Knix leakproof underwear review: does it work for bladder leaks?

Name: Knix leakproof underwear review: does it work for bladder leaks?
Creator: MenoWoman

Knix underwear can catch light bladder leaks and may replace a pad for some women, but it only contains leaks; it does not treat them. Supervised pelvic floor training is the recommended first treatment and can reduce leaks over time.

Researched by the MenoWoman team. Edited by Marcela Sat. Updated 7 November 2026. We may earn from links.

See a doctor if you leak often, have blood in your urine, pain or burning when you pee, a feeling of something bulging in the vagina, or sudden changes in bladder control. Get urgent help if you cannot pass urine or lose bowel or bladder control with back pain or numbness.

What it is and what the brand claims

Knix makes reusable, washable underwear with an absorbent panel in the gusset. It is sold in several absorbency levels for periods and light bladder leaks, with a dedicated bladder leaks range.¹

The brand rates absorbency in tampon terms. For example, it says its light level holds one to three regular tampons' worth, and its heavy level four to seven super tampons' worth.¹ This is an evidence review, not a hands-on test.

How it works for bladder leaks

Leakproof underwear uses layers that absorb fluid, lock it away from the skin, and block it from passing through. That can work for small leaks when you cough, laugh, sneeze or exercise, which is common after menopause.

Urine flows faster than period blood and can come in a larger gush. Tampon-based ratings may not show how a pair handles a sudden leak. The brand's own figures for bladder leak volume are given for its men's range, not its women's range.¹ Larger leaks may need a purpose-made continence product.

We found no published studies testing Knix, or any brand of leakproof underwear, in women with bladder leaks.

What the research shows: containment vs treatment

Underwear and pads hide leaks but do not change the cause. Leaks after menopause often come from weak pelvic floor muscles and thinning tissues as estrogen falls. Many women can improve them.

NICE, the UK guideline body, says women with stress urinary incontinence should be offered supervised pelvic floor muscle training for at least three months as the first treatment.⁴ Other options include bladder training, vaginal estrogen and medicines, which a doctor can discuss. See our pages on bladder leaks and pelvic floor exercises after menopause.

Many women use both. Leakproof underwear can give confidence while pelvic floor training builds strength over weeks and months.

Leaks can also come from an overactive bladder, which causes a sudden urge to go. That type responds to different treatments, so it helps to get the kind of leak checked rather than guess.

Safety and the PFAS question

PFAS are long-lasting "forever chemicals" sometimes used to make fabrics resist water and stains. In 2022, a US class action alleged that Knix underwear contained PFAS, based on fluorine testing cited in the complaint.² Knix disputed the claims and sought sanctions against the lawyers behind the suit.³ The plaintiffs dropped the case in 2023, and no court ruled on whether the claims were true.²

Knix says it does not intentionally use PFAS in its leakproof products. It says an independent third-party lab has tested its fabrics for PFAS since 2020, and that its most recent results, from August 2026, found no PFAS or organic fluorine at the testing limits.¹ It also says it cannot promise every product is PFAS-free, because PFAS are widespread in the environment.¹ These results are published by Knix itself; we found no recent testing by a regulator or an independent group.

A US poison control center notes that no published studies have measured harm from PFAS in period underwear, and that absorption through the skin is thought to be less likely.⁵ Wash new pairs before use, and stop if you get itching or a rash. Change damp underwear promptly to protect your skin.

Who it might suit and alternatives

Knix may suit women with light, occasional leaks, or with leaks during perimenopause alongside irregular or heavy periods. For heavy periods, see heavy periods in perimenopause.

Women with frequent or larger leaks should see a doctor, nurse or pelvic health physiotherapist. Compare other options on our period and leak underwear and pelvic floor product pages.

Some women also prefer reusable underwear to cut waste from disposable pads. If you are allergic to certain fabrics or elastics, check the materials list before buying.

Price and value

Knix underwear is sold by the pair or in multipacks as one-off purchases. Because it is reusable, it may cost less than disposable pads over time, depending on how often you need it and how long each pair lasts. Check the current price.

Follow the brand's washing advice, since heat and fabric softener can affect absorbent layers.

What it is used for: evidence rated

Option	Evidence	What the research shows
Supervised pelvic floor muscle training	Strong evidence	NICE recommends at least three months as the first treatment for stress urinary incontinence.⁴
Catching light bladder leaks	Weak evidence	Brand absorbency ratings only; no published studies test Knix or similar underwear for bladder leaks.¹
Free of PFAS	Weak evidence	Knix reports that independent-lab tests it arranged found none at testing limits, but says it cannot guarantee zero; no regulator or independent testing was found.¹
Treating stress leaks long-term	No evidence	Underwear contains leaks but does not change the cause.

Ratings explained: how we rate. Always talk to a doctor or pharmacist before starting a medicine or supplement.