Knee replacement:
every degree of flexion counts
One number that governs the rest
After a knee replacement, your recovery comes down largely to one number: how many degrees your knee agrees to bend.
Your physiotherapist will measure it at every session. Around 90 degrees by the second week, and you can sit down and stand up normally. Around 110 to 120, you can climb stairs, get into a car, put on a sock. Below that, everyday life stays complicated.
What stops the knee from bending
Swelling first. A knee full of fluid does not bend, mechanically. The volume takes up the space and blocks the range before pain even gets involved. It is the first lock to release, and the one that responds fastest.
A quadriceps on standby next. After the operation, the muscle at the front of the thigh barely answers. You ask it to straighten the leg and nothing comes. It is a reflex rather than weakness: a swollen knee cuts the signal. Without that muscle there is no control of the knee, and no safe progress in flexion.
Time, finally. A knee that stays barely mobile becomes a stiff knee. That is why the first weeks matter more than the ones after: degrees won early come more easily.
Week by week: the reference points
The first milestone
You walk on day one or day two, with a walker or crutches. Pain peaks in the first 48 to 72 hours, then decreases. Expected flexion by the end of the week: 60 to 80 degrees.
This is also the week electrical stimulation can start: in the reference trial after knee replacement, Compex® sessions on the quadriceps began 48 hours after surgery, twice a day2. Cold and compression are at their most useful in the same window.
Where it is decided
Pain drops, rehabilitation steps up, you see your physiotherapist several times a week. The target: 90 degrees by the second week, 110 by the sixth. Regaining full extension, knee perfectly straight at 0 degrees, counts as much as flexion. Swelling is still there at the end of the day and still needs treating.
Stairs become possible again
Walking outdoors becomes comfortable again, stairs become manageable. Expected flexion: 120 degrees and above. Stationary cycling, swimming and walking resume on your physiotherapist's advice.
Strength comes back
Swelling gradually disappears and strength keeps rebuilding. The knee is still stiff some mornings or at the end of the day, and that is normal.
The plateau
Between 6 and 12 months you reach your optimal level of recovery. Some patients keep progressing up to 18 months.
Cold and compression: what the trial shows
Cryocompression combines controlled cold with dynamic compression that inflates and deflates, like a light massage. It acts on swelling and on pain at the same time, which is to say on both locks that hold flexion back.
A 2024 randomised trial compared the Game Ready® with ice packs in 40 patients after knee replacement, all of them in a rehabilitation centre and all receiving the same rehabilitation programme1.
What this means precisely: by the end of the three weeks, both groups reached comparable flexion1. What cryocompression changes is not the ceiling you will reach, it is how fast you get there. And those first weeks are what decide the comfort of your days, and how easily the rest of the rehabilitation goes.
In practice: sessions of 20 to 30 minutes, several times a day in the first week, then before or after physiotherapy. A session before lets you mobilise a less painful knee, a session after limits the inflammation the exercises cause. At day twenty one, the patients in the cryocompression group covered about a hundred metres more on the six minute walk test1. You will not gain extra degrees in the end, you will gain them sooner.
Sources
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Randomized controlled trial of compressive cryotherapy versus standard cryotherapy after total knee arthroplasty: pain, swelling, range of motion and functional recovery. BMC Musculoskeletal Disorders. 2024.
Quesnot A, Mouchel S, Ben Salah S, Baranes I, Martinez L, Billuart F.
DOI 10.1186/s12891-024-07310-7 · PMID 38419032 -
Early neuromuscular electrical stimulation to improve quadriceps muscle strength after total knee arthroplasty: a randomized controlled trial. Physical Therapy. 2012.
Stevens-Lapsley JE, Balter JE, Wolfe P, Eckhoff DG, Kohrt WM.
DOI 10.2522/ptj.20110124 · PMID 22095207
This article is for information only. It does not replace the advice of your surgeon, doctor or physiotherapist. Always follow the recommendations of your medical team.