Felt a Pop After Knee Surgery? Re-Tear or Setback, and When to Call

The story below is a composite of real experiences; details changed.

Wade steps off his van’s back bumper with a box of tile on his shoulder. His right foot lands, the knee twists, and something pops.

He’s 44 and lays floors for a living. Four months ago, a surgeon stitched a torn meniscus in that knee. He’d just started kneeling on the job again.

He finishes the job anyway, kneeling on his left. By evening, the right knee is filling up, tight and puffy around the kneecap.

At 2 a.m. he’s still awake, doing the math: another surgery, more weeks with no pay. Did one bad step just undo the whole surgery?

Here’s how often re-tears really happen, which signs to report, how a normal setback tends to look, and when to call.

How often a repair or graft actually fails

That 2 a.m. math runs high.

For a stitched meniscus, three big reviews, all built on low-level evidence such as look-back studies:

• Over about 7 years. Twelve studies, 864 people. About 1 in 5 repairs (19%) needed another operation. (Knee Surgery, Sports Traumatology, Arthroscopy, 2022)
• Over about 3.5 years. Fifty-one studies, close to 4,000 repairs. About 1 in 7 (15%) failed. (American Journal of Sports Medicine, 2024)
• Age 40 and up. Across 14 studies of 466 people chosen for a repair, about 1 in 8 repairs (12%) failed, as each study defined it. That was not significantly different from people under 40. (Orthopaedic Journal of Sports Medicine, 2024)

A trim cuts the damaged tissue away. (AAOS OrthoInfo) So after a trim, a “re-tear” is a new tear in what’s left. In one 2011 review, about 1 to 4 in 100 trims (1.4% to 3.9%) needed another operation, depending on follow-up. (Arthroscopy, 2011)

For an ACL graft:

• Across 14 studies. In younger athletes (study average ages about 16 to 29), grafts tore again in 7%, about 1 in 14. Studies counted re-tears differently, and counting only repeat surgery can miss some. (American Journal of Sports Medicine, 2016)
• Over age 40. Across 21 studies, the middle graft rupture rate was 2.7%, under 3 in 100. In the 9 that reported overall failure, the middle rate was 5%, about 1 in 20. Only 4 defined failure explicitly. (Arthroscopy, Sports Medicine, and Rehabilitation, 2024)

Re-tears are real, and they’re the exception. In these studies, about 4 in 5 or more repairs and 9 in 10 or more grafts didn’t fail, as each study counted it.

Re-tear or setback: what tends to separate them

We found no tested home check that tells them apart. But sources describe the signs of a tear, and how a setback tends to look.

For a meniscus tear, AAOS lists a pop, pain, stiffness and swelling, and catching or locking. It adds giving way, and a knee that can’t move through its full range of motion. (AAOS OrthoInfo)

For an ACL tear, the AAOS list includes a pop, pain, a knee that gives out, and swelling within 24 hours. (AAOS OrthoInfo) A failed graft, one review says, may bring pain, lost motion and repeated giving way. (Annals of Joint, 2018)

The AAOS lists describe first tears. We found no study of how a failed meniscus repair feels.

“Locking” has two meanings. True locking, where a torn piece blocks the knee from straightening, is less common than stiffness from swelling or pain, one review says. (Australian Family Physician, 2012)

A setback looks different. One NHS leaflet for knee injuries calls a small rise in pain or swelling normal if it settles within 24 hours of exercise. (East Lancashire Hospitals)

After ACL surgery or a meniscus repair, hospital leaflets say rising or excessive swelling may mean you’re doing too much. (Royal United Hospitals Bath, 2021; East Kent Hospitals) Don’t stop walking or doing your exercises, the meniscus leaflet says, just change how many you do. (East Kent Hospitals)

A pop starts the story. Locking, giving way and a knee you can’t straighten are the parts to report.

When the risk runs highest

In the 7-year meniscus review, 87 of the 165 failures had a known date. About two-thirds of those (64%) came within 2 years, and about 1 in 3 later. (Knee Surgery, Sports Traumatology, Arthroscopy, 2022)

One NHS trust says to avoid squatting past 90 degrees, pivoting and twisting for 3 months after a repair. (University Hospitals Coventry and Warwickshire, 2024)

Another NHS leaflet says a repair is more likely to fail if you don’t follow the post-op advice and rehab. (Lancashire Teaching Hospitals, 2023) For floor work, see kneeling after knee surgery.

Of 755 people from one surgeon’s practice, 673 were followed up. An estimated 1 in 20 ACL grafts (5%) had torn again by year 2, and about 1 in 9 (11%) by year 15. Techniques have changed since those 1993 and 1994 surgeries. (American Journal of Sports Medicine, 2012)

One study followed 106 athletes in pivoting sports for 2 years after ACL surgery. Each extra month before returning to sport, up to 9 months, was linked to a 51% lower knee reinjury rate, about half. (British Journal of Sports Medicine, 2016)

That was sport, not work. For timing by job, see return to your kind of work after meniscus surgery.

The first 2 years carry more of the risk. Sticking with your restrictions and rehab is the part you control.

What your surgeon will likely check

For a meniscus, expect pressing along the joint line and the McMurray test, which bends, straightens and rotates the knee. (AAOS OrthoInfo) For an ACL graft, expect looseness tests such as the Lachman and the pivot shift. (Annals of Joint, 2018)

An MRI after a repair is harder to read. (Radsource, 2020) One with contrast dye does better than a plain one. (American Journal of Roentgenology, 2018)

In 84 people with no symptoms, about 3 years after a repair, about 2 in 5 (39%) had MRIs read as “not healed.” The authors called them active patients. That was one hospital in Argentina, and the full group’s average age was 27. (World Journal of Orthopedics, 2023)

A re-tear doesn’t automatically mean another operation. For a failed ACL graft, one review says the reason to redo it is ongoing instability in daily life or sport. It lists a lack of significant symptoms as a reason not to operate. (Annals of Joint, 2018)

Bring your operative report: it helps the radiologist read your MRI. (Radsource, 2020) For more, see five questions to ask before you leave.

A scan is one piece of evidence. How your knee behaves is the other.

What to do tonight and tomorrow morning

You can’t diagnose a re-tear at home. You can hand your surgeon a clear picture.

Write it down tonight. Tomorrow, the log does the talking.

Back at the van

At 6 a.m., Wade checks the knee against his notes. It’s up 1.5 cm, but it straightens almost all the way. No limp, no catching, no buckling.

At 8, log in hand, he calls the surgeon’s office from the van. They book an exam that week.

He still doesn’t know if it’s a re-tear. At 2 a.m., the math was surgery and lost pay. Now it’s a page of facts, and a surgeon will read it.

If the scare shook your faith in the knee, read you used to trust your body.

Your next step: tonight, write down what happened and measure both knees. Tomorrow, finish the log before work and call your surgeon’s office.

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Wade is a composite, drawn from the kinds of stories tradespeople describe after knee surgery. The details are illustrative.