Knee Sports MCQs

The structure shown is the posterolateral bundle of the anterior cruciate ligament (ACL). This bundle is optimally positioned in the knee to resist rotatory forces during terminal knee extension. "Resist anterior translation during knee flexion" best describes the anteromedial bundle. "Resist rotatory loads during knee flexion" is unlikely because the posterolateral bundle is tightest during knee extension. The posterior cruciate ligament, not the ACL, functions to resist posterior translation.

The T2-weighted sagittal MRI scan shows the classic "bone bruise" pattern seen with an anterior cruciate ligament (ACL) tear. These lesions are thought to represent subcortical trabecular hemorrhages and are manifested as an increase in signal intensity on T2-weighted images and diminished signal intensity on T1-weighted images. They are classically located in the mid-portion of the lateral femoral condyle and posterior aspect of the lateral tibial plateau. This is due to the fact that an ACL tear typically is the result of a valgus-external rotation of the femur on the fixed tibia. This places most of the weight-bearing stress on the lateral femoral condyle, which rotates laterally and impacts the posterior lip of the lateral tibial plateau. This may result in an impaction fracture if the force is great enough, but more frequently causes merely a microfracture of the involved subcortical trabeculae.

A tibial tubercle-trochlear groove (TT-TG) distance > 20mm is highly associated with patellar instability secondary to rotational malalignment and is an indication for anteromedialization of the tibial tubercle (AMZ), pictured in Figures A and B, to enhance patellofemoral stability and decrease patellofemoral contact pressures in the setting of cartilage restoration procedures.Recurrent patellar instability is often associated with chondral lesions of the patellofemoral joint. In addition to managing the cartilage injury, the underlying etiology of the instability must also be addressed to ensure a successful outcome. Patellar instability may arise from coronal or rotational malalignment, patella alta, trochlear dysplasia or damage to soft tissue restraints including the medial patellofemoral ligament (MPFL). Rotational malalignment, defined by a TT-TG distance > 20mm, can be addressed by AMZ. Medialization of the tubercle restores a normal TT-TG distance while anteriorization of the tubercle unloads patellofemoral contact forces.Beck et al performed a cadaveric study measuring patellofemoral contact pressures on the trochlear surface following AMZ. They found that anteromedialization decreased the mean contact pressures and shifted contact pressures to the medial trochlea. The authors concluded that while this procedure successfully unloads the lateral trochlea, it likely has minimal benefit for central chondral defects and may be detrimental for medial chondral defects where contact pressures are increased.Strauss et al authored a review article detailing the surgical treatment options for patellofemoral cartilage lesions, including concomitant realignment/unloading procedures. AMZ is designed to correct rotational malalignment while unloading the patellofemoral compartment in the setting of cartilage restoration surgery. While AMZ has demonstrated good outcomes for lesions located in the lateral facet or distalpole of the patella, poor outcomes have been seen with medial facet or central trochlear lesions.Figures A and B are the AP and lateral radiographs, respectively, of a knee s/p AMZ, also know as a Fulkerson procedure. Illustration A is an algorithm detailing the approach to recurrent patellar instability in both skeletally immature and mature patients. Illustration B demonstrates how to measure the TT-TG distance, the distance between two lines drawn perpendicular to the posterior condylar axis to the tibial tubercle and deepest portion of the trochlear groove (normal 8-10mm). Illustration C depicts the measurement of the femoral trochlear angle or sulcus angle (normal 137°+/- 8°). Illustration D shows how to measure lateral patellar tilt (normal < 5°). Illustration E is a postoperative radiograph after AMZ. A long (> 5cm) and thick (> 0.75cm) osteotomy cut is required to allow adequate fixation with two screws.Incorrect Responses:

Proximal medial collateral ligament (MCL) injuries adjacent to the medial epicondyle heal robustly. These proximal injuries are more prone to calcification, characterized clinically with temporarily increased pain and stiffness. The distal MCL, despite its long attachment site on the proximal tibia, heals less well. MCL injuries associated with other ligament injuries heal less reliably.

MR images reveal a posterior horn root tear of the medial meniscus. LaPrade and associates found that outcomes after posterior meniscal root repair significantly improved postoperatively and patient satisfaction was high, regardless of age or meniscal laterality. Patients aged <50 years had outcomes similar to those of patients ≥50 years, as did patients who underwent medial versus lateral root repair. In patients undergoing pullout fixation for posterior medial meniscus root tear, Chung and associates found that patients with decreased meniscus extrusion at postoperative 1 year have more favorable clinical scores and radiographic findings at midterm follow-up than those with increased extrusion at 1 year. Krych and associates found that nonoperative treatment of medial meniscus posterior horn root tears is associated with poor clinical outcome, worsening arthritis, and a relatively high rate of arthroplasty at 5-year follow-up. Reconstruction would have no role in the setting of a reparable meniscal root tear.

The anterior cruciate ligament is attached to a portion of the lateral femoral condyle. The posterior cruciate ligament attaches to the medial femoral condyle. The lateral collateral and oblique popliteal ligaments attach proximal to this fragment. The intermeniscal ligament attaches the anterior horns of the menisci.

Discussion: The arthroscopic images show a microfracture procedure. Perforation of the subchondral bone results in so-called “marrow stimulation” that results in the formation of fibrocartilage. This reparative tissue is composed predominantly of type I collagen with a disorganized matrix lacking a true tidemark, as opposed to hyaline cartilage which is composed primarily of type II collagen. This operation is indicated for full-thickness chondral defects without associated degenerative arthrosis.

The patient has sustained a complex tear involving the posterior horn of the medial meniscus. Localizing joint line tenderness is the most sensitive physical examination finding for this injury.Many provocative tests have been described to aid in the diagnosis of meniscus tears.The Apley test is performed with the patient prone, by axially loading the tibiofemoral joint at 90° of knee flexion. Pain with compression and external rotation (medial meniscus) or internal rotation (lateral meniscus) is considered positive.The Ege's test is performed by having the patient squat with their knees maximally externally rotated or internally rotated. The test is positive when pain and/or a click is felt by the patient.The McMurray test is performed by passively moving the knee from flexion to extension while externally or internally rotating the leg. A palpable click at the joint line with external rotation (medial meniscus) or internal rotation (lateral meniscus) is considered positive.The Thessaly test is performed by supporting the patient as they internally or externally rotate their knee and body while keeping the foot planted, with the knee in 5° of flexion and then 20° of flexion. The test is positive when joint line pain and/or sense of locking/catching is experienced by the patient.Ryzewicz et al. performed a systematic review of prospective cohort studies comparing magnetic resonance imaging (MRI) and clinical examination to arthroscopy in the diagnosis of meniscus tears. The Apley test, Ege's test, McMurray test and Thessaly test at 5° were shown have high specificity but low sensitivity. Joint line tenderness has a higher sensitivity, but lower specificity. The Thessaly test at 20° demonstrated the highest sensitivity and specificity, although there was only one available study evaluating this test.Abdon et al. performed a prospective study looking at 68 clinical parameters todetermine which combinations of symptoms and signs indicated the presence of a meniscus tear. They found that joint-line tenderness and mechanical locking were predictive of a meniscus tear, while the McMurray sign did not prove valuable. Pain at rest, sick leave and medial patellar tenderness all negated the presence of a meniscus tear. The clinical accuracy in diagnosing meniscal tears was 61% in this study.Figures A and B are T1 sagittal MR images demonstrating an intact anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL), respectively. Figures C and D are T2 coronal and sagittal MR images showing a complex tear of the posterior horn of the medial meniscus. Illustration A demonstrates the Ege's test. Illustration B shows the Thessaly test at 5° of flexion.Incorrect

The clinical description and MR image point to an injury to the posterior cruciate ligament (PCL). This ligament is thought to be primarily composed of anterolateral and posteromedial bundles, with the former tightening in flexion and the latter in extension. Because of alterations in knee kinematics and increased varus alignment in PCL insufficiency, contact stresses and cartilage loads increase in the patellofemoral and medial compartments. Although good outcomes may be obtained with transtibial, open inlay, and arthroscopic inlay techniques, one major difference is the creation of the “killer-turn” during the transtibial approach. This sharp turn in the graft as it emerges from the tibia appears to lead to more pronounced attenuation and thinning of the graft during cyclic loading. The scenario describes a patient with chronic PCL and posterolateral corner (PLC) injury, as evidenced by the varus thrust and abnormal Dial test finding. A valgus-producing osteotomy may be effective, and, in fact, may be the only treatment necessary to address chronic PLC injury. Accordingly, an opening lateral osteotomy would not be appropriate. Of the remaining responses, an osteotomy that increases tibial slope would also address the PCL deficiency by reducing posterior tibial sag. Vascular injury is an uncommon, but potentially devastating, complication associated with PCL surgery and may occur regardless of the technique used.Numerous strategies have been described to reduce the risk, including use of a posteromedial accessory incision to allow finger retraction of the popliteal neurovascular bundle, oscillating drills to prevent excessive soft-tissue entanglement, and tapered (rather than square) drill bits that may minimize cut-out of sharp edges as drilling reaches the posterior tibial cortex. Knee extension lessens, rather than increases, the distance between the posterior tibia and the neurovascular bundle and increases, not lessens, risk for vascular injury.

OCD is an acquired lesion of the subchondral bone. Patients with OCD initially report nonspecific pain and variable amounts of swelling. Initial radiographs help identify the lesion and establish the status of the physes. An MRI scan is useful for assessing the potential for the lesion to heal with nonsurgical treatment. Nonsurgical treatment is appropriate for small, stable lesions in patients with open physes and focuses on activity restriction for 3 to 9 months. Surgical treatment is necessary for unstable or detached lesions. Stable lesions with intact articular cartilage can be treated with subchondral drilling to stimulate vascular ingrowth, with radiographic healing at an average of 4.4 months. Fixation is indicated for unstable or hinged lesions, and stabilization of the fragment can be achieved using a variety of implants through an arthroscopic or open approach. The fragment should be salvaged and the normal articularsurface restored whenever possible.

The injury mechanism involves a valgus load applied to the knee with the foot in external rotation. The primary stabilizer to valgus laxity is the medial collateral ligament. The secondary restraints to valgus rotation are the cruciate ligaments. Examination indicates disruption of the medial collateral and anterior cruciate ligaments. Valgus opening in extension should also arouse suspicion for an injury to the posterior cruciate ligament; however, in this patient, the valgus opening in extension is mild. The slight opening in extension and the increased anterior drawer, especially with external rotation, indicate disruption of the posteromedial capsule and posterior oblique ligament. Figure 21a shows complete disruption of the superficial and deep medial collateral ligaments involving the meniscofemoral ligament. Figure 21b shows a more posterior coronal section with a torn posterior oblique ligament. Figure 21c shows disruption of the anterior cruciate ligament, while the posterior cruciate ligament at the tibial insertion appears with a homogenous normal signal.

DISCUSSION: The radiographs show a posterior knee dislocation. Knee dislocations almost always involve rupture of both the anterior and posterior cruciate ligaments. Collateral ligament injuries also are common. Arterial, nerve, and tendon injuries each occur in less than half of knee dislocations.

In the quadriceps active drawer test, with the subject supine, the leg is relaxed and supported with the knee flexed 70 to 90 degrees. The examiner must adequately support the patient’s thigh so that the subject’s muscles are completely relaxed. The patient is then asked to perform a gentle quadriceps contraction without extending the knee. In the normal knee in 90 degrees of flexion, the patellar ligament is already slightly posterior, and contraction of the quadriceps does not result in an anterior shift of the tibia. However if the PCL is ruptured, the tibia sags into a posteriorly subluxed position, and the patellar ligament is then directed anteriorly. In this situation, contraction of the quadriceps muscle in the posterior cruciate deficient knee results in an anterior shift of the tibia 2mm or more. The examiner can visualize this anterior shift of the tibia with the knee is 90 degrees of flexion.

OCD is an acquired lesion of the subchondral bone. Patients with OCD initially report nonspecific pain and variable amounts of swelling. Initial radiographs help identify the lesion and establish the status of the physes. An MRI scan is useful for assessing the potential for the lesion to heal with nonsurgical treatment. Nonsurgical treatment is appropriate for small, stable lesions in patients with open physes and focuses on activity restriction for 3 to 9 months. Surgical treatment is necessary for unstable or detached lesions. Stable lesions with intact articular cartilage can be treated with subchondral drilling to stimulate vascular ingrowth, with radiographic healing at an average of 4.4 months. Fixation is indicated for unstable or hinged lesions, and stabilization of the fragment can be achieved using a variety of implants through an arthroscopic or open approach. The fragment should be salvaged and the normal articular surface restored whenever possible.

DISCUSSION: The flexed knee and ankle mechanism of injury can result in a PCL and/or posterolateral corner injury. The examination reveals an isolated injury to the posterolateral corner (arcuate, popliteus, posterolateral capsule). This results in increased posterior translation and external rotation, as well as varus that is most notable at 30° of flexion and decreases as the knee is further flexed to 90°. Combined PCL and posterolateral corner injuries are characterized by increasing instability as the knee is flexed to 90° from 30°, while isolated PCL tears show the greatest degree of instability at 90° of flexion. A rupture of the quadriceps tendon would not affect anterior or posterior stability, whereas an isolated rupture of the lateral collateral ligament, which is a rare injury, is characterized by varus instability at 30° of knee flexion without posterior translation.

DISCUSSION: A discoid meniscus is a large disk-like meniscus. It is seen in the lateral meniscus in 3% of the population; a discoid medial meniscus is much less common. It can be identified on the coronal view by noting meniscal tissue extending into the tibial spine at the intercondylar notch. The average width of a normal meniscus is less than 11 mm. A bow-tie appearance should not be seen on more than two consecutive sagittal images because the conventional thickness of the sagittal slices is 3 mm and the interval between two consecutive slices is 1.5 mm. Two sagittal slices will cover a 9-mm thickness. A discoid meniscus can be diagnosed on the sagittal views by noting a bow-tie appearance on more than two consecutive images.

It is critical for graft isometry and knee stability that the femoral tunnel be placed as far posterior as possible on the lateral femoral condyle. Superiorly, the graft should be at the one o’clock position on the left knee. Resident’s ridge is a false posterior shelf that often seems like the extreme posterior cortex. Abnormal tunnel placement results in a variety of complications, including an unstable knee, early graft failure, and joint stiffness.

All of the answers are possible complications of meniscal repair. There are large volumes of literature evaluating the results of meniscal repair, both for the all-inside technique, as well as the inside-out technique. Failure rates are similar. Intra-articular synovitis occurs with absorbable sutures and absorbable implants. Peroneal nerve injuries are more common with the lateral-sided repairs. Saphenous nerve injuries are more common with medial-sided tears. Because of the incision required and the technique of tying over soft tissue, the risk of a saphenous nerve injury is greater with an inside-out technique than with an all-inside technique.

The middle genicular artery supplies the posterior capsule and intracapsular structures (anterior cruciate ligament, posterior cruciate ligament, posterior horns of the meniscus).

The rugby player has sustained an injury to his anterior cruciate ligament (ACL), as demonstrated by the Segond fracture on radiograph and bone-bruising pattern on magnetic resonance imaging (MRI). The presence of a Segond fracture (avulsion fracture of the proximal lateral tibia) is pathognomonic for an ACL rupture.