Twenty-five years after ACL reconstruction, patients were playing more sport than controls

Most of what is known about anterior cruciate ligament reconstruction ends at two years. Return-to-sport rates, graft failure rates and patient-reported knee scores are almost all reported inside that window, because that is how long trial funding and patient follow-up usually last. A prospective cohort published on 22 October reports the same patients at 25 years [s1].

The headline number is counterintuitive. At 25 years after surgery, the reconstructed group was participating in sport at higher levels than uninjured, matched controls (P = .005) and over longer periods (P = .032) [s1].

The cohort

Sixty-two people underwent ACL reconstruction — 44 males, mean age 27 years — split evenly between bone-patellar tendon-bone grafting (31) and semitendinosus/gracilis grafting (31) [s1]. Thirty uninjured individuals matched for age, sex and sporting activity served as controls [s1]. Sporting activity was scored on a six-point scale based on pivoting demands, assessed pre-injury, at six years and at 25 years [s1].

At 25 years, 50 of the 62 reconstructed patients (81%) and 20 of the 30 controls (67%) were available for follow-up [s1].

Of the reconstructed group, 88% were still active in sport, and 22% were playing vigorous pivoting sports [s1]. Three had undergone total knee replacement, nine had ruptured the contralateral ACL, and eight had ruptured their graft [s1].

Graft type did not separate

The patellar tendon versus hamstring tendon question has occupied ACL surgery for decades. In this cohort it produced nothing. There was no significant difference between graft types in the level of sport played before surgery (P = .442), at six years (P = .511), or at 25 years (P = .100) [s1].

That is a null result in a small sample, not proof of equivalence — 31 per arm cannot exclude a modest difference. But it is a null result measured over the longest horizon anyone has reported, and it is consistent with the direction the graft-choice literature has been drifting.

The control-group problem

The finding that reconstructed patients out-participated uninjured controls is the part that needs the most care.

The most likely explanation is not that ACL surgery improves athletic longevity. It is selection. People who tear an ACL in a pivoting sport at a mean age of 27, and who then commit to a year of rehabilitation to get back to it, are by construction a group with unusually high sporting motivation. The matched controls were matched on sporting activity at baseline, but not on the disposition that produces a mid-twenties ACL rupture in the first place.

The differential follow-up rate compounds this. Eighty-one percent of the surgical group was traced at 25 years against 67% of controls [s1]. Surgical patients stay in touch with the clinic that operated on them; healthy volunteers drift away, and the ones who drift are plausibly the ones who stopped playing.

The authors report the comparison as observed. Readers should treat "ACL reconstruction patients play longer" as a description of this cohort rather than a causal claim about surgery.

What the injury counts say

The interesting durability signal is in the injury tally rather than the participation score. Across 50 followed patients there were nine contralateral ACL ruptures and eight graft ruptures [s1] — roughly a third of the cohort sustained a second ACL injury on one side or the other over 25 years. Three knees ended in total replacement [s1].

Sustained sport participation and accumulating knee pathology are not alternatives here. Both happened in the same people.

A parallel argument about mechanism

A brief review published on 13 October makes a claim that reframes what a cohort like this is measuring [s2]. It argues that hamstring strain and ACL injuries — conventionally classified as acute — may at least partly be overuse injuries resulting from mechanical fatigue [s2].

The evidence assembled is indirect but consistent. Human studies show no kinematic deviation in the stride during which a hamstring injury occurs compared with the preceding strides [s2]. The location and ultrastructural damage of hamstring injuries resembles what repetitive muscle-tendon lengthening produces in animal experiments [s2]. Repetitive simulated jump landings have caused ACL failure at loads well below the ligament's ultimate strength [s2]. And ACL explants taken from non-contact injured patients during reconstruction show damage similar to cadaveric specimens that were repetitively loaded [s2].

The review's own framing is that further research is needed to substantiate these hypotheses [s2]. It is an argument, not a demonstration.

But if mechanical fatigue is a real contributor, then a 25-year cohort with nine contralateral ruptures is not describing bad luck twice. It is describing tissue that keeps accumulating submaximal load, on both sides, in people who keep playing pivoting sports into their fifties. The review notes that recognising fatigue as a factor opens the door to modelling approaches and wearable sensors that monitor tissue load and damage [s2].

Limits worth stating plainly

Sixty-two patients is a small cohort by any modern standard, and the control group of 30 is smaller still. Sport participation was captured on a six-point ordinal scale, which is coarse. Nothing here speaks to pain, function, imaging-confirmed osteoarthritis or quality of life — the outcomes that usually dominate long-term ACL discussion.

What the study does establish, within its limits, is that a substantial majority of people reconstructed in their twenties were still playing sport at 50-plus, that graft choice did not visibly determine that, and that a second ACL injury was common along the way [s1].

Sources

• [s1] Sports Participation 25 Years After Anterior Cruciate Ligament Reconstruction: A Prospective Longitudinal Study Comparing Patients With Patellar Tendon and Hamstring Tendon Grafting to Uninjured Controls — The American Journal of Sports Medicine, published online 22 October 2025. https://doi.org/10.1177/03635465251380293
• [s2] Rethinking Acute Sports Injuries: Evidence for an Overuse Mechanism in Hamstring and ACL Injuries — Scandinavian Journal of Medicine & Science in Sports, published online 13 October 2025. https://doi.org/10.1111/sms.70146