Elizabeth Wellsandt

Decreased Knee Joint Loading Associated With Early Knee Osteoarthritis After Anterior Cruciate Ligament Injury

Background: Anterior cruciate ligament (ACL) injury predisposes individuals to early-onset knee joint osteoarthritis (OA). Abnormal joint loading is apparent after ACL injury and reconstruction. The relationship between altered joint biomechanics and the development of knee OA is unknown. Hypothesis: Altered knee joint kinetics and medial compartment contact forces initially after injury and reconstruction are associated with radiographic knee OA 5 years after reconstruction. Study Design: Case-control study; Level of evidence, 3. Methods: Individuals with acute, unilateral ACL injury completed gait analysis before (baseline) and after (posttraining) preoperative rehabilitation and at 6 months, 1 year, and 2 years after reconstruction. Surface electromyographic and knee biomechanical data served as inputs to an electromyographically driven musculoskeletal model to estimate knee joint contact forces. Patients completed radiographic testing 5 years after reconstruction. Differences in knee joint kinetics and contact forces were compared between patients with and those without radiographic knee OA. Results: Patients with OA walked with greater frontal plane interlimb differences than those without OA (nonOA) at baseline (peak knee adduction moment difference: 0.00 ± 0.08 N·m/kg·m [nonOA] vs −0.15 ± 0.09 N·m/kg·m [OA], P = .014; peak knee adduction moment impulse difference: −0.001 ± 0.032 N·m·s/kg·m [nonOA] vs −0.048 ± 0.031 N·m·s/kg·m [OA], P = .042). The involved limb knee adduction moment impulse of the group with osteoarthritis was also lower than that of the group without osteoarthritis at baseline (0.087 ± 0.023 N·m·s/kg·m [nonOA] vs 0.049 ± 0.018 N·m·s/kg·m [OA], P = .023). Significant group differences were absent at posttraining but reemerged 6 months after reconstruction (peak knee adduction moment difference: 0.02 ± 0.04 N·m/kg·m [nonOA] vs −0.06 ± 0.11 N·m/kg·m [OA], P = .043). In addition, the OA group walked with lower peak medial compartment contact forces of the involved limb than did the group without OA at 6 months (2.89 ± 0.52 body weight [nonOA] vs 2.10 ± 0.69 body weight [OA], P = .036). Conclusion: Patients who had radiographic knee OA 5 years after ACL reconstruction walked with lower knee adduction moments and medial compartment joint contact forces than did those patients without OA early after injury and reconstruction.

Predictors of knee joint loading after anterior cruciate ligament reconstruction.

Anterior cruciate ligament (ACL) injury results in altered knee joint mechanics which frequently continue even after ACL reconstruction. The persistence of altered mechanical loading of the knee is of concern due to its likely role in the development of post‐traumatic osteoarthritis (OA). Joint contact forces are associated with post‐traumatic OA development, but evaluation of factors influencing the magnitude of contact forces after ACL injury is needed to advance current strategies aimed at preventing post‐traumatic OA. Therefore, the purpose of this study was to identify predictive factors of knee joint contact forces after ACL reconstruction. Thirty athletes completed standard gait analysis with surface electromyography 6 months after ACL reconstruction. An electromyographic‐driven musculoskeletal model was used to estimate joint contact forces. External knee adduction moment was a significant predictor of medial compartment contact forces in both limbs, while vertical ground reaction force and co‐contraction only contributed significantly in the uninvolved limb. The large influence of the knee adduction moment on joint contact forces provides mechanistic clues to understanding the mechanical pathway of post‐traumatic OA after ACL injury.

Gait mechanics in those with/without medial compartment knee osteoarthritis 5 years after anterior cruciate ligament reconstruction

The objective of the study was to evaluate differences in gait mechanics 5 years after unilateral anterior cruciate ligament reconstruction surgery, for non‐osteoarthritic (n = 24) versus osteoarthritic (n = 9) subjects. For the involved knee, the osteoarthritic group demonstrated significantly lower peak knee flexion angles (non‐osteoarthritic = 24.3 ± 4.6°, osteoarthritic = 19.1 ± 2.9°, p = 0.01) and peak knee flexion moments (non‐osteoarthritic = 5.3 ± 1.2% Body Weight × Height, osteoarthritic = 4.4 ± 1.2% Body Weight × Height, p = 0.05). Differences in peak knee adduction moment approached significance, with a higher magnitude for the osteoarthritic group (non‐osteoarthritic = 2.4 ± 0.8% Body Weight × Height, osteoarthritic = 2.9 ± 0.5% Body Weight × Height, p = 0.09). Peak medial compartment joint load was evaluated using electromyography‐informed neuromusculoskeletal modeling. Peak medial compartment joint load in the involved knee for the two groups was not different (non‐osteoarthritic = 2.4 ± 0.4 Body Weight, osteoarthritic = 2.3 ± 0.6 Body Weight). The results suggest that subjects with dissimilar peak knee moments can have similar peak medial compartment joint load magnitudes. There was no evidence of inter‐limb asymmetry for either group. Given the presence of inter‐group differences (non‐osteoarthritic vs. osteoarthritic) for the involved knee, but an absence of inter‐limb asymmetry in either group, it may be necessary to evaluate how symmetry is achieved, over time, and to differentiate between good versus bad inter‐limb symmetry, when evaluating knee gait parameters.

Hip joint biomechanics in those with and without post-traumatic knee osteoarthritis after anterior cruciate ligament injury

Background: Anterior cruciate ligament injury results in altered kinematics and kinetics in the knee and hip joints that persist despite surgical reconstruction and rehabilitation. Abnormal movement patterns and a history of osteoarthritis are risk factors for articular cartilage degeneration in additional joints. The purpose of this study was to determine if hip joint biomechanics early after anterior cruciate ligament injury and reconstruction differ between patients with and without post‐traumatic knee osteoarthritis 5 years after reconstruction. The studys rationale was that individuals who develop knee osteoarthritis after anterior cruciate ligament injury may also demonstrate large alterations in hip joint biomechanics. Methods: Nineteen athletes with anterior cruciate ligament injury completed standard gait analysis before (baseline) and after (post‐training) extended pre‐operative rehabilitation and at 6 months, 1 year, and 2 years after reconstruction. Weightbearing knee radiographs were completed 5 years after reconstruction to identify medial compartment osteoarthritis. Findings: Five of 19 patients had knee osteoarthritis at 5 years after anterior cruciate ligament reconstruction. Patients with knee osteoarthritis at 5 years walked with smaller sagittal plane hip angles (P: 0.043) and lower sagittal (P: 0.021) and frontal plane (P: 0.042) external hip moments in the injured limb before and after reconstruction compared to those without knee osteoarthritis. Interpretation: The current findings suggest hip joint biomechanics may be altered in patients who develop post‐traumatic knee osteoarthritis. Further study is needed to confirm whether the risk of non‐traumatic hip pathology is increased after anterior cruciate ligament injury and if hip joint biomechanics influence its development. HighlightsPost‐traumatic osteoarthritis has been linked to early knee joint unloading.Later knee osteoarthritis found to relate to smaller hip joint angles and moments.Further study needed to determine if abnormal hip biomechanics lead to hip pathology.

Anterior Cruciate Ligament Injury—Who Succeeds Without Reconstructive Surgery? The Delaware-Oslo ACL Cohort Study:

Background: More than 50% of highly active patients with an anterior cruciate ligament (ACL) injury who choose nonsurgical treatment (active rehabilitation alone) have successful 2-year outcomes and comparable knee function to an uninjured population. Early predictive factors for a successful outcome may aid treatment decision making in this population. Purpose: To identify early predictors of a successful 2-year outcome in those who choose nonsurgical treatment of an ACL injury. Study Design: Cohort study; Level of evidence, 2. Methods: This prospective cohort study consisted of ACL-injured athletes who were consecutively screened for inclusion. A total of 300 patients were included from 2 sites (Oslo, Norway, and Delaware, USA), and the 118 patients who initially chose not to undergo ACL reconstruction were included. All patients participated in pivoting sports before the injury, and none had significant concomitant injuries. A successful 2-year outcome was defined as having 2-year International Knee Documentation Committee (IKDC) scores ≥15th normative percentile and not undergoing ACL reconstruction. Multivariable logistic regression models were built using demographic and knee function data (quadriceps muscle strength, 4 single-leg hop tests, IKDC score, and Knee Outcome Survey–Activities of Daily Living Scale [KOS-ADLS] score) collected at baseline or after a 5-week neuromuscular and strength training (NMST) rehabilitation program. Results: After 2 years, 52 of 97 (53.6%) patients had a successful outcome. In the multivariable baseline model, older age, female sex, better performance on the single-leg hop test, and a higher KOS-ADLS score were significantly associated with successful 2-year outcomes. After the 5-week NMST rehabilitation program, older age, female sex, and a higher IKDC score increased the odds of a successful 2-year outcome. The 2 models had comparable predictive accuracy (post-NMST area under the curve [AUC], 0.78 [95% CI, 0.68-0.88]; baseline AUC, 0.81 [95% CI, 0.72-0.89]). Conclusion: Clinicians and patients can be more confident in a nonsurgical treatment choice (active rehabilitation alone) in athletes who are female, are older in age, and have good knee function, as measured by single-leg hop tests and patient-reported outcome measures, early after an ACL injury. Prediction models that include measures of knee function, assessed either before or after rehabilitation, can estimate 2-year prognoses for nonsurgical treatment and thereby assist shared treatment decision making.

High muscle co-contraction does not result in high joint forces during gait in anterior cruciate ligament deficient knees: MUSCLE CO-CONTRACTION AND JOINT FORCES

The mechanism of knee osteoarthritis development after anterior cruciate ligament injuries is poorly understood. The objective of this study was to evaluate knee gait variables, muscle co‐contraction indices and knee joint loading in young subjects with anterior cruciate ligament deficiency (ACLD, n = 36), versus control subjects (n = 12). A validated, electromyography‐informed model was used to estimate joint loading. For the involved limb of ACLD subjects versus control, muscle co‐contraction indices were higher for the medial (p = 0.018, effect size = 0.93) and lateral (p = 0.028, effect size = 0.83) agonist–antagonist muscle pairs. Despite higher muscle co‐contraction, medial compartment contact force was lower for the involved limb, compared to both the uninvolved limb (mean difference = 0.39 body weight, p = 0.009, effect size = 0.70) as well as the control limb (mean difference = 0.57 body weight, p = 0.007, effect size = 1.14). Similar observations were made for total contact force. For involved versus uninvolved limb, the ACLD group demonstrated lower vertical ground reaction force (mean difference = 0.08 body weight, p = 0.010, effect size = 0.70) and knee flexion moment (mean difference = 1.32% body weight * height, p = 0.003, effect size = 0.76), during weight acceptance. These results indicate that high muscle co‐contraction does not always result in high knee joint loading, which is thought to be associated with knee osteoarthritis. Long‐term follow‐up is required to evaluate how gait alterations progress in non‐osteoarthritic versus osteoarthritic subjects.

Does Anterior Cruciate Ligament Reconstruction Improve Functional and Radiographic Outcomes Over Nonoperative Management 5 Years After Injury

Background: Current practice patterns for the management of anterior cruciate ligament (ACL) injury favor surgical reconstruction. However, long-term outcomes may not differ between patients completing operative and nonoperative treatment of ACL injury. Differences in outcomes between operative and nonoperative treatment of patients in the United States is largely unknown, as are outcomes in long-term strength and performance measures. Purpose: To determine if differences exist in 5-year functional and radiographic outcomes between patients completing operative and nonoperative treatment of ACL injury when both groups complete a progressive criterion-based rehabilitation protocol. Study Design: Cohort study; Level of evidence, 2. Methods: From an original group of 144 athletes, 105 participants (mean ± SD age, 34.3 ± 11.4 years) with an acute ACL rupture completed functional testing (quadriceps strength, single-legged hop, and knee joint effusion testing; patient-reported outcomes) and knee radiographs 5 years after ACL reconstruction or completion of nonoperative rehabilitation. Results: At 5 years, patients treated with ACL reconstruction versus rehabilitation alone did not differ in quadriceps strength (P = .817); performance on single-legged hop tests (P = .234-.955); activity level (P = .349-.400); subjective reports of pain, symptoms, activities of daily living, and knee-related quality of life (P = .090-.941); or presence of knee osteoarthritis (P = .102-.978). When compared with patients treated nonoperatively, patients treated operatively did report greater global ratings of knee function (P = .001), and lower fear (P = .035) at 5 years but were more likely to possess knee joint effusion (P = .016). Conclusion: The current findings indicate that favorable outcomes can occur after both operative and nonoperative management approaches with the use of progressive criterion-based rehabilitation. Further study is needed to determine clinical algorithms for identifying the best candidates for surgical versus nonoperative care after ACL injury. These findings provide an opportunity to improve the educational process between patients and clinicians regarding the expected clinical course and long-term outcomes of operative and nonoperative treatment of ACL injuries.

Hop Test Symmetry Scores Early after Rehab Predict Successful 2 Year Outcomes of ACLR

Objectives: Return to pre-injury function, return to pre-injury activity, and avoiding repeated knee joint instability are common goals of anterior cruciate ligament reconstruction (ACLR). None of these goals, however, are guaranteed through surgical intervention. Clinical test batteries are able to differentiate between those with good and poor knee function after ACL injury, but the usefulness of this battery after reconstruction to predict longer-term outcomes is unknown. The purpose of this study is to determine if a test battery consisting of clinical, functional, and patient-reported measures 6 months after surgery is predictive of a successful outcome 2 years after ACLR. Methods: This is a secondary analysis of prospectively collected data. Seventy-three athletes after acute, isolated, unilateral ACL rupture were included in this analysis. All subjects underwent ACLR, and returned for follow-up testing at 6 and 24 months after reconstruction. A test battery consisting of quadriceps strength symmetry (QI), 6-meter timed hop test symmetry (TimHP), the Knee Outcome Survey Activities of Daily living (KOS), and the Global Rating (GLO) was administered 6 months after reconstruction. At 2 year follow-up, all athletes completed the International Knee Documentation Committee Subjective Knee Form 2000 (IKDC) and self-reported whether they had returned to their pre-injury sports and if they had a second ACL injury to the ipsilateral or contralateral knee. A successful outcome was considered achieving at least the 15th percentile of age and sex matched IKDC normative values, returning to pre-injury sports, and not having a second ACL injury at 2 years. Logistic regression was used to predict a successful outcome 2 years after ACLR. Receiver operating characteristic curve (ROC), positive and negative likelihood ratios were calculated for any statistically significant individual predictors. Significance was set at .05 a priori. Results: Fifty-five (75%) of the 73 athletes had a successful outcome. There were no differences between groups in age, sex, graft type or body mass index (p >.05). The test battery performed 6 months after ACLR was predictive of 2 year success (r2=.307;p=.005). The TimHP (p=.018; exp(b)=1.11) was the only significant individual predictor in the test battery. Maximizing sensitivity and specificity (Table 1), a cutoff score of 96% symmetry for the TimHP had a positive likelihood ratio of 1.95 and a negative likelihood ratio of 0.4. Conclusion: A test battery of clinical, functional, and patient-reported measures was predictive of success 2 years after ACLR. Achieving 96% symmetry on the 6-meter timed hop test 6 months after ACLR was associated with almost twice the probability of a successful outcome while not achieving that cutoff was associated with 2.5 times less likely of having a successful outcome. Return to sport criteria have typically suggested 85-90% symmetry cutoffs, and this work suggests those cutoffs might be too low. While delaying return to sport for high risk athletes is warranted, clinical and functional measures should still be maximized early after ACLR to optimize outcomes. Table 1: Discriminate and ROC Curve Analysis of 6-Meter Timed Hop Symmetry Scores TimHP Successful Unsuccessful Total Pass 41 4 45 Fail 14 14 28 Total 55 18 73 Optimum Cutoff Sensitivity Specificity Positive Likelihood Ratio Negative Likelihood Ratio TimHP 96 .750 .615 1.95 0.40

Nonoperative Management of ACL Rupture

Anterior cruciate ligament (ACL) reconstruction is common after ACL injury, particularly in young, active individuals. ACL reconstruction does not have universally good outcomes. Not all athletes will return to sport after ACL reconstruction (ACLR), and after reconstruction these individuals are at a high risk for second ACL injury and osteoarthritis. The best evidence suggests that ACLR is not necessary for everyone. This chapter will discuss the management of athletes after acute ACL rupture. Long- and short-term outcomes of operative and nonoperative management as well as determinants of success will be discussed. Athletes can return to their prior levels of sports without ACL reconstruction with progressive rehabilitation after ACL rupture. With recent evidence that outcomes after operative and nonoperative ACL injury management do not necessarily favor surgery, the authors recommend that athletes undergo a progressive physical therapy regimen that includes strengthening and neuromuscular training after ACL injury prior to the decision to undergo ACLR. If nonoperative management is elected as progressive, a criterion-based rehabilitation program culminating in a structured return to activity progression and battery of tests to determine readiness for return to sports should be employed.

Early predictors of outcomes following non-operative management of ACL injury: The delaware-oslo ACL cohort study

Objectives: Identification of patient characteristics early after injury that influences long-term outcomes is needed to guide appropriate decision-making with regard to surgical management. The purpose of this study was to determine factors early after ACL injury which predict outcomes following non-operative management of ACL injury. Methods: 59 (52.5% F; mean age 31.3±10.7 yrs) athletes completed rehabilitation to resolve knee joint range of motion, effusion, pain and gait impairments (quiet knee) after ACL injury. Patients then completed 10 additional rehabilitation sessions over 5 weeks consisting of progressive strengthening and neuromuscular training. Quadriceps strength testing, 4 single-legged hop tests, the Knee Outcome Survey Activities of Daily Living Scale (KOS), Global Rating Scale for Perceived Function (GR), and International Knee Documentation Committee 2000 form (IKDC) were completed following these 10 sessions. Two years after non-operative rehabilitation patients again completed the IKDC. “Normal” knee function was defined as an IKDC score in the top 85% of scores reported by uninjured people of the same age and sex, with “below normal” knee function equal to scores in the bottom 15% of normative data. Fishers exact tests and Mann-Whitney U tests were used to test differences in baseline and clinical measures after non-operative rehabilitation between those with “normal” and “below normal” knee function at 2 years. A logistic regression model was used to identify factors predictive of 2 year knee function. A prior significance level was set at p≤.05. Results: 11 patients (18.6%) reported knee function <15% on the IKDC at 2 years (Normal: 93.8±4.5%, 95% CI: 92.3-95.1; Below Normal: 72.1±12.7%, 95% CI: 63.6-80.6). No group differences existed for age (p=0.613) or sex (p=0.320) between those who scored in the normal range and those who scored <15%. Patients with self-reported IKDC knee function <15% had significantly lower IKDC scores at baseline (p=0.010; Normal: 83.0±10.0%, 95% CI: 80.1-85.9; Below Normal: 72.7±10.8%, 95% CI: 64.9-80.4) and required a greater number of days to achieve a quiet knee after injury (p=0.005; Normal: 58.5±21.9 days, 95% CI: 52.1-64.8; Below Normal: 77.6±17.7 days, 95% CI: 65.7-89.5). A trend toward significance was present for quadriceps strength (p=0.076; Normal: 93.5±9.1%, 95% CI: 90.8-96.1; Below Normal: 88.4±7.4%, 95% CI: 83.4-93.4) but no group differences were present for hop scores (single: p=0.684; crossover: p=0.630; triple: p=0.724; 6-meter timed: p=0.341), KOS (p=0.119), or GR (p=0.136). A logistic regression model including IKDC, days to achieve a quiet knee, and quadriceps strength was statistically significant with IKDC and days to achieve a quiet knee being significant predictors of knee function at 2 years (p=0.001; R2=0.433; IKDC: p=0.040, OR=0.909; days to achieve a quiet knee: p=0.014, OR=1.054; quad strength: p=0.220, OR=0.941). Conclusion: Only 18% of active individuals managed non-operatively after ACL injury had IKDC scores <15% of norms 2 years after injury and rehabilitation. Lower baseline subjective knee function was predictive of poorer self-reported non-operative outcomes despite similar hop scores to those reporting normal knee function at 2 years. Longer time from injury to resolution of initial knee impairments also predicted poorer self-reported knee function, highlighting the importance of early rehabilitation with aggressive intervention to resolve impairments.