1.1 General data
Patients diagnosed with unilateral KOA in the outpatient clinic and awaiting TKA in 2020–2021 were divided into an experimental group and a control group using a random number table. All procedures described in this study were reviewed by the Chinese Clinical Trial Registry (ChiCTR2000032857), were approved by the Hospital Ethics Committee (Ethics Number: 2022016), and complied with the requirements listed in the 1975 Declaration of Helsinki and its amendment in 2008.
Inclusion criteria: 1) Patients diagnosed with unilateral KOA and awaiting TKA, 2) those aged > 55 years, 3) those with clear consciousness and ability to communicate, and 4) those who provided consent to participate in this study.
Exclusion criteria: 1) Patients with a history of hip or knee surgery, 2) those with contraindications to exercise or diseases affecting leg activity, and 3) those who had incomplete follow-up data or withdrew from the study midway.
1.2 Methods
With the same standardised preoperative protocol and surgical technique, TKA was performed by the same experienced surgeon on all patients. Posterior cruciate substituting prostheses and tourniquets were used in all cases.
Routine nursing and rehabilitation procedures were done in the control group. After admission, nurses conducted routine nursing education. Before operation, patients and their families attended a meeting jointly held by orthopaedic surgeons, physiotherapists, and anaesthetists on the operation method, the risks from the operation and anaesthetic, and postoperative rehabilitation. After operation, patients underwent active and continuous passive motion exercises to enhance their leg strength and increase knee mobility. These patients were followed up by telephone and clinic visit after discharge.
In the experimental group, 4-week preoperative strength training and balance training were additionally given, with the preoperative training programme and content kept confidential. One training session was required before the formal preoperative training, and the patients were tested for 1–4 days after mastering the training content and methods until they and the assessor were satisfied with their mastery of the training methods. The training programme aimed to enhance both strength and balance in the peri-knee muscles. The strength training focussed in particular on knee flexor-extensor strength, and weight on the knee gradually increased from 0 to a maximum of 2 or 3 kg. Strength training was followed by manual therapy, proprioceptive training, and ice compression. The detailed programme is shown in Table 1. Training sessions were completed within 4 weeks, 5 days per week (1 hour per session). The physiotherapist responsible for this rehabilitation programme did not participate in any of the assessments during this study.
Table 1
Strength training programme for the experimental group
Warm-up exercises | Strength exercises | Balancing exercises | Ending Exercise |
1.Step up and down 20 times *2 | 1.Knee flexion and extension 10RM*5 | 1.Stand with feet aligned for 1 min*2 | Light static stretching of hip abductors, knee flexors and ankle plantar flexor extensors for 5min |
2.Calf raises 20 times *2 | 2.Standing on the forefoot and opposite heel for 1 min*2 |
3.Light resistance exercises 10 times | 2.Hip flexion and extension. Adduction, abduction 10RM*5 | 3.Standing on the forefoot for 3s* 15 |
4.Walk along a straight line10 m *4 |
Warm-up exercises were required before training to reduce muscle strain. Specifically, the strength training consisted of five sets of 10 repetitions, with a 60-s rest period between two sets. The intensity was regulated by weight and was based on the 10-repetition maximum. Exercises included knee extension and flexion; hip extension, adduction, and abduction; and standing balance. The training ended with a 5-min light static stretching of the hip abductors, knee flexors, and ankle plantar flexors and extensors.
1.3 Assessment methods
The baseline data of patients in both groups were measured at the time of consent to participate in this study (T1), before operation (T2), 3 months after operation (T3), and 12 months after operation (T4). All assessors were professionally trained and were unaware of the grouping.
1.3.1 Muscle strength test
To measure the maximal isometric knee flexion and extension strength, the patients were instructed to sit on the edge of the examining table with their thighs in contact with the table, their hips at a constant angle (90°), and their trunk not tilted backwards. In an exercise before the formal assessment, the patients were asked to generate the maximum possible force on the dynamometer held by the assessor. In the isometric knee extension strength test, the dynamometer was fixed perpendicularly to the tibia by a strap 3 cm above the ankle joint, with the other end of the strap fixed to the base. In the isometric knee flexion strength test, the dynamometer was placed on the posterior part of the lower leg and fixed by a strap to the handle of a glass suction cup on the wall. The patients were told to perform three isometric maximal voluntary contractions, the average maximal strength of which was taken for analysis. The hand-held dynamometer showed good inter- and intra-assessor reliability in the assessment of knee flexors (ICC: 0.76–0.94) and knee extensors (ICC: 0.92–0.97) in the affected and unaffected knees[7].
1.3.2 Active knee range of motion (ROM)
The active knee ROM was measured using a digital goniometer. Specifically, the patients were instructed to lie in the supine position, with the knee extended, the hip in a neutral position, and the upper thigh exposed so that the greater trochanter could be seen. They flexed and extended the knee to its maximum, and the central pivot point of the goniometer was placed on the lateral epicondyle of the femur, with the proximal arm aligned with the lateral midline of the femur (the greater trochanter as a reference) and the distal arm aligned with the lateral midline of the fibula (the lateral malleolus and fibular head as references). In this way, the flexion and extension ROM was measured three times, and the average was taken. The knee ROM assessment of KOA patients showed high reliability, with ICCs of 0.96 and 0.81, respectively, for flexion and extension[8].
1.3.3 Stair ascend/descend test
The patients walked up and down four flights of stairs (50 cm wide, 15 cm high and 25 cm deep each flight) once as quickly but as safely as possible. They stood at the bottom of the first flight of stairs, went up the stairs, turned around on the top step, and kept going until both feet were on the floor. The handrail could be held if needed[9]. The total duration of this test was measured and averaged with a stopwatch, which stopped when the patient reached the starting line after going up and down the stairs[10]. The test was performed twice with a 30-s rest period. The stair ascend/descend test was highly reliable, with a test–retest reliability coefficient of 0.93 and an ICC of 0.94 for inter-assessor reliability[11].
1.3.4 Timed up and go (TUG) test
The TUG test is an easy-to-perform test that assesses mobility, leg function, and fall risk without any specific equipment needed[12]. The patients stood up from a standard armchair (without using their arms), walked to a straight line on the floor 3 metres away, turned around, walked back to the chair, and sat down again. The duration of the above process was recorded as the TUG result[13].
1.3.5 Knee function
The Knee Society score (KSS) is one of the most widely used knee function scores in clinical practice. KSS assesses knee pain, ROM, and stability and serves as a reliable indicator of knee recovery and function.
1.3.6 Balance
The Berg balance scale (BBS) was used to assess the patient's balance. The patient does 14 related activities, such as sit-to-stand transfer, unsupported standing, and unsupported sitting. The maximum BBS score is 56. The higher the score, the better the balance.
1.4 Statistical analysis
In the pre-test, the standard deviation and error of the baseline KSS were 7.5 and 2.9, respectively, the statistical power was 90%, and the level of significance was p < 0.05. At least 29 patients were needed in each group.
IBM SPSS 21.0 software (Chicago, USA) was used for statistical analysis. Measurement data such as age and joint function scores are described as mean ± standard deviation (‾x ± s), and data such as osteoarthritis K-L classification and sex are described as percentage (%). Data were tested for normality using the Shapiro-Wilk test. Student’s t-test was used to compare the means of normally distributed data between the two groups, the Mann–Whitney test for non-normally distributed data, and the chi-squared test for differences in composition ratios. Differences in ROM, TUG test result, and muscle strength test result were analysed using repeated-measures analysis of variance, where group, time, and group×time interaction were the independent variables. p < 0.05 was significant.