Exercise before and after total knee or hip arthroplasty: what three systematic reviews show

Whether exercising before a joint replacement, or choosing a particular rehabilitation program afterward, changes recovery is addressed by three systematic reviews published in 2023 and 2024 for total knee arthroplasty (TKA), one of which also covers total hip arthroplasty (THA) ^[1][2][3]. The answer they give is narrower than many readers may expect. Several findings are hedged as what programs "may" do, the knee findings in the 2023 reviews carry low strength of evidence, and for hip arthroplasty the trial evidence on prehabilitation is absent or insufficient ^[1][2][3].

Terms used in this evidence

Hip arthroplasty is another name for hip replacement, an operation in which the surgeon removes damaged cartilage and bone from the hip joint and replaces them with new, man-made parts ^[5]. The 2024 meta-analysis describes TKA as an operation that successfully alleviates pain from knee osteoarthritis, while muscle strength and function remain reduced for a long period afterward ^[3]. In the 2023 prehabilitation review, prehabilitation refers to interventions for patients who are scheduled to undergo the operation ^[2]. Both 2023 review teams assessed strength of evidence for their findings ^[1][2]. The 2024 meta-analysis combined trial results and reported effects as mean differences (MD) or standardized mean differences (SMD) with 95% confidence intervals (CI) ^[3].

Before surgery: what prehabilitation may change

The 2023 prehabilitation review covered patients scheduled for elective, unilateral TKA or THA for primary osteoarthritis, and searched seven databases from January 1, 2005, through May 3, 2021 ^[2]. Eligible designs were randomized controlled trials and adequately adjusted nonrandomized comparative studies reporting performance-based, patient-reported or healthcare utilization outcomes ^[2]. Evidence from 13 TKA randomized controlled trials suggested that prehabilitation may result in increased strength and reduced length of stay, and may not lead to increased harms ^[2]. Pain, range of motion and activities of daily living may be comparable with and without prehabilitation ^[2]. These knee findings were all rated low strength of evidence, and the authors noted that large heterogeneity across the programs evaluated limited strong conclusions ^[2]. There was no evidence or insufficient evidence for all other outcomes after TKA ^[2].

At the strength reported, the review's knee findings concern strength and length of stay, whereas pain may be comparable with and without prehabilitation ^[2].

After knee arthroplasty: does the type of program matter

A companion 2023 systematic review examined rehabilitation after elective, unilateral TKA for primary osteoarthritis, using the same search window and the same eligible study designs ^[1]. Evidence from 53 randomized controlled trials suggested that various rehabilitation programs may lead to comparable improvements in pain, range of motion and activities of daily living ^[1]. Rehabilitation in the acute phase may lead to increased strength, and may result in similar strength when delivered in the postacute phase ^[1]. No studies reported evidence of risk of harms from rehabilitation delivered in the acute period, and risk of harms among various postacute programs seemed comparable ^[1]. All findings were of low strength of evidence ^[1]. The authors concluded that evaluation of rehabilitation after TKA needs a systematic overhaul, including standardized intervention components and core outcomes, to sufficiently guide future practice or research ^[1].

Resistance exercise specifically

The 2024 meta-analysis asked a more focused question: the effects of lower-limb active resistance exercise on mobility, physical function, muscle strength and pain in patients with TKA, compared with no intervention or a rehabilitation program without it ^[3]. It included 14 randomized controlled trials involving 880 patients, searched databases through September 2023, and used GRADE to assess the quality of evidence ^[3]. Compared with conventional exercise, immediately after the intervention, resistance exercise showed significantly greater improvement in these measures ^[3]:

• Maximal walking speed, a mobility outcome: MD 0.13 (95% CI 0.08 to 0.18; P < 0.00001) ^[3].
• Timed Up and Go, a physical function outcome: MD -0.92 (95% CI -1.55 to -0.28; P = 0.005) ^[3].
• Knee extension power: SMD 0.58 (95% CI 0.20 to 0.96; P = 0.003) ^[3].
• Knee flexion power: SMD 0.38 (95% CI 0.13 to 0.63; P = 0.003) ^[3].
• Knee flexion range of motion: MD 2.74 (95% CI 1.82 to 3.67; P < 0.00001) ^[3].
• Pain on a visual analogue scale (VAS): MD -4.65 (95% CI -7.86 to -1.44; p = 0.005) ^[3].

The groups did not differ significantly on the 6-Minute Walk Test (MD 7.98; 95% CI -4.60 to 20.56; P = 0.21), the Stair Climb Test (MD -0.79; 95% CI -1.69 to 0.10; P = 0.08) or knee extension range of motion (MD -0.60; 95% CI -1.23 to 0.03; P = 0.06) ^[3]. The authors concluded that patients who receive lower-extremity resistance exercise show better clinical effects in pain relief, strength recovery and knee range of motion, and that it may be beneficial for mobility and physical function ^[3].

These findings differ in emphasis from the 2023 rehabilitation review, which found various post-TKA programs may lead to comparable improvements; the two reviews asked different questions, with ^[1] comparing rehabilitation programs and ^[3] comparing resistance exercise against no intervention or rehabilitation without it ^[1][3].

Hip arthroplasty: what is and is not known

The prehabilitation review identified six THA randomized controlled trials, yet found no evidence or insufficient evidence for all THA outcomes ^[2]. As background, MedlinePlus describes hip replacement as surgery for people with severe hip damage, most commonly from osteoarthritis, which might be an option if treatments such as physical therapy, pain medicines and exercise have not helped ^[5]. It lists hip dislocation as the most common problem after surgery, because a man-made hip is smaller than the original joint and the ball can come out of its socket, and notes that the surgery can also cause blood clots and infections ^[5]. People with a hip replacement might need to avoid activities such as jogging and high-impact sports ^[5].

Where AthleticsMD fits

AthleticsMD describes itself as Maryland's first independent Comprehensive Outpatient Rehabilitation Facility (CORF), with locations in Columbia and Laurel/Fort Meade ^{[AthleticsMD]}. It offers PREOOP surgical pre-optimization programs and physical and occupational therapy, and was founded by a critical care anesthesiologist and a general surgeon ^{[AthleticsMD]}. Questions about whether prehabilitation or a specific rehabilitation approach suits a particular person belong with a health care provider ^[4].

Limitations

• This explainer relies on the published abstracts, which do not report the units for several outcomes in the resistance exercise meta-analysis or its GRADE ratings ^[3].
• The rehabilitation review rated all its findings low strength of evidence, and the prehabilitation review rated its reported knee findings low ^[1][2].
• Both 2023 reviews listed adequately adjusted nonrandomized studies as eligible, but the findings their abstracts report are attributed to randomized controlled trials ^[1][2].
• Heterogeneity across prehabilitation programs limited strong conclusions ^[2].
• The resistance exercise results describe outcomes immediately after the intervention, so durability is not addressed ^[3].
• The 2023 reviews' searches ended May 3, 2021, and the 2024 review's in September 2023, so later trials are not captured ^[1][2][3].
• The 2023 reviews were limited to elective, unilateral surgery for primary osteoarthritis, so their findings may not extend to other indications ^[1][2].