Before surgery, everyone tells you the same thing: do your physical therapy, no matter what. What they don't tell you is how much it can hurt.
In knee replacement forums and support groups, the stories are strikingly similar. Tears on the therapy table. Swelling that takes days to go down. Dread the night before every appointment. If that sounds familiar, here are seven things other patients wish someone had told them.
For many people, PT hurts more than the surgery did
You were asleep for the surgery. You're wide awake for PT, and the work of bending a freshly operated knee is done by you, often several times a week. Patients say it plainly:
"My physical therapy for my knee replacement hurt more than the surgery." — Knee replacement patient, online forum
"I have screamed and often cried as the PT pushed me to pull the strap back harder to increase the flex." — Total knee replacement patient, 10 weeks post-op
If you've cried in PT, you're in very large company. One 67-year-old man wrote that he was "in tears during many of those sessions until I said enough is enough."
The swelling after a session is the real setback
The session itself ends. The swelling doesn't. Patients describe a knee that puffs up after therapy, stiffens overnight and takes days to settle, often just in time for the next appointment.
"They physically manipulate my knee to the point of extreme pain… It takes 2 days to recover, then I'm back for another 3x week session." — Total knee replacement patient, 4½ weeks post-op
Another patient summed up the cycle in one line: "Forcing pain causes swelling; swelling restricts movement and causes more pain."
That's why swelling is where red and near-infrared light therapy (photobiomodulation, or PBM) has been studied most after knee replacement. Every randomized trial in a 2026 Journal of Orthopaedics review that measured swelling found less of it with light therapy.
Knee replacement patients received 650 nm red + 850 nm near-infrared light daily on post-op days 1–5.
Swelling was significantly lower in the light therapy group by day 6 (p < 0.001).
How much the thigh swelled by day 3 after knee replacement (80 patients). Lower is better.
22% less swelling with light therapy than with Celebrex (celecoxib), a prescription anti-inflammatory (p = 0.021). This trial used an 810 nm light source before surgery.
A bad session can wreck your home exercises too
PT isn't just the hour in the clinic. You're also expected to do exercises at home, sometimes several times a day. When one session leaves you swollen and sore, those home exercises are the first thing to go.
"Overdoing can cause you to be in so much pain at first you can't work on your own in between visits… Go slow." — Experienced knee replacement patient, advice to a newcomer
"I'm not sure if PT days are this much worse for everyone or if it's just me… the rest of the day is rough each time." — Knee replacement patient, recovery forum
The faster your knee settles after a session, the sooner you can get back to the gentle movement your recovery depends on.
You're allowed to tell your therapist "that's too much"
Many patients don't realize they can ask for changes. Those who did often say it made the difference, and they still reached their goals.
"If there was an exercise I felt was too much I said no and they modified it... Listening to my body worked for me." — Knee replacement patient who met all his milestones
"PT should not be painful, discomfort is common, but pain is a no go for me." — Member of a knee replacement support forum
Physical therapy is one of the most important parts of recovery, so don't skip it. But you can talk to your therapist and surgeon about pacing, especially when swelling is high.
Calm the swelling between sessions. RedRelief uses 660 nm red + 850 nm near-infrared light, the same bands as the knee replacement trials.
See How RedRelief Works →Timing pain pills around PT gets old fast
One of the most common tips in knee replacement groups is to take pain medication before every session:
"I saved my pain meds for PT. It helps to get the most out of your sessions." — Knee replacement patient, recovery forum
That works for many people, but patients also worry about side effects and dependence. One wrote, "I am not a drug addict, but feel like I'm a suspected addict."
In the 2026 trial of 80 knee replacement patients, light therapy was compared directly with Celebrex. Pain at rest 24 hours after surgery was statistically no worse with light therapy than with the drug (3.9 vs 3.7 out of 10), with fewer stomach problems:
Light therapy doesn't replace the pain plan your surgeon gives you. It's a drug-free tool you can add alongside it.
Light therapy alongside rehab helped patients reach their bend
Every PT session is chasing the same number: how far your knee will bend. In a 2023 randomized trial (Alghamdi et al.), 44 knee replacement patients all did rehab. Half also received 650 nm red light for 12 sessions over 6 weeks.
The light therapy group had significantly better knee flexion and significantly better WOMAC scores, a standard measure of pain, stiffness and daily function.
2-minute walk test result reported by post-op day 6. Higher is better.
As reported in the 2026 Journal of Orthopaedics scoping review of knee replacement trials.
What you do between sessions matters as much as PT itself
Patients who got through PT most comfortably built a recovery routine for the hours after each session. The most common pieces:
- Ice and elevate. One patient's routine: "I ice, elevate for about 20 minutes 4-5 times a day."
- Rest the next day if a session leaves the knee extra swollen, with only gentle movement.
- Add red and near-infrared light while you're resting. It's passive and nothing is forced.
"After a few weeks of regular sessions, I noticed reduced stiffness and less swelling, especially after long walks or physical therapy. It didn't completely replace exercises or pain management, but it made the recovery process feel a bit smoother and more comfortable." — Knee replacement patient on using red light therapy, Facebook support group
Because RedRelief is cordless, you can wear it for a 20–25 minute session while your leg is up and iced after PT.
What the research does and doesn't say
- Swelling: the most consistent finding. Every knee replacement trial that measured it found less swelling with light therapy.
- Knee bend and function: positive in the trials that measured them, though not every trial showed a difference in bend.
- Pain: results are mixed. One trial found significantly less pain; another found no difference.
- No study has tested whether light therapy makes PT sessions themselves less painful. The trials are small (30–80 patients) and used clinic devices.
