Congenital absence of the anterior cruciate ligament associated with a ring meniscus

Helix meniscus - A novel anatomical discovery

Many anatomical variations of the meniscus have been reported. In this report, we present a case of a novel pattern of meniscal morphology showing a helix structure. A 14-year-old boy presented with knee pain without an apparent cause. Arthroscopic surgery was performed, revealing a helical-shaped meniscus on the lateral side, without injury or degeneration. Partial meniscectomy resulted in symptom improvement. A helix meniscus is very rare and should be recognized as a novel anatomical variant. While arthroscopic meniscectomy improved symptoms, careful consideration is needed when determining surgical indications, as long-term effects remain unknown.

Regeneration of a Discoid Meniscus: A Case Report

CASE

A 4-year-old girl with no relevant medical history presented with left knee swelling. Knee laxity, magnetic resonance imaging findings of anterior cruciate ligament (ACL) deficiency and discoid meniscus, and the chronicity of symptoms prompted arthroscopic ACL reconstruction and meniscal saucerization. Pain and swelling continued, and repeat arthroscopy revealed regeneration of the discoid meniscus at 18-month follow-up.

CONCLUSION

In this unusual case, a discoid lateral meniscus regenerated after saucerization. Regeneration could be attributed to the robust vascularity of the meniscus in pediatric patients. Surgeons should counsel about the risk of recurrence after treatment of discoid meniscus.

"Ring-shaped" meniscus and accompanying intermeniscal bridge meniscus: a rare combined variant resembling a bucket-handle tear

Many anatomical variations have been described in the menisci, especially in the lateral meniscus. Among these, discoid meniscus is the most common variation. Others are described in the literature as double-layered meniscus, accessory meniscus, ring-shaped meniscus, and hypoplastic meniscus. Also, combined variations associated with ring-shaped meniscus have been described, and they can be confused with fragmented complex tears and cause unnecessary surgery. Increasing awareness of the imaging features of these accompanying combined variations may aid in the recognition and differentiation of this entity from meniscus tears. We report the case of a ring-shaped meniscus and accompanying intermeniscal bridge meniscus, which has not been described before in the literature, highlighting the MRI and arthroscopic imaging findings of it.

Ring-Shaped Meniscus, MRI Features, and Diagnosis: A Report of 2 Cases

CASE

A ring-shaped meniscus (RSM) is a rare malformation of debatable origin usually occurring on the lateral meniscus. Here, we present 2 cases of RSM with differing etiologies and discuss the current literature on the topic. These reports may help with the identification of RSMs in the future and assist in understanding the true etiopathogenesis of individual cases.

CONCLUSION

These 2 cases exemplify the variation in presentations of ring-shaped menisci and their radiological features on both x-ray and magnetic resonance imaging. This reinforces the idea that there may be both a congenital and an iatrogenic etiology to this rare condition.

High and Varied Anterior Condyle of the Distal Femur Is Associated with Limited Flexion in Varus Knee Osteoarthritis

OBJECTIVE

This study aimed to evaluate variations in anterior condylar height (ACH) of the distal femur in varus knee osteoarthritis and evaluate the association between ACH and knee flexion.

DESIGN

Computed tomography (CT) images of 171 knees (143 patients; age 73.7 ± 8.3 years; 132 females, 39 males) with symptomatic primary knee osteoarthritis and varus alignment undergoing primary total knee arthroplasty, unilateral knee arthroplasty, or high tibial osteotomy were evaluated. Several other anatomic parameters were measured on CT or radiography. The ACH and knee flexion correlation was analyzed, and factors contributing to knee flexion were determined using multivariable regression analysis.

RESULTS

Medial ACH (mean, 8.1 mm; range, -2.8 to 19.9 mm) was smaller (P < 0.001) but more variable (F = 1.8, P < 0.001) than lateral ACH (mean, 10.7 mm; range, 3.6-18.3 mm). Medial ACH was moderately correlated with flexion (r = -0.44, 95% confidence interval [CI], -0.55 to -0.32), whereas lateral ACH was weakly correlated (r = -0.38; 95% CI, -0.50 to -0.25). On multivariable linear regression analysis of knee flexion, body mass index (B [partial regression coefficient] = -1.1), patellofemoral Kellgren-Lawrence grade (B = -4.3), medial ACH (B = -1.2), medial posterior condylar offset (B = 1.2), age (B = -0.4), and varus alignment (B = -0.6) remained significant independent variables (adjusted R² = 0.35).

CONCLUSIONS

Wide variation and anteriorization of the anterior condyle of the distal femur was observed in advanced osteoarthritis, as an independent determinant of limited knee flexion.

MR- arthrography: anatomic variant from link between lateral meniscus and anterior and posterior cruciate ligaments. A case report and review of the literature

Menisci congenital anomalies are rare morphologic abnormalities including accessory meniscus, discoid meniscus, double-layered meniscus, hypoplastic meniscus and ring-shaped meniscus (RSM). In a 35 year-old male patient, MR arthrography showed a bridging accessory bundle connecting the anterior cruciate ligament and posterior cruciate ligament with the posterior horn of the lateral meniscus. Arthroscopic examination showed a fan-like obstacle embracing the posterior horn of the lateral meniscus. It would be important to correctly identify this anatomical variant, because the bundle connecting the external meniscus to the ligaments of the central pivot can be misinterpreted as a meniscal fragment.

Bilateral congenital absence of the anterior cruciate ligament associated with bilateral knee and hip osteoarthritis: Case report

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Reports of the progression of congenital absence of cruciate ligament were very rare in old age.

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Authors reported a case of congenital absence of cruciate ligament with severe knee instability, knee and hip osteoarthritis.

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Congenital absence of cruciate ligament may progress to osteoarthritis, so early detection and proper management is needed.

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Total knee arthroplasty is useful for the treatment of arthritis and instability following congenital absence of cruciate ligament.

Introduction

Congenital absence of the cruciate ligaments is very rare condition. Its association with congenital abnormalities of the spine, knee and hip, has been rarely reported. Most of the case reports were mostly reported before adolescence, so reports of the progression of this congenital disease at old age were extremely rare.

Presentation of case

A 65-year-old woman had a 7-year history of both knee and hip pain. On physical examination, valgus and varus instability on both knees and painful limitation of motion in both hip joints were observed. Radiography and magnetic resonance imaging showed the absence of the anterior cruciate ligament with osteoarthritis on both knees and hip osteoarthritis. Total knee and hip arthroplasties were performed on both knee joints and total hip arthroplasty. The pain and instability of both knees and hips were lost for follow up of more than a year, and the patient is doing well in daily life.

Discussion

Congenital absence of cruciate ligament may progress to osteoarthritis, do early detection and proper management is needed. In the treatment of older aged patients. Reports of treatment for this disorder are also very rare in older age. In old age, arthroplasty can be a useful treatment when the severe osteoarthritis is accompanied by instability.

Conclusion

Since the congenital absence of the ACL in old age could lead to hip and knee osteoarthritis, periodic follow-up is necessary and arthroplasty can be a useful treatment when the severe osteoarthritis is accompanied by instability.

Ring-shaped meniscus formation may arise from the regenerative response to meniscectomy during growth spurts: A case report

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We presented a case of newly formed ring-shaped meniscus-like tissue after partial resection of discoid lateral meniscus.

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The newly formed interhorn bridge could have represented a meniscus-like tissue that appeared secondary to tissue repair.

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Intra-patient findings indicate that growth spurts may promote the tissue repair.

Introduction

Ring-shaped meniscus is very rare and generally considered to be a congenital malformation. Here, we report a case of newly formed ring-shaped meniscus-like tissue following arthroscopic partial meniscectomy for a complete discoid lateral meniscus.

Presentation of case

A 14-year-old boy underwent arthroscopic partial meniscectomy for complete discoid lateral meniscus of the left knee. The growth plates were present at the surgery. Although pain improved immediately after surgery, he reported left knee pain at the 7-month follow-up. Magnetic resonance imaging revealed a bucket-handle tear of the lateral meniscus and a second arthroscopic surgery was performed. During arthroscopy, we found that the anterior and posterior horns of the lateral meniscus were connected by meniscus-like tissue forming a ring-shaped meniscus and the newly formed interhorn meniscal bridge was resected. Histological evaluation indicated that the newly formed tissue was meniscus-like tissue that had appeared secondary to tissue repair. He visited our hospital at 16 years old, after the growth plates had closed, complaining of right knee pain. Arthroscopic partial meniscectomy was performed for complete discoid lateral meniscus of the right knee. As of two years after this surgery, no morphological changes have been observed.

Discussion

Although the exact mechanisms of meniscus-like tissue formation remain unclear, the growth spurt may promote the mechanisms of tissue repair, forming ring-shaped meniscus-like tissue.

Conclusion

This is the first case of ring-shaped meniscus-like tissue forming after partial resection of a complete discoid lateral meniscus. Ring-shaped meniscus-like tissue can develop in growing patients.

Classification of Cruciate Ligament Dysplasia and the Severity of Congenital Fibular Deficiency

BACKGROUND

Dysplasia of the cruciate ligaments has been found in many patients with congenital fibular deficiency. A recent classification system has shown that radiographic tibial spine changes can predict the hypoplasia and aplasia of the cruciate ligaments. We used this radiographic classification to determine the frequency of these abnormalities and how they correlate with the severity of fibular deficiency and lateral femoral condylar hypoplasia.

METHODS

Using a hospital database search for fibular deficiency, 99 patients ≥6 years with unilateral fibular deficiency were identified. Existing radiographs of both knees were available for 75 patients and reviewed for the tibial spine changes and Achterman and Kalamchi classification of the fibular deficiency. Measurements of femoral condyle heights in 74 of 75 patients were recorded before any surgery to the distal femoral physis to assess lateral femoral condylar hypoplasia.

RESULTS

Twenty-two patients had hypoplasia of the lateral tibial spine+normal medial spine, 29 had absence of the lateral tibial spine+hypoplastic medial spine, and 11 had absence of both tibial spines. Five tibial spines were normal and 8 were unclassifiable. The severity of the tibial spine dysplasia, particularly absence of the lateral tibial spine, correlated with the severity of the fibular deficiency. (P<0.0001) The mean lateral femoral condylar hypoplasia, measured by involved: uninvolved lateral condyle heights, was 0.85±0.11. Those with some preservation of the lateral tibial spine had less lateral femoral condylar hypoplasia (P=0.0009). This lateral femoral condylar hypoplasia was positively associated with the severity of the fibular absence (P=0.039) and foot ray deficiency (P=0.036).

CONCLUSIONS

The severity of cruciate ligament dysplasia in fibular deficiency is directly correlated with the severity of fibular absence, lateral femoral condylar hypoplasia, and the absence of foot rays. This suggests that the embryological factors involved have a complex interplay for all of these clinical findings.

LEVEL OF EVIDENCE

Level III.

Reconstruction of Symptomatic Congenital Anterior Cruciate Ligament Insufficiency

BACKGROUND

Hypoplasia or congenital absence of the anterior cruciate ligament (ACL) is a rare disorder occurring in ∼1 in every 6000 births. Although some patients with hypoplasia or agenesis of the ACL may not complain of instability, others desire to participate in more demanding activities that require the stability of a competent ACL. There are limited reports of surgical treatment of this patient population. The purpose of this study was to report ACL reconstruction in a case series of patients with symptomatic congenital ACL deficiency.

METHODS

A retrospective medical record review of the surgical treatment of 14 knees (13 patients) with congenital absence of the ACL at a tertiary care institution from 1995 to 2012 was performed. Patients with a minimum of 1 year of clinical follow-up were eligible for inclusion.

RESULTS

The mean age at time of surgery was 12.6 (range, 3 to 22), including 6 patients <12 years of age. Mean follow-up was 2.9 years (range, 1 to 6.6). Nine of 13 patients (69%) had underlying congenital abnormalities/associated syndromes. Preoperative Lachman and pivot shift examination was International Knee Documentation Committee grade C or D in all but 1 knee. ACL reconstruction was performed with combined intra-articular/extra-articular physeal sparing reconstruction with iliotibial band (n=5), autograft hamstring (n=2) or bone-patellar tendon-bone (n=3), or allograft (n=4). Multiligament reconstruction of associated ligamentous deficiency was performed in 7 knees (50%). Postoperative Lachman and pivot shift testing was International Knee Documentation Committee (IKDC) grade A or B in all but 1 knee. One patient with congenital absence of multiple knee ligaments required revision ACL reconstruction surgery, with concurrent first-time posterior cruciate ligament reconstruction, due to persistent instability. None required revision surgery due to graft tear at a minimum of 1-year follow-up.

CONCLUSIONS

Surgical stabilization of symptomatic congenital ACL insufficiency, with associated ligamentous reconstruction as required on a case-by-case basis, results in improved stability at early clinical follow-up, with low complication rates.

LEVEL OF EVIDENCE

Level IV-retrospective case series.

Post-arthroscopic osteonecrosis of the medial tibial plateau: a case series

Background

Avascular necrosis after arthroscopic surgery of the knee has already been published. The purpose of this article is to report on the frequently misdiagnosed entity of osteonecrosis of the medial tibial plateau.

Case presentation

Charts and radiographs of a consecutive series with isolated medial tibial plateau osteonecrosis were analyzed. The criterion for inclusion was the absence of trauma. Six caucasian female patients with an average age of 76.5 years complied with this criterion. Three of these cases had had arthroscopic intervention for medial meniscal lesion within the previous year.

Conclusions

The etiology of these necroses remains unclear. Osteonecrosis must be taken into account as a possible cause of persistent knee pain after surgery. Correlation between arthroscopic treatment and necrotic processes in the tibial plateau must still be regarded with skepticism.

Arthroscopic Meniscectomy for Medial Meniscus Horizontal Cleavage Tears in Patients under Age 45

Purpose

The purpose of this study was to evaluate the demographics, clinical features, and outcomes of arthroscopic partial meniscectomy (APM) for isolated medial meniscus horizontal cleavage tears (MMHCTs) in patients under 45 years of age.

Materials and Methods

We retrospectively reviewed 98 patients (100 knees) under 45 years who underwent APM for MMHCTs. Clinical outcomes were assessed using International Knee Document Committee (IKDC) subjective core, Tegner activity scale, visual analog scale (VAS) pain score, and a question on the symptom relief.

Results

79% were male and 70% had no trauma. The mean symptom duration was 10 months. At arthroscopy, a flap tear was identified in 75%. At a mean of 19-month follow-up, the IKDC subjective score, Tegner activity scale, and VAS pain score were significantly improved compared to the preoperative values (p=0.025, p=0.043, and p=0.032, respectively). While 85% were free of symptoms, 15% had persistent pain. No significant differences in outcomes were observed based on the tear type and the presence of flap tears. No progression or development of radiographic degenerative changes was observed in all knees.

Conclusions

Demographics of MMHCTs under age 45 showed a male dominance and higher frequency of non-traumatic tears. APM was beneficial to symptomatic HCTs in this cohort during the short-term follow-up. Type of HCTs and combined flap tears did not affect clinical outcomes.

Patterns and Influencing Factors of Medial Meniscus Tears in Varus Knee Osteoarthritis

Purpose

To investigate the patterns of medial meniscus (MM) tears in patients with varus knee osteoarthritis who underwent total knee arthroplasty and analyze the factors that could affect MM tears.

Materials and Methods

The patients (365 knees, 268 patients) were classified into three groups; group I with MM posterior horn (PH) tear only; group II with MM root tear only; and group III with MMPH plus root tear. The following factors were evaluated: age, gender, body mass index, varus deviation of the mechanical axis, medial proximal tibial angle, posterior tibial slope (PTS), and anterior cruciate ligament (ACL) integrity (normal, degeneration, and tear or absence).

Results

MM tears were identified in all knees. The patterns of the combined MMPH tears in group III were less complex than those in group I. Varus deviation and PTS were significantly greater in group III than groups I and II. In group III, there were significantly more cases of ACL tear or absence than groups I and II. The others showed no differences among three groups.

Conclusions

Severe varus knee osteoarthritis was always accompanied by MM tears. Risk factors for MMPH plus root tears were severe varus deformity, great PTS, and ACL tear or absence.

Hypoxia-inducible factor-2α induces expression of type X collagen and matrix metalloproteinases 13 in osteoarthritic meniscal cells

OBJECTIVES

To evaluate whether Hypoxia-inducible factor-2α (HIF-2α) regulates expression of endochondral ossification-related molecules in human OA meniscus.

METHODS

Expressions of HIF-2α, type X collagen (COL10), matrix metalloproteinase (MMP)-13, and vascular endothelial growth factor (VEGF) in non-OA and OA menisci were analyzed by real-time RT-PCR and immunohistochemistry (IHC). Meniscal cells from OA patients were treated with interleukin-1β (IL-1β) and gene expression was analyzed. After knockdown of HIF-2α in OA meniscal cells, COL10 and MMP-13 expression were analyzed by RT-PCR, western blotting, immunofluorescence and ELISA.

RESULT

Histological analysis demonstrated weak staining of the superficial layer and large round cells in OA meniscus. RT-PCR analysis showed that HIF-2α, COL10, MMP-13, and VEGF mRNA expressions were higher in OA than non-OA meniscal cells. IHC showed a coordinated staining pattern of HIF-2α, COL10, and MMP-13 in OA meniscus. IL-1β treatment increased HIF-2α, COL10, and MMP-13 expressions in OA meniscal cells, and knockdown of HIF-2α suppressed IL-1β-mediated increase in COL10 and MMP-13 expression.

CONCLUSIONS

These results suggested that HIF-2α may cause meniscal matrix degradation by transactivation of MMP-13. HIF-2α may be a therapeutic target for modulating matrix degradation in both articular cartilage and meniscus during knee OA progression.

Ring-shaped lateral meniscus with hypoplasic anterior cruciate ligament

Knee joint lesions can be solitary or occur concomitantly with other lower limb abnormalities. Ring-shaped lateral meniscus (RSM) and hypoplasic anterior cruciate ligament (ACL) are two rare malformations. The therapeutic management of such abnormalities is not consensual, and highly depends on clinical symptomatology. We report a case of a 25-year-old girl with progressive knee pain whose MRI demonstrated a continuous segment of lateral meniscus situated along the medial aspect of the lateral compartment, continuous with the otherwise normal-appearing lateral meniscus, compatible with an RSM. This anatomic variant can be mistaken by a displaced meniscal fragment, like a bucket-handle tear, a central tear of a discoid meniscus, or incomplete discoid meniscus, as previously reported. Her MRI examination also showed a thinned ACL with anomalous lateral course. This abnormality may be mistaken for an ACL rupture and/or a meniscofemoral ligament with agenesis of ACL. Multiple images in different planes as well as following the course of meniscal and ligaments are critical clues to avoid misdiagnosis. As a result, the diagnosis of an RSM along with hypoplasic ACL with abnormal attachment was assumed based on MRI and confirmed during arthroscopy. The patient was treated conservatively with clinical outcome improvement.

Kinematic change of the meniscus and the tibiofemoral joint space in asymptomatic volunteers using a wide bore 3T closed MRI system

OBJECTIVES

To evaluate kinematic changes in menisci and tibiofemoral joint spaces in extension and flexion using asymptomatic volunteers using a wide-bore 3-T closed MRI system.

METHODS

Twenty-two knees from asymptomatic volunteers were examined in knee extension and flexion using a 3-T MRI (sagittal 2D FSE T2-weighted sequence and sagittal 3D isotropic FSE proton density-weighted cube sequence). The meniscal positions, meniscal floating and flounce were evaluated. The widths of the medial and lateral tibiofemoral joint spaces and coronal tibiofemoral angles were measured.

RESULTS

In the anteroposterior direction, meniscal extrusion was most frequently seen in the anterior horn of the medial menisci (100%) in extensions (maximum 6.04 mm). Most of the menisci moved significantly to the posterior side from extension to flexion. The anteroposterior meniscal movement was the greatest for the anterior horn of the medial meniscus and least for the posterior horn of the medial meniscus. In the mediolateral direction, meniscal extrusion was seen in 52% of the medial menisci in extensions (maximum 1.91 mm) and 29% of lateral menisci in flexions (maximum 2.36 mm). From the extension to flexion, all medial and lateral menisci moved significantly to the lateral side. Meniscal floating was frequently observed in the posterior horn of medial menisci in extension. Meniscal flounce was frequently seen in lateral menisci in flexion with a widened lateral tibiofemoral joint space gap. The coronal tibiofemoral angle showed medial wedging in flexion, but not in extension.

CONCLUSIONS

Wide-bore 3-T closed MRI revealed significant kinematic changes in the menisci and tibiofemoral joint spaces in asymptomatic volunteers.

Medial meniscus tear morphology and related clinical symptoms in patients with medial knee osteoarthritis

PURPOSE

The objective of this study was to examine the association between clinical symptoms and arthroscopic meniscal findings in patients with early to moderate medial knee osteoarthritis.

METHODS

One hundred and four patients (110 knees) were selected from a group of 132 patients (140 knees) aged ≥50 years who underwent arthroscopic surgery for medial meniscal tears. Inclusion criteria were as follows: (a) medial knee osteoarthritis and (b) simple medial meniscal tears extending to ≥1/4 of the meniscal margin. Subjective symptoms, location and nature of the pain, as well as the physical findings observed during initial assessment were evaluated using a standardized assessment chart. The relationship between arthroscopic meniscal findings and clinical symptoms was then analysed.

RESULTS

Isolated meniscal tears were classified into four types: radial tear of the middle segment; posterior root tear; horizontal tear of the posterior segment; and flap tear. The following symptoms were reported at significantly higher frequencies: pain on standing and a catching sensation in patients with flap tears; pain on walking and nocturnal pain on rolling over in bed in patients with radial tears of the middle segment; and popliteal pain in patients with posterior root tears.

CONCLUSIONS

This study demonstrates a relationship between the type of medial meniscal tear and characteristic clinical symptoms reported by patients with medial knee osteoarthritis. These results suggest that clinical symptoms in patients with osteoarthritis of the knee may be caused by meniscal tears. This evidence may help to better inform patients and surgeons regarding choice of treatment.

LEVEL OF EVIDENCE

Case control study, Level III.

Surgical treatment of a rare isolated bilateral agenesis of anterior and posterior cruciate ligaments

The isolated bilateral agenesis of both cruciate ligaments is a rare congenital disorder. A 17-year-old male came to our attention due to an alteration in gait pattern, pain, and tendency to walk on the forefoot with his knee flexed. The patient did not recall previous injuries. Upon physical examination anterior and posterior chronic instability were observed. Radiographic examination of both knees showed hypoplasia of the tibial eminence, a hypoplastic lateral femoral condyle, and a narrow intercondylar notch. MRI brought to light a bilateral agenesis of both posterior cruciate ligaments. Arthroscopic evaluation confirmed bilateral isolated agenesis of both cruciate ligaments. We recommended a rehabilitation program to prepare the patient for the arthroscopic construction of both cruciate ligaments.

Osteochondritis dissecans of the lateral tibial condyle associated with agenesis of both cruciate ligaments

Osteochondritis dissecans is a rare cause of painful knees in children. Only 10 cases of lateral tibial condyle involvement have been reported in the literature. Congenital agenesis of both cruciate ligaments has been described even less, and its prevalence is unknown. The authors report an atypical association of osteochondritis dissecans of the tibia with congenital absence of both cruciate ligaments. A 12-year-old male soccer player presented with a painful right knee. Magnetic resonance imaging revealed the diagnosis. The child was treated conservatively. At 18-month follow-up, radiographs showed osseointegration of the osteochondritis dissecans, and the patient had resumed normal athletic activity without pain. To the authors' knowledge, this is the only report describing such an association. The authors discuss the possible etiology of osteochondritis dissecans associated with agenesis of the cruciate ligaments and highlight the possibility of this association when osteochondritis dissecans of the tibia is diagnosed in a child with a painful knee. In this patient, the strain due to anteroposterior instability may have been the cause of osteochondritis. Conservative treatment should be considered in this setting.

Agenesis of the posterolateral bundle of anterior cruciate ligament

The objective of this article is to report an anterior cruciate ligament variation that has not been previously described, in which the posterolateral bundle of anterior cruciate ligament is congenitally not developed. The clinical picture and the magnetic resonance images are presented, and the arthroscopic appearance is described.

Patellofemoral osteoarthritis

Patellofemoral arthritis is a fairly common disease, and it has been gaining interest with increasing number of studies due to its diverse treatment methods. Patellofemoral arthritis has a broad range of management options according to the characteristics of individual diseases. Identifying whether patellofemoral arthritis is the primary cause of knee pain and is compartment arthritis is necessary for establishing an adequate treatment method. Through investigation of the literature, the issues of recent knowledge of femoropatella arthritis and the diagnosis and treatment of which were studied.

Congenital absence of the cruciate ligaments

Congenital absence of the cruciate ligaments is a rare condition with a prevalence of 0.017 per 1,000 live births. The most important finding of this study was the presence of a posterior menisco-femoral ligament of Wrisberg with cruciate ligaments agenesia and the hypothesis advanced about the development of the ligamentous structures of the knee. Reviewing the literature, we assume that the congenital anomaly that causes the anatomical defect expresses itself around the 7th to 8th post-ovulatory week. Literature teaches us that the need for a knee replacement seems to be inevitable before or after and during the life of a patient without cruciate ligaments.

Discoid meniscus associated with agenesis of the anterior cruciate ligament in an 8-year-old child

Among the congenital anomalies involving the lateral compartment of the knee, the combination of both a discoid meniscus and agenesis of the anterior cruciate ligament (ACL) is extremely rare and probably underestimated due to the presence of a meniscofemoral ligament often mistaken for an intact ACL. The therapeutic management of such abnormalities is not univocal and highly depends on their clinical impact. We report on the observations of an 8-year-old boy presenting with a cystic formation on a lateral discoid meniscus associated with agenesis of the ACL and the presence of an anterior lateral meniscofemoral ligament.

Ligament reconstruction in congenital absence of the anterior cruciate ligament: a case report

Congenital absence of the cruciate ligament is an extremely rare condition that was first reported in Giorgi's radiographic study in 1956. The authors report on a case of anterior cruciate ligament reconstruction performed on a 21-year-old female patient with congenital anterior cruciate ligament absence. We also discuss radiographic evidence that could provide clues to the congenital absence and possible difficulties that may be encountered during surgery with a review of the relevant literature.

The relationship between prevalent medial meniscal intrasubstance signal changes and incident medial meniscal tears in women over a 1-year period assessed with 3.0 T MRI

OBJECTIVE

Intrasubstance meniscal signal changes not reaching the articular surface on fast spin echo (FSE) sequences are considered to represent mucoid degeneration on MRI. The aim of this study was to evaluate the association of prevalent intrasubstance signal changes with incident tears of the medial meniscus detected on 3.0 T MRI over a 1-year period.

MATERIALS AND METHODS

A total of 161 women aged ≥ 40 years participated in a longitudinal 1-year observational study of knee osteoarthritis. MRI (3.0 T) was performed at baseline and 12-month follow-up. The anterior horn, body, and posterior horn of the medial meniscus were scored by two experienced musculoskeletal radiologists using the Boston-Leeds Osteoarthritis Knee Score (BLOKS) system. Four grades were used to describe the meniscal morphology: grade 0 (normal), grade 1 (intrasubstance signal changes not reaching the articular surface), grade 2 (single tears), and grade 3 (complex tears and maceration). Fisher's exact test and the Cochran-Armitage trend test were performed to evaluate whether baseline intrasubstance signal changes (grade 1) predict incident meniscal tears/maceration (grades 2 and/or 3) in the same subregion of the medial meniscus, when compared to subregions without pathology as the reference group (grade 0).

RESULTS

Medial meniscal intrasubstance signal changes at baseline did not predict tears at follow-up when evaluating the anterior and posterior horns (left-sided p-values 0.06 and 0.59, respectively). No incident tears were detected in the body.

CONCLUSION

We could not demonstrate an association between prevalent medial meniscal intrasubstance signal changes with incident tears over a 1-year period.

Repair of horizontal meniscal cleavage tears with exogenous fibrin clots

PURPOSE

A novel indication and technique using exogenous fibrin clots to repair horizontal cleavage tears of the meniscus is presented.

METHODS

Vertical sutures were placed on the meniscus using FasT-Fix (Smith & Nephew Endoscopy, Andover, MA, USA), and exogenous fibrin clots were inserted within the cleft to promote healing and to preserve function.

RESULTS

Repeat arthroscopy showed healing and closure of the cleft of the meniscus without affecting the articular cartilage. Three medial and six lateral menisci were treated, and all of the patients showed improvements in their functional scores and their quality of life.

CONCLUSIONS

It appears that the exogenous fibrin clots act as a scaffold to promote the healing process and that growth factors in the fibrin clots had a beneficial effect on meniscal healing. This procedure should be considered to treat degenerative menisci for which repair options have been limited until now.

LEVEL OF EVIDENCE

IV.

Anterior lateral meniscofemoral ligament with congenital absence of the ACL

PURPOSE

to describe agenesis of the anterior cruciate ligament (ACL) with an anterior lateral meniscofemoral ligament.

METHODS AND RESULTS

case report of a 13-year-old girl with an absent ACL and with an anterior lateral meniscofemoral ligament instead, as well as absence of the anterior insertion of the lateral meniscus in the tibia and a discoid ring-like lateral meniscus, with hypoplasia of the lateral femoral condyle. At arthroscopy, the anterior lateral meniscofemoral ligament was found to arise from the anterior horn of the lateral meniscus and insert into the posterolateral aspect of the intercondylar notch, mimicking the course of the native ACL on magnetic resonance imaging (MRI).

CONCLUSION

ACL agenesis may be associated with an anomalous anterior lateral meniscofemoral ligament that may mimic a normal ACL on MRI.

Epidemiology and imaging of the subchondral bone in articular cartilage repair

Articular cartilage and the subchondral bone act as a functional unit. Following trauma, osteochondritis dissecans, osteonecrosis or osteoarthritis, this intimate connection may become disrupted. Osteochondral defects-the type of defects that extend into the subchondral bone-account for about 5% of all articular cartilage lesions. They are very often caused by trauma, in about one-third of the cases by osteoarthritis and rarely by osteochondritis dissecans. Osteochondral defects are predominantly located on the medial femoral condyle and also on the patella. Frequently, they are associated with lesions of the menisci or the anterior cruciate ligament. Because of the close relationship between the articular cartilage and the subchondral bone, imaging of cartilage defects or cartilage repair should also focus on the subchondral bone. Magnetic resonance imaging is currently considered to be the key modality for the evaluation of cartilage and underlying subchondral bone. However, the choice of imaging technique also depends on the nature of the disease that caused the subchondral bone lesion. For example, radiography is still the golden standard for imaging features of osteoarthritis. Bone scintigraphy is one of the most valuable techniques for early diagnosis of spontaneous osteonecrosis about the knee. A CT scan is a useful technique to rule out a possible depression of the subchondral bone plate, whereas a CT arthrography is highly accurate to evaluate the stability of the osteochondral fragment in osteochondritis dissecans. Particularly for the problem of subchondral bone lesions, image evaluation methods need to be refined for adequate and reproducible analysis. This article highlights recent studies on the epidemiology and imaging of the subchondral bone, with an emphasis on magnetic resonance imaging.

Unilateral aplasia of both cruciate ligaments

Aplasia of both cruciate ligaments is a rare congenital disorder. A 28-year-old male presented with pain and the feeling of instability of his right knee after trauma. The provided MRI and previous arthroscopy reports did not indicate any abnormalities except cruciate ligament tears. He was referred to us for reconstruction of both cruciate ligaments. The patient again underwent arthroscopy which revealed a hypoplasia of the medial trochlea and an extremely narrow intercondylar notch. The tibia revealed a missing anterior cruciate ligament (ACL) footprint and a single bump with a complete coverage with articular cartilage. There was no room for an ACL graft. A posterior cruciate ligament could not be identified. The procedure was ended since a ligament reconstruction did not appear reasonable. A significant notch plasty if not a partial resection of the condyles would have been necessary to implant a ligament graft. It is most likely that this would not lead to good knee stability. If the surgeon would have retrieved the contralateral hamstrings at the beginning of the planned ligament reconstruction a significant damage would have occurred to the patient. Even in seemingly clear diagnostic findings the arthroscopic surgeon should take this rare abdnormality into consideration and be familiar with the respective radiological findings. We refer the abnormal finding of only one tibial spine to as the "dromedar-sign" as opposed to the two (medial and a lateral) tibial spines in a normal knee. This may be used as a hint for aplasia of the cruciate ligaments.

Incidental meniscal findings on knee MRI in middle-aged and elderly persons

BACKGROUND

Magnetic resonance imaging (MRI) of the knee is often performed in patients who have knee symptoms of unclear cause. When meniscal tears are found, it is commonly assumed that the symptoms are attributable to them. However, there is a paucity of data regarding the prevalence of meniscal damage in the general population and the association of meniscal tears with knee symptoms and with radiographic evidence of osteoarthritis.

METHODS

We studied persons from Framingham, Massachusetts, who were drawn from census-tract data and random-digit telephone dialing. Subjects were 50 to 90 years of age and ambulatory; selection was not made on the basis of knee or other joint problems. We assessed the integrity of the menisci in the right knee on 1.5-tesla MRI scans obtained from 991 subjects (57% of whom were women). Symptoms involving the right knee were evaluated by questionnaire.

RESULTS

The prevalence of a meniscal tear or of meniscal destruction in the right knee as detected on MRI ranged from 19% (95% confidence interval [CI], 15 to 24) among women 50 to 59 years of age to 56% (95% CI, 46 to 66) among men 70 to 90 years of age; prevalences were not materially lower when subjects who had had previous knee surgery were excluded. Among persons with radiographic evidence of osteoarthritis (Kellgren-Lawrence grade 2 or higher, on a scale of 0 to 4, with higher numbers indicating more definite signs of osteoarthritis), the prevalence of a meniscal tear was 63% among those with knee pain, aching, or stiffness on most days and 60% among those without these symptoms. The corresponding prevalences among persons without radiographic evidence of osteoarthritis were 32% and 23%. Sixty-one percent of the subjects who had meniscal tears in their knees had not had any pain, aching, or stiffness during the previous month.

CONCLUSIONS

Incidental meniscal findings on MRI of the knee are common in the general population and increase with increasing age.

Isolated congenital absence of posterior cruciate ligament? A case report

A rare case of a 28-year-old Asiatic male with the isolated absence of a posterior cruciate ligament is reported. Clinical features, diagnostic steps, therapeutic strategies and follow-up are described. A review of the literature is also presented.

[Isolated congenital aplasia of the anterior cruciate ligament treated by reconstruction in a 5-year-old boy]

Agenesia of the anterior cruciate ligament is a rare entity which is exceptionally symptomatic. We report a case observed in a 5-year-old boy who presented an unstable knee which was treated by Clocheville ligamentopàlasty. At five years followup, the functional outcome was satisfactory. The patient was symptom free and practiced sports activities. He did not develop any complications excepting flexion which was limited to 130 degrees . Magnetic resonance imaging demonstrated good integration of the autograft. Anterior instability in the child limits physical activity and can cause meniscal injury and early osteoarthritis. The Clocheville technique is adapted for pediatric patients with knee instability caused by a congenital defect or injury.

To run or not to run: a post-meniscectomy qualitative risk analysis model for osteoarthritis when considering a return to recreational running

The increased likelihood of osteoarthritic change in the tibiofemoral joint following meniscectomy is well documented. This awareness often leads medical practitioners to advise patients previously engaged in recreational running who have undergone meniscectomy to cease all recreational running. This literature review examines the following questions: 1) Is there evidence to demonstrate that runners, post-meniscectomy, incur a great enough risk for early degenerative OA to cease all running? 2) Does the literature yield risk factors for early OA that would guide a physical therapist with regard to advising the post-meniscectomy patient contemplating a return to recreational running? Current literature related to meniscal structure and function, etiology and definition of osteoarthritis, methods for assessing osteoarthritis, relationship between running and osteoarthritis, and relationship between meniscectomy and osteoarthritis are reviewed. This review finds that while the probability for early osteoarthritis in the post-meniscectomy population is substantial, it is a probability and not a certainty. To help guide a physical therapist with regard to advising the patient for a safe return to running following a meniscectomy, a qualitative risk assessment based on identified risk factors for osteoarthritis in both the running and the post-meniscectomy populations is proposed.

[Congenital absence of the anterior cruciate ligament: eight cases in the same family]

PURPOSE OF THE STUDY

The purpose of this work was to present a descriptive analysis of eight cases of congenital agenesia of the anterior cruciate ligament (ACL). Congenital absence of the ACL is rare. The few series reported in the literature have been limited to sporadic cases all associated with diverse malformations. We report a series of eight cases knees in five patients presenting congenital knee laxity. These patients were all members of the same family, raising the question of an inherited condition. We describe the characteristic features and natural history of ACL agenesia compared with post-traumatic loss of the ACL.

MATERIAL

This descriptive study included five patients (eight knees) with agenesia of the ACL. There were four men and one woman, mean age 46 years. All five patients had a common ancestor.

RESULTS

The main symptom was medial femorotibial and patellofemoral pain, present in all patients. Physical examination revealed major anterior laxity (positive pivot test, Trillat Lachman test) involving the posterior capsule and ligament structures and an abnormal knob on the anterior tibial tubercle. Plain x-rays demonstrated an abnormal aspect of the tibial spines, suggestive of ACL agenesia. The spines were flat in three knees, smooth in three, and dome shaped in two. On the lateral view, the femoral condyles presented an abnormal rounded posterior curvature in all of the affected knees. The tibial slope was increased in all knees, 20.6 degrees on average. MRI and arthroscopy confirmed the diagnosis in three knees.

DISCUSSION

Examining our cases and the data in the literature led to the following remarks. The family pedigree in our patients suggested autosomal dominant inheritance. Episodes of serious laxity are rare in subjects with congenital absence of the ACL compared with posttrauma patients, probably due to adaptation since infancy. Hypoplasia of the tibial spine and the lateral femoral condyle are characteristic consequences of ACL agenesia. In comparison with posttrauma cases, the natural history of ACL agenesia is characterized by better functional tolerance and inevitable progression to osteoarthritis due to the permanent anterior laxity. Degenerative disease may develop late and more slowly than after traumatic injury of the ACL. Unlike common arthrosis, the lateral femorotibial and patellofemoral compartments are preserved longer.

CONCLUSION

Though rare, congenital absence of the ACL should be evoked as a possibility in patients with chronic anterior laxity without trauma. The radiological aspect is highly suggestive of the diagnosis which can be confirmed by MRI or arthroscopy. Study of the present series enabled a description of the natural history of ACL agenesia, which is different from that of traumatic ACL tears because of the lack of secondary meniscal lesions and the later progression of osteoarthritic degeneration.

An arthroscopic analysis of lateral meniscal variants and a comparison with MRI findings

We reviewed 164 consecutive cases (158 patients) of arthroscopic examinations for lateral meniscal variants during the last 10 years. We classified lateral meniscal variants into four types by arthroscopic appearance, into six tear patterns by modifying O'Connor's classification, and compared magnetic resonance images (MRI) with arthroscopic findings. Regarding the four types, 131 cases were complete, 25 cases were incomplete, 4 cases were Wrisberg, and 4 cases were ring-shaped meniscus. The six tear patterns were as follows: 33 simple horizontal, 21 combined horizontal, 37 longitudinal, 27 central, 14 complex, and 12 radial tear. Among the 31 knees with a central tear or ring-shaped meniscus, we reviewed 25 MR images. Fifteen (60%) MRI findings were interpreted to represent a bucket-handle (displaced) tear of the normal C-shaped meniscus; 7(28%) MRI findings, a discoid meniscal tear; and the remaining 3(12%) MRI findings, a simple meniscal tear. Moreover, all ring-shaped menisci were interpreted as a displaced lateral meniscal tear on the MRI findings. Twelve patients (13 knees, 7.9%) had osteochondritis dissecans: Nine patients (10 knees) of them had a central tear, two patients (2 knees) of them had a simple horizontal tear of the discoid meniscus, and one patient (1 knee) had a ring-shaped meniscus. Twenty three patients (92.6%) with a central tear of the discoid meniscus did not have any traumatic events. For the differential diagnosis of a central tear or a ring-shaped meniscus from a bucket-handle tear of the normal C-shaped meniscus, we should take a careful history, in particular any traumatic events, we should also consider the possibility of misinterpreting the MR images though these images can provide additional information about associated abnormalities and probe carefully in the arthroscopic operations.

Knee reconstruction in syndromes with congenital absence of the anterior cruciate ligament

The authors review their experience with four patients with congenital deficiency of the anterior cruciate ligament (ACL) who underwent surgical treatment of symptomatic knee instability at a mean age of 15.8 years (range 14-17 years). Associated syndromes included fibular hemimelia, congenital short femur, and an unspecified skeletal dysplasia. All patients had undergone multiple previous realignment and leg lengthening procedures and were skeletally mature at the time of the reconstruction. All four patients underwent ACL reconstruction, and one patient underwent concomitant posterolateral corner reconstruction. One patient required an osteochondral autograft transplant procedure in addition to ACL reconstruction. Hypertrophy of the meniscofemoral ligament of Humphrey was a consistent anatomic finding at surgery. The patients were followed for a mean of 38 months (range 26-58 months) after the reconstruction. The mean preoperative Lysholm II score was 38 (range 28-56); the score had improved to a mean of 81 (range 78-93) at the latest follow-up. The authors conclude that reconstructive surgery is a viable option for restoration of knee stability and function in appropriately selected patients with congenital ACL deficiency.

The prevalence of soft tissue injuries in nonoperative tibial plateau fractures as determined by magnetic resonance imaging

OBJECTIVE

To determine the incidence of meniscus tears and complete ligament disruption in nondisplaced and minimally displaced tibial plateau fractures, which are otherwise amenable to nonoperative management.

DESIGN

Prospective clinical study.

SETTING

Level I urban trauma center.

INTERVENTION

Magnetic resonance imaging of 20 consecutive nonoperative tibial plateau fractures.

RESULTS

Magnetic resonance imaging was performed on 20 consecutive nonoperative (nondisplaced or minimally displaced) tibial plateau fractures to determine the frequency of significant soft tissue injuries. Ninety percent (18 of 20) had magnetic resonance imaging-diagnosed significant injuries to the soft tissues, including 80% (16 of 20) with meniscal tears, and 40% (8 of 20) with complete ligament disruptions.

CONCLUSIONS

This study found a high prevalence of soft tissue injuries with nondisplaced fractures of the tibial plateau and cautions the physician and patient with respect to future knee function and possible arthrosis.

Observation of anomalous insertion of the medial meniscus on the anterior cruciate ligament

We wanted to determine the frequency of occurrence and types of anomalous insertions of the medial meniscus to the anterior cruciate ligament (ACL) in Finnish patients. In 987 consecutive arthroscopies from January 1996 to August 1998, the meniscal pathology was mapped using videoprints and drawings. We found 11 anomalous medial meniscus insertions to the ACL. There were 4 female and 6 male patients in the series. In 1 woman, the anomaly was bilateral. The mean age of the patients was 30.6 years (range 14 to 63 years). The anomalous band was excised in all patients. The anomaly usually was not the finding that caused the need for arthroscopy. In 3 knees, the anomaly was the only pathologic finding. The frequency of this anomaly occurring was approximately 1.2%. The anomalous medial meniscus insertion to the ACL is a very rare clinical finding. Arthroscopic surgeons should be aware of its existence as well as of other anterior horn insertion variations of the medial meniscus.

Symptomatic ring-shaped lateral meniscus

Abnormalities of the lateral meniscus in humans are a long-known fact. Three different types of discoid menisci are described in Watanabe's atlas, being considered as congenital malformations. For the second time in the literature, a fourth ring-shaped type of discoid lateral meniscus was described as an incidental finding in this Journal by Monllau et al. in 1998. The present case is the first description of a symptomatic, ring-shaped lateral meniscus with a concomitant, recurrent cyst at the lateral aspect of a child's knee.

Abnormal band of the lateral meniscus of the knee

We report 2 cases of an abnormal band of the lateral meniscus of the knee joint. A 23-year-old man complained of mechanical symptoms in both knees and an arthroscopic procedure was performed. We found meniscal abnormalities in the both knees. A 20-year-old man sustained a posterior cruciate ligament injury. In the course of an arthroscopy for his torn posterior cruciate ligament, an abnormal band of the lateral meniscus was seen. It was characteristic that the upper abnormal band was loose and serpentine and connected at the posterior horn and the middle segment of the lower normal lateral meniscus. Arthroscopic resection of abnormal bands successfully eliminated the symptoms. Because of its characteristic appearance and bilaterality, it was evident that this abnormal band was a congenital anomaly.

Nitric oxide production and apoptosis in cells of the meniscus during experimental osteoarthritis

OBJECTIVE

To examine the pathologic changes in meniscus tissue during experimental osteoarthritis (OA) and to determine the relationship between nitric oxide (NO) synthesis, apoptosis, and meniscus degradation.

METHODS

OA was induced in rabbits by anterior cruciate ligament (ACL) transection. Knees were harvested after 9 weeks and assessed for OA severity. Menisci were subjected to histologic, immunohistochemical, and electron microscopic analyses for the presence of nitrotyrosine and apoptosis. Menisci were also cultured for analysis of NO production.

RESULTS

All menisci from joints with ACL transection demonstrated degenerative changes. A high number of apoptotic cells was present in the medial part of menisci, which contains chondrocytic cells. Menisci from nonoperated contralateral knees contained only small numbers of cells in apoptosis. Conditioned media from meniscus cultures contained similarly elevated levels of nitrite as cartilage cultures from the same arthritic knees. Nitrotyrosine immunoreactivity, an indicator of in vivo NO production, was prominent in menisci from knees with ACL transection. In addition, menisci from normal knees produced high levels of NO in response to in vitro stimulation with interleukin-1beta or lipopolysaccharide.

CONCLUSION

These observations suggest that pathologic changes in menisci are a regular feature of experimentally induced OA and are associated with NO production and meniscus cell apoptosis.

Intraarticular anatomic variants associated with discoid meniscus in Koreans

From July 1990 through June 1994, 106 knees (102 patients) were treated for discoid meniscus. Fifteen knees (15 patients) were associated with other intraarticular anatomic variants. There were eight knees (8 patients) with anomalous insertion of the anterior horn of the medial meniscus into the anterior cruciate ligament, and seven knees (7 patients) with anterior expansion of the anterior portion of the anterior cruciate ligament below the anterior tibial margin. Among the latter, one patient also had anterior transposition of the anterior insertion of the medial meniscus, while obliteration of the popliteal hiatus was seen in another patient. The discoid menisci were reshaped in 13 knees (13 patients), totally resected in one knee, and in one patient the discoid meniscus was treated with repair of a peripheral tear and reshaping. Followup ranged from 24 to 54 months (average, 37 months) after surgery. The results were excellent in eight knees, good in five knees, and fair in two knees as graded using the Ikeuchi scale. These anatomic variants, other than the discoid meniscus, did not seem to be related to the patient's symptoms.

Arthroscopic studies of variants of the anterior horn of the medical meniscus

The objective of this study was to arthroscopically analyse the morphology and dynamics of variants of the anterior horn of the medial meniscus of the knee (VAMM) and to then consider the pathological significance of these variants. VAMM was defined as knees in which the anterior horn of the medial meniscus is not attached to the tibia. Between April 1992 and March 1995, arthroscopy was performed on 953 knees of 903 patients. At the time of this examination, observation and probing were performed to determine the condition of the synovium, the synovial plica, the cartilage in all compartments, the meniscus, the cruciate ligaments, and the popliteal tendon. In particular, detailed examination was made of the anterior horn of the medial meniscus with regard to the point of insertion to the tibia and the degree of movement in knee flexion/ extension. Cases of VAMM diagnosed on the basis of the arthroscopic findings were classified into the following four categories: the ACL (anterior cruciate ligament) type, where the anterior horn of the medial meniscus was attached to the ACL; the transverse ligament type, where the anterior horn of the medial meniscus was attached to the transverse ligament; the coronary ligament type, where the anterior horn of the medial meniscus was attached to the coronary ligament; and the infrapatellar fold type, where the anterior horn of the medial meniscus was attached to the infrapatellar synovial fold. These patients were then analyzed with regard to the arthroscopic findings and the intra-articular lesions other than VAMM. In 98 (10.9%) of the total patients, 103 knees were classified as VAMM. Classification of those 103 knees using the above criteria showed 39 ACL type knees, 51 transverse ligament type knees, 11 coronary ligament type knees, and 2 infrapatellar fold type knees. The arthroscopic findings indicated that the anterior horn of the medial meniscus was not attached directly to the tibia in any of these knees. Probing and flexion/extension of the knee revealed hypermobility at the anterior horn of the medial meniscus. In this study, anterior knee pain syndrome was diagnosed in 12 (11.7%) of the 103 VAMM knees. In addition, there was no clear history of trauma in 20 of 23 knees found to have an isolated medial meniscus tear. In these cases, even detailed arthroscopic observation proved the causes of the symptoms or injury. On the basis of these findings, we surmised that the anterior portion shows hypermobility at the time of flexion/extension of the knee, regardless of the type of VAMM. In this study, we discussed the possibility that the existence of VAMM may become the cause of pain or injury to the meniscus.

The anterior cruciate ligament

Our knowledge of the anterior cruciate ligament has expanded rapidly over the last decade. Recent advances in arthroscopic techniques, the development and release of synthetic stents and prostheses, increasing laboratory and clinical data involving allograft implantation, and biomechanical research in knee rehabilitation have led to a bewildering array of choices for treatment of anterior cruciate ligament deficiency. As new information and techniques are presented, and new synthetic and biological materials become available, orthopedic surgeons must judge their value and modify treatment recommendations accordingly. A thorough knowledge of the basic science and clinical information is necessary to appropriately evaluate these new advances. A review of our current knowledge of the anterior cruciate ligament is presented to facilitate this evaluation process.