Anterior Cruciate Ligament Injury and Reconstruction

Abstract

ACL injuries are a common reason for knee surgery in young healthy patients. The clinical diagnosis of ACL tear is straightforward, though coexistent pathology is frequently present and must be recognized for surgical and rehabilitation planning. A careful history, physical examination including provocative maneuvers, and imaging as dictated from the exam are key in establishing an appropriate diagnosis. MRI is useful in identifying ACL injuries and their concomitant knee pathologies though certain cases may be challenging. This chapter outlines cases of ACL injury and reconstruction and discusses surgical intervention, which can be pursued in the carefully chosen active patient through an individualized approach. Techniques for improving ACL reconstruction are under constant analysis and development.

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Introduction

Anterior cruciate ligament (ACL) tears are a common knee injury, especially in young and physically active individuals. The ACL has been perhaps the most studied ligament in the human body in the last decade. Its importance to knee function has been demonstrated by the substantial functional impairment and decreased performance experienced after ACL injury [1]. This is especially true in the high-level athlete performing cutting, pivoting, and kicking activities [2]. The ACL confers stability to the knee by resisting both rotational and translational forces, thereby facilitating the normal kinematics of the knee [3–5]. Anatomic, hormonal, environmental, and biomechanical factors appear to influence the incidence of ACL injuries with females having a four- to sixfold increase in rate of ACL injury compared to men [3].

The clinical diagnosis of an ACL injury can be challenging, and concomitant pathology is important to recognize. The classic history for an ACL tear is a noncontact pivoting injury resulting in immediate swelling after hearing a “pop.” The patient is typically unable to return to play because of pain and difficulty with pivoting and cutting. The key physical examination maneuver to diagnose an ACL injury is the Lachman, performed in 20–30° of knee flexion. Perceived side-to-side difference should be assessed and determination of an “end point” of translation noted. The pivot shift is also helpful, but the maneuver is sometimes difficult to perform in the clinic because of guarding by the patient. Least reliable is the anterior drawer, performed at 90° knee flexion, as hamstring spasticity and difficulty with motion can mask an injury.

Plain radiography is often the first study ordered to rule out other abnormalities and may demonstrate a Segond fracture, which is pathognomonic for ACL injury. Magnetic resonance imaging (MRI) remains the imaging technique of choice for patients with suspected ACL tear where the diagnosis is in question. MRI is also useful in identifying concomitant knee pathology. Arthroscopy remains the gold standard for diagnosing ACL rupture and meniscal tear in a patient with persistent symptoms.

ACL reconstruction has evolved considerably over the past 30 years. Advances have largely centered on an understanding of the anatomy of footprint of the ACL. Recent studies have identified the importance of anatomic ACL reconstruction to restore the ACL to its native dimensions, insertion sites, and collagen orientation to confer ideal rotational and translational stability [2, 6–8]. The anatomy of the ACL consists of two distinct bundles; the anteromedial and posterolateral, representing intracapsular structures supplied predominately by the middle geniculate artery.

Treatment for ACL injuries includes operative reconstruction or nonoperative rehabilitation. The age and level of activity of the patient must be considered prior to making any recommendations. The primary candidates for ACL reconstruction are active patients with functional instability. Current evidence suggests that ACL deficiency can lead to chondral damage as well as meniscal tears and that reconstruction leads to long-term functional and cost benefits in the right patient though some studies suggest increased arthrosis on later follow-up [5, 9].

Standard management protocol includes early active range of motion to regain full knee range of motion with closed chain weight bearing exercises prior to surgical reconstruction. After the pathology is characterized by diagnostic arthroscopy, treatment options depend upon the patient, injury, and surgeon preferences. Concomitant pathology, including meniscal tears, chondral defects, or other ligamentous injuries, can be addressed in the same setting.

This chapter will utilize a case-based format to demonstrate the correlation between MRI and arthroscopy for pathology and review the diagnosis and management of each patient. Three cases will be presented, including a complete ACL rupture requiring reconstruction, a partial ACL injury and a bony avulsion injury of the tibial insertion of the ACL.

Case 1: ACL Rupture

History/Exam

An 18-year-old rugby player presented to our orthopedic clinic 1 week following a tackling injury where another player’s head collided with his knee during play. A patella dislocation was reduced on the field and a large effusion was evident immediately. One week later, he reported a resolving effusion as well as feeling of instability with attempted return to play. He had sought advice from his trainer and team physical therapist concerning his symptoms and presented to our orthopedic clinic for further evaluation.

On physical examination, the patient was found to have a moderate effusion with obvious lack of end point with Lachman examination. Lateral joint line tenderness was notable with a positive McMurray’s. A pivot shift was noticeably positive in the office. No varus or valgus opening or asymmetry with the contralateral knee was noted on examination. The patient was otherwise neurovascularly intact and without symptoms in his contralateral knee. He had pain and difficulty with straight leg raise without a palpable patella tendon defect. Given the patient’s examination and desire to return to competitive play, advanced imaging was obtained to evaluate for additional pathology.

Imaging

Plain radiographs were obtained demonstrating no bony avulsions or other associated injuries. There was no evidence of arthritic changes or areas of significant cartilage loss. Magnetic resonance imaging was obtained to further evaluate the patient’s ACL, menisci, and other soft tissue structures, given his persistent symptoms. A complete sequence of images was obtained, including coronal fat-saturated T1 and T2 sequences, sagittal T1 and fat-saturated T2, and axial T1 and T2 sequences. Sagittal T2-weighted images are demonstrated in Fig. 5.1a, and coronal T2-weighted images are demonstrated in Fig. 5.1b.

Fig. 5.1

(a, b) T2 sagittal image is shown demonstrating absence of the ACL as well as the typical bone bruise pattern. Coronal T2-weighted image demonstrates the “empty notch sign”

A complete midsubstance ACL tear was present as shown in Fig. 5.2a, b. Acute hemarthrosis was present with a typical bone contusion pattern present as shown in Fig. 5.3. The ACL is seen as an edematous mass without the typically taught fibers. The lateral meniscus visualized best on the sagittal T2-weighted image (Fig. 5.3) showed no meniscal tear. The medial meniscus was intact as was the MCL. No posterior cruciate ligament or articular cartilage pathology was present. The patella tendon was partially disrupted with a wavy appearance to a portion of its fibers (Fig. 5.2b).

Fig. 5.2

T2 sagittal imaging demonstrates edema within the substance of the ACL with complete disruption (a). Partial tearing of the patella tendon is seen at this level (b)

Fig. 5.3

The typical bone bruise pattern is shown on T2-weighted imaging about the lateral femoral condyle and posterolateral tibial plateau. Additionally, the tibia is noted to be translated forward relative to the posterior aspect of the distal femur producing an “anterior drawer” on imaging

MRI allowed for confirmation of ACL tear as well as diagnosis of a patella tendon disruption of uncertain severity. This was consistent with the patient’s clinical examination; therefore, risks and benefits of operative intervention were discussed with the patient. He elected to proceed with possible patella tendon repair and planned reconstruction of the ACL given his age and hopes to continue to compete at a collegiate level.

Arthroscopy

The patient was taken to the operating room and placed supine with a post placed in the appropriate position. Given recent evidence suggesting graft size is an important factor in ACL reconstruction failure, we typically prep in the other lower extremity when utilizing hamstring graft to reserve the ability to take contralateral graft if needed. The hamstring tendon graft was harvested in the usual fashion. The graft was prepared on the back table, and a standard diagnostic arthroscopy of the knee was completed. The ACL was completely absent with a remaining stump seen demonstrated in Fig. 5.4 with no intact fibers remaining. The articular cartilage and medial meniscus were found to be intact. This correlated well with the findings on MRI.

Fig. 5.4

Arthroscopic visualization of the intercondylar notch reveals a complete tear of the ACL with fibrous proliferation and remaining stump on the tibial side

Following diagnostic arthroscopy, the tibial footprint and ACL over the top position in the back of the notch were debrided using arthroscopic baskets and shaver. Next, the appropriate position off the back of the posterolateral notch was chosen for guide pin placement (Fig. 5.5a). An offset guide can be used here to retain 1–2 mm of posterior wall following drilling. We like to use an accessory medial (AM) portal for separate femoral tunnel drilling to allow more horizontal, anatomic femoral tunnel drilling with the knee in hyperflexion (Fig. 5.5b) [8].

Fig. 5.5

ACL reconstruction steps are shown with placement of a guide pin in the anatomic position utilizing an accessory inferomedial portal (AM portal) (a). Femoral tunnel drilling is performed with a skid in place in hyperflexion to protect the femoral condyle (b). Both needle and suture are passed through the tunnel to allow for graft shuttling (c). The autograft is fixed with interference screw fixation (d)

Once the femoral tunnel is drilled to the appropriate depth, a commercially available tibial guide is used to place a guide wire for the tibial tunnel using intra-articular landmarks. Once the tibial tunnel is prepared, a Beath needle is used to pass the graft utilizing suture (Fig. 5.5c), and it is fixed on the femoral side with an interference screw. Once the femoral side is fixed, the knee is cycled through the complete ROM, and the graft is tensioned and the tibial side fixed. The final graft was inspected and noted to have excellent tension in Fig. 5.5d. Finally, the patella tendon was repaired using a Krackow suture technique as shown in Fig. 5.6a, b.

Fig. 5.6

Intraoperative photo demonstrates a partial patella tendon rupture (a). This is repaired primarily utilizing Krackow suture technique (b)

Discussion

MRI demonstrated a complete ACL tear. Several direct MRI signs suggest complete disruption of the ACL in this case. The ACL is discontinuous and does not have the turgor of a normal ACL (Fig. 5.1a). This is best examined on MRI in the sagittal plane where the fibers seen on the T2-weighted image as no longer taught. In the acute setting, the ACL appears as an edematous mass, producing the so-called empty notch sign where fluid rather than ACL fills the intercondylar notch (Fig. 5.1b).

The indirect signs of an ACL injury on MRI are also seen here including the typical hemarthrosis, though this is a largely nonspecific finding. Additionally, the characteristic bone bruise pattern is noted about the lateral femoral condyle and posterolateral tibial plateau due to the prior pivoting event (Fig. 5.3). Often an anterior drawer can be seen where the tibia sits slightly more anterior to a line drawn parallel to the posterior aspect of the distal femur (Fig. 5.3). A Segond fracture which is noticeable on X-ray can also be seen on MRI as shown in the T1 image in Fig. 5.7. The PCL may also appear buckled in some cases.

Fig. 5.7

T1-weighted coronal image demonstrates a Segond fracture

Case 2: Partial ACL Rupture

History/Exam

A 20-year-old female collegiate soccer player sustained a noncontact injury to her left knee during play. She was seen on the sidelines and noted to have a sizeable effusion and pain with knee range of motion and was unable to return to play. She was subsequently seen in our sports medicine clinic several days later and exhibited an ongoing effusion.

Physical examination of the knee demonstrated no opening with varus or valgus stress. A pivot shift was not possible in the office due to her pain and swelling. She did however have a 2+ Lachman’s on her symptomatic side as compared to her asymptomatic side. Patellar apprehension testing was negative as was McMurray’s provocative maneuvers. Given the patient’s desire to continue to play collegiate soccer and her examination, advanced imaging was obtained to confirm suspected ACL injury and evaluate for additional pathology.

Imaging

Initial plain radiography was unremarkable for any bony abnormality. Given the persistent symptoms, concerning examination and effusion, MRI without contrast was obtained. A complete sequence of images was obtained, including sagittal gradient, STIR, proton density, coronal gradient and fat-saturated T2, and axial fat-saturated T2 without contrast. Coronal T2-weighted images and sagittal images are demonstrated in Fig. 5.8a, b.

Fig. 5.8

Sagittal MRI demonstrates edema within the ACL with remaining intact fibers (a). The coronal plane imaging is shown which reveals increased fluid and potential disruption in the anteromedial aspect of the tibial footprint (b)

The sagittal images showed no abnormality in the medial and lateral meniscus with a normal cartilage layer throughout. The ACL visualized in the sagittal plane T2 weighted revealed increased signal evident within the substance of the ACL with some remaining continuity (Fig. 5.8a). The PCL, LCL, and MCL were all intact with no focal abnormalities. In the coronal plane, the more medial portion of the ACL attachment to the tibial spine was noted to have increased edema and possible midsubstance tearing (Fig. 5.9a, b). No significant bony edema was seen in the STIR sequences.

Fig. 5.9

A partial empty intercondylar notch is shown on coronal T2-weighted MRI (a). A partially intact ACL is shown on arthroscopy (b)

The patient’s history, physical exam, and MRI were consistent with an ACL tear though MRI imaging was not convincing of a complete ACL injury. A lengthy discussion was had with the patient and her family, trainer, and coach regarding the risks and benefits of watchful waiting versus early arthroscopic exploration and possible reconstruction. They elected to undergo arthroscopy as opposed to attempted early rehabilitation, with a plan to address her ACL with reconstruction if found to be compromised.

Arthroscopy

On the day of surgery following a preoperative nerve block, the patient was taken to the operating room and placed supine upon the operating room table and positioned for ACL reconstruction given our suspicion of ACL injury. Examination under anesthesia was performed as previously described. If the examination is unclear, a diagnostic arthroscopy is always performed before harvesting graft. Again under anesthesia, a Lachman was performed which showed side-to-side difference with a soft end point. A nonsterile tourniquet was placed around the operative extremity. Standard inferolateral and inferomedial portals were made and a diagnostic arthroscopy completed to establish whether her ACL was in fact torn. We evaluated the patellofemoral joint, medial and lateral gutters, and compartments to assess for any meniscal disease, loose bodies, or cartilage injury of which none were found.

Visualization of the notch of the ACL demonstrated a partial ACL injury as shown in Figs. 5.9a, b and 5.10a, b. The posterolateral bundle of the ACL appeared intact and taught. The anteromedial bundle however was not intact, and a residual stump was present on the tibial side from the prior attachment. The rest of the diagnostic scope was unremarkable for chondral damage or meniscal injury. Given the patient’s expectations preoperatively and her current activity as a collegiate soccer player, decision was made to perform arthroscopic-assisted ACL reconstruction.

Fig. 5.10

Arthroscopic visualization of the notch demonstrates intact posterolateral bundle (a) with obviously less caliber than a typical ACL. The remaining stump of likely the anteromedial bundle of the ACL is seen as a cyclops lesion on the tibial side (b) with some remaining intact fibers shown

Although several graft options are available, autograft is a common graft option and has been demonstrated to lead to lower failure rates than allograft options in young patients [10]. In this case bone patella bone and hamstring autograft are reasonable options for this young athlete. With a combination of arthroscopic punch, motorized shaver, and electrocautery as needed, the ACL footprint was debrided. After debriding the ruptured ACL fibers, tunnels are drilled in the tibia and femur for the prepared grafts after sizing (Fig. 5.11a–d). In our hands, grafts are subsequently fixed utilizing interference screw fixation. We prefer to place the tibial tunnel in the posteromedial aspect of the ACL footprint and the femoral tunnel in the 10–10:30 position for the right knee leaving 2 mm of posterior wall in a more horizontal graft orientation. We performed a single-bundle technique utilizing an accessory inferomedial portal for guide wire placement and independent femoral drilling to allow for more anatomic graft placement [7, 8] (Fig. 5.11d). This portal is approximately 3–4 cm medial to the patellar tendon though should be localized under arthroscopy. Double-bundle techniques and individual-bundle techniques are described though they have not been widely adopted by most surgeons [11, 12].

Fig. 5.11

Following complete debridement of the remaining ACL, a guide pin is placed through an accessory AM portal on the femoral side (a) and later the tibial side (b). Final graft is taught and well fixed (c, d)

Discussion

MRI is the study of choice when ACL injury is uncertain or exam is equivocal. Diagnostic arthroscopy in this situation may be necessary to establish an absolute diagnosis. With partial ACL injuries, the remaining fibers appear taught and the percentage remaining must be assessed. The typical bone contusion pattern present with most ACL complete tears (72 % in complete tears) is often not present in the setting of a partial ACL injury (12 % incidence) [13]. The final determination is whether the knee is stable or unstable with only the remaining ACL fibers. This discussion should be undertaken with the patient, family, and athletic trainer.

With appropriate indications and proper surgical technique, ACL reconstruction outcomes after partial ACL injury are very good overall. However, many surgeons choose to treat partial injuries nonoperatively in the less-active patient without overt knee instability. Comparative studies looking at hamstring and patella tendon autograft have yielded equivalent results [10]. Athletes can often return to play at 4 months postoperatively. Controversy remains regarding the technique for ACL reconstruction and the ideal graft choice; however, most literature suggests equivalent outcomes between autograft choices [10].

Case 3: Bony ACL Avulsion Injury

History/Exam

A 35-year-old male presented to our sports medicine clinic with pain in his left knee that began approximately 4 days prior. The patient reported that while coaching his daughter’s basketball team, his knee gave way when he was running down the court. He had immediate pain and swelling and was able to bear weight but unable to continue coaching that day. He was seen at a local clinic where he was given crutches and a soft brace. An aspiration performed by the clinic improved his pain tremendously. Prior to this injury, he had one prior knee arthroscopy of which he does not remember the details. He had tried nonsteroidal anti-inflammatories, muscle relaxants, physical therapy, and stretching prior to presentation without relief.

On physical examination, he was noted to have pain with range of motion and a moderate effusion. Range of motion was noted to be limited compared to the contralateral side. He lacked approximately 10° extension, with flexion up to 90° with significant effort. Additionally, lateral joint line tenderness was present and McMurray’s exam was positive in the clinic. Lachman’s was grossly positive with no firm end point and a pivot shift was reproducible. There was no opening with varus or valgus stress and a negative posterior drawer.

Given the acute nature of his injury as well as difficulty with range of motion, decision was made to evaluate further with MRI. Additionally, the brace was discontinued at this time with instructions to work on aggressive range of motion with formal physical therapy. The initial radiographs obtained at the outside clinic revealed a bony abnormality not fully appreciated about the tibial spine.

Imaging

Radiographs obtained at the outside hospital suggested a possible injury about the tibial spine. There was no evidence of arthritic changes in the medial and lateral compartments. MRI without contrast was obtained to further evaluate the patient’s soft tissue anatomy. A complete sequence of images was obtained, including sagittal gradient, STIR, proton density, coronal gradient and fat-saturated T2, and axial fat-saturated T2 without contrast. Coronal fat-saturated T2-weighted images are demonstrated in Fig. 5.12a, b, and sagittal stir images are demonstrated in Fig. 5.13a, b.

Fig. 5.12

Coronal MRI STIR imaging reveals increased signal in the proximal tibial eminence at the ACL attachment (a, b)

Fig. 5.13

ACL fibers appear taught attached to the elevated tibial eminence (a). The bony attachment of the ACL is elevated anteriorly with little remaining posterior cortical attachment (b)

The sagittal images (Fig. 5.13a, b) demonstrate normal medial meniscus with an anterior horn root insertion of the lateral meniscus avulsed with a bone fragment along with the adjacent ACL. A focal radial tear of the posterior horn of the lateral meniscus can be seen on the sagittal STIR image as well. Increased signal is evident within the substance of the ACL with avulsion of the anterior tibial spine noted in coronal T2-weighted image (Fig. 5.12a, b). The PCL, LCL, and MCL were all intact with no focal abnormalities. Mild focal thickening and edema are present within the patella tendon possibly from chronic patella tendinitis.

In addition to the bony avulsion of the ACL and the anterior horn of the lateral meniscus, a very minimally depressed lateral tibial plateau fracture is seen at the posterior aspect of the plateau. Typical lipohemarthrosis is seen within the joint. The patient’s history, physical exam, and MRI were consistent with an ACL tear. His symptoms were persistent with consistent sense of instability with any activity and stair climbing. Surgical intervention was offered, with a plan to address his ACL with either fixation depending on the size of the bony fragment or ACL reconstruction with hamstring autograft. Additionally, arthroscopy would allow for evaluation of his lateral meniscus.

Arthroscopy

The patient was taken to the operating room and placed supine upon the operating room table with a post placed in the appropriate position as well as the leg holder appropriately positioned. Once the patient was asleep, an exam under anesthesia was performed as we always do prior to any knee arthroscopy. A pivot shift was reproducible in the operating room. Both extremities were prepped in as we typically do when considering hamstring reconstruction to allow for contralateral harvest if needed to supplement a small graft. A tourniquet was placed nonsterile around the operative extremity. Standard inferolateral and inferomedial portals were made and a diagnostic arthroscopy completed. Of note, arthroscopy was performed first in this situation given the uncharacteristic findings on MRI.

Following evacuation of bloody effusion, we were able to visualize the joint, which had no evidence of chondromalacia. No loose bodies were noted on arthroscopy. The camera was brought into the notch where the ACL was seen to be intact throughout its midsubstance Fig. 5.14a. However, when the scope was brought more anterior and inferior, the entire tibial eminence of the ACL was noted to have pulled off with an associated bleeding bony bed (Fig. 5.14a, b). This bed was covered with a layer of fibrous tissue deposited over the previous weeks leading up to surgery. Examination of the medial compartment revealed no medial meniscus tear. The knee was then brought into the figure-of-four position, and the arthroscope was brought into the lateral compartment where the anterior horn of the lateral meniscus was displaced and attached to the bony tibial eminence piece.

Fig. 5.14

Bloody effusion is noted on arthroscopy due to the acuity of the fracture. The ACL remains completely attached to a large tibial eminence avulsion and is being pulled down with an arthroscopic probe with attached anterior horn of the lateral meniscus (a). The bed beneath the elevated ACL is covered with fibrous tissue (b). An arthroscopic burr is used to debride the overlying tissue and recess the bony bed (c). Once reduction is achieved, two guide wires are placed medial and lateral to the patella tendon to hold the reduction (d)

We prepared the bony bed of the meniscus and ACL tibial attachment using an arthroscopic shaver to remove the underlying fibrinous material. A burr was utilized to aid in the reduction of the bony fragment (Fig. 5.14b, c) to allow for slight recession of the fragment. The ACL fully attached to the bony fragment was then reduced to its native position with an arthroscopic probe. Guide pins for screw fixation were placed medial and lateral to the patella tendon in a converging fashion (Fig. 5.14d). We confirmed this reduction under fluoroscopy and direct visualization. We were pleased with the length of our pins and subsequently predrilled and tapped. Two partially threaded 6.5 mm screws and washers were placed over guide wire (Fig. 5.15a–d) with excellent reduction confirmed under arthroscopy and fluoroscopy with final radiographs taken postoperatively (Fig. 5.16a, b).

Fig. 5.15

Two partially threaded 6.5 mm screws are placed over guide wire along with washers (a, b, c). Excellent reduction is achieved with no notch impingement noted on full extension (d)

Fig. 5.16

Postoperative radiographs demonstrate divergent screw fixation with reduction of the tibial eminence (a, b)

Following fixation, the ACL was once again examined and was taught. The lateral meniscus was once again examined, and the posterior lateral meniscus tear was found to have healed needing no further intervention. The arthroscope was removed and a Lachman test was performed with a firm end point noted. The patient was placed in an IROM set from 0 to 90 to begin range of motion immediately with protected weight bearing for 2 weeks.

Discussion

MRI is the imaging of choice for possible ACL avulsion injuries. While CT may help with establishing the amount of bone avulsed off the tibial eminence, MRI allows for simultaneous diagnosis of other concomitant knee pathology, which in this case included lateral meniscal pathology. MRI is estimated to have a sensitivity and specificity over 90 % for detecting ACL injury in the setting of bony avulsion injury. MRI is the preferred modality for evaluating the other soft tissue structures of the knee that may be causing symptoms.

Tibial eminence fractures are well described in the orthopedic literature [14]. Anatomically, they represent avulsion injuries to the insertion of the anterior cruciate ligament (ACL) on the tibia and are considered the childhood equivalent of an ACL tear. Tibial avulsion injuries of the ACL are less common in the adult patient though they do occur [15]. Management of these injuries can include nonsurgical or surgical options. Nonoperative modalities include therapy, range of motion, and strengthening programs with appropriate utilization of nonsteroidal anti-inflammatory agents (NSAIDS). Surgical options include ACL reconstruction with allograft or autograft or fixation in the setting of a large bony fragment.

Meyers and McKeever described a classification of these injuries dividing them into three types [16]. Type I describes a nondisplaced or minimally displaced eminence fracture, which can be treated nonoperatively. In type II, the anterior third is displaced proximally with up to one half of the attachment off though the posterior attachment is still present. Type III fractures represent complete displacement. Immobilization in extension can be pursued for type I and some type II injuries with most type III injuries requiring fixation. Regardless of the treatment method, residual laxity may be present after tibial eminence avulsion injuries. Arthroscopy and MRI for damage to other attached soft tissue structures allow for accurate reduction and treatment of these injuries [17]. Fixation can be achieved with sutures or hardware [17–22]. Outcomes for different fixation methods do not appear to differ [20].

Conclusions

ACL injuries are a common reason for knee surgery in young and healthy patients. The clinical diagnosis of ACL tear is straightforward, though coexistent pathology is frequently present and must be recognized for surgical and rehabilitation planning. A careful history, physical examination including provocative maneuvers, and imaging as dictated from the exam are key in establishing an appropriate diagnosis. Magnetic resonance imaging (MRI) remains the imaging technique of choice for patients with suspected ACL tear. MRI is also useful in identifying concomitant knee pathology that may change staging of intervention. Surgical intervention can be pursued in the carefully chosen active patient, and the approach must be individualized. Lower demand patients may be better managed with nonoperative care. Treatment options are few including autograft, allograft, and double-bundle reconstruction though some extra-articular techniques are still used in some centers. Techniques for improving ACL reconstruction are under constant analysis and development.