Effect of Quadriceps and Hamstring Strength Relative to Body Weight on Risk of a Second ACL Injury: A Cohort Study of 835 Patients Who Returned to Sport After ACL Reconstruction.

Background: Anterior cruciate ligament (ACL) injuries are common sports-related injuries with a high risk of reinjury after return to sport (RTS). Rehabilitation aims to regain symmetrical knee strength and function to minimize the risk of a second ACL injury after RTS. Purpose: To determine the effect of absolute quadriceps and hamstring strength, normalized by body weight, on the risk of a second ACL injury during the first 2 years after RTS in patients who have undergone ACL reconstruction (ACLR). Study Design: Cohort study; Level of evidence, 3. Methods: Data from patients after index ACLR at the time of RTS were extracted from a rehabilitation registry-Project ACL. Patients who had performed isokinetic tests for quadriceps and hamstring strength and hop tests before RTS were included. The endpoint was a second ACL injury or a follow-up of 2 years after RTS after ACLR. Results: A total of 835 patients (46% women), with a mean age of 23.9 ± 7.7 years, were included. During the study period, 69 (8.3%) second ACL injuries (ipsilateral and contralateral) occurred. Greater relative quadriceps strength in the injured leg increased the risk of a second ACL injury (relative risk [RR], 1.69 [95% CI, 1.05-2.74]; P = .032). In patients who had recovered symmetrical quadriceps strength (limb symmetry index ≥90%), there was no effect of quadriceps strength on the risk of second ACL injury (RR, 1.33 [95% CI, 0.69-2.56]; P = .39). Quadriceps strength on the healthy side or hamstring strength, regardless of side, had no effect on the risk of a second ACL injury. Conclusion: Greater relative quadriceps strength in the injured leg at the time of RTS after ACLR was associated with an increased risk of a second ACL injury. There was no effect of relative quadriceps strength on the risk of a second ACL injury in patients who had recovered symmetrical quadriceps strength.

Persistent knee flexor strength deficits identified through the NordBord eccentric test not seen with "gold standard" isokinetic concentric testing during the first year after anterior cruciate ligament reconstruction with a hamstring tendon autograft.

OBJECTIVE: To investigate the recovery of knee flexor muscle strength evaluated with a Nordic hamstring eccentric test (NordBord) compared with an isokinetic concentric test (Biodex) during the first year after anterior cruciate ligament (ACL) reconstruction using a hamstring tendon autograft. DESIGN: Prospective observational registry study; level of evidence, 3. SETTING: Primary care. PARTICIPANTS: Cross-sectional data of 127 patients (45% women, mean age 24.9 ± 8.1 years) were extracted from a rehabilitation outcome registry at 10 weeks and 4, 8 and 12 months after ACL reconstruction with hamstring tendon autograft. MAIN OUTCOME MEASURES: All patients performed a concentric Biodex test, and an eccentric NordBord test on the same occasion or within seven days of the concentric test. The primary outcome was the limb symmetry index between the respective tests. RESULTS: A greater knee flexor symmetry deficit was observed with the eccentric test compared with the concentric test at all follow-ups with clinically relevant differences at 4 (11.8% ± 12.7% [CI 7.8-15.8%]) and 8 months (13.4 ± 11.9 [CI 9.7-17.2%]. CONCLUSION: The eccentric NordBord test was able to identify clinically relevant deficits in knee flexor strength symmetry that were not identified by gold standard isokinetic concentric testing during the first year among patients treated with an ACL reconstruction using a hamstring tendon autograft.

Psychological impairments after ACL injury - Do we know what we are addressing? Experiences from sports physical therapists.

Psychological impairments can follow an anterior cruciate ligament (ACL) injury and can impact the rehabilitation process. Our aim was to investigate experiences of sports physical therapists (PTs) in addressing psychological impairments in patients after ACL injury. We conducted four focus group interviews with fourteen sports PTs. The PTs' experiences of working with psychological impairments after ACL injury were summarized in four main categories: (1) "Calling for a guiding light", where PTs stated that the most common method of acquiring knowledge on addressing psychological impairments was through discussions with colleagues, and, at the same time, PTs expressed an insufficient knowledge of how to address psychological impairments; (2) "Meeting the burden of psychological impairments" where PTs stated that psychological impairments are greater than physical; (3) "Trying to balance physical and psychological aspects" where patient education and assessments were reported to be important in order to understand psychological impairments during rehabilitation; and (4) "Goal setting: a helpful challenge" where sports PTs expressed a need for specific knowledge of the rehabilitation of psychological impairments following ACL injury. To help provide the current best practice, we encourage researchers to develop psychologically centered interventions for rehabilitation after an ACL injury, and PTs to stay up-to-date with the literature published on the subject, including to implement eventual interventions.

The mechanism of hamstring injuries - a systematic review.

BACKGROUND: Injuries to the hamstring muscles are among the most common in sports and account for significant time loss. Despite being so common, the injury mechanism of hamstring injuries remains to be determined. PURPOSE: To investigate the hamstring injury mechanism by conducting a systematic review. STUDY DESIGN: A systematic review following the PRISMA statement. METHODS: A systematic search was conducted using PubMed, EMBASE and the Cochrane Library. Studies 1) written in English and 2) deciding on the mechanism of hamstring injury were eligible for inclusion. Literature reviews, systematic reviews, meta-analyses, conference abstracts, book chapters and editorials were excluded, as well as studies where the full text could not be obtained. RESULTS: Twenty-six of 2372 screened original studies were included and stratified to the mechanism or methods used to determine hamstring injury: stretch-related injuries, kinematic analysis, electromyography-based kinematic analysis and strength-related injuries. All studies that reported the stretch-type injury mechanism concluded that injury occurs due to extensive hip flexion with a hyperextended knee. The vast majority of studies on injuries during running proposed that these injuries occur during the late swing phase of the running gait cycle. CONCLUSION: A stretch-type injury to the hamstrings is caused by extensive hip flexion with an extended knee. Hamstring injuries during sprinting are most likely to occur due to excessive muscle strain caused by eccentric contraction during the late swing phase of the running gait cycle. LEVEL OF EVIDENCE: Level IV.