Quadriceps Tendon for ACL Reconstruction: Benefits, Limitations and Recovery Considerations

After an anterior cruciate ligament (ACL) tear, ACL reconstruction is a common treatment for people whose knee remains unstable, who want to resume running and jumping, or who need to return to sports such as football, basketball or skiing.

The operation uses a tendon graft to replace the ACL that has lost its function. The quadriceps tendon (QT) is one of the autografts commonly used today.

Compared with traditional bone–patellar tendon–bone and hamstring tendon grafts, the quadriceps tendon offers a larger cross-sectional area, adjustable graft dimensions and potentially less anterior knee pain after harvesting. Its clinical use has increased in recent years.

However, patients should also understand that harvesting the quadriceps tendon may cause an early reduction in knee extension strength, donor-site pain and slower quadriceps recovery during the initial stages of rehabilitation.

The ACL lies in the centre of the knee. Its main role is to limit excessive forward movement of the tibia relative to the femur, while also helping control knee rotation. After a complete tear, the ligament has limited capacity to regain its stabilising function on its own, particularly in younger patients with high sporting demands.

ACL reconstruction uses a piece of the patient’s own tissue capable of withstanding substantial tensile loads. It is secured through tunnels in the femur and tibia, close to the position of the original ACL. The graft then gradually undergoes revascularisation, tissue remodelling and tendon-to-bone healing, ultimately taking on the role of stabilising the knee.

Common autografts include hamstring tendon, bone–patellar tendon–bone and quadriceps tendon. The choice takes into account the patient’s age, sport, previous surgery, occupation and need to kneel, as well as the reconstruction techniques familiar to the surgeon.

The quadriceps is a group of four main muscles at the front of the thigh. They converge into the thick quadriceps tendon, which attaches to the upper border of the patella, or kneecap. When the quadriceps contracts, this extensor mechanism helps straighten the knee, making it essential for walking, running, climbing and descending stairs, standing up and jumping.

ACL reconstruction usually uses only part of the quadriceps tendon. The graft can consist entirely of soft tissue or include a small block of bone from the patella.

The most obvious advantage of the quadriceps tendon is its substantial thickness.

An ACL graft needs adequate diameter and strength. Some patients have relatively thin hamstring tendons, and it is difficult to predict the exact graft size before harvesting. The quadriceps tendon usually provides a generous amount of tissue, allowing the surgeon to adjust the length, width and thickness to the patient’s anatomy.

Another practical advantage is the option to use it with a bone block or as an all-soft-tissue graft.

A quadriceps tendon graft with a patellar bone block allows bone-to-bone healing between the block and the bone tunnel at one end. An all-soft-tissue graft avoids harvesting bone from the patella. Both techniques are currently used in clinical practice.

Hamstring tendon has long been a very common choice for ACL reconstruction. Harvesting requires a relatively small incision, and there is extensive long-term clinical experience with it. However, removing the semitendinosus and gracilis tendons can affect some knee flexion and internal rotation strength, and tendon size varies considerably between patients.

Using the quadriceps tendon preserves the hamstring structures. This may appeal to people whose activities involve frequent knee flexion, running and explosive movements.

A 2024 systematic review restricted to randomised controlled trials analysed 474 patients undergoing ACL reconstruction. It found no clear differences between quadriceps and hamstring tendon grafts in functional scores such as IKDC, Lysholm and Tegner, graft failure rates or overall adverse events. Harvest-site symptoms were less frequent in the quadriceps tendon group, although the quality of the evidence remained insufficient to establish its overall superiority over hamstring tendon.

A bone–patellar tendon–bone graft usually consists of a strip from the middle of the patellar tendon, together with a small bone block from both the patella and the tibial tubercle. It allows direct healing between the bone blocks and bone tunnels and has long been widely used in elite athletes and some high-risk patients.

Donor-site symptoms are a notable concern. Some patients develop anterior knee pain, pain when kneeling or patellar tendon discomfort after surgery. A small number may also experience a patellar fracture or complications involving the patellar tendon.

The quadriceps tendon is harvested above the patella, which can reduce interference with the patellar tendon itself.

This may be a factor in graft selection for people who frequently kneel at work, including construction workers, maintenance workers and some other manual workers.

The harvest site forms part of the knee’s extensor mechanism, so patients may experience quadriceps inhibition and reduced knee extension strength after ACL reconstruction. Pain, joint effusion and restricted movement caused by ACL surgery itself also inhibit the quadriceps. The additional effect of harvesting can make early weakness more pronounced.

Patients commonly report difficulty lifting the leg, poor control when going downstairs, noticeable weakness in the operated leg during single-leg squats and a thinner muscle contour at the front of the thigh compared with the other side.

Most patients improve gradually with structured rehabilitation, but recovery takes longer than a few weeks. For athletes who need to run, jump, stop abruptly and change direction, the extent to which quadriceps strength recovers towards that of the unaffected side directly influences the timing of return to sport.

Pain, numbness, scarring, tendon discomfort or anterior knee pain may also persist at or around the harvest site.

Both techniques can be used for ACL reconstruction.

A quadriceps tendon graft with a patellar bone block provides bone-to-bone healing at one end and uses well-established fixation methods. However, harvesting bone from the upper border of the patella adds bone-block-related concerns, such as pain at the bone harvest site and a rare risk of patellar fracture.

An all-soft-tissue quadriceps tendon graft avoids removing a patellar bone block and reduces bone harvesting, but both ends depend on soft-tissue healing within the bone tunnels.

No single patient group is currently required to use a quadriceps tendon graft. For primary ACL reconstruction, it is one of the main autograft options alongside hamstring tendon and bone–patellar tendon–bone.

The quadriceps tendon may offer some advantages for people concerned about anterior knee pain when kneeling. It may also be considered by those who wish to preserve hamstring tendon function.

In revision ACL reconstruction, the quadriceps tendon can provide another autograft source if the hamstring or patellar tendon was used in the first operation.

If the knee remains unable to straighten fully after ACL reconstruction, walking mechanics, quadriceps activation and patellofemoral movement can all be affected.

Early on, patients often focus on how far they can bend the knee, but full extension is equally important. Marked swelling, pain or fear of movement can lead to a habit of keeping the knee slightly bent, which makes recovery more difficult over time.

Early rehabilitation therefore usually addresses effusion and pain while gradually restoring extension close to that of the unaffected knee. Persistent loss of extension, obvious locking or a prolonged lack of improvement in range of motion should be assessed promptly by the surgeon or rehabilitation therapist.

The ACL graft undergoes biological remodelling after surgery, and muscle strength, proprioception and movement control also need to be rebuilt. Being able to walk without pain in daily life does not necessarily mean that the knee is ready for running.

Before starting a running programme, the knee usually needs to have no significant effusion, near-normal range of motion, stable performance of single-leg movements and a sufficient degree of quadriceps strength recovery.

If a substantial difference in knee extension strength remains after a quadriceps tendon graft, running too early may lead to compensation through the hips, the unaffected leg or other muscle groups.

The decision to resume running should therefore consider time, strength and movement quality together.

Many repeat ACL tears occur in young people with high sporting demands. Returning to football, basketball, badminton or skiing involves sudden stops, turns, jumps and single-leg landings, all of which place much greater demands on the ACL graft than everyday walking.

Assessment usually includes quadriceps and hamstring strength, single-leg hop tests, symmetry between the legs, landing control, dynamic balance and psychological readiness.

Alongside the risks shared by ACL reconstruction procedures, including infection, blood clots, joint stiffness, graft retear and problems involving bone tunnels or fixation devices, quadriceps tendon grafts have their own donor-site risks.

These may include pain at the front of the thigh or above the patella, reduced quadriceps strength, local numbness, haematoma and harvest-site discomfort. Techniques using a bone block also add the possibility of patellar complications.

A 2023 systematic review covering 2,389 knees reconstructed with quadriceps tendon grafts reported a range of postoperative complications, with persistent knee pain among the more common problems.