Total knee arthroplasty (TKA), commonly known as a total knee replacement, is a treatment approach to relieve the pain associated with end-stage knee osteoarthritis. Although a TKA successfully relieves the pain, there are major decreases in strength and function. Before the TKA surgery, it is common to have around a 36% decrease in quadriceps strength while, immediately post-surgery, the quadriceps strength decreases by 60% compared to age and gender matched individuals. Even more striking is that these strength deficits extend to 6 months post-operation. Clearly, TKA rehabilitation needed a different approach due to the lack of effectiveness in restoring muscle strength. In 2002, the National Institutes of Health recognized TKA rehabilitation as one of the most understudied areas in physical therapy. A few years later some evaluation studies were done and physical therapy was shown to be ineffective in producing long-term benefits for those with TKA’s. This launched a revolution that provided many new approaches to TKA rehabilitation, of which the most effective is described here and utilized by Rehab Plus.
The quadriceps muscle group is the most affected area with the greatest strength losses occurring within the first month. Due to this critical window, gaining back quadriceps muscle strength is essential and the primary goal during rehabilitation. A major way to reduce these strength decreases is through neuromuscular electrical stimulation (NMES). Rehabilitation programs that utilized NMES were extremely successful up until around 6 weeks with the greatest improvements seen around weeks 3-4. The benefits of NMES are clearly seen when looking at long term studies that give only half their subjects electrical stimulation. Both groups receive traditional physical therapy, but the group that additionally receives NMES has significantly greater improvements that even extend to one year. A key point is that the subjects who achieve the highest electrical stimulation have the greatest improvements. It is essential that the patient try and achieve the highest volitional stimulation to experience the best results.
With NMES being a major component of successful TKA rehabilitation, the second and final component was revolutionary. As mentioned earlier, a few years ago physical therapy practices for TKA were shown to be ineffective. Most clinics during that time were using lower intensity resistance training. This is most likely the cause for the lack of long-term benefits which promoted the use of higher intensity training for TKA’s. Since deficits in muscular strength are seen, it makes sense that higher intensity protocols, which elicit greater strength gains, lead to greater improvements. Successful high intensity protocols involved progressively overloading all major muscle groups of the legs with a 3-4 sets of 10 repetitions at 75% of one repetition maximum general outline. The concept of progressive overload is noteworthy here because, clearly, one could not start at a high intensity right after surgery. Rather, a lower intensity utilizing resistance bands or ankle weights are used early on with resistances increased over time as muscle fatigue no longer occurs. Integrated within the high intensity training are exercises that function to increase range of motion. Compared to rehab patients that don’t receive higher intensity training, utilization of intense protocols leads to greater improvements that extend even to one year. One concern with more intense training may be an increased risk of injury. However, this has not been reported in studies utilizing these protocols. As long as a professional physical therapist or trainer is emphasizing proper form, the risk of injury decreases. The usage of higher intensity training has allowed modern physical therapy practice to have a major and lasting impact on TKA’s and even has the potential to restore function back to normal levels.

References:
Bade, M.J., & Stevens-Lapsley, J.E. (2012). Restoration of physical function in patients following total knee arthroplasty: an update on rehabilitation practices. Current Opinion in Rheumatology, 24(2), 208 – 214.

Minns Lowe, C.J., Barker, K.L., & Dewey, M. (2007). Effectiveness of physiotherapy exercise after knee arthroplasty for osteoarthritis: systematice review and meta-analysis of randomized controlled trails. British Medical Journal, 335, 812.

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