To educate health and fitness professionals about the benefits of prehabilitation for patients undergoing a Total Knee Arthroplasty (TKA).
To provide health and fitness professionals with an overview of the peer-reviewed literature for the efficacy of prehabilitation resistance training as a treatment for Total Knee Arthroplasty.
To provide health and fitness professionals with the guidelines for an effective and safe prehabilitation resistance training program for patients undergoing a Total Knee Arthroplasty.
One of the most common chronic health problems affecting more than 7 million Americans is Osteoarthritis (OA) (24). In the United States there are more than 381,000 TKAs performed annually and by the year 2030 the number of TKAs performed annually is predicted to increase by more than 600% (24).
OA leads to the need for TKA in order to alleviate pain and increase physical function (24). However, following a TKA, full recovery of strength and physical function is rare (18).
Low quadriceps muscle strength has been associated with patients
who have OA and it has been shown to be a direct predictor of functional ability. Because of this direct relationship, prehabilitation resistance training is often recommended (24) with the hope of improving post-operative outcomes for the patient.
Therefore, this article will review the peer-reviewed literature in respect to the effects of prehabilitation resistance training on patients undergoing total knee arthroplasty and its efficacy on their postoperative strength, pain, and functional ability.
Why Osteoarthritis Leads to Total Knee Arthroplasty
Patients suffering from OA report symptoms of achy, burning, or sharp pain in the knee. These symptoms can prevent patients from completing day to day tasks. As a result, the patient’s quadriceps muscle strength continues to decrease due to inactivity, failure of voluntary muscle activation, and muscle atrophy (10, 16). It is typical to see abnormal gait patterns in patients suffering from OA in order to compensate for their symptoms and loss of quadriceps strength (14).
Postoperative Problems Following TKA
TKA is performed in order to reduce pain and improve knee function (18). However, it is not that simple; there are still biomechanical, strength, and functional ability issues following the surgery.
Biomechanical compensation caused by knee pain leads to altered joint loading and compensation in the trunk and opposite leg along with decreased hip and knee flexion, resulting in reduced strength in the operated leg known as “quadriceps avoidance” (15, 27). Gait asymmetry occurs for 3 months following TKA and improves gradually up to 12 months postoperative (26).
Following a TKA patients exhibit a significant decrease in the contribution of the quadriceps muscles (vastus medialis, vastus intermedius, vastus lateralis, and rectus femoris) (15). This greatly affects the patients posture through the activation of trunk muscles during gait when walking as a compensatory response to aid momentum during propulsion; particularly in the erector spinae and the internal and external oblique muscles when compensating for “quadriceps avoidance” (14, 15).
Gait adaptive functional habits are seen pre- and post-operatively in TKA patients, such as increased dorsiflexion of the ankle during gait to compensate for impaired knee function (14). The increase in dorsiflexion of the ankle allows for a greater power output during propulsion, resulting in increased momentum during gait (14).
In recovery, quadriceps dysfunction is often acknowledged and targeted during therapy. However, patients who undergo TKA show high levels of co-activation between the quadriceps and hamstrings (18). This excessive co-activation may result in impaired movement and overuse caused by muscle weakness in the operated knee potentially causing extra wear and tear on the knee prosthesis through increased compressive forces and joint loading (18), and chronic tendinopathy in the postoperative knee and leg; resulting in increased pain (18). Some patients have prolonged strength deficits in the operated leg. This is caused by adaptive functional habits such as co-activation and knee joint loading patterns that were learned prior to surgery to compensate for knee pain and decreased functional ability (10, 14).
Society is continually improving technology and this can result in patients expecting greater postoperative performance and this expectation continues to rise as the arthroplasty population becomes younger (10). However, quadriceps muscle function and strength are direct determinants of this outcome (10).
Role of Strength in Recovery
Resistance Training (RT) at 50%, 60%, 70% and 80% of 1 Rep Max increases muscle strength and power in men and women when performed 2-3 times per week over 4-6 weeks (9). These initial gains in strength are attributed to neural adaptations followed by gains in muscle hypertrophy after 6 weeks of RT (6, 13).
Patient’s quadriceps strength does not return to preoperative values until 6 months following the TKA (27). If patients are participating in pre- and post- physical therapy and performing their prescribed exercises, why does it take so 6 months or more to recover preoperative strength, if they fully recover it at all? This leads to the following questions: is prehabilitation effective, should TKA patients be prescribed prehabilitation to improve postoperative outcomes, and what can we do differently to achieve these outcomes?
Why Prehabilitation Might be Effective
Patients suffering from OA and who participate in prehabilitation see a significant increase in quadriceps strength and reduced pain prior to surgery (23). Research has shown that lower quadriceps muscle strength prior to TKA is correlated with lower functional endpoints following TKA. Therefore, strengthening of the quadriceps through prehabilitation should theoretically improve functional ability and strength of the patient post-surgery (28) as well as improve gait during walking (15). It is known that hamstring dysfunction and co-activation is present following TKA, therefore in addition to quadriceps strengthening it could be suggested in theory that strengthening the hamstrings during prehabilitation would reduce postoperative co-activation and its side effects.
Adaptive functional habits are known to transfer from pre- to post- operative performance in patients, therefore it could be suggested that optimizing gait performance prior to surgery could theoretically improve gait and functional ability following TKA (14, 15).
In addition to gait mechanics, breaking habits such as using the upper body extremities to arise form a seated position could improve strength and function (10). By strengthening the muscles around the knee joint there will be a stronger loading ability during gait(27). Therefore, strengthening the muscles around the knee stabilizes the knee joint and improves day to day functional ability or will postpone TKA for the patient (27).
Justification for Prehabilitation
The strength gains form preoperative resistance training do not transfer as equal strength following TKA (19). Quadriceps strength decreases to 60% of preoperative levels one month following TKA (18).
However, prehabilitation has shown to increase functional ability following TKA (see Figure 1) (24). Preoperative exercise duration of 6
weeks dramatically reduces the odds of inpatient rehabilitation (4, 23); thus there is an increase in functional ability following TKA with 6 weeks of prehabilitation (24).
As previously mentioned, in theory, failure in the progression of strength following TKA could be due to chronic and worsening patterns of coactivation that developed prior to surgery. There is
efficacy to suggest that preoperative improvement of muscle recruitment patterns through strength training and improved gait patterns could positively influence postoperative outcomes (25).
There is a positive correlation between quadriceps strength and gait performance (10, 20, 27). However, it is important to remind the reader that correlation does not imply causation. This correlation could suggest a necessity for pre- and postoperative resistance training in both the operated and non-operated leg in order to prevent asymmetrical strength, thus reducing alterations in gait patterns (3, 21). Bilateral TKA with prehabilitation results in increased pain caused by the inability to compensate with one good leg caused by intra- and between-limb compensations during gait (21). The significant decrease in postoperative strength suggests a need to prevent bilateral-TKA in patients (2, 3, 21).
There is conflicting research regarding whether or not rehabilitation resistance training is beneficial for recovery after a TKA (1, 7). The efficacy of the literature on prehabilitation was difficult to analyze because of the low number of patients included in the studies and the methods utilized. This left the studies highly underpowered with a high number of dropouts, no matched control populations, different physical training protocols, and the use of functional scores or inadequate parameters (5).
Figure 1: shows the effect of prehabilitation on the
functional ability of TKA patients (24).
Recommended Prehabilitation Treatments
Prehabilitation treatments should be focused on pain relief (30), greater functional ability (8) and therapeutic gait retention (14). Strength training is a primary treatment to achieve these results (8, 11, 23, 24).
Prior to exercise it is important to identify specific gait impairments (14) and an intent-to-treat analysis recommended for progressive and adapted training programs (5). Supervised physical training 3 times per week for a minimum duration of 6-8 weeks (5, 24) is necessary to see benefits of preoperative physical training and is recommended (5).
There are a variety of recommended strength training tools and techniques. The use of Thera-Bands, weights and body weight are dependent on the exercise and the patient’s ability (24). There is equivocal research showing Thera-Bands or weights as being more effective for strength gains in patients with OA, this is due to inconsistent physical training protocols between studies. The higher the volume, the greater the correlation is to increased strength and decreased pain prior to TKA, and increased functional ability before and after TKA (3). Volume is dependent on what the patient can handle (3, 24). Utilize closed chain kinetic exercises over open chain kinetic exercises to improve functional ability and reduce pain (19).
Adjunctive Neuromuscular Electrical Stimulation (NMES) has been shown to produce greater quadriceps strength before and after total TKA than static strengthening exercises alone (29).
The highest tolerated NMES intensity is recommended to be performed 5 dayper week for 6 weeks and a 20 min duration- alternating 5 sec on, 10 sec off (29). However, the use of NMES on the quadriceps should be preceded with caution as it can cause over reaching and delayed adaptations, but results in increased voluntary muscle contractions when used properly (31).
Simultaneous strength and flexibility training is often prescribed in treatment; however it is shown that flexibility does not positively or negatively influence strength gains (17). This is due to the performed full range of motion during strength training which stretches the muscle (17). However, patients with OA may not be able to perform through the full range of motion, thus additional stretching exercises could be beneficial to functional ability (17).
In order to improve gait patterns prior to surgery, strengthening exercises for the hip, ankle, and knee are essential (14). Strength exercises for the quadriceps and hamstrings to reduce co-activation should also be included (14, 16, 18), as well as teaching patients to properly shift their body weight to the operated leg to reduce “quadriceps avoidance” (15, 27).
Prehabilitation does show significant gains in strength and reduction of pain prior to surgery (3, 22). However, the strength gained from prehabilitation drops between 50%- 60% in the first month of the preoperative value following the TKA (3, 18, 22).
Prehabilitation reduces postoperative physical therapy (4, 12, 23) and results in an earlier increase to functional ability when compared to non-prehabilitation TKA patients (3, 25). Prehabilitation does show significant reduction in pain and increased functional ability before and after TKA (23, 24). However, the reduction in pain post-surgery is subjective; the TKA could be overshadowing the benefits of the prehabilitation (7).
Patients with OA and undergoing a TKA depend on the other leg prior to surgery and during recovery; effecting the patients gait pattern (3, 21). Since there is a positive correlation between quadriceps strength and gait performance (20, 27), this results in a necessity for pre- and postoperative resistance training in both the operated and non-operated leg in order to prevent asymmetrical strength and alterations in gait patterns (3, 21).
Quadriceps avoidance is common in patients before and after TKA; this could be linked to the decrease in vasti and rectus femoris muscle strength in the operated leg and gait variability (15, 27). Adaptive functional habits and co-contraction development prior to surgery can persist following TKA, causing improper gait mechanics, decreased quadriceps strength and can lead to chronic tendinopathy and damage to the prosthesis.
Condensed Version and Bottom Line
Prehabilitation is recommended for patients with OA and is beneficial for decreasing pain and increasing functional ability and muscle strength prior to TKA. However, only reduced time to a return of significant functional ability is a result from prehabilitation following TKA. It is suggested that strength training in combination with breaking adaptive habits and corrective gait mechanics will benefit the patient’s postoperative outcomes when utilized in prehabilitation.
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