Applied Evidence

Efficacy of Active Exercises to Improve Range of Motion in Knee Joint After Total Knee Arthroplasty. A Randomized Controlled Trial.

Physiotherapy research international : the journal for researchers and clinicians in physical therapy · 2026 · RCT · PT

Lisbeth Mogensen, Torben Rasmussen, Julie Rasmussen and 1 others

PMID 42125998

Doing knee flexion exercises eight times a day instead of twice produced a 4.1° greater gain in flexion over 18 days in patients with knee flexion under 105° after knee replacement.

Both groups improved substantially, and the extra gain was modest.

Key findings

1The high-frequency group gained 14.2° of knee flexion compared with 10.1° in the low-frequency group, a between-group difference of 4.1° (p = 0.007).

2No secondary outcome showed a significant between-group difference, and most secondary outcomes improved within both groups.

3The high-frequency group averaged 5.3 flexion sessions per day against a target of 8, and the low-frequency group averaged 1.7 against a target of 2.

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What it does not show

The high-frequency group averaged only 5.3 flexion sessions per day against a target of 8, so the effect of full adherence is unknown and the dose-response question remains open. Cluster randomisation by admission day introduces intra-cluster correlation that can reduce the effective sample size and inflate type-I error if not accounted for. Follow-up was limited to the 18-day hospitalisation; no assessment was done at 3 months or later, so durability of the gain is unknown. The amount of pressure applied during the flexion and extension exercises was not standardised and likely varied between participants. Preoperative knee flexion was not recorded, so the degree of surgical loss versus pre-existing stiffness cannot be separated. The dose-response analysis did not adjust for potential confounders.

Declared interests

The authors declare no conflicts of interest and report no funding.

The easy way to misread this

Do not read the 4.1° between-group difference as a large clinical effect. The study expected an 8° gap, and both groups improved substantially on their own. The high-frequency group also averaged only 5.3 sessions per day against a target of 8, so the true effect of full adherence is unknown.

Summarised by AI from the full paper, without a clinician reviewing it. Check it against the source before it changes what you do. Read it on PubMed →


The study

Participants
83 completed (44 high-frequency, 39 low-frequency); 85 enrolled, 2 withdrew before starting
Certainty of evidence
Moderate

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Lisbeth Mogensen, Torben Rasmussen, Julie Rasmussen, et al. Efficacy of Active Exercises to Improve Range of Motion in Knee Joint After Total Knee Arthroplasty. A Randomized Controlled Trial. Physiotherapy research international : the journal for researchers and clinicians in physical therapy. 2026.

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