ACL Surgery: Necessary or Not? What Happens Without Reconstruction — in Athletes and Less Active Adults

Key Takeaways: ACL Surgery

An ACL tear is not an automatic indication for surgery. In KANON and COMPARE, about half of the patients who started with structured rehabilitation had not undergone reconstruction by the end of follow-up [1][2].
Function matters as much as laxity. A knee can remain loose on Lachman or anterior drawer testing without causing major functional instability [1][5][9]. Persistent giving way is much more important clinically and shifts the balance toward reconstruction [2][3][4].
Activity demands change the decision. Reconstruction is favoured for patients returning to frequent cutting and pivoting sport, whereas non-operative treatment is a recognised option for more straight-line activities if the knee becomes functionally stable [4].
Meniscal protection is a reasonable concern, but the evidence is mixed. Randomised studies have not shown a clear increase in meniscal procedures with a rehab-first strategy, while observational studies suggest higher risk in persistently ACL-deficient knees [1][7][16][17].
Reconstruction has not been shown to reliably prevent osteoarthritis. Osteoarthritis occurs after both operative and non-operative treatment, and pooled long-term data show no significant difference in radiographic osteoarthritis [4][17].
Some ACL tears can regain continuity on MRI without surgery. In KANON, this was especially common among patients who remained managed with rehabilitation alone, although MRI healing does not necessarily mean normal mechanical stability [5][6].
Rehabilitation is part of both treatment strategies. Surgery is not a shortcut around physiotherapy, and the patient’s goals, resources and ability to engage with rehabilitation matter whichever strategy is chosen [2][3][4].
The same MRI diagnosis can mean very different things in different patients. A young pivoting athlete, a recreational runner and a middle-aged patient with degenerative changes may all need different treatment strategies.

Introduction: ACL Surgery

“Do I need ACL surgery?” is usually one of the first questions once an anterior cruciate ligament tear has been confirmed on MRI. In North America, Europe and Australia, most ACL ruptures are treated with reconstruction, and reconstruction rates have been rising, as the authors of a KANON secondary analysis note [5]. Yet the assumption that a torn ACL automatically needs to be operated on has now been tested in randomised trials — and the answer is more nuanced than a simple yes or no [1][2][3].

ACL injuries are also something I encounter from time to time in clinical practice. The history can immediately raise suspicion: a forceful step or landing combined with a twisting movement of the knee, sometimes accompanied by a distinct pop and sudden pain. On examination, increased anterior translation on tests such as the Lachman or anterior drawer can strengthen that suspicion. In the acute phase, however, swelling, pain and guarding can make the examination much less clear-cut. In practice, when the mechanism and overall presentation are strongly suggestive of an ACL injury, I tend to have a relatively low threshold for further assessment with MRI and, when appropriate, orthopaedic evaluation.

In this article, “ACL surgery” means ACL reconstruction: the torn ligament is replaced with a graft, usually tissue taken from the patient’s own body [3]. The alternative is a structured, progressive rehabilitation programme, with reconstruction kept as an option if the knee does not become functionally stable. An international expert consensus group regards both strategies as acceptable, with the choice depending on the individual patient [4].

The questions patients care about are usually practical. Is surgery necessary? What happens if I do not have it — will the knee keep giving way, damage the meniscus or wear out earlier? And does the answer differ between a footballer, a recreational runner and someone whose most demanding activity is walking the dog? The evidence is not the same for all of these situations, which is why I think the decision is better framed around functional stability, activity demands and associated injuries rather than the MRI finding alone. KANON enrolled adults aged 18–35 and COMPARE adults aged 18–65 [1][2]; ACL injuries in children and adolescents are outside the scope of this article.

What Reconstruction and Rehabilitation Are Each Trying to Achieve

The two strategies target different problems. According to the Panther Symposium consensus statement, operative treatment aims to reduce knee laxity, while non-operative treatment aims to reduce functional instability — and both are intended to prevent further damage to the menisci and cartilage, which may contribute to post-traumatic osteoarthritis [4].

In plain terms, laxity is how far the shinbone can be moved relative to the thighbone when a clinician examines the knee. Functional instability is what the patient experiences: the knee buckling or “giving way” during activity. As the trials below show, the two do not always move together — which is part of why the surgery-versus-rehabilitation debate is not as simple as it looks.

The same consensus statement describes three typical responses after an ACL injury [4]:

Copers return to their pre-injury activity level without surgery and without feeling unstable.
Adapters reduce their activity level to avoid instability.
Non-copers cannot return to their pre-injury level because of subjective instability and episodes of giving way.

One point is easy to miss: “non-operative treatment” does not mean rest. The consensus group specifies that non-operative treatment implies completing a progressive, staged rehabilitation programme [4]. From a clinical perspective, rehabilitation is relevant regardless of whether reconstruction is ultimately performed, because recovering function still requires active work. In my experience, this is often the part patients underestimate: rehabilitation can be prolonged, and it may require considerable consistency and effort. The operation, when chosen, is therefore only one part of the overall treatment process rather than a substitute for rehabilitation.

Is ACL Surgery Necessary? What the Randomised Trials Show

Three major randomised trials have reported clinical outcomes comparing a strategy of reconstruction with a strategy of rehabilitation and optional later reconstruction. They studied different populations at different stages after the injury, and that difference explains most of their apparently conflicting results.

KANON: acute tears in young, active adults

The Swedish KANON trial randomised 121 young, active adults (mean age 26) with an acute ACL injury to a previously uninjured knee [1]. Participants were 18–35 years old and had been injured no more than 4 weeks earlier; professional athletes and people with less than a moderate activity level were excluded [1]. Everyone received the same structured rehabilitation; 62 were also assigned to early reconstruction and 59 to the option of a delayed reconstruction if needed [1].

Over 5 years, 30 of the 59 patients (51%) in the rehabilitation arm went on to delayed reconstruction, seven of them between years 2 and 5 [1]. The primary outcome — the change in KOOS4 from baseline to 5 years — was 42.9 points after early surgery and 44.9 points with rehabilitation first (between-group difference 2.0 points; 95% CI −8.5 to 4.5) [1]. There were no significant differences in any KOOS subscale, general health (SF-36), activity level (Tegner), incident radiographic osteoarthritis or the number of knees that had meniscus surgery, and in the authors’ as-treated comparison, results did not differ between knees reconstructed early, reconstructed late, or treated with rehabilitation alone [1].

The trial has since reported 11-year results, with 88% of the cohort followed up (54 of the 59 patients in the rehabilitation-first group); the authors reported that 52% of those assigned to rehabilitation first had undergone reconstruction by then [15]. Mean improvement in KOOS4 from baseline was 46 points in the early reconstruction group and 45 points in the rehabilitation-first group (between-group difference 1.6 points; 95% CI −8.8 to 5.6; P=0.67), and the authors concluded that there were no differences in patient-reported outcomes at 11 years [15].

At 5 years, the authors concluded that these findings should encourage young active adults and their clinicians to consider rehabilitation as a primary treatment option, while noting that the results do not apply to professional athletes or to less than moderately active people [1].

COMPARE: acute tears in a broader adult population

The Dutch COMPARE trial randomised 167 patients aged 18–65 (mean age 31.3) with an acute ACL rupture: 85 to early reconstruction and 82 to rehabilitation, with the option of reconstruction after at least 3 months [2]. In the rehabilitation group, 41 patients (50%) had a reconstruction during the 2-year follow-up, on average 10.6 months after randomisation [2].

At 2 years, the early reconstruction group had a better IKDC score (84.7 vs 79.4; difference 5.3, 95% CI 0.6 to 9.9) [2]. The difference was statistically significant, but at no time point did it exceed the lowest minimal clinically important difference reported in the literature (11.5–20.5 points), and the authors described its clinical importance as unclear [2]. Early in follow-up the pattern was reversed: at 3 months, the rehabilitation group scored 9.3 points better [2].

The authors stressed that half of the patients randomised to rehabilitation did not need reconstruction [2]. They also noted that KANON’s participants were about 5 years younger and had a higher pre-injury sport level than COMPARE’s [2].

ACL SNNAP: knees that still give way months after the injury

The UK ACL SNNAP trial asked a different question. It recruited 316 patients with a non-acute ACL injury and persistent symptoms of instability from 29 NHS orthopaedic units; mean age was 32.9, and 207 (66%) had been injured more than 4 months earlier [3]. Patients were randomised to reconstruction or to rehabilitation, with reconstruction allowed later if instability persisted [3].

At 18 months, mean KOOS4 was 73.0 in the surgery group and 64.6 in the rehabilitation group, an adjusted difference of 7.9 points (95% CI 2.5–13.2) in favour of surgery [3]. The trial had used 8 points as its minimal clinically important change for the sample-size calculation [3]. Within 18 months, 65 of 160 patients (41%) in the rehabilitation group had a reconstruction for ongoing symptoms [3]. At 18 months, 83% of the surgery group and 68% of the rehabilitation group rated their knee as better than before treatment [3].

The authors concluded that for symptomatic, unstable patients with a non-acute injury, reconstruction should be the treatment of choice — while adding that patients who do not want surgery can still improve with non-operative care, and that later reconstruction remains possible [3]. They emphasised that their findings apply only to non-acute injuries [3].

Reading the three trials together

The three trials are less contradictory than they first appear, because they answer different questions. KANON and COMPARE asked what to do soon after an acute tear; in both, about half of the patients who started with rehabilitation did not undergo reconstruction during follow-up, and differences in patient-reported outcomes were absent (KANON, at both 5 and 11 years) or of unclear clinical importance (COMPARE, 2 years) [1][15][2]. ACL SNNAP asked what to do when the knee is still unstable months later — and there, ACL surgery came out ahead [3]. The practical reading is that a rehab-first strategy is a reasonable starting point for many acute tears, while persistent giving way despite rehabilitation is a strong reason to move to reconstruction. This is consistent with the consensus statement that a patient who remains unstable in their desired activity despite optimal rehabilitation should be referred for surgery [4].

In clinical practice, ACL injuries can sometimes feel as though they are placed on a fairly direct path toward reconstruction, particularly in people who are physically active. I think that is understandable: an athlete often has a strong desire to return to demanding activity, and mechanical instability can become a major concern. At the same time, the randomised evidence does not support treating every ACL tear as an automatic indication for surgery. For many patients, a structured rehabilitation-first approach can be a reasonable way to determine whether the knee becomes functionally stable without reconstruction.

The practical side is more complicated than the trial results alone suggest. A successful rehabilitation-first strategy asks a great deal from the patient over time. In my experience, this can become especially relevant for working adults with busy family lives, where time, energy and access to regular rehabilitation may all be limited. The same issue can arise in younger people who are not particularly motivated by sport or structured exercise.

I also sometimes see a different challenge in middle-aged and older adults. Their goals and expectations for their body may have changed considerably from when they were younger. Some no longer expect, or necessarily aim, to return to the physical level they had in their twenties, and that can influence how motivated they feel about a long rehabilitation process. I do not think this should simply be interpreted as poor motivation. Often it is more useful to understand what level of function actually matters to that individual and how much time and effort they realistically want to invest in reaching it.

That does not make surgery an easier alternative. Reconstruction also requires a substantial rehabilitation process, and choosing surgery does not remove the need for sustained work afterward. This is one reason I find it more useful to think of the decision as a choice between two treatment strategies rather than between “rehabilitation” and “surgery.” Both paths depend heavily on rehabilitation; the difference is whether reconstruction becomes necessary to achieve the level of stability and function the patient needs.

What Happens If You Don’t Have ACL Surgery?

The knee stays looser — but that does not automatically mean worse function

On average, knees managed without reconstruction remain mechanically looser in the comparative studies. In KANON, knee stability at rest at 5 years was significantly better in knees assigned to early reconstruction, as measured by the Lachman and pivot-shift tests [1] — yet patient-reported outcomes did not differ between the strategies [1]. A later KANON analysis likewise found that fewer patients managed without reconstruction had normal or nearly normal passive laxity than those who had been reconstructed [5]. In a 20-year follow-up of high-level athletes, knee stability was better after operative treatment, but this did not translate into better subjective or objective function [9].

This is something that can become very apparent in practice. A clinician may detect increased anterior laxity on the Lachman or anterior drawer test, while the patient reports little or no sense of instability in everyday life. When that happens, I think the important question becomes what the examination finding actually means for the patient. Mechanical laxity matters, but it is not the same as impaired function. From a clinical perspective, how stable the knee feels during the activities the patient actually wants to perform is often at least as important as the amount of laxity that can be demonstrated on examination.

Giving way

Giving way, rather than laxity on examination, is where the difference becomes clinically meaningful. In COMPARE, where giving way was one of the secondary outcomes, 15.0% of the rehabilitation group reported giving way at 2 years, compared with 2.5% of the early surgery group [2]. The 41 COMPARE patients who crossed over to reconstruction all met the Dutch guideline criteria for reconstruction: giving way plus rotational instability confirmed by a positive pivot-shift test [2].

The consensus group identifies persistent instability as a risk factor for further damage to the meniscus and cartilage, and recommends referral for reconstruction when instability persists during the patient’s desired activity despite optimal rehabilitation [4].

Meniscus damage

One argument for early ACL surgery is protecting the meniscus from repeated episodes of instability; the COMPARE authors describe this as a reason for choosing reconstruction in daily practice [2]. The randomised data are more reassuring than the argument suggests, although they are not the whole story.

In KANON, 61 knees (51%) had meniscus surgery over 5 years — 29 in the early surgery group and 32 in the rehab-first group — with no significant difference between groups [1]. When repeated operations on the same meniscus were counted, however, the early reconstruction group had fewer meniscus procedures [1]. In a secondary analysis of COMPARE, 25 of 85 patients (29%) randomised to early reconstruction and 17 of 82 (21%) randomised to rehabilitation had a meniscal procedure over 2 years (risk ratio 0.67 for the rehabilitation strategy relative to early reconstruction; 95% CI 0.40 to 1.12; p=0.12, not statistically significant), and the authors concluded that starting with non-surgical treatment did not lead to more meniscal procedures over that period [16]. The main trial report noted that some meniscal procedures after reconstruction followed new injuries, and the authors suggested that reconstruction will not decrease this risk [2]. In ACL SNNAP, newly acquired meniscal pathology was recorded in three patients in the rehabilitation group and one in the surgery group [3].

Observational data point the other way. In a population-based cohort of 964 patients with isolated ACL tears followed for a mean of 13.7 years, patients treated non-operatively had a higher risk than those treated with reconstruction of a secondary meniscal tear (hazard ratio 5.4; 95% CI 3.8–7.6), a diagnosis of arthritis (HR 6.0; 95% CI 4.3–8.4) and knee replacement (HR 16.7; 95% CI 5.0–55.2) [7]. This was a retrospective study in which treatment was not randomised, so the patients who did and did not have surgery may have differed in ways that affect these outcomes — an interpretive caveat rather than a finding of the study. In the same cohort, reconstruction performed 1 year or more after the injury was associated with a higher risk of secondary meniscal tear (HR 3.9; 95% CI 2.2–6.9) and arthritis (HR 6.2; 95% CI 3.4–11.4) than reconstruction within the first year [7].

Pooled data are less clear-cut. A 2026 meta-analysis found no significant difference in secondary meniscal surgery between reconstruction and non-operative management (risk ratio 0.79; 95% CI 0.52–1.21), although the certainty of this evidence was very low [17].

A rehab-first strategy is a structured way of finding out whether reconstruction is needed at all. It is not the same as postponing a reconstruction that has already been judged necessary, and the delayed-reconstruction findings above are one reason not to let a clearly unstable knee drift for years.

The practical importance of meniscal protection also depends heavily on what the knee is expected to do. For someone aiming to return to frequent cutting, pivoting and high-demand sport, recurrent instability carries more potential consequence, and this is the group in whom expert consensus tends to favour reconstruction. The same logic can become relevant in other highly active patients whose work or recreation repeatedly places rotational demands on the knee.

For a patient with more modest activity goals, the balance can look different. If the knee becomes functionally stable with rehabilitation and the person does not need to return to high-demand pivoting activity, the argument for reconstruction purely to protect the meniscus is much less straightforward. In practice, I would not reduce this to whether someone is an “athlete” or not. What matters more is the level and type of activity they actually want to return to, whether the knee continues to give way, and whether there are associated injuries that change the risk profile.

Age and the condition of the rest of the knee also change the context. In a younger athlete with otherwise healthy joint surfaces, preserving meniscal tissue may carry a different long-term significance than it does in a middle-aged or older patient whose knee already shows substantial degenerative change. In practice, when osteoarthritis is beginning to dominate the clinical picture, the meniscus is often part of that

Osteoarthritis

Reconstruction has been hypothesised to protect against post-traumatic osteoarthritis, but the consensus group notes that this preventive effect still needs to be evaluated in prospective randomised trials [4]. In KANON, among knees with 5-year radiographs, 12% had developed tibiofemoral and 19% patellofemoral radiographic osteoarthritis, with no significant difference between the treatment strategies [1]; the authors concluded that reconstruction did not protect the injured knee from structural changes consistent with osteoarthritis over that period [1]. At 11 years, 44% had developed radiographic osteoarthritis of the injured knee [15].

Longer-term data are mostly observational. A systematic review of 41 studies with more than 10 years of follow-up after ACL tear found radiographic osteoarthritis prevalence ranging from 0% to 100%, with low methodological quality in over half of the studies; meniscectomy was the only consistent risk factor, and the two studies that assessed symptomatic osteoarthritis reported 35% in the tibiofemoral and 15% in the patellofemoral joint [8]. In a retrospective pair-matched study of 50 high-level athletes, knee osteoarthritis at 20 years was found in 80% of the operative group and 68% of the non-operative group, a non-significant difference — in a setting where treatment had been allocated according to each patient’s response to 3 months of non-operative care [9]. A 2026 systematic review of 18 studies (33,540 patients, mean follow-up 12.3 years) pooled 15 of them for radiographic osteoarthritis and found no significant difference between reconstruction and non-operative management (risk ratio 1.01; 95% CI 0.79–1.27), with a similar result when only level 1–2 studies were analysed [17]. Reconstruction was associated with a lower rate of knee replacement (risk ratio 0.17; 95% CI 0.07–0.43), but the certainty of evidence for both outcomes was low, and the authors identify confounding by indication as an important limitation, because patients who undergo reconstruction tend to be younger and more active [17].

The consensus group concluded that osteoarthritis after ACL injury is multifactorial, is seen after both operative and non-operative treatment, and that the evidence is inconclusive [4]. The single observational cohort described above points the other way [7], whereas the pooled 2026 analysis did not [17]. Clinical synthesis: because meniscectomy is the clearest long-term risk factor in this literature [8], meniscal status appears to be an important part of long-term osteoarthritis risk after ACL injury, alongside — not only through — the reconstruction decision.

Can a torn ACL heal without surgery?

A ruptured ACL has traditionally been assumed not to heal. A secondary analysis of KANON challenged that. At 2 years, 16 of 54 patients (30%) randomised to rehabilitation with optional reconstruction showed MRI evidence of ACL healing (a continuous ligament); among those who had not crossed over to reconstruction, the figure was 16 of 30 (53%) — and 58% of the 24 participants still managed with rehabilitation alone at 5 years [5]. Signs of healing were visible as early as 3 months: among patients with a 3-month MRI, a complete rupture was still visible in 4 of 12 (33%) of those who stayed with rehabilitation, versus 13 of 14 (93%) of those who later had a reconstruction [5]. Patients with MRI evidence of healing reported better sport/recreation function and knee-related quality of life at 2 years than the non-healed, delayed-reconstruction and early-reconstruction groups [5]. The subgroups were small, and the analysis was exploratory [5].

A separate case series from Australia went further. Eighty consecutive patients managed within 4 weeks of injury with the Cross Bracing Protocol — the knee braced at 90° of flexion for 4 weeks, with range of motion then increased progressively until the brace was removed at 12 weeks, alongside supervised rehabilitation — showed MRI evidence of ACL healing in 90% at 3 months [6]. Eleven patients (14%) re-injured the ACL during follow-up. Two patients developed a below-knee deep vein thrombosis in the second week, before thromboprophylaxis was added to the protocol; both resolved with treatment [6]. As a case series without a comparison group, it cannot show how these results compare with reconstruction or rehabilitation alone; the authors note that it is not known whether a continuous ACL on MRI reflects restored pre-injury function, and that longer-term follow-up and clinical trials are needed to inform clinical practice [6].

The first comparative data have since been less encouraging. A 2026 observational prospective cohort from a private sports orthopaedic practice followed 80 skeletally mature patients aged 16–40 with an acute, isolated, non-contact ACL rupture who took part in pivoting sports and intended to return to them; 40 chose the Cross Bracing Protocol and 40 chose surgical stabilisation [14]. At 2 years, the bracing group had significantly more recurrent instability (70% vs 2.5%) and medial meniscal tears (62% vs 2.5%), and worse scores on all patient-reported outcome measures; the authors concluded that the protocol is associated with an unacceptably high rate of recurrent instability in patients taking part in pivoting sports [14]. The groups were similar in age, BMI, gender, dominance of the injured knee and posterior tibial slope [14], but patients chose their own treatment, so they may still have differed in ways the study could not control — an interpretive caveat rather than a finding of the study. Randomised comparisons are still lacking.

One intriguing possibility is that patients who do well without reconstruction are not always functioning with a permanently “ACL-deficient” knee. In KANON, MRI evidence of ACL continuity was particularly common among patients who remained managed with rehabilitation alone: 16 of 30 (53%) showed a continuous ACL at 2 years, and patients with MRI evidence of healing also reported better sport/recreation function and knee-related quality of life than the non-healed, delayed-reconstruction and early-reconstruction groups [5].

This raises the possibility that spontaneous biological healing may partly explain why some patients become good “copers,” whereas persistent non-healing may contribute to ongoing instability and eventual reconstruction [5]. However, this remains an association rather than a proven causal pathway. MRI continuity does not perfectly correspond to mechanical stability, and the KANON healing analysis was exploratory with relatively small subgroups [5].

Who Is More Likely to Need Reconstruction?

The research and consensus literature identify several factors that shift the balance towards — or away from — reconstruction:

A repairable meniscal tear or an injury to more than one knee ligament. The consensus group regards either as an indication for early reconstruction, with the other injured structures treated at the same time [4].
Persistent giving way despite good rehabilitation. The consensus statement treats this as a key indication for reconstruction [4], and ACL SNNAP found a surgery-first strategy superior in patients with non-acute, symptomatic instability [3].
A goal of returning to jumping, cutting and pivoting sport. Reconstruction is the consensus-preferred option for these athletes [4].
Anatomical factors. Bony morphology such as an increased posterior tibial slope or severe varus alignment should be considered in the decision and is regarded as a relative indication for surgery [4].
Younger age and a higher pre-injury activity level make later reconstruction more likely after starting with rehabilitation. A 2025 scoping review of 10 studies found these to be the only characteristics reported in at least three studies — the threshold the authors used to define a predictor; a further 12 possible predictors each came from individual studies only [18].
Factors favouring success without surgery in one cohort: among pivoting-sport athletes in the Delaware-Oslo cohort, older age, female sex and good knee function early after the injury were associated with a successful outcome without reconstruction [10]. Apart from age, these factors were not among the predictors that met the scoping review’s threshold [18].
MRI appearance after a period of rehabilitation is an emerging, exploratory factor: in KANON, most patients who later chose reconstruction still had a complete rupture on their 3-month MRI [5].

The consensus group recommends that the final choice be made through shared decision-making between the patient and clinician, based on the patient’s presentation, goals and expectations and a balanced presentation of the evidence [4].

What a Rehab-First Approach Actually Involves

“Trying rehab first” in these trials meant a structured, supervised programme — not waiting to see what happens. In COMPARE, patients in the rehabilitation arm completed at least 3 months of supervised physical therapy before they could opt for reconstruction if instability persisted or they had not reached their desired activity level [2]. In ACL SNNAP, the rehabilitation protocol specified at least six sessions over at least 3 months, covering control of pain and swelling, range of motion, neuromuscular control, muscle strength, normal gait and a graded return to function, activity or sport [3]. Surgery could be considered before the 3 months were up if instability or symptoms occurred earlier, and the authors describe the 3-month period as somewhat arbitrary, though in line with normal clinical practice [3]. The consensus group recommends a period of progressive rehabilitation before either strategy, because swelling, restricted range of motion and reduced quadriceps strength are common early after the injury [4].

Regaining muscle strength is one of these components [3], and the principle of gradually increasing the load the knee can tolerate is the same one discussed in squat knee stress. For people living with an ACL-deficient knee, the evidence on functional bracing — and what a brace can and cannot do — is reviewed in Best Knee Brace for ACL and Arthritis.

Importantly, starting with rehabilitation does not close the door on surgery. In KANON’s as-treated comparison, outcomes did not differ between knees reconstructed early and those reconstructed later [1]. In ACL SNNAP, patients in the rehabilitation arm who later had reconstruction progressed slowly at first but reached KOOS4 scores similar to the surgery group by 18 months, whereas those who stayed with rehabilitation alone improved faster early on and then plateaued at around 12 points below the surgery group [3]. These subgroups were not randomised, so the comparison is descriptive.

From a practical perspective, this is also why motivation and the ability to engage with rehabilitation matter before surgery, not only after it. I have heard orthopaedic surgeons make the point that if a patient is unlikely to participate meaningfully in physiotherapy, reconstruction may not solve the problem, because the operation itself still depends on a substantial rehabilitation process to restore function. I think that is an important part of shared decision-making: surgery is not a shortcut around rehabilitation.

In publicly funded care, this practical reality may also influence how the overall balance of benefit, burden and surgical risk is considered. I would be cautious about framing this as withholding surgery because a patient is “unmotivated.” A more useful question is whether the patient is realistically able and willing to complete the rehabilitation that either treatment strategy requires. If not, the expected benefit of reconstruction may be lower, while the patient is still exposed to the burdens and risks of surgery.

Conclusion: ACL Surgery

Is ACL surgery necessary? For some patients, reconstruction is clearly favoured — particularly when the knee continues to give way despite good rehabilitation, when there is a repairable meniscal tear or a multi-ligament injury, or when the goal is a return to demanding cutting and pivoting sport [3][4]. For many others, however, an ACL tear does not automatically mean that surgery is needed. In the acute-tear trials, about half of the patients who started with structured rehabilitation had not undergone reconstruction by the end of follow-up [1][2].

From a clinical perspective, I think function matters more than the MRI finding alone. A knee may remain measurably loose on Lachman or anterior drawer testing while the patient feels stable in everyday life. Conversely, repeated giving way can make reconstruction much more relevant. The important question is therefore not simply whether the ACL is torn, but whether the knee is stable enough for the activities the patient actually wants to perform.

Activity level, age and the condition of the rest of the knee all change that balance. A young pivoting athlete with an otherwise healthy joint is a very different case from a recreationally active or middle-aged patient with degenerative changes. Protecting the meniscus may carry more weight in the former, whereas in the latter the whole joint context becomes increasingly important.

Rehabilitation is also central whichever strategy is chosen. A rehab-first approach is not passive waiting, and reconstruction is not a shortcut around physiotherapy. Both require time, consistency and patient engagement. Some ACL tears may even regain continuity on MRI without reconstruction, although this does not necessarily mean normal mechanical stability [5][6].

For me, the most useful way to frame the decision is: What does this knee need to be able to do, does it remain functionally unstable despite rehabilitation, and which treatment strategy best fits the patient’s goals and circumstances? The final decision should be individual and made together with the treating orthopaedic surgeon.