A rare case of heritable congenital tibio-femoral subluxation in a mother and child

Himanshu Sharma and J Robertson

Abstract

We report an interesting case of a mother and son with heritable congenital tibiofemoral subluxation, which is very similar to congenital genu recurvatum, but should be considered as a separate entity.

Keywords: Congenital genu recurvatum, Heritable congenital tibio-femoral subluxation, Knee joint.

Introduction

Congenital genu recurvatum is defined as hyperextension of the knee present since birth. It can be categorised into three pathologic variants: hyperextension of the knee, anterior subluxation of the tibia, and anterior dislocation of the tibia [1].

Heritable congenital tibiofemoral subluxation is characterised by mild hyperextension, normal quadriceps and normal range of knee flexion with a strong familial linkage [2]. We report the case of a mother and son incidentally discovered with heritable congenital tibiofemoral subluxation.

Case Report

A 70-year-old lady presented with right knee deformity since birth. She had been asymptomatic till now, although she developed primary degenerative osteoarthritis in the contralateral knee. There was no past history of trauma to the right knee. There were no other associated congenital deformities. Past medical history, drug and family history was insignificant. On knee examination, she had mild recurvatum. There was no skin callus with normal quadriceps. The range of movement was from -25 degrees to 100 degrees. The lateral radiographs of the right knee revealed mild tibiofemoral subluxation with posterior tibial beaking and overlapping tibiofemoral condylar shadow in anteroposterior radiograph (Figure 1A and 1B).

Figure 1A	Figure 1B
Lateral and anteroposterior radiograph of the right knee of the mother

Her son, now aged 50, was born with a congenitally deformed left knee. His back knee deformity was only discovered incidentally when he accompanied his mother to the orthopaedic clinic. He was clinically asymptomatic. Again there was no history of trauma to the knee and his past medical history, drug and family history were all insignificant. There were no other congenital deformities found on examination. Physical examination revealed mild genu recurvatum of the left knee without any skin callosity, no quadriceps wasting with range of movements varied from -30 degrees to 110 degrees. The lateral radiographs of the left knee again revealed tibiofemoral subluxation with posterior tibial beaking and overlapping condylar shadows in anteroposterior radiograph (Figure 2A and 2B).

Figure 2A	Figure 2B
Lateral and anteroposterior radiograph of the left knee of the son

Discussion

Congenital genu recurvatum, also known as back knee deformity, is categorised into three pathological variants: hyperextension of the knee, anterior subluxation of the tibia and anterior dislocation of the tibia. Heritable congenital tibiofemoral subluxation is a very similar, but distinct entity. It is characterised by mild hyperextension, normal quadriceps, and normal range of knee flexion with a strong familial linkage [1,2].

The aetiology of heritable congenital tibiofemoral subluxation has been postulated to be multifactorial. The various theories include genetic, environmental, mechanical, endocrinal, mesenchymal and teratogenic. The associated abnormalities are congenital talipes equinovarus, congenital dislocation of the hip, dislocation of the elbow, spina bifida, hydrocephalus, imperforate anus, facial palsy, cryptorchidism, scoliosis, torticollis, angiomata, strabismus and absent patella. Ehlers-Danlos syndrome, Larsen's syndrome, arthrogryposis multiplex congenita may have coexisting congenital genu recurvatum [3]. It has been found that females, breech presentation, oligohydramnios, foetal malposition, quadriceps fibrosis and hypoplastic distal femoral condyle all predispose patients to this condition [4,5].

The treatment options include conservative management in the form of serial casting, manipulation and traction in the paediatric age group. The aim of surgical treatment is to obtain a stable, straight limb that permits ambulation. This can be achieved through soft tissue release and quadricepsplasty. The osteotomy of the distal part of the femur and/or arthrodesis of the knee has been tried in recalcitrant cases [2,3,6]. In the reported case, the deformity was of mild degree and did not cause any long term functional disability.

This case highlights the difference between congenital genu recurvatum and congenital heritable tibiofemoral subluxation, which have a variable effect on the course and prognosis. Interestingly in this case, we were able to detect the deformity in mother and son who had this deformity for between five and seven decades without any significant sequelae.

References

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2. Curtis BH, Fisher RL. Heritable congenital tibiofemoral subluxation. Clinical features and surgical treatment. J Bone Joint Surg Am. 1970 Sep; 52(6):1104-14.

3. Dungy CI, Leupp M. Congenital hyperextension of the knees in twins. Clin Pediatr (Phila) 1984 Mar; 23(3):169-72.

4. Laurence M. Genu recurvatum congenitum. J Bone Joint Surg Br 1967 Feb; 49B:121-35.

5. Charif P, Reichelderfer TE. Genu recurvatum congenitum in the newborn: its incidence,course, treatment, prognosis. Clin Peditr 1965 Oct 4(10):587-94.

6. Powell HDW. Genu recurvatum congenitum. Proc R Soc Med. 1971Jul; 64(7):714-5.