The Knee That Buckles on One Landing: What Actually Goes Wrong
Last season, at the training facility of a professional women's handball club, a defender cut hard to close down an attacker, planted, and landed with her knee suddenly folding inward. There was a dull pop, and she went down on the court immediately. The MRI read as a complete tear of the anterior cruciate ligament (ACL). Reconstruction and rehab took eight months, and in her first season back she never quite returned to her pre-injury numbers. Any trainer who has spent a season with an amateur or collegiate team has likely seen some version of this exact sequence play out.
Most ACL tears are non-contact injuries. They do not happen because two players collide, they happen in the split second of landing, decelerating, or cutting, when the knee caves inward into what is called dynamic valgus. At the instant the foot strikes the ground, if the quadriceps fire dominantly and the hamstrings are too slow or too weak to counterbalance them, the shin bone is pulled forward relative to the thigh and the ligament is asked to absorb a load equal to several times body weight in a fraction of a second. The hamstrings matter here for a purely mechanical reason: they run behind the knee and resist the same forward shin translation the ACL would otherwise have to restrain alone, so a strength imbalance between the two muscle groups turns an ordinary landing into a high-risk one. Layer on a valgus moment pulling the knee inward, a trunk that leans away from the landing leg, and a nearly straight knee absorbing impact stiffly instead of bending into it, and the risk climbs sharply, because each of those adds a rotational or shearing component the ligament fibers are poorly built to resist.
One factor that gets overlooked on the sideline is fatigue. Team injury logs repeatedly show non-contact injuries clustering late in games, especially in overtime or the second game of a doubleheader. The reason is not simply tired legs, it is that fine neuromuscular control, the split-second timing that keeps the knee aligned during landing, tends to degrade before raw strength does. An athlete who has previously sprained an ankle often lands differently without realizing it, the whole kinetic chain compensates, which is why finishing an ankle rehab protocol is not the same as confirming the landing pattern itself is clean. That is worth checking separately rather than assumed.
What makes this harder to accept is what comes after. A large share of athletes who undergo reconstruction take close to a year to return to their pre-injury level of play, and within the first two years after the original injury, a second tear, either to the surgical graft or to the previously healthy knee, is reported more often than in athletes with no ACL history. That pattern is exactly why sports medicine groups increasingly favor spending limited resources on reducing the risky landing pattern in the first place, rather than getting better at fixing the damage after it happens. Treating well after the fact is still necessary, but it is the costlier strategy per athlete kept on the field.
This article works through a training-focused approach to correcting landing mechanics: a short self-check, what the published evidence for neuromuscular training and photobiomodulation actually supports, an eight-week protocol broken down week by week, the mistakes that show up most often in practice and how to correct them, and the warning signs that mean it is time to see a clinician instead of pushing through. A near-infrared wellness device is discussed only as a conditioning tool that can sit alongside this training, not as something that prevents ligament injury on its own. That distinction matters enough to state upfront.
Self-Check: Is Your Team in a Higher-Risk Group
Before starting a full program, there is a short self-check a coach or athlete can do without any equipment, a mirror or a phone camera is enough. Score two or more of the following as true and the case for prioritizing prevention work gets a lot stronger.
- On a slow single-leg squat, the knee travels inside the line of the second toe.
- Landing from a small jump, the two feet make noticeably different sounds, one lands louder and heavier than the other.
- On a cutting move or sudden stop, the upper body leans hard away from the landing leg.
- There is a history of ankle sprain on one side, and landing on that leg still feels distinctly less stable since.
- Weight tends to shift onto one leg out of habit, or the gap in single-leg hop distance between the two legs is visible without measuring.
Three groups deserve a closer look first: adolescent female athletes going through a growth spurt after menarche, athletes who have previously injured the opposite knee, and anyone returning to full-intensity play after an off-season with no conditioning work. The common thread across all three is a mismatch, either neuromuscular control has not caught up with a recent jump in limb length and strength, or a previous injury has left behind a compensation pattern the athlete is not consciously aware of, or the body has simply lost the conditioning base it had going into an injury-free season. None of these groups is guaranteed an injury, and a clean self-check is not a guarantee of safety either, but the result is a genuinely useful input for deciding how much training intensity to allow early on.
It is worth repeating this check more than once, before the season starts and again whenever training intensity jumps sharply. Measuring single-leg hop distance with a tape measure and writing it down turns a difference that is hard to judge by eye into a number both coach and athlete can agree on, which removes a surprising amount of back-and-forth disagreement about whether something has actually improved. Without a written baseline, it is hard to tell real progress apart from wishful thinking, a point worth keeping in mind since memory of how a landing felt three weeks ago is notoriously unreliable.
How Far the Evidence for Training and NIR Actually Goes
The case for neuromuscular training programs rests on more than one study. A randomized controlled trial by Soligard and colleagues, published in the BMJ in 2008, compared 65 Norwegian youth women's soccer clubs and 1,892 players running the FIFA 11+ warm-up against clubs training as usual. Teams that stuck with the program consistently showed significantly lower overall acute injury rates than the control group, and the reduction was larger among players with higher adherence to the sessions. The trial has real limits worth naming: participating clubs volunteered rather than being randomly selected from the wider population, and the sample was not large enough to isolate the effect on ACL injuries specifically, as opposed to acute injuries overall.
A 2015 meta-analysis by Sugimoto and colleagues in the British Journal of Sports Medicine pooled multiple prevention-program studies and found that programs combining Valsalva-position landing correction, lower-limb strength work, and plyometrics produced a clearly lower ACL injury risk in the high-adherence group compared with the low-adherence group. Because the pooled studies were overwhelmingly conducted on young female athletes, the authors themselves flag caution about generalizing the finding to male athletes or adult recreational players. Earlier landing-specific work by Hewett and colleagues reported statistically significant reductions in knee valgus moment and ground reaction force after training, which supports the idea that the key variable is not raw strength but how well the nervous system learns to control the landing instant.
What the Research on NIR Wellness Support Actually Says
Photobiomodulation's effect on muscle fatigue and recovery has been studied as its own separate question. A small randomized crossover study by Ferraresi and colleagues, published in Lasers in Medical Science in 2012, found that red and near-infrared light applied before resistance exercise tended to lower post-exercise creatine kinase levels and delayed-onset muscle soreness. The study ran in a controlled lab setting with a modest number of participants, so whether the effect transfers cleanly into an actual field training session still needs more testing. A 2018 systematic review by Vanin and colleagues in the same journal similarly suggested pre-exercise NIR exposure may push back the point at which muscular fatigue sets in, but the review also concluded that wavelength and dosage varied so much from study to study that no standard protocol could yet be recommended with confidence. The mechanism most often proposed in this literature is that red and near-infrared wavelengths are absorbed by cytochrome c oxidase inside the mitochondria, thought to support cellular energy production during and after exertion, though this remains a proposed pathway rather than something demonstrated to directly affect ligament tissue.
Put together, there is research suggesting an NIR wellness device may help manage muscle condition, but nothing in the literature shows it prevents ligament injury directly or can substitute for neuromuscular training. The actual prevention effect, in every study cited above, comes from correcting landing posture and balancing muscle strength. That remains the consensus position in sports medicine.
The 8-Week Program: What Changes Week by Week
A prevention program is generally organized around four pillars: mobility and activation, strength training, plyometrics, and agility with directional change. The table below lays out what each pillar targets.
| Component | Representative exercises | Training goal |
|---|---|---|
| Mobility and activation | Dynamic stretching, core bracing | Range of motion, trunk stability |
| Strength training | Single-leg deadlift, Nordic hamstring curl | Hamstring-to-quadriceps balance |
| Plyometrics | Box jumps, lateral hops | Knee alignment on landing |
| Agility and cutting | Cutting drills, zigzag runs | Postural control under deceleration and rotation |
Weeks 1 and 2 are for slowing everything down until the movement itself is second nature. During single-leg deadlifts or squats, check in a mirror on every set that the knee, hip, and ankle stay in a straight line. The gate to the next phase here is not a calendar date, it is the movement itself, once an athlete can perform the same drill five times in a row with no visible breakdown in form, only then does the intensity go up. Advancing on schedule instead of on this competence check is one of the most common mistakes seen in practice.
Weeks 3 through 5 add plyometric elements like box jumps and lateral hops. The repeated goal is landing with the knee bending, quietly and under control, rather than absorbing the impact through a stiff joint. If the landing is still loud or an asymmetry between the two legs is visible, drop the jump height and go back to landing drills rather than pushing through. Weeks 6 through 8 bring in cutting drills and sudden direction changes that mimic real competition, testing whether the posture learned at slow speed actually holds up at game speed. If form breaks down again in this final stretch, that is not a sign the training failed, it is a sign the athlete is not yet ready for full competitive intensity, and treating it that way is the safer read.
A few concrete markers help decide readiness at each transition. Moving from week 2 to week 3 should wait until five consecutive clean reps of the single-leg squat and deadlift are achieved without a verbal cue mid-set. Moving from week 5 to week 6 should wait until the plyometric drills show no audible landing asymmetry and no visible knee cave on video review, checked from the front, not just from the side. A stop signal at any stage is any sharp pain during a drill, a knee that feels like it is about to give way, or swelling that shows up within a few hours of a session, any of those means backing off the current phase rather than pushing to the next one. Two to three sessions a week for at least eight weeks is generally what it takes for the new neuromuscular pattern to settle in. When a team trains together, having a coach or trainer give each athlete individual feedback on landing posture is repeatedly cited as the single factor that most improves both adherence and results.
Where an NIR Wellness Session Fits In
An NIR wellness device is used only as a supporting tool inside this training block. Before training, apply it to the quadriceps and hamstrings for 8 to 10 minutes at a wavelength centered near 850nm and a power density of about 30 to 50mW per square centimeter, treating it as a way to pre-warm local blood flow and muscle temperature ahead of the session. Right after training, a 10 to 15 minute application on the same muscle groups can be folded into a cool-down and recovery routine. Keep the device 0 to 3cm from the skin. To work out the delivered energy in joules per square centimeter, multiply the power density in mW/cm² by the exposure time in seconds and divide by 1000, a session at 40mW/cm² for 10 minutes, 600 seconds, works out to roughly 24J/cm². On days without training, moving the NIR session to an evening conditioning routine makes it easier to manage the training-and-recovery cycle across a full week rather than deciding on the fly each day.
Further reading: Total Knee Replacement Recovery With LED Light Therapy
Mistakes Seen Often in Practice, and Fixes
Watching several teams adopt an eight-week program, the reasons it fails tend to cluster around a small handful of patterns. The table below lists the mistakes that show up repeatedly, why they matter, and how to correct each one.
| Common mistake | Why it matters | Fix |
|---|---|---|
| Focusing only on knee alignment while ignoring hip strength | Weak hip abductors cannot stop the knee from caving inward on landing | Add hip abductor work like clamshells and lateral band walks into every strength session |
| Jumping into higher-intensity plyometrics without landing practice first | Once speed increases, conscious control over form gets harder, and the risky pattern gets reinforced instead of corrected | Only raise intensity after passing the five-consecutive-clean-reps checkpoint |
| Training only the previously injured leg | The uninjured leg usually shares the same underlying risk factors | Train both legs with equal volume and track progress with a left-right comparison |
| Reaching for the NIR device only when pain flares up | Treating it as a painkiller shortcut leads to neglecting the actual training | Schedule it as a fixed pre- and post-training routine, and see a clinician first if pain persists |
| Dropping the program once the season schedule gets busy | A neuromuscular pattern degrades within a few weeks once the stimulus stops | Cut session length in half if needed, but keep the frequency |
Of these, the one that is most common and slowest to get noticed is skipping hip strength work. A program built entirely around knee cues does nothing to reduce the actual inward pull on the knee at landing, so a team can be doing the sessions faithfully and still show no improvement on landing video. A coach who makes a habit of glancing at even a few seconds of landing footage every session tends to catch this pattern early, before it becomes the reason the whole program looks like it is not working.
Another recurring problem is bringing the program in only right before a tournament. A neuromuscular pattern does not change in a matter of days, so cramming landing drills into the week before competition mostly just adds fatigue from unfamiliar movement with almost no protective benefit. The eight-week window itself is already close to the minimum the evidence supports, so the more reliable fix is blocking out those eight weeks on the season calendar from the start rather than trying to retrofit them later.
Fitting the CIRIUS Device Into a Daily Routine
The CIRIUS healthcare device pairs 660nm red light with 850nm near-infrared LEDs in a single unit, built to let a training conditioning routine continue at home around practice sessions. Medical-grade LED components are arranged to deliver a consistent power density across the treated surface, and a built-in automatic timer keeps a session from running past the intended duration. The ergonomic shape lets it sit flush against several areas of the lower body, the front of the thigh, around the knee, or the calf.
How it actually gets placed in a week depends on the training schedule. A team running plyometric-heavy sessions on Tuesday and Thursday might apply it to the quadriceps and hamstrings for 8 to 10 minutes, centered near 850nm, 20 to 30 minutes before training starts as a warm-up, then repeat a 10 to 15 minute application on the same muscles right after training, folded into foam-rolling or stretching as part of the cool-down. On a non-training day, Wednesday or over the weekend, a roughly 20-minute, broader conditioning session rounds out the week.
Someone training alone needs a different approach. Without a coach giving real-time feedback the way a team gets, propping a phone on a small tripod to film every landing session and reviewing the footage once a week is a realistic substitute. Fixing the NIR session to the same time every evening makes it much less likely to get skipped. On first use, start with a shorter setting, five to eight minutes, and watch how the skin responds before working up to the full recommended duration, and if several athletes share one device, wiping the contact surface down between users is a hygiene step worth building into the routine, not an optional extra.
Off-season, or during the run-up to returning from an injury, the placement shifts again. Training intensity is naturally lower in this window, so it makes sense to lean the NIR sessions toward recovery, keeping a light evening routine after strength work to ease muscle tightness, and only adding back a morning or pre-training warm-up application once full-intensity training actually resumes. Adjusting the pattern to match the season and the training cycle, rather than running the identical routine year-round, is the more practical way to use it.
For a weekend recreational player who only gets on the court once or twice a week, trying to replicate a full team protocol is not realistic and is not necessary. A single evening conditioning session on a non-training day, paired with five to ten minutes of landing-focused warm-up before playing, covers most of the practical benefit without turning a hobby into a second training job. The detail that tends to get missed in this group is the warm-up, skipping it because the game is casual is exactly the setting where a tired, unwarmed knee meets an unplanned hard cut.
Recommended reading: ACL Reconstruction Rehabilitation: The Complete Return-to-Play Guide
Warning Signs That Mean It Is Time to See a Doctor
Even in the middle of a prevention program, the following signs mean it is time to stop self-managing and see an orthopedic or sports medicine specialist.
- A popping sound in the knee during training, followed by difficulty putting weight on it
- Swelling and warmth in the knee along with difficulty fully straightening or bending it
- A repeated feeling of the knee suddenly giving way or buckling when going up or down stairs or changing direction
- Existing knee pain or a feeling of instability that gets worse after starting the program rather than better
- Muscle soreness or joint discomfort that does not settle within two days and instead keeps getting worse
There are a few checks worth keeping in mind when using an NIR wellness device alongside this training. Never point it directly at the eyes. If taking a photosensitizing medication, such as tetracyclines, amiodarone, or methotrexate, check with a physician before using it. Pregnant users should avoid direct exposure over the abdomen, and it should not be used over an active malignancy or an acute infection site. If persistent redness, blistering, or worsening pain shows up on the skin, stop immediately and consult a professional.
Athletes starting a prevention program for the first time are better off having a qualified trainer or physical therapist check their form for the first two to three weeks. Repeating a movement with bad form does not just fail to help, it cements the bad habit and cancels out the preventive benefit the program was supposed to deliver. Adolescents still growing need intensity adjusted for growth-plate status and musculoskeletal development, so a school or club rolling this program out is well served by getting a sports medicine professional to tailor it to the sport and age group. If the program gets interrupted and restarted, start again at a lower intensity and build back up gradually over two to three weeks rather than resuming where it left off.
Keeping records is not a minor detail. A short note after every session, what drills were done, how fatigued the athlete felt, whether there was any pain, makes it possible to trace back a few weeks later exactly when a warning sign actually started. Confirming from a written log that pain built up gradually over several days rather than appearing suddenly is genuinely useful for deciding whether to see a doctor now or keep watching it a little longer, a judgment call that is much harder to make from memory alone.
An NIR wellness device supplements neuromuscular training and professional medical guidance, it does not replace either one. Persistent or worsening knee pain or instability should always be evaluated by a medical professional. For anyone already dealing with an injury and in the graft-healing phase of recovery, the article below is worth a look.
