The Chrisman-Snook procedure is a surgical reconstruction for chronic lateral ankle instability that uses a strip of the peroneus brevis tendon, rerouted through a bone tunnel in the fibula, to replace the function of two damaged ankle ligaments. First described in 1969 as a modification of an older technique called the Elmslie procedure, it remains one of the most recognized non-anatomic approaches to stabilizing an ankle that keeps giving way despite months of physical therapy and bracing.1Foot & Ankle Surgery: Techniques, Reports & Cases. A Re-look at chrisman-snook: A narrative review and technique guide for lateral ankle ligament reconstruction with tendon allograft While anatomic repairs like the modified Broström have become the default first-line surgery for most patients, the Chrisman-Snook fills a specific niche where those simpler repairs are unlikely to hold up.
How the Procedure Works
Chronic lateral ankle instability usually traces back to two ligaments on the outside of the ankle: the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL). The ATFL is the first to tear during an inversion sprain, and the CFL follows if the force continues.2PubMed. Chronic ankle instability: biomechanics and pathomechanics of ligaments injury and associated lesions When both are chronically stretched or torn beyond the point where they can heal meaningfully, the ankle develops mechanical laxity, the classic “loose ankle” that rolls easily and unpredictably.
In an anatomic repair, the surgeon works with whatever native ligament tissue remains, tightening and reattaching it. The Chrisman-Snook takes a different approach entirely. It harvests roughly half of the peroneus brevis tendon, one of the muscles running along the outside of the lower leg, and threads that strip through a drill hole in the fibula (the thin outer bone of the lower leg). The graft is then routed to reconstruct the paths of both the ATFL and CFL in a non-anatomic configuration, meaning the new tendon graft doesn’t follow the exact original ligament paths but still checks side-to-side and front-to-back looseness at the ankle.3Foot & Ankle Surgery: Techniques, Reports & Cases. A Re-look at chrisman-snook: A narrative review and technique guide for lateral ankle ligament reconstruction with tendon allograft This distinguishes it from the Watson-Jones procedure, which uses the peroneus brevis to reconstruct only the ATFL.4Operative Techniques in Sports Medicine. Chronic lateral ligament laxity: Reconstruction by the chrisman-snook and watson-jones peroneus brevis transfers and the modified brostrom procedure
A modified version of the technique, widely used in practice, splits the peroneus brevis rather than detaching the entire distal half, preserving more function in the donor tendon. This modification has been applied across both adult and pediatric populations.5PubMed Central. Modified Chrisman–Snook repair for the treatment of chronic ankle ligamentous instability in children and adolescents
Who Is a Candidate
The Chrisman-Snook is not a first-line surgery for the typical patient with chronic ankle instability. It is a heavier intervention, and surgeons reserve it for situations where a simpler anatomic repair is either impractical or has already failed. The recognized indications include patients with combined ankle and subtalar instability, obese patients whose body weight places extra stress on a repair, athletes in sports that impose repetitive inversion and rotational forces (football linemen are a classic example), people with connective tissue disorders like Ehlers-Danlos syndrome where native tissue is inherently weak, and patients whose previous anatomic repair did not hold.6Operative Techniques in Sports Medicine. Chronic lateral ligament laxity: Reconstruction by the chrisman-snook and watson-jones peroneus brevis transfers and the modified brostrom procedure
The thread connecting these indications is that the patient’s native ligament tissue either never existed in a usable form, has deteriorated too far to tighten effectively, or faces demands that a repair of the native tissue cannot withstand. When the remaining ligament tissue is too thin, too lax, or simply absent, there is nothing for an anatomic repair to work with. Harvesting a tendon graft and building a new restraint from scratch becomes the logical alternative.
Why Surgeons Often Prefer the Modified Broström Instead
For most patients with chronic lateral ankle instability, the modified Broström procedure is the preferred surgery. It repairs the native ATFL and reinforces it by advancing the nearby inferior extensor retinaculum over the repair site. It is less invasive, does not sacrifice part of a functioning tendon, and in cadaver testing has actually shown greater mechanical restraint against talar tilt and anterior drawer than either the Chrisman-Snook or Watson-Jones reconstructions.7PubMed. Comparison of lateral ankle ligamentous reconstruction procedures
A prospective randomized comparison of the two procedures in patients with chronic instability found that both achieved good or excellent stability in more than 80 percent of cases. However, patients who underwent the modified Broström scored higher on the Sefton functional rating scale, and a greater proportion of complications occurred in the Chrisman-Snook group.8PubMed. Outcomes of the Chrisman-Snook and modified-Broström procedures for chronic lateral ankle instability. A prospective, randomized comparison This study is one of the few head-to-head randomized trials in the ankle instability literature, and it carries real weight in guiding clinical decisions. It does not mean the Chrisman-Snook is a bad operation. It means that when native tissue quality allows, the simpler repair delivers at least as much stability with fewer trade-offs.
The Chrisman-Snook earns its place when the modified Broström is not feasible or when it has already been tried and failed. Thinking of it as a salvage or augmented option is more accurate than thinking of it as a competing choice.
The Biomechanical Trade-Off Between Stability and Stiffness
This is where the Chrisman-Snook gets complicated, and where the science is genuinely interesting. The procedure does an effective job eliminating laxity. Cadaver studies have shown it is the only reconstruction, compared to Evans and Watson-Jones techniques, that significantly stabilizes the ankle joint complex against inversion-eversion stress beyond what is achieved by simply cutting the ATFL alone.9PubMed. Biomechanical comparison of reconstruction techniques in simulated lateral ankle ligament injury It also restores anterior-posterior stability in ankles with both the ATFL and CFL cut. By those metrics, it works.
But eliminating laxity is not the same as restoring normal motion. A study measuring ankle kinematics after the Chrisman-Snook found that while the “neutral zone” laxity (the looseness you feel when the joint is at rest) was reduced to below-normal levels, the ankle’s overall flexibility was significantly greater than normal. In other words, the joint becomes tighter at rest but doesn’t move normally under load. The reconstruction does not reproduce the natural kinematics of the ankle.10PubMed. Laxity and flexibility of the ankle following reconstruction with the Chrisman-Snook procedure This mismatch between how tight the ankle feels and how it actually behaves during movement may explain some of the stiffness complaints and functional limitations that patients report after the surgery.
The subtalar joint, which sits just below the ankle joint and is responsible for the side-to-side rocking motion of the foot, is particularly affected. Because the Chrisman-Snook reconstructs the CFL, which crosses both the ankle and subtalar joints, the graft inevitably constrains subtalar motion. One study found that post-operative subtalar tilt averaged about 2.8 degrees compared to 7.2 degrees on the non-operative side.11PubMed. A modified Chrisman-Snook procedure for reconstruction of the lateral ligaments of the ankle: review of 18 cases Cadaver data echoed this, showing that the Chrisman-Snook produced ankles with significantly less subtalar motion than even intact ankles under anterior-posterior loading.12PubMed. Biomechanical comparison of reconstruction techniques in simulated lateral ankle ligament injury
For a patient whose main concern is stopping the ankle from rolling, this restriction can feel like a success. For an athlete on uneven terrain who needs that subtalar motion for agility, it can be a meaningful limitation. Surgeons discuss this trade-off with patients beforehand, but it is worth understanding going in: the ankle will be tighter and more stable, but it will not feel exactly like it did before the instability started.
Return to Sport and Functional Outcomes
One of the most common questions patients ask before surgery is how long until they can get back to activity, and whether they’ll perform at the same level. The evidence is encouraging but comes with caveats. In a study of athletes who underwent the Chrisman-Snook reconstruction, 80 percent returned to sport at a median of six months after surgery. Average dorsiflexion loss compared to the non-operative side was just two degrees, which is modest. About 85 percent of patients were satisfied with their result at a mean follow-up of just over four years.13PubMed. Clinical results and functional evaluation of the Chrisman-Snook procedure for lateral ankle instability in athletes
The 20 percent who did not return to sport deserve attention, though. Some of these patients experienced peroneal tendon scarring that required a second procedure called tenolysis, in which the scar tissue around the tendon is released. In that same study, about 14 percent of patients underwent reoperation, with peroneal tendon scarring being the most common reason.14PubMed. Clinical results and functional evaluation of the Chrisman-Snook procedure for lateral ankle instability in athletes Harvesting part of the peroneus brevis creates a surgical wound in a tendon that is critical for everting the foot, and scar tissue formation around that donor site is one of the procedure’s known downsides.
Older literature paints a somewhat rosier picture for highly competitive athletes. An earlier series reported that instability was abolished in all cases after the Chrisman-Snook reconstruction, with excellent or good results in the majority. The three top-level athletes in that study returned to their pre-injury level without restrictions.15PubMed. Secondary reconstruction of the lateral ligaments of the ankle by the Chrisman-Snook technique These are small numbers, and patient selection likely played a role, but the pattern across studies is consistent: most patients do get back to activity, and instability symptoms improve substantially. The ceiling for how “normal” the ankle feels depends on the individual’s anatomy, sport, and tolerance for the subtalar restriction discussed earlier.
The Procedure in Children and Adolescents
Chronic ankle instability is not just an adult problem. Kids and teens who are involved in sports can develop the same pattern of recurrent sprains, and when bracing and rehab fail, surgical stabilization becomes a conversation. The concern with younger patients is the presence of open growth plates, but the modified Chrisman-Snook has been used successfully in this population with promising results.
A study of 44 ankles in 38 patients treated with a modified Chrisman-Snook repair in children and adolescents found that talar tilt dropped from an average of 14.5 degrees before surgery to 4 degrees afterward. On a subjective outcomes questionnaire, patients rated their pain and instability at extremely low levels (around 1 out of 10) and their function at a high level (around 8 out of 10). All patients said their expectations were met. There was no radiographic evidence of degenerative arthritis at follow-up.16PubMed. Treatment of ankle instability in children and adolescents with a modified Chrisman-Snook repair: a clinical and patient-based outcome study A larger consecutive series of 100 surgeries in 66 children by a single surgeon using a split peroneus brevis technique confirmed the procedure’s applicability in skeletally immature patients with chronic ligamentous laxity.17PubMed Central. Modified Chrisman–Snook repair for the treatment of chronic ankle ligamentous instability in children and adolescents
One notable detail from the pediatric literature: a patient with generalized systemic ligamentous laxity who had undergone bilateral Evans procedures (a different non-anatomic reconstruction) that failed was successfully treated with the Chrisman-Snook.18PubMed. Treatment of ankle instability in children and adolescents with a modified Chrisman-Snook repair: a clinical and patient-based outcome study This reinforces the procedure’s role as a reliable option when other approaches have not held, whether in adults or younger patients.
Long-Term Joint Health and Osteoarthritis Concerns
Whenever a surgery changes the way a joint moves, there is a reasonable worry about accelerated wear over time. The Chrisman-Snook restricts subtalar motion, and altered mechanics can theoretically lead to cartilage breakdown in the subtalar joint. Of course, chronic instability itself also damages cartilage: years of abnormal loading, impingement, and repetitive micro-trauma are known to cause osteochondral lesions and eventual arthritis even without surgery.19PubMed. Chronic ankle instability: biomechanics and pathomechanics of ligaments injury and associated lesions
A recent study specifically examined rates of subtalar joint osteoarthritis after the modified Chrisman-Snook. On a standardized grading scale, the average arthritis score increased slightly from 0.56 before surgery to 0.81 afterward, a change that did not reach clinical significance. The researchers noted that more surveillance is needed over the medium and long term to understand whether the mild increase is transient, permanent, or subject to continued progression.20PubMed. Rates of subtalar joint osteoarthritis after modified Chrisman-snook In the pediatric series discussed earlier, there was no radiographic evidence of degenerative arthritis at follow-up, which is reassuring but also expected given the younger patients’ shorter time horizon for wear.21PubMed. Treatment of ankle instability in children and adolescents with a modified Chrisman-Snook repair: a clinical and patient-based outcome study
The honest summary of the arthritis question is that the data so far does not show alarming joint degeneration, but follow-up periods in most studies are still relatively short, generally under a decade. Whether a 25-year-old who has the surgery will see meaningful subtalar arthritis by age 50 remains genuinely unknown. This is a gap in the literature, not a reassurance, and patients considering the procedure should understand that long-term data is still accumulating.
Allograft Variations and the Evolving Technique
One of the persistent criticisms of the classic Chrisman-Snook is that it sacrifices part of a healthy tendon. The peroneus brevis is not a disposable structure; it actively stabilizes the ankle during walking and running. Taking half of it weakens eversion strength, and scarring around the harvest site can cause its own set of problems. This has motivated interest in performing the same reconstruction using donor tissue (allograft) rather than the patient’s own tendon.
A narrative review and technique guide published in 2024 revisited the Chrisman-Snook concept using tendon allograft, arguing that the procedure’s core principle of routing a graft through a fibular tunnel to reconstruct both the ATFL and CFL remains biomechanically sound, even if the graft source changes.22Foot & Ankle Surgery: Techniques, Reports & Cases. A Re-look at chrisman-snook: A narrative review and technique guide for lateral ankle ligament reconstruction with tendon allograft The appeal is obvious: if you can reconstruct the ligaments without weakening the peroneus brevis, you eliminate the donor-site morbidity that accounts for a good chunk of the complications. Allograft tissue also provides a larger and more consistent graft size, which can matter in revision cases where the patient’s own peroneus brevis may already be compromised from a prior surgery.
The trade-off with allograft is that it takes longer to incorporate into the surrounding bone and tissue. Autograft, your own tissue, has living cells that jump-start the healing process. Allograft is essentially a biological scaffold that your body needs to repopulate with its own cells over time. This slower incorporation can mean a longer period of protected weight-bearing and a more cautious return to activity. The concept is still being refined, and large outcome studies comparing autograft versus allograft in this specific reconstruction are not yet available. But the direction of travel, reducing what the surgery takes from the patient, aligns with broader trends in orthopedic reconstruction.