Working Diagnosis:
Congenital absence of the bilateral anterior and posterior cruciate ligaments.

Treatment:
Due to the failure of conservative measures, including extensive physical therapy, severity of her clinical symptoms, and functional limitations, surgical reconstruction of the ACL and PCL was deemed necessary. The reconstruction procedure started with the right knee in October. The surgery consisted of an arthroscopic exam notable for a macerated medial meniscus, preserved cartilage, complete absence of an intercondylar notch with hypoplastic tibial eminences, and complete absence of an ACL and PCL Case Photo #6 . A notchplasty was performed to recreate an intercondylar notch Case Photo #7 , using the intact meniscofemoral ligament as a guide to determine the desired notch width. ACL reconstruction was performed using an anterior tibialis allograft, and an all-inside PCL reconstruction was performed using a quadrupled hamstring allograft. The ACL and PCL were fixated on the femur and tibia with suspensory fixation Case Photo #8 .

Outcome:
Post-operatively, the patient was advised to use crutches with 50% weight bearing and to gradually increase activities while wearing a knee brace. She started physical therapy afterward, with follow-up appointments at 2 weeks, 6 weeks, and 3 months. At her 6-week appointment, she was walking with minimal assistance, reported major improvements in stability and knee pain, exhibited a range of motion from 0 to 80 degrees, and showed stable results on the Lachman and posterior drawer tests.

Author's Comments:
The case of congenital ACL and PCL absence in a teenager highlights the need for early diagnosis and intervention for rare ligament abnormalities. This condition affects knee stability, but timely surgical reconstruction can enhance outcomes. Clinicians should consider ligament agenesis in cases of unexplained knee instability, particularly with congenital anomalies. Further research is needed to examine genetic factors and improve treatment and long-term outcomes.

Editor's Comments:
This case exemplifies the critical importance of recognizing congenital cruciate ligament agenesis in adolescents presenting with unexplained knee instability, particularly when associated with underlying skeletal anomalies. Congenital absence of the ACL and PCL is an exceptionally rare disorder with a prevalence of approximately 1.7 per 100,000 live births, though it may be underdiagnosed in asymptomatic individuals. Diagnosis requires high clinical suspicion, as patients often present with chronic knee pain and subjective instability rather than acute traumatic injury. Radiographic hallmarks include absence of the femoral intercondylar notch, hypoplastic or absent tibial eminences, and trochlear dysplasia, which can be identified on plain radiographs and confirmed with MRI. The Manner classification system categorizes cruciate dysplasia into three types, with Type III representing complete absence of both ligaments and corresponding bony landmarks (as in this case). Genetic factors play an important role, as evidenced by familial cases and identification of copy number variations in the CEP57L1 gene associated with autosomal dominant transmission. The condition frequently coexists with other congenital anomalies including multiple synostosis syndrome, as seen in this patient.
Management strategies range from physical therapy for minimally symptomatic patients to surgical reconstruction for those with functional limitations. Surgical reconstruction includes notchplasty to recreate the intercondylar notch, followed by ACL and PCL reconstruction using allograft or autograft tissue. Although optimal timing of reconstruction remains unclear, early outcomes demonstrating improved stability and functional scores in reconstructed patients along with the condition’s association with meniscal injury and early osteoarthritis, support early surgical intervention. However, even with reconstruction, long-term prognosis remains guarded, as the literature suggests eventual knee arthroplasty may be inevitable. This case highlights the need for early diagnosis, individualized surgical decision-making, genetic counseling, and sensitive longitudinal care for patients with this life-altering condition.

References:
Berruto M, Gala L, Usellini E, Duci D, Marelli B. Congenital absence of the cruciate ligaments. Knee Surg Sports Traumatol Arthrosc. 2012;20(8):1622-1625. doi:10.1007/s00167-011-1816-2

Garcia N, Debandi A, Delgado G, et al. Isolated posterior cruciate ligament aplasia: a case report. Skeletal Radiol. 2019;48(9):1439-1442. doi: 10.1007/s00256-019-3161-3.

Gavvala SN, Giliyaru S, Ariyaratne S, et al. Congenital absence of anterior and posterior cruciate ligaments – A rare case report and review of literature. J Arthrosc Surg Sports Med. 2024;5(1):38-40. doi:10.25259/JASSM_3_2024

LaPrade CM, Civitarese DM, Rasmussen MT, LaPrade RF. Emerging Updates on the Posterior Cruciate Ligament: A Review of the Current Literature. Am J Sports Med. 2015;43(12):3077-3092. doi:10.1177/0363546515572770

Liu Y, Li Y, March ME, et al. Copy number variation in CEP57L1 predisposes to congenital absence of bilateral ACL and PCL ligaments. Hum Genomics. 2015;9:31. Published 2015 Nov 11. doi:10.1186/s40246-015-0053-z

Manner HM, Radler C, Ganger R, Grill F. Dysplasia of the cruciate ligaments: radiographic assessment and classification. J Bone Joint Surg Am. 2006;88(1):130-137. doi:10.2106/JBJS.E.00146

Sachleben B, Nasreddine A, Nepple J, Tepolt F, Kasser J, Kocher M. Reconstruction of Symptomatic Congenital Anterior Cruciate Ligament Insufficiency. Journal of Pediatric Orthopaedics. 2019; 39 (2): 59-64. doi: 10.1097/BPO.0000000000000940.

Waghe VR, Tikhile P, Patil DS. The integral role of physiotherapy in combined complete anterior cruciate ligament and posterior cruciate ligament arthroscopic reconstruction: a case report. Cureus. 2024;16(4):e57556. doi: 10.7759/cureus.57556.

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