Tendon Transfers for Foot Drop and Reconstruction

A tendon transfer in the foot is a surgical procedure that reroutes a working tendon from its original attachment to a new location, effectively reassigning that muscle’s pulling force to compensate for one that no longer works. The technique is used to restore lost motion, correct deformity, or reinforce a damaged tendon across a wide range of foot and ankle conditions. An ideal donor tendon needs adequate strength, range of motion, and a line of pull compatible with its new job.¹ Because the procedure repurposes something the body already has rather than implanting something artificial, outcomes tend to be durable over many years, though they come with trade-offs worth understanding before you agree to surgery.

Why a Tendon Transfer Might Be Recommended

The single most common reason for a foot tendon transfer is foot drop, the inability to lift the front of your foot during walking. This typically results from damage to the common peroneal nerve, which is the most frequent lower-extremity nerve palsy and produces a characteristic foot that drags and turns inward.² When nerve recovery stalls after roughly a year of observation, surgeons consider a tendon transfer to permanently bypass the paralyzed muscles rather than relying on a brace for life.

Foot drop is not the only scenario. Tendon transfers also address varus deformity (where the foot tilts inward, often from cerebral palsy or stroke), chronic Achilles tendon ruptures too large for a simple repair, adult-acquired flatfoot from a failing posterior tibial tendon, and the high-arched cavovarus foot seen in neurological conditions. Each condition calls for a different donor tendon and a different attachment point, but the underlying logic is the same: borrow a functioning muscle to do the job of one that cannot.

The Posterior Tibial Transfer for Foot Drop

The workhorse procedure for foot drop is a transfer of the tibialis posterior tendon. This muscle normally helps point the foot downward and inward. By detaching it from its original insertion and rerouting it through a window cut in the membrane between the tibia and fibula, surgeons redirect its pull so it lifts the foot upward instead. The transferred tendon is typically secured to the tendons that extend the toes and the big toe on the top of the foot, restoring active ankle dorsiflexion where it had been completely lost.³

The results, in most studies, are encouraging. In one long-term series following patients for an average of seven and a half years after surgery for drop foot caused by nerve palsy, ten of twelve patients achieved good or excellent results, and eleven of twelve recovered strong dorsiflexion power. The transferred muscle did generate only about 30% of the torque measured on the healthy side, so the foot lifts but not with the same force as a normal ankle.⁴ That sounds like a big drop-off, but in practice it is usually enough for comfortable walking, stair climbing, and most daily activities. You just may not have the snap you once did when pushing off during a sprint.

A systematic review examining over 300 patients across 22 studies found that roughly 93% were using an ankle-foot orthosis (brace) before surgery, and 91% of those people abandoned the brace entirely afterward. About 94% of patients reported being satisfied with the outcome.⁵ For someone who has spent a year or more strapping on a brace every morning, that freedom matters enormously.

A separate study specifically looking at foot drop after knee dislocation, a somewhat unusual but serious injury pattern, also found that posterior tibial tendon transfer reliably improved function and recommended the procedure for drop foot persisting at least a year after the injury.⁶

Correcting a Varus Foot

When a stroke, cerebral palsy, or other neurological condition causes spasticity that pulls the foot inward and downward, the problem is different from simple paralysis. Here, the muscles are overactive rather than absent, and they create a deformity that makes it hard to place the foot flat on the ground. A common solution is the split anterior tibial tendon transfer, often abbreviated SPLATT. Instead of moving the entire tendon, the surgeon divides it lengthwise and reroutes the outer half to the lateral side of the foot. This rebalances the pull so the foot no longer rolls onto its outer edge.

In a large series of 132 operated feet in adults (average age 46), this procedure allowed 80 patients to walk barefoot, 74 to increase their walking distance, and 73 to regularly wear normal shoes, with very few complications over a follow-up averaging about five years.⁷ One interesting finding from that study was a strong relationship between preserved sensation on the sole of the foot and the quality of the functional result. If you still have good feeling in the bottom of your foot before surgery, you are more likely to walk well afterward.

In children with cerebral palsy, the SPLATT procedure corrected the deformity in about 77% of cases, but roughly 23% developed either an overcorrection (the foot drifting outward) or a recurrence of the inward tilt, sometimes more than two years later. Some of those required revision surgery.⁸ The growing skeleton makes these corrections less predictable in children, and families should be prepared for the possibility that the foot’s alignment may shift as the child grows.

Rebuilding a Chronic Achilles Rupture

When an Achilles tendon rupture goes unrepaired for weeks or months, the gap fills with scar tissue that cannot generate the force needed to push off while walking. Once the surgeon clears away the fibrotic tissue, the remaining gap can measure five centimeters or more, far too large for a direct stitch. In these cases, the flexor hallucis longus tendon, the muscle that curls the big toe, is transferred into the defect to serve as a living scaffold and active motor.

In a study of 28 patients followed for an average of about five years after this procedure, no one re-ruptured, functional scores improved dramatically, and all patients returned to their pre-injury daily activities.⁹ Patients did have some weakness in curling the big toe, but none found it bothersome in everyday life. A separate study confirmed that the transferred muscle actually bulks up over time, suggesting it actively contributes to push-off power rather than just acting as a passive bridge.¹⁰ The primary benefits patients reported were pain relief and increased strength.

Another series treating defects averaging over seven centimeters reported excellent outcomes with the same technique, reinforcing the idea that even quite large gaps can be bridged.¹¹ The flexor hallucis longus is favored because it runs close to the Achilles, has a similar line of pull, and is a strong muscle whose loss at its original site produces minimal functional consequences.

The Cavovarus Foot and Peroneal Rebalancing

A cavovarus foot has a high arch and an inward-tilted heel, often caused by progressive neurological conditions. One of the driving forces behind this deformity is the peroneus longus muscle, which presses the first metatarsal downward and accentuates the arch. Transferring the peroneus longus tendon to reinforce the peroneus brevis can remove that deforming force while strengthening the muscle that pulls the heel outward.

In a study of patients with cavovarus feet who underwent peroneus longus transfer combined with bone procedures, functional scores improved from an average of 57 to 83 on a standard 100-point scale over two to six years of follow-up.¹² All feet did retain some residual cavovarus on X-rays, meaning the surgery improved the foot substantially but did not make it architecturally normal. This is a realistic expectation for most cavovarus corrections: the goal is a foot that is functional and pain-free, not one that looks perfect on imaging.

Flatfoot Reconstruction and an Honest Look at the Evidence

Adult-acquired flatfoot most commonly results from degeneration of the posterior tibial tendon, and a flexor digitorum longus transfer to the navicular or medial cuneiform bone has been standard practice for decades. The idea is that the transferred tendon substitutes for the failing posterior tibial tendon and helps support the arch.

The evidence base here is surprisingly thin. A systematic review concluded that there is poor-quality clinical evidence to support the flexor digitorum longus transfer for this condition, and biomechanical studies actually cast doubt on whether the transfer itself does much. It remains unclear whether the clinical improvements patients experience come from the tendon transfer or from the bone procedures typically performed at the same time, such as a calcaneal osteotomy or medializing slide.¹³ A cadaver study found that when comparing three different attachment sites for this transfer, all performed similarly and produced only minimal changes compared to the flatfoot condition.¹⁴

This does not mean the overall surgery is ineffective. Patients with flatfoot reconstruction often do very well. It just means the tendon transfer component may be less important than surgeons have traditionally believed, and the bony realignment may be doing most of the heavy lifting. If your surgeon recommends this procedure, it is worth understanding that the transfer is usually one piece of a larger reconstruction rather than a standalone fix.

How the Tendon Is Secured and Why It Matters

Once a tendon has been rerouted, it must be firmly anchored to bone at its new site. The two most common methods are interference screws (which wedge the tendon into a bone tunnel) and suture anchors (which tack the tendon onto the bone surface). A biomechanical comparison found that interference screws provided significantly greater strength, with an average failure load of 150 newtons compared to 103 newtons for suture anchors.¹⁵

Separate testing of bioabsorbable interference screws found that a 7-millimeter screw provided about three times the strength needed to resist the forces of passive foot movement, while a 5-millimeter screw provided about one and a half times that threshold but was technically harder to place.¹⁶ In practical terms, both methods work, but the stronger fixation of an interference screw gives the surgeon more confidence that the attachment will hold during early rehabilitation when the healing bond between tendon and bone is still immature.

Getting the tension right at the time of fixation is another critical detail. For a tibialis posterior transfer treating foot drop, surgeons typically set the tension with the ankle held in 20 to 30 degrees of dorsiflexion.¹⁷ Too loose and the transfer will not lift the foot adequately; too tight and the ankle may be pulled into an overcorrected position. There is no simple formula for this, which is one reason that surgical experience matters in tendon transfer surgery.

Recovery and Retraining the Brain

After surgery, the foot is initially immobilized in a cast or boot. A randomized trial compared starting active motion at five days versus the more traditional approach of four weeks of immobilization. Both groups ultimately achieved similar outcomes, but the details of the rehabilitation protocol varied between them.¹⁸ Protocols are trending toward earlier motion at many centers, but the specific timeline should be set by your surgeon based on the quality of the fixation and the health of the tissue.

One aspect of recovery that surprises many patients is the neuromuscular re-education phase. After a posterior tibial tendon transfer for foot drop, for example, the brain must learn that the command “lift the foot” now needs to fire the muscle that previously pulled the foot downward. This sounds baffling, and it is genuinely difficult for some people in the early weeks. Research on tendon transfers in the upper limb has shown that the brain physically reorganizes in response. Motor cortex mapping studies in patients who had tendon transfers for grip reconstruction found that the brain area controlling the transferred muscle shifted toward the area that normally controls the movement’s new function.¹⁹ In other words, the brain does rewire, but it takes time and deliberate practice.

Gait studies in patients after foot drop tendon transfers show that, once retrained, the pressure distribution on the sole of the foot during walking is not meaningfully different from the non-operated leg.²⁰ The foot works well enough that the ground reaction forces look essentially normal, which is a strong objective measure of functional recovery.

When Transfers Fail and Who Is Most at Risk

Tendon transfers do not always succeed. A review of split posterior tibial tendon transfers in children with cerebral palsy identified several risk factors for failure: age under eight at the time of surgery, inability to walk independently before the procedure, and quadriplegic rather than hemiplegic cerebral palsy. Surgical factors that contributed to poor outcomes included incorrect tensioning of the transfer, residual spasticity that was not addressed, over- or under-correction, and leaving a bony deformity untreated.²¹

A large long-term study of posterior tibial tendon transfers in cerebral palsy patients followed for an average of over nine years confirmed this pattern. Among hemiplegic patients (one side affected), 27 of 30 feet achieved a good or excellent result. In paraplegic patients (both legs affected but arms spared), 12 of 16 feet did well. But among quadriplegic patients (all four limbs affected), only 2 of 11 feet had a good outcome.²² The degree of neurological involvement strongly predicts how well the transfer will perform, and surgeons must weigh expected benefit against surgical burden carefully in more severely affected patients.

The Donor-Site Trade-Off

Every tendon transfer takes something from one part of the foot to give to another. When the tibialis posterior is rerouted for foot drop, the foot loses a muscle that normally helps control pronation and support the arch. In younger patients, this can occasionally lead to progressive flatfoot on the operated side years later. When the flexor hallucis longus is harvested for Achilles reconstruction, the big toe loses its primary flexor. Patients may notice reduced push-off strength from the big toe, though as noted earlier, this rarely causes problems in daily life.²³

Toe deformities remain a commonly associated problem after split anterior tibial tendon transfers for spastic varus foot, even when the overall correction is considered successful.²⁴ These are not failures of the procedure in the traditional sense; they are downstream consequences of rearranging the mechanical balance of the foot. You should discuss them with your surgeon so you know what to watch for in the months and years after surgery.

The Growing Role of Allograft Tendon

An emerging alternative to traditional tendon transfers uses donated (allograft) tendon tissue to reconstruct a deficient tendon rather than sacrificing one of the patient’s own tendons. The appeal is straightforward: an allograft can be matched in size to the original tendon, and it eliminates the donor-site consequences described above. Allograft tissue has been used increasingly for the Achilles tendon, the anterior tibial tendon, the peroneals, and the posterior tibial tendon, with early reports suggesting it may improve functional outcomes in certain settings by providing a more anatomically comparable replacement.

Imaging Before and After Surgery

MRI has become central to planning tendon transfers and evaluating how they heal. Preoperatively, it shows the health of the donor muscle, whether it has atrophied or developed fatty infiltration that would make it a poor candidate for transfer. It also reveals the condition of the tendons at the planned insertion site and any associated bone abnormalities that might need to be addressed at the same time.²⁵ After surgery, MRI can confirm that the transfer is intact, identify early complications like fluid collections or bone-tunnel widening, and assess whether the transferred muscle is bulking up with use or slowly wasting. If you have a scan ordered in the months after your procedure, this is typically what the surgeon is looking for.