Cruciate ligament tensile forces during the forward and side lunge

My Top Five Concepts for Selecting Lower Extremity Exercises For Cruciate Ligament and Patellofemoral Rehabilitation

This clinical commentary will address five key concepts that can be used by clinicians as criteria for selecting lower extremity weight bearing exercises (WBE) and non-weight bearing exercises (NWBE) employed for cruciate ligament and patellofemoral rehabilitation. The following will be discussed for both cruciate ligament and patellofemoral rehabilitation: 1) Knee loading varies between WBE and NWBE; 2) Knee loading varies with technique variations within WBE and NWBE; 3) Knee loading varies between different WBE; 4) Knee loading varies as a function of knee angle; and 5) Knee loading increases with increased knee anterior translation beyond toes.

Influence of Different Load Conditions on Lower Extremity Biomechanics during the Lunge Squat in Novice Men

Objective: The lunge squat is one of the exercises to strengthen the lower limbs, however, there is little evidence of the effects of different equipment. The purpose of this study was to investigate the biomechanical effects of different types of equipment and loads on the lunge squat’s effect on the lower limbs. Methods: Fourteen male fitness novices participated in the experiment. Kinematics and kinetics in the sagittal plane using dumbbells, barbells, and weighted vests were measured using OpenSim. Two-way repeated measures ANOVA and one-dimensional statistical parametric mapping were used in the statistical analysis (SPM1D). Results: Range of motion (ROM) change in the knee joint was more obvious when using a barbell, whereas ROM when using a dumbbell was minimal. Compared to other joints, the joint moment at the hip joint was the largest and changed more significantly with increasing weight-bearing intensity, and the change was more pronounced with the dumbbell. For the center of pressure (COP) overall displacement, the dumbbell produced a smaller range of displacement. Conclusions: Dumbbells are suggested for male beginners to improve stability, barbells for the more experienced, and a low-weighted vest may be more appropriate for those with knee pain.

Effects of and Response to Mechanical Loading on the Knee

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Optimal Distraction Force for Evaluating Tibiofemoral Joint Gaps in Posterior Stabilized Total Knee Arthroplasty

BACKGROUND

Obtaining well-balanced soft tissues is important to achieve natural knee kinematics after total knee arthroplasty (TKA). In conventional procedures, soft tissue balance is evaluated with spacer blocks or lamina spreaders. However, the evaluation depends on the surgeons' experience and is not quantitative. This study aims to measure the mechanical properties of knee soft tissue with a new ligament balancer and to determine the optimal distraction force for evaluating tibiofemoral joint gaps in TKA.

METHODS

This study included 30 consecutive patients with medial knee osteoarthritis who were scheduled to undergo posterior stabilized TKA. The mean age of patients was 73 ± 9.6 years at the time of surgery, and the mean hip-knee-ankle angle was 13.1 ± 6.5° in varus. After distal femoral and proximal tibial resections, the tibiofemoral joint gaps under several distraction forces were measured in extension and at 90° flexion. The load-displacement curves in extension and flexion were drawn with these data, and the stability range, which was defined as the shift range from the toe region to the linear region in the curves, was calculated.

RESULTS

The stability ranges were 160 Newtons (N) in extension and 140 N in flexion.

CONCLUSIONS

These displacement forces were considered optimal for evaluating tibiofemoral joint gaps during surgery and ensuring knee stability after TKA.

Knee Kinetics in Baseball Hitting and Return to Play after ACL Reconstruction

The purpose of this study was to describe the knee kinetics of baseball hitting, develop a tool to predict knee kinetics from easily obtainable measures, and to compare knee kinetics to other exercises along the rehabilitation continuum to determine a timeline for when hitting may resume after ACL reconstruction. Nineteen high school baseball athletes (16.3±0.8 yrs, 180.6±5.7 cm, 78.4±10.8 kg) participated. Participants took ten swings off a tee. Kinetic data were recorded using an electromagnetic tracking system. Data from swings with the top three exit velocities were averaged for analysis. Linear regressions were used to determine if predictors of height, mass, age and exit velocity could predict the following torques: bilateral knee net, extension, internal and external rotation, valgus and varus torque; and anterior force. Backwards regression models revealed independent variables could significantly predict front knee net, internal and external rotation, extension, and varus torque, and anterior force; and back knee net and valgus torque. Based on the kinetics of baseball hitting compared to those of rehabilitation exercises, if the involved knee is the front, we suggest tee hitting may be initiated at 13 weeks after ACL reconstruction. If the involved knee is the back, we suggest tee hitting may initiated at 17 weeks after ACL reconstruction.

Forward lunge before and after anterior cruciate ligament reconstruction: Faster movement but unchanged knee joint biomechanics

The forward lunge (FL) may be a promising movement to assess functional outcome after ACL reconstruction. Thus, we aimed to investigate the FL movement pattern before and after ACL reconstruction with a comparison to healthy controls to determine if differences were present. Twenty-eight ACL injured participants and 28 matched healthy controls were included. They performed FL movements while sagittal plane biomechanics of the knee and electromyography (EMG) of nine leg muscles was assessed. The ACL injured group was tested before and 10 months after surgery. The perceived knee function and activity level was assessed by questionnaires. The ACL injured group performed the FL significantly slower than the controls before surgery (mean difference: 0.41 s [95%CI: 0.04-0.79 s; p<0.05]) while they performed the FL as fast as the controls after surgery (~28% movement time reduction post-surgery). Perceived knee function and activity level improved significantly post-surgery. The knee joint flexion angle, extensor moment, power, angular velocity in the ACL injured group did not differ from pre to post-surgery. For the ACL injured group, the peak knee extensor moment observed both pre and post-surgery was significantly lower when compared to the controls. The EMG results showed minimal differences. In conclusion, at 10 months post-surgery, the FL was performed significantly faster and the movement time was comparable to that of the controls. While the perceived knee function and activity level improved post-surgery, the knee joint biomechanics were unchanged. This may reflect that knee joint function was not fully restored.

Current Concepts and Controversies in Rehabilitation After Surgery for Multiple Ligament Knee Injury

PURPOSE OF REVIEW

The purpose of this manuscript is twofold: (1) to review the literature related to rehabilitation after surgery for multiple ligament knee injury (MLKI) and after isolated surgery for the posterior cruciate ligament (PCL), posterolateral corner (PLC), and medial side of the knee and (2) to present a hierarchy of anatomic structures needing the most protection to guide rehabilitation.

RECENT FINDINGS

MLKIs continue to be a rare but devastating injury. Recent evidence indicates that clinicians may be providing too much protection from early weight bearing and range of motion, but an accelerated approach has not been rigorously tested. Consideration of the nature and quality of surgical procedures (repair and reconstruction) can help clinicians determine the structures needing the most protection during the rehabilitation period. The biomechanical literature and prior clinical experience can aid clinicians to better structure rehabilitation after surgery for MLKI and improve clinical outcome for patients.

Comparison of Joint Loading in Badminton Lunging between Professional and Amateur Badminton Players

The knee and ankle are the two most injured joints associated with the sport of badminton. This study evaluates biomechanical factors between professional and amateur badminton players using an injury mechanism model. The aim of this study was to investigate the kinematic motion and kinetic loading differences of the right knee and ankle while performing a maximal right lunge. Amateur players exhibited greater ankle range of motion (p < 0.05, r = 0.89) and inversion joint moment (p < 0.05, r = 0.54) in the frontal plane as well as greater internal joint rotation moment (p < 0.05, r = 0.28) in the horizontal plane. In contrast, professional badminton players presented a greater knee joint moment in the sagittal (p < 0.05, r = 0.59) and frontal (p < 0.05, r = 0.37) planes, which may be associated with increased knee ligamentous injury risk. To avoid injury, the players need to forcefully extend the knee with internal rotation, strengthen the muscles around the ankle ligament, and maximise joint coordination during training. The injuries recorded and the forces responsible for the injuries seem to have developed during training activity. Training programmes and injury prevention strategies for badminton players should account for these findings to reduce potential injury to the ankle and knee.

Rehabilitation Principles of the Anterior Cruciate Ligament Reconstructed Knee: Twelve Steps for Successful Progression and Return to Play

The rehabilitation process begins immediately after injury to the anterior cruciate ligament (ACL). The goal of preoperative rehabilitation is to prepare the patient for surgery. Current rehabilitation programs focus on strengthening exercises and proprioceptive and neuromuscular control drills to provide a neurologic stimulus. It is also important to address preexisting factors, especially for the female athlete, that may predispose to future injury, such as hip and hamstring weakness. Our goal in the rehabilitation program is to restore full, unrestricted function and to assist the patient to return to 100% of the preinjury level while achieving excellent long-term outcomes.

Quantification of functional brace forces for posterior cruciate ligament injuries on the knee joint: an in vivo investigation

PURPOSE

Counteracting posterior translation of the tibia with an anterior force on the posterior proximal tibia has been demonstrated clinically to improve posterior knee laxity following posterior cruciate ligament (PCL) injury. This study quantified forces applied to the posterior proximal tibia by two knee braces designed for treatment of PCL injuries.

METHODS

The forces applied by two knee braces to the posterior proximal tibia and in vivo three-dimensional knee kinematics of six adult, male, healthy volunteer subjects (mean ± standard deviation: height, 182.5 ± 5.2 cm; body mass, 83.2 ± 9.3 kg; body mass index, 24.9 ± 1.5 kg/m(2); age, 25.8 ± 2.9 years) were measured using a custom pressure mapping technique and traditional surface marker motion capture techniques, while subjects performed three functional activities. The activities included seated unloaded knee flexion, squatting, and stair descent in a new generation dynamic force (DF) PCL brace and a static force (SF) PCL brace.

RESULTS

During unloaded flexion at the lowest force level setting, the force applied by the DF brace increased as a function of flexion angle (slope = 0.7 N/°; p < 0.001) compared to the SF brace effect. Force applied by the SF brace did not significantly change as a function of flexion angle (slope = 0.0 N/°; n.s.). By 45° of flexion, the average force applied by the DF brace (48.1 N) was significantly larger (p < 0.001) than the average force applied by the SF brace (25.0 N). The difference in force continued to increase as flexion angle increased. During stair descent, average force (mean ± standard deviation) at toe off was significantly higher (p = 0.013) for the DF brace (78.7 ± 21.6 N) than the SF brace (37.3 ± 7.2 N). Similar trends were observed for squatting and for the higher force level settings.

CONCLUSIONS

The DF brace applied forces to the posterior proximal tibia that dynamically increased with increased flexion angle. Additionally, the DF brace applied significantly larger forces at higher flexion angles compared to the SF brace where the PCL is known to experience larger in situ forces. Clinical studies are necessary to determine whether the loading characteristics of the DF brace, which more closely replicated the in situ loading profile of the native PCL, results in long-term improved posterior knee laxity following PCL injury.

LEVEL OF EVIDENCE

II.

A historical perspective of PCL bracing

PURPOSE

Currently there are many functional knee braces but very few designed to treat the posterior cruciate ligament (PCL). No PCL braces have been biomechanically validated to demonstrate that they provide stability with proper force distribution to the PCL-deficient knee. The purpose of this review was to evaluate the history and current state of PCL bracing and to identify areas where further progress is required to improve patient outcomes and treatment options.

METHODS

A PubMed search was conducted with the terms "posterior cruciate ligament", "rehabilitation", "history", "knee", and "brace", and the relevant articles from 1967 to 2011 were analysed. A review of the current available PCL knee bracing options was performed.

RESULTS

Little evidence exists from the eight relevant articles to support the biomechanical efficacy of nonoperative and postoperative PCL bracing protocols. Clinical outcomes reported improvements in reducing PCL laxity with anterior directed forces to the tibia during healing following PCL tears. Biomechanics research demonstrates that during knee flexion, the PCL experiences variable tensile forces. One knee brace has been specifically designed and clinically validated to improve stability in PCL-deficient knees during rehabilitation. While available PCL braces demonstrate beneficial patient outcomes, they lack evidence validating their biomechanical effectiveness.

CONCLUSIONS

There is limited information evaluating the specific effectiveness of PCL knee braces. A properly designed PCL brace should apply correct anatomic joint forces that vary with the knee flexion angle and also provide adjustability to satisfy the demands of various activities. No braces are currently available with biomechanical evidence that satisfies these requirements.

LEVEL OF EVIDENCE

IV.

Posterior cruciate ligament tears: functional and postoperative rehabilitation

PURPOSE

Historically, the results of posterior cruciate ligament (PCL) reconstructions are not as favourable as anterior cruciate ligament (ACL) reconstructions, and it is well recognized that nonoperative treatment and postoperative rehabilitation for PCL injuries must be altered compared to those for ACL injuries. The purpose of this article was to review current peer-reviewed PCL rehabilitation programmes and to recommend a nonoperative and postoperative programme based on basic science and published outcomes studies.

METHODS

To discover the current practices being used to rehabilitate PCL injuries, we conducted a search of PubMed with the terms "posterior cruciate ligament" and "rehabilitation" from 1983 to 2011. All articles within the reference lists of these articles were also examined to determine their rehabilitation programmes.

RESULTS

A review of peer-reviewed PCL rehabilitation protocols revealed that the treatment of PCL injuries depends on the timing and degree of the injury. Rehabilitation should focus on progressive weight bearing, preventing posterior tibial subluxation and strengthening of the quadriceps muscles. General principles of proper PCL rehabilitation, whether nonoperative or postoperative, should include early immobilization (when necessary), prone passive range of motion to prevent placing undue stress on grafts or healing tissue, and progression of rehabilitation based on biomechanical, clinical, and basic science research.

CONCLUSIONS

An optimal set of guidelines for the nonoperative or postoperative management of PCL injuries has not yet been defined or agreed upon. Based on the current review study, suggested guidelines are proposed.

LEVEL OF EVIDENCE

IV.

Quadriceps and hamstrings coactivation during common therapeutic exercises

CONTEXT

Anterior tibial shear force and knee valgus moment increase anterior cruciate ligament (ACL) loading. Muscle coactivation of the quadriceps and hamstrings influences anterior tibial shear force and knee valgus moment, thus potentially influencing ACL loading and injury risk. Therefore, identifying exercises that facilitate balanced activation of the quadriceps and hamstrings might be beneficial in ACL injury rehabilitation and prevention.

OBJECTIVE

To quantify and compare quadriceps with hamstrings coactivation electromyographic (EMG) ratios during commonly used closed kinetic chain exercises.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-seven healthy, physically active volunteers (12 men, 15 women; age = 22.1 ± 3.1 years, height = 171.4 ± 10 cm, mass = 72.4 ± 16.7 kg).

INTERVENTION(S)

Participants completed 9 separate closed chain therapeutic exercises in a randomized order.

MAIN OUTCOME MEASURE(S)

Surface electromyography quantified the activity level of the vastus medialis (VM), vastus lateralis (VL), medial hamstrings (MH), and biceps femoris (BF) muscles. The quadriceps-to-hamstrings (Q:H) coactivation ratio was computed as the sum of average quadriceps (VM, VL) EMG amplitude divided by the sum of average hamstrings (MH, BF) EMG amplitude for each trial. We used repeated-measures analyses of variance to compare Q:H ratios and individual muscle contributions across exercises (α = .05), then used post hoc Tukey analyses.

RESULTS

We observed a main effect for exercise (F(3,79) = 22.6, P< .001). The post hoc Tukey analyses revealed smaller Q:H ratios during the single-limb dead lift (2.87 ± 1.77) than the single-limb squat (5.52 ± 2.89) exercise. The largest Q:H ratios were observed during the transverse-lunge (7.78 ± 5.51, P< .001), lateral-lunge (9.30 ± 5.53, P< .001), and forward-lunge (9.70 ± 5.90, P< .001) exercises.

CONCLUSIONS

The most balanced (smallest) coactivation ratios were observed during the single-limb dead-lift, lateral-hop, transverse-hop, and lateral band-walk exercises. These exercises potentially could facilitate balanced activation in ACL rehabilitation and injury-prevention programs. They also could be used in postinjury rehabilitation programs in a safe and progressive manner.

Cruciate ligament loading during common knee rehabilitation exercises

Cruciate ligament injuries are common and may lead to dysfunction if not rehabilitated. Understanding how to progress anterior cruciate ligament and posterior cruciate ligament loading, early after injury or reconstruction, helps clinicians prescribe rehabilitation exercises in a safe manner to enhance recovery. Commonly prescribed therapeutic exercises include both weight-bearing exercise and non-weight-bearing exercise. This review was written to summarize and provide an update on the available literature on cruciate ligament loading during commonly used therapeutic exercises. In general, weight-bearing exercise produces smaller loads on the anterior cruciate ligament and posterior cruciate ligament compared with non-weight-bearing exercise. The anterior cruciate ligament is loaded less at higher knee angles (i.e. 50-100 degrees). Squatting and lunging with a more forward trunk tilt and moving the resistance pad proximally on the leg during the seated knee extension unloads the anterior cruciate ligament. The posterior cruciate ligament is less loaded at lower knee angles (i.e. 0-50 degrees), and may be progressed from level ground walking to a one-leg squat, lunges, wall squat, leg press, and the two-leg squat (from smallest to greatest). Exercise type and technique variation affect cruciate ligament loading, such that the clinician may prescribe therapeutic exercises to progress ligament loading safely, while ensuring optimal recovery of the musculoskeletal system.

Computational modeling of a forward lunge: towards a better understanding of the function of the cruciate ligaments

This study investigated the function of the cruciate ligaments during a forward lunge movement. The mechanical roles of the anterior and posterior cruciate ligament (ACL, PCL) during sagittal plane movements, such as forward lunging, are unclear. A forward lunge movement contains a knee joint flexion and extension that is controlled by the quadriceps muscle. The contraction of the quadriceps can cause anterior tibial translation, which may strain the ACL at knee joint positions close to full extension. However, recent findings suggest that it is the PCL rather than the ACL which is strained during forward lunging. Thus, the purpose of the present study was to establish a musculoskeletal model of the forward lunge to computationally investigate the complete mechanical force equilibrium of the tibia during the movement to examine the loading pattern of the cruciate ligaments. A healthy female was selected from a group of healthy subjects who all performed a forward lunge on a force platform, targeting a knee flexion angle of 90°. Skin-markers were placed on anatomical landmarks on the subject and the movement was recorded by five video cameras. The three-dimensional kinematic data describing the forward lunge movement were extracted and used to develop a biomechanical model of the lunge movement. The model comprised two legs including femur, crus, rigid foot segments and the pelvis. Each leg had 35 independent muscle units, which were recruited according to a minimum fatigue criterion. This approach allowed a full understanding of the mechanical equilibrium of the knee joint, which revealed that the PCL had an important stabilizing role in the forward lunge movement. In contrast, the ACL did not have any significant mechanical function during the lunge movement. Furthermore, the results showed that m. gluteus maximus may play a role as a knee stabilizer in addition to the hamstring muscles.

Evaluation and management of posterior cruciate ligament injuries

BACKGROUND

Posterior cruciate ligament injuries are increasingly recognized, the result of various sports activities, and while most athletes return to sports the development degenerative joint changes is common.

OBJECTIVE

To provide a synopsis of the current best evidence regarding the recognition and treatment of posterior cruciate ligament injuries.

DESIGN

Structured narrative review.

METHODS

Keyword search of Medline, CINAHL, and PEDro databases for studies published in English from January 1975 to July 2011. Additionally, the reference lists from articles obtained were manually searched for relevant literature.

SUMMARY

The manuscript provides an overview of posterior cruciate ligament injury, discusses diagnostic methods to include radiographic examination techniques, and presents information on surgical and conservative management of PCL injuries.

CONCLUSION

Understanding the mechanism of injuries and most effective examination methods can aide in effective early recognition of PCL injuries. Appropriate management of the patient with PCL deficiency or reconstructed knee will optimize outcomes and potentially affect long term knee function.

Anterior cruciate ligament strain and tensile forces for weight-bearing and non-weight-bearing exercises: a guide to exercise selection

There is a growing body of evidence documenting loads applied to the anterior cruciate ligament (ACL) for weight-bearing and non-weight-bearing exercises. ACL loading has been quantified by inverse dynamics techniques that measure anterior shear force at the tibiofemoral joint (net force primarily restrained by the ACL), ACL strain (defined as change in ACL length with respect to original length and expressed as a percentage) measured directly in vivo, and ACL tensile force estimated through mathematical modeling and computer optimization techniques. A review of the biomechanical literature indicates the following: ACL loading is generally greater with non-weight-bearing compared to weight-bearing exercises; with both types of exercises, the ACL is loaded to a greater extent between 10° to 50° of knee flexion (generally peaking between 10° and 30°) compared to 50° to 100° of knee flexion; and loads on the ACL change according to exercise technique (such as trunk position). Squatting with excessive forward movement of the knees beyond the toes and with the heels off the ground tends to increase ACL loading. Squatting and lunging with a forward trunk tilt tend to decrease ACL loading, likely due to increased hamstrings activity. During seated knee extension, ACL force decreases when the resistance pad is positioned more proximal on the anterior aspect of the lower leg, away from the ankle. The evidence reviewed as part of this manuscript provides objective data by which to rank exercises based on loading applied to the ACL. The biggest challenge in exercise selection post-ACL reconstruction is the limited knowledge of the optimal amount of stress that should be applied to the ACL graft as it goes through its initial incorporation and eventual maturation process. Clinicians may utilize this review as a guide to exercise selection and rehabilitation progression for patients post-ACL reconstruction.

Recent advances in the rehabilitation of anterior cruciate ligament injuries

Rehabilitation following anterior cruciate ligament surgery continues to change, with the current emphasis being on immediate weight bearing and range of motion, and progressive muscular strengthening, proprioception, dynamic stability, and neuromuscular control drills. The rehabilitation program should be based on scientific and clinical research and focus on specific drills and exercises designed to return the patient to the desired functional goals. The goal is to return the patient's knee to homeostasis and the patient to his or her sport or activity as safely as possible. Unique rehabilitation techniques and special considerations for the female athlete will also be discussed. The purpose of this article is to provide the reader with a thorough scientific basis for anterior cruciate ligament rehabilitation based on graft selection, patient population, and concomitant injuries.