Avulsion of the tibial tuberosity: muscles too strong for a growth plate.

PURPOSE: To ascertain whether there were significant knee extension strength differences between two adolescent male gymnasts (patient 1: age, 14.5 years; height, 159.3 cm; weight, 52.2 kg; patient 2: age, 15 years; height, 160.6 cm; weight, 54.8 kg) with avulsion of the tibial tuberosity associated with avulsion of the patellar tendon.

CASE SUMMARY: Two adolescent male gymnasts underwent open reduction and internal fixation for avulsion of the tibial tuberosity associated with avulsion of the patellar tendon. Isometric extension strength of the contralateral uninjured knee and of the operated knee was significantly greater than for nonathletic adolescents of the same age (one-way analysis of variance [ANOVA], p = 0.001), and was at a higher part of normal strength than their gymnastic peers.

DISCUSSION: A maximal contraction of the quadriceps is able to overcome the strength of the upper tibial epiphysis disrupting the extensor mechanism of the knee.

RELEVANCE: Greater-than-usual strength, although normally of no undesired consequence, may play a role in avulsion injuries of major muscles.