Variability in leg muscle power and hop performance after anterior cruciate ligament reconstruction

The purpose of this prospective study was to describe the variability in leg muscle power and hop performance up to 2 years among patients following ACL reconstruction and specifically to illustrate the effects of various criteria for an acceptable level of muscle function. Eighty-two patients (56 men and 26 women) with a mean age of 28 years, who underwent ACL reconstruction using either hamstring tendons ( = 46) or a patellar tendon ( = 36), were assessed pre-operatively and 3, 6, 12 and 24 months post-surgery with a battery of three lower extremity muscle power tests and a battery of three hop tests. Leg symmetry index (LSI) values at group level ranged between 73 and 100% at all follow-ups. When the tests were evaluated individually, patients reached an average LSI of a parts per thousand yen90% at 24 months. The success rate at 24 months for the muscle power test battery, that is, patients with an LSI of a parts per thousand yen90% in tests, was 48 and 44% for the hop test battery. The success rate at 24 months for both test batteries on was 22%. The criterion of an LSI of a parts per thousand yen80% resulted in 53% of the patients having an acceptable level on all six tests, while with a criterion of an LSI of a parts per thousand yen100%, none of the patients reached an acceptable level. At group level and in single muscle function tests, the muscle function outcome 1 and 2 years after ACL reconstruction is satisfactory in the present study and on a par with the results presented in the literature. However, when using more demanding criteria for a successful muscle function outcome, using batteries of tests or increasing the acceptable LSI level from a parts per thousand yen90% to a parts per thousand yen95% or a parts per thousand yen100%, the results are considered to be poor. It is suggested that this should be taken into consideration when presenting results after ACL rehabilitation, deciding on the criteria for a safe return to sports, or designing rehabilitation programmes after ACL reconstruction. Prognostic prospective cohort study, Level I.