KOOS).

Results

No significant difference in outcome after all studied types of meniscus surgeries between younger-aged and middle-aged patients.Younger patients with APM or meniscus suture repair, with or without, ACLR score lower than the normal population in all subscales of KOOS (p<0.001), except in Activities of Daily Living (ADL) for meniscus suture patients.Middle-aged patients with APM score lower in all subscales than the normal population (p≤0.009). Those with meniscus suture repair score lower than the normal population only for the subscales Sport/Rec and quality of life (p<0.001).Both younger-aged and middle-aged patients achieve better KOOS values after meniscus suture repair and ACLR than after all other combinations of surgery.

Conclusion

Patients with meniscus injuries do not reach the same KOOS score as the normal population, irrespective of age or type of meniscus surgery performed. However, combined with ACLR in younger-aged and middle-aged patients, meniscus suture gives a better subjective outcome than isolated meniscus surgery.

Meniscal Repair Outcomes at Greater Than 5 Years: A Systematic Review and Meta-Analysis

BACKGROUND

The utilization of meniscal repair techniques continues to evolve in an effort to maximize the rate of healing. Meniscal repair outcomes at a minimum of 5 years postoperatively appear to better represent the true failure rates. Thus, a systematic review and meta-analysis of the current literature was conducted to assess the rate of failure at a minimum of 5 years after meniscal repair.

METHODS

We performed a systematic review of studies reporting the outcomes of meniscal repair at a minimum of 5 years postoperatively. A standardized search and review strategy was utilized. Failure was defined as recurrent clinical symptoms or a meniscal reintervention to repair or resect the meniscus in any capacity, as defined by the study. When reported, outcomes were assessed relative to anterior cruciate ligament (ACL) status, sex, age, and postoperative rehabilitation protocol. Meta-analyses were performed with a random-effects model.

RESULTS

A total of 27 studies of 1,612 patients and 1,630 meniscal repairs were included in this review and meta-analysis. The pooled overall failure rate was 22.6%, while the failure rate of modern repairs (excluding early-generation all-inside devices) was 19.5%. Medial repairs were significantly more likely to fail compared with lateral repairs (23.9% versus 12.6%, p = 0.04). Failure rates were similar for inside-out (14.2%) and modern all-inside repairs (15.8%). Early-generation all-inside devices had a significantly higher failure rate (30.2%) compared with modern all-inside devices (15.8%, p = 0.01). There was no significant difference in meniscal failure rate between repairs with concomitant ACL reconstruction (21.2%) and repairs in ACL-intact knees (23.3%, p = 0.54).

CONCLUSIONS

Modern meniscal repair had an overall failure rate of 19.5% at a minimum of 5 years postoperatively. Modern all-inside techniques appear to have improved the success rate of meniscal repair compared with use of early-generation all-inside devices. Lateral repairs were significantly more likely to be successful compared with medial repairs, while no difference was seen between patients undergoing meniscal repair with and without concomitant ACL reconstruction.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

A longer duration from injury to surgery is associated with preoperative deterioration of an isolated meniscal tear in patients aged 40 years or older

PURPOSE

To evaluate the preoperative deterioration of an isolated meniscal tear in patients aged 40 years or older, and whether time from injury to surgery is associated with worsening of a meniscal tear.

METHODS

Patients aged 40 years or older who underwent arthroscopic surgery for isolated meniscal tear between 2014 and 2019 were retrospectively reviewed. The diagnostic magnetic resonance imaging (MRI) findings and arthroscopic findings were compared to evaluate the deterioration of meniscal tears. Predictors of the development of meniscal tears; patient demographic factors, duration from injury to surgery (injury to MRI and MRI to surgery), and image findings were assessed.

RESULTS

A total of 58 patients (58 knees) were included (mean age, 55.9 ± 8.5 years; male/female, 31/27). An isolated meniscal tear deteriorated in 28 (48.3%). Compared patients with and without deteriorated meniscal tear, significant differences were found in the MRI grade of meniscal tear (p = 0.03), duration from injury to MRI (164.2 ± 167.9 vs 45.2 ± 48.7 days, p < 0.001), and from MRI to surgery (148.8 ± 91.1 vs 67.6 ± 56.7 days, p < 0.001). A multivariate regression analysis showed that the duration from injury to MRI (odds ratio [OR], 1.03; p < 0.001) and from MRI to surgery (OR, 1.02; p < 0.001) were independent predictors.

CONCLUSION

Approximately 50% of isolated meniscal tears deteriorated preoperatively in patients aged 40 years or older. The duration from injury to surgery was an independent predictor of worsening of an isolated meniscal tear.

Superior Outcome of Early ACL Reconstruction versus Initial Non-reconstructive Treatment With Late Crossover to Surgery: A Study From the Swedish National Knee Ligament Registry

BACKGROUND

Although comparable clinical and functional outcomes have been reported after nonsurgical and surgical anterior cruciate ligament (ACL) treatment, few studies have investigated the effects of early versus late ACL reconstruction with initial rehabilitation.

PURPOSE

To determine patient-reported knee function in patients who initially undergo nonreconstructive treatment after an ACL injury but who later choose to undergo ACL reconstruction as compared with (1) patients undergoing ACL reconstruction close to the index injury and (2) patients treated nonreconstructively at 1 to 10 years of follow-up.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Results from the Knee injury and Osteoarthritis Outcome Score (KOOS) were extracted from the Swedish National Knee Ligament Registry for patients treated with nonreconstruction, early ACL reconstruction, and initial nonreconstruction but subsequent ACL reconstruction (crossover group). The KOOS₄ (a mean of 4 KOOS subscales) was analyzed cross-sectionally at baseline and at the 1-, 2-, 5-, and 10-year follow-ups. Additionally, the Patient Acceptable Symptom State (PASS) was applied to all KOOS subscales from baseline to the 10-year follow-up.

RESULTS

A total of 1,074 crossover, 484 nonreconstruction, and 20,352 early ACL reconstruction cases were included. The crossover group reported lower KOOS₄ values than the group undergoing early ACL reconstruction at baseline and at all follow-ups (mean difference [95% CI]): baseline, -6.5 (-8.0 to -5.0); 1 year, -9.3 (-10.9 to -7.7); 2 years, -4.8 (-6.3 to -3.2); 5 years, -6.1 (-8.8 to -3.4); and 10 years, -10.9 (-16.3 to -5.2). Additionally, a smaller proportion of the crossover cohort achieved a PASS on KOOS subscales at baseline and through the 1-, 2-, 5-, and 10-year follow-ups as compared with the early ACL reconstruction cohort. No differences were observed between crossover and nonreconstruction cases on either the KOOS₄ or the PASS at any follow-up.

CONCLUSION

A greater proportion of patients treated with early ACL reconstruction reported acceptable knee function and superior overall knee function as compared with patients who decided to cross over from nonreconstructive treatment to ACL reconstruction.

Lateral meniscal posterior root tears experience acceptable healing status after transtibial repair technique

PURPOSE

To evaluate patient MRI results, demography and clinical outcome following transtibial repair of lateral and medial meniscal posterior root tears.

METHODS

Patients treated with transtibial repairs of posterior meniscal root tears from 2015 through 2018 performed pre- and postoperative MRI scans. Outcome measures were continuity/discontinuity of the meniscal root and change in meniscal extrusion on MRI. Other outcomes were KOOS, Lysholm score, Tegner activity scale and the Global Rate of Change (GRoC) score for function and pain at follow-up.

STUDY DESIGN

Retrospective case-series.

RESULTS

Of 41 patients, 36 attended follow-up at mean 26 (12-38) months postoperatively. At follow-up, 11 out of 18 lateral meniscus posterior root tear (LMPRT) versus 5 out of 18 medial meniscus posterior root tear (MMPRT) repairs were classified as healed. Meniscal extrusion decreased in LMPRTs from of 2.3 ± 1.5 mm to 1.4 ± 1.09 mm (p = 0.080) and increased in MMPRTs from 3.1 ± 1.6 mm to 4.8 ± 1.9 mm (p = 0.005) at FU (between-group difference, p < 0.001). LMPRT repairs were associated with ACL injury and additional meniscal injury and were younger and with lower BMI. No between-group differences were found for KOOS, Lysholm or GRoC Function scores. Tegner scale was higher and GRoC Pain score lower in the LMPRT group compared to the MMPRTs.

CONCLUSION

Following transtibial repair for meniscal posterior root repairs, the LMPRTs had a higher frequency of healing, whereas most MMPRTs continued to extrude, despite surgical intervention. The study confirmed that LMPRTs and MMPRTs differ in demography and associated injuries.

Coronal subluxation of the tibiofemoral joint before and after anterior cruciate ligament reconstruction

Background

Studies have shown that medial subluxation of the tibia occurs after anterior cruciate ligament (ACL) rupture. However, it is unclear whether anterior cruciate ligament reconstruction (ACLR) can correct tibial coronal subluxation.

Purpose

To determine whether the tibia is medially subluxated after ACL rupture, and whether ACLR can correct medial subluxation of the tibia.

Study design

Case series; Level of evidence, 4, Retrospective clinical study.

Methods

The distance of tibial coronal subluxation before and after ACLR surgery was measured in 48 patients with ACL rupture and meniscus injury. Tibiofemoral subluxation was defined as the perpendicular distance between the long axis of the tibia and a second parallel line originating at the most proximal aspect of the femoral intercondylar notch. To determine the long axis of the tibia, two circles separated by 5 cm were centered on the proximal tibia. The proximal circle is 5 cm from the tibial plateau, and the distal circle is 5 cm from the proximal circle. The line passing through the center of the two circles was considered the long axis of the proximal tibia. Care was taken to ensure that each patient lied on the back with their patellae facing upward, to minimize rotational variation among the radiographs. At the same time, 30 patients with simple meniscus injury who underwent arthroscopy during the same period were selected to determine the degree of tibiofemoral coronal subluxation as the baseline value. The changes before and after operation were compared, as well as the differences with the baseline data.

Result

The average follow-up period was 21.2 ± 5.8 months. The average distance of tibial coronal subluxation before ACLR was 5.5 ± 2.1 mm, which was significantly different from that of baseline group (7.3 ± 2.1 mm) (P < 0.001). The tibial subluxation after ACLR was 7.7 ± 2.6 mm, which was significantly different from that before operation (P < 0.001). There was no significant difference in the distance between postoperative tibial subluxation and baseline group (P = 0.472).

Conclusion

The tibia was coronally medially subluxated after ACL rupture. ACLR can correct the medial subluxation of tibia. This finding is helpful in the diagnosis of ACL rupture, and can be used to assess the imaging status of the tibiofemoral joint on the coronal plane during or after ACLR.

[Consequences of anterior cruciate ligament rupture: a systematic umbrella review]

INTRODUCTION

 The treatment of an anterior cruciate ligament rupture is still controversial. In particular, this applies to the question of conservative versus surgical treatment. The answer to this question is often based on consequential damage such as the development of posttraumatic osteoarthritis, secondary damage to the meniscus or cartilage, and participation in sports. If there are significant differences in these parameters between the individual treatment options, the results will be of great importance for the development of evidence-based treatment pathways. Therefore, the aim of this work was to evaluate the development of knee osteoarthritis after rupture of the anterior cruciate ligament and the corresponding treatment (conservative or surgical).

MATERIAL AND METHODS

 To answer the above question, a systematic literature search was conducted in Medline via Pubmed, the Cochrane Library and in CINAHL. Only systematic reviews with a minimum follow-up period of 10 years were included. The search was conducted in January 2020 and updated in January 2021. Investigated cohorts included patients with a rupture of the anterior cruciate ligament who had undergone either conservative or surgical treatment. Osteoarthritis was diagnosed either radiologically (recognized scores) or clinically (pain and impaired function). Appropriate reviews were qualitatively evaluated using the AMSTAR-2 questionnaire.

RESULTS

 The literature research initially identified n = 42 reviews from which 14 reviews were included. After full-text review and qualitative evaluation, only n = 2 systematic reviews remained for evaluation. The results of both papers show imprecise data with a high variability. However, it can be assumed with high probability that the development of osteoarthritis of the knee is increased after a rupture of the anterior cruciate ligament. There is no evidence that the incidence of joint degeneration may be reduced by reconstruction of the anterior cruciate ligament, nor is there a difference when comparing conservative and surgical treatment directly.

CONCLUSION

 Patients with an anterior cruciate ligament rupture are likely to be at a greater risk of developing progressive joint degeneration. A protective effect of cruciate ligament surgery has not been found in the evaluated studies. A general argument in favour of cruciate ligament surgery aiming to achieve a protective effect on hyaline articular cartilage seems obsolete based on the results and should therefore not be used in patient education in the future.

Clinical Outcomes of Meniscus Repair with or without Multiple Intra-Articular Injections of Platelet Rich Plasma after Surgery

Preservation of the meniscal volume is crucial in meniscus repair. The goal of this study was to evaluate the clinical outcome of repeated intra-articular platelet-rich plasma (PRP) injections after arthroscopic repair of a traumatic meniscal tear. We retrospectively reviewed 61 primary meniscal repairs in 61 patients (PRP group: 30; non-PRP: 31) from 2017 to 2018. Patients in the PRP group received repeated intra-articular PRP injections in week 2,4,6 after the primary meniscus repair. Subsequent meniscal repair treatment or meniscectomy, knee arthroplasty, and IKDC changes of less than 11.5 points were defined as healing failures. After following up for at least 24 months, the IKDC score was 75.1 ± 13.6, and the Lysholm score was 80.6 ± 14.9 in the PRP group and 72.6 ± 15.8 (IKDC) and 77.7 ± 17.2 (Lysholm) in the non-PRP group. Healing rates of the PRP and the non-PRP groups were 93.3% (Kaplan-Meier 91.6%) and 87.1% (Kaplan-Meier 84.7%), respectively (log rank test p = 0.874). Our study is the first to use multiple intra-articular PRP injections to facilitate meniscal healing after meniscal repair. Though selection bias may be present in this study, the PRP group had similar functional outcome and healing rate compared to non-PRP group.

Mesenchymal stromal cell products for intra-articular knee injections for conservative management of osteoarthritis

Sports injuries and secondary joint problems, mainly of the knee, are common, especially in sports associated with high impact activities and/or torsional loading. The consequences can be career ending in elite athletes and reduce exercise activities in recreational people. Various cell products can be injected intra-articularly. First, fresh cellular mixtures can be prepared and injected in the same day, such as stromal vascular fraction of adipose tissue (SVF) and bone marrow concentrates (BMCs). Second, autologous mesenchymal stromal cells (MSCs) can be isolated from BMCs or SVF and, after several weeks of laboratory expansion, several millions of MSCs can be obtained for intra-articular injection. Finally, allogeneic MSCs from the bone marrow, adipose tissue or perinatal tissues of selected donors constitute an ‘off-the-shelf’ experimental treatment for injection delivery in patients with osteoarthritis of the knee. The perceived efficacy of all these products is based on the hypothesis of a paracrine mechanism of action: when living cells are delivered within the joint, they establish a molecular cross-talk with immune cells and local cell phenotypes, thereby modulating inflammation with subsequent modifications in the catabolic/degenerative milieu. Current clinical research examines whether injection delivery of MSCs translates into actual clinical benefits. Overall, clinical studies lack the quality needed to answer major research questions, including clinical and structural efficacy, optimal cell dose, and number of injections and specific protocol for cell delivery. Poor experimental designs are exacerbated by the diversity of patient phenotypes that hinder comparisons between treatments. Further understanding of disease pathology is paramount to develop potent function assays and understand whether the host tissue, the cell product or both should be primed before MSCs are injected intra-articularly.