Functional outcome following quadriceps tendon lengthening in congenital dislocation of the knee, with special reference to extensor weakness.

This study reports the incidence and proposes a probable cause of flexion deformity and extensor weakness following lengthening of quadriceps tendon for the congenital dislocation of the knee and also proposes a modification of the functional grading given in the literature to this effect. Seventeen knees in ten patients were treated with a follow-up from 3 to 8 years. Fifteen knees were grade III and were operated with quadriceps lengthening and anterior capsulotomy. Two knees were Grade II and were initially closed reduced, but operated later due to recurrence. The results were graded on a modification of functional grading system given in the literature [1]. There were excellent results in four, good in five and fair in eight knees. There was an extensor weakness in ten knees (average 12.2°) and flexion deformity (15°) in one. Eight patients could squat and all started walking independently by 10-20 months of age, except one. V-lengthening of the quadriceps tendon produced a satisfactory improvement in the knee function. The theoretical role of the gastrocnemius and hamstring muscles in abetting flexion deformity and extensor weakness is suggested.