Yes, the quadriceps tendon does grow back after being harvested for ACL reconstruction. Imaging studies show the donor site heals by about 93% within six months, and some patients achieve full defect closure in that same timeframe. The tissue that fills in is not identical to the original tendon, but it restores structural continuity and, for most people, functional strength.
What Gets Removed During Surgery
During ACL reconstruction using a quad tendon autograft, the surgeon removes a strip of tendon from just above the kneecap. The graft is typically about 10 mm wide and 7 mm thick, taken from a tendon that averages roughly 43 mm wide at its attachment point. So the harvest removes a relatively small portion of the overall tendon, leaving the majority of the structure intact. This partial-thickness approach is one reason the donor site heals as well as it does.
How the Donor Site Heals
After the strip is removed, the body fills the gap with new tissue over the following months. Ultrasound imaging at around six and a half months post-surgery shows the defect heals by an average of 93%, with some patients showing complete closure of the harvest site. The remaining gap at that point is small: roughly 20 mm long, 5.6 mm wide, and 1.6 mm thick on average.
For comparison, when the patellar tendon is used instead (the bone-patellar tendon-bone graft), about 70% of patients show full donor site recovery at six months and 100% by twelve months. The quad tendon appears to heal at a similar or slightly faster rate.
It’s worth noting that the tissue filling the gap is primarily fibrovascular scar tissue rather than a perfect replica of the original tendon. It’s functional and restores the structural profile of the tendon, but under a microscope it looks different from native tissue. For practical purposes, this distinction rarely matters. The tendon works.
How Strength Recovers
The bigger issue for most people isn’t whether the tendon fills in (it will) but how long it takes to rebuild quadriceps strength. At six months after ACL reconstruction, the operated leg typically shows a 23% strength deficit compared to the other leg, with a wide range from 3% to 40%. By twelve months, that gap narrows to about 14% on average, though some people still show deficits ranging from 3% to 28%.
These strength numbers reflect ACL reconstruction in general, not just quad tendon grafts specifically. The deficit comes from a combination of factors: the surgical trauma, weeks of limited activity, muscle inhibition from swelling, and the time it takes to progressively reload the quadriceps. Targeted rehab is the main driver of recovery, not just waiting for the tendon to heal on its own.
What Rehab Looks Like
Rehabilitation after a quad tendon ACL reconstruction follows a careful progression designed to protect both the new ACL graft and the healing donor site. In the first four weeks, the focus is on basic quadriceps activation: isometric contractions (tightening the muscle without moving the joint) and straight-leg raises. The goal is to “wake up” the quad and restore its connection to the nervous system, since the muscle often shuts down after knee surgery.
From weeks four through eight, you begin light knee extensions through a limited range of motion, starting unresisted and adding light resistance around week six. The restriction is specific: no loaded open-chain knee extension beyond 45 degrees for the first eight weeks. This protects the healing donor site while gradually introducing stress to encourage tissue remodeling.
After that, the program progressively adds squats, lunges, and eventually sport-specific movements. Most protocols aim for a return to full activity between 9 and 12 months, depending on strength testing and functional benchmarks.
Less Donor Site Pain Than Other Grafts
One of the reasons quad tendon autografts have gained popularity is that they cause less long-term discomfort at the harvest site than the traditional patellar tendon graft. In a 10-year follow-up study, 64% of patellar tendon patients still reported pain with kneeling (23% describing it as severe), compared to 33% of quad tendon patients, all of whom rated their pain as mild. Pain during squatting followed the same pattern: 55% in the patellar tendon group versus 29% in the quad tendon group at the decade mark.
Compared to hamstring tendon grafts, the quad tendon also performs well. Only about 5% of quad tendon patients reported tenderness, numbness, or irritation at the donor site, versus 15% in the hamstring group. A larger systematic review put anterior knee pain after quad tendon harvest at about 10% and kneeling pain at roughly the same rate.
Functional outcomes between graft types are comparable. Studies show no significant differences in knee stability or function at one year or ten years, regardless of which tendon was used. The main advantage of the quad tendon graft is the lower rate of lingering donor site symptoms, which matters for anyone who kneels, squats, or loads their knee heavily in daily life or sport.