Summary

The purpose of this systematic review is to review current literature for joint-specific and global lower extremity testing to determine the most valid functional test that can be utilized to reduce the risk of re-injury as athletes return to sport (RTS).

Abstract

Introduction

Lower extremity injuries account for a significant portion of sports medicine cases in the United States each year; anterior cruciate ligament (ACL) injuries alone account for greater than 50% of all knee injuries affecting over 200,000 people per year in the United States. Unfortunately, even after a lengthy recovery process, athletes who recover from injury are at an increased risk for subsequent injuries. A portion of this high re-injury rate is likely due to the lack of a standardized criterion for return to sport (RTS) testing to safely guide the return of athletes to play after a lower extremity injury. There has been research and debate over whether hop testing with limb symmetry index (LSI) is valid to warrant clearance for RTS in the ACL population, but no test battery has been officially agreed upon. The gold standard for strength testing is considered to be isokinetic dynamometry. However, due to the expense with these machines, they are typically only found in research settings. Some hop tests have been suggested, but there is no validated test battery to date.

Methods

A systematic search of PubMed, PubMed Central, Cochrane Library, OVID, and Embase databases was conducted to identify clinical studies that included evaluation of a return to sport test or functional test for the lower extremities. Both operative and non-operative treatments were included in this review.

Results

Of 8,705 studies, 65 (0.7%) studies published through October of 2021 met inclusion criteria and were analyzed. Eighty percent (52/65) of articles discussed RTS for the knee. Furthermore, 96 % (50/52) specifically analyzed RTS following ACLR. The most common RTS test was isokinetic dynamometry testing which is seen in 73% (38/52) of studies. Unfortunately, only 6.2% (4/65) studies analyzed RTS for the hip and only one study looked at ankle RTS. The remaining studies analyzed healthy participants only.

Conclusion

More research is clearly required to identify the most valid functional test batteries for joint-specific RTS lower extremity testing. Even with the enormous amount of literature that exists regarding ACL injuries and testing there is no standardized criterion for RTS clearance. As seen in this review, the research available for the hip and ankle RTS is severely lacking. We hope that the suggested test batteries from this review can serve as a framework for future research and validation for joint-specific RTS functional testing.