Total endoprosthesis of the knee

Inserting an endoprosthesis of the knee is one of the most common orthopedic surgeries. The reasoning for undergoing the procedure is based on a progressed state of illness and a state where non-surgical methods and other reconstructive surgical procedures fail to improve treatment (15).

Medical science is ever evolving and improving. In endoprosthetics, by using modern materials and surgical techniques, in conjunction with appropriate presurgical preparation and quality rehabilitation, we can help the individuals regain their complete quality of life. That is, the individual whose severe pain, limited mobility, and instability while walking prevented them from completing everyday activities.

To some degree, non-surgical procedures can prove effective and are therefore the first choice of treatment – this includes all physiotherapeutic methods and a carefully planned exercise program. However, when all options are exhausted, the condition does not better and no further improvement can be expected, the only long-term solution is a total endoprosthesis of the knee. 

The knee joint is the most complex joint in the human body. Because of its structure, exposure to external forces, and great functional requirements it is the most frequently injured one. The bones to which it is connected are the femur, tibia, and patella.

The fibula, the thinner bone of the shin, connects to the tibia and, while not directly part of the knee joint, plays an important role in regard to the muscle’s insertion and knee ligaments. The stability of the knee joint is made possible by means of the cruciate ligaments, menisci, collateral ligaments, joint capsule and tendomuscular apparatus.

The joint allows movement in the direction of extension and flexion and, while the knee is bent, also facilitates slight medial and lateral rotations.

The number of procedures performed on the knee is increasing constantly, in Slovenia, as well as in the world (10). The indicator for surgical treatment is most frequently a progressed state of primary or secondary arthrosis.

Osteoarthrosis (OA) is a degenerative process that damages the articular cartilage, which is then after unable to absorb the forces caused by movement, consequently causing damage to the bone surface. This is evidenced by pain and limited mobility. Later on, these can be accompanied by grinding or creaking in the joint (crepitations), joint effusion caused by secondary inflammation, muscle weakness, contractures, ankylosis, and an enlarged or deformed joint (15).

In 2018, 90,4% of all surgical procedures in Slovenia were performed due to the diagnosis of OA (7). Other diagnoses represented post-traumatic injuries, rheumatoid / psoriatic arthritis, aseptic necrosis and consequences of meniscus or ligament injuries (7). Statistically, they consist of a predominantly female population, in the ages of about 60-70, where the majority of patients is either overweight or morbidly obese (7).

The development of AO is greatly shaped by the lifestyle one lives from the viewpoint of physical activity and diet – habits that we can alter. Also contributing to its development are all previous injuries and surgeries of the knee, congenital malformations and other adjacent autoimmune diseases.

As life expectancy increases so does the number of individuals with various degenerative knee joint diseases. The changes brought about by ageing are simply impossible to be averted, which is why a mere “bad x-ray” is insufficient reasoning to undergo the surgical procedure.

The primary reason for inserting a prosthetic joint is persistent, severe pain that is caused by a worn-out knee and which often does not even cease at night. The pain is frequently accompanied by limited mobility and instability while walking causing problems in everyday activities.

At the early onset of problems all conservation treatments with physiotherapy and kinesiotherapy need to be exhausted and only thereafter, if the pain management and improvement of the basic functionality prove unsuccessful, can the surgical procedure be considered.

Why is the surgical procedure not carried out as soon as changes or pain in the knee appears? The knee has a complex flexibility along and around all three axes, which are constantly shifting during movement.

Biomechanically, the knee endoprosthesis is far more complicated than a hip prosthesis (10). Statistical data for Slovenia between the years 2002 and 2018, comparing knee and hip endoprostheses, shows greater incidence (14,4 %) of instability, poor placement and decreased range of motion after knee prosthesis surgery compared to hip prostheses (0%).

Revision surgeries and the occurrence of pain is also more prevalent among knee than among hip endoprostheses (7). Nevertheless, the only long-term solution for major issues remains solely a knee replacement surgery (total knee arthroplasty).

Total knee arthroplasty (TKA) serves as a bone surface replacement. The prosthesis is composed of metal and polyethylene inserts.

Both cemented and cementless techniques are used, the latter ones being used predominantly in younger patients with well-preserved bone mass, where the knee biomechanics are still relatively intact and good retention of the metal part of the prosthesis can be expected.

Considering the deformation and condition of the surrounding soft tissues, the surgeon can also choose between inserting an unconstrained or semiconstrained endoprosthesis with either the preservation or removal of the posterior cruciate ligament (10).

Various research studies suggest that preoperative exercise improves postoperative functional results. Patients who have gone through a preoperative exercise programme tend to have shorter inpatient hospital stays, quicker physical recovery (2), reduced pain and improved quality of life (13).

Increased stability during standing can also be achieved with proprioceptive (»balance«) training (5). 

According to the latest clinical guidelines (2020) preoperative exercise is encouraged, as it reduces pain, improves balance, enhances the range of motion of the knee joint as well as the isometric force of the knee and hip muscles.

As a result of all above-mentioned parameters, improved quality of life can be achieved along with a faster and more successful treatment outcome (6).

The primary surgical procedure usually takes about 1 to 2 hours. During this time, the surgeon removes the damaged cartilage and bone tissue and inserts new metal and plastic inserts (3). It is common to feel pain immediately after the surgical procedure.

In the first days following the surgery, the pain can be treated by using analgesics and with the help of non-pharmacological approaches such as cooling and lifting of the operated leg (6).

The postoperative rehabilitation process is generally longer and more complex than after hip replacement surgery (10). With age natural neuromotor changes occur, which leads to decreased muscle strength, with the surgical procedure causing a further decrease of at least 24 % in muscle strength compared to the contralateral side (6).

This is why a complex rehabilitation process is necessary in order to achieve a positive treatment outcome which will help to eliminate any muscle deficits.

Phase I: From the surgical procedure up to 2-3 weeks after surgery

The most important objective in the first days following the surgery is to carefully manage and alleviate the pain and swelling, as well as to pay special attention to the surgical wound, ensuring its healing without getting infected (3). As the wound is healing, avoid bending the knee more than 90° in the first two weeks.

The extension in the knee joint is not restricted and should be encouraged in order to achieve the maximum range of motion. Some exercises that can be performed in the hospital bed include: active movement of the ankle joint in order to stimulate blood circulation, isometric exercises for the anterior thigh muscles, active bending and extending of the knee within the recommended range of movement and lifting of the extended leg (6).

In individuals found to have muscle activation deficits, neuromuscular electric stimulation (NMES) is advised. It should be started as soon as possible following the surgical procedure and should be performed for at least 3 weeks. The use of NMES will result in the improvement of the maximal voluntary muscle contraction (6).

Phase II: 4-6 weeks after surgery

The aim of the second phase is to achieve a normal walking pattern without limping as well as to regain the initial flexibility and strength.

The exercises are carried out twice a week, the frequency can be increased or decreased according to the individual progress of the patient. The exercises are targeted at gradually regaining the neuromuscular control and increasing the muscle strength of the operated leg (12).

Phase III: 6-8 weeks after surgery

In this phase we want to achieve good control when standing on one leg as well as incorporate various lateral movements into the exercise regime, such as taking lateral steps or step overs. Later more emphasis is placed on increasing muscle strength and endurance.

In this phase the individual should be able to walk without limping (12). Studies that incorporated sensorimotor exercises into the rehabilitation process have shown improved walking function (8). Participants self-evaluation showed better physical functionality and ability to engage in recreational activities in individuals who took part in balance improvement exercises (1).

Therefore, it is safe to assume that the incorporation of such exercises is beneficial.

Phase IV: 8-12 weeks after surgery

The emphasis of the fourth phase of the rehabilitation process is to gradually include specific exercises needed to allow the patient to return to daily activities such as household chores, work specific activities and sports.

Until the end of the 12th week the patient is encouraged to take part only in non-contact physical activities and advised against pivoting and rotating on the operated leg (12).

1. Bruun-Olsen, V., Heiberg, K.E., Wahl, A.K. & Mengshoel, A.M., 2013. The immediate and long-term effects of a walking-skill program compared to usual physiotherapy care in patients who have undergone total knee arthroplasty (TKA): a randomized controlled trial. Disabil Rehabilm, 35, pp. 2008–2015.
2. Calatayud, J., Casana, J., Ezzatvar, Y., Jakobsen, M.D., Sundstrup, E. & Andersen, L.L., 2017. High-intensity preoperative training improves physical and functional recovery in the early post-operative periods after total knee arthroplasty: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc, 25, pp. 2864–2872.
3. Foran. J. Total Knee Replacement. OrthoInfo. Available at: https://orthoinfo.aaos.org/en/treatment/total-knee-replacement/ [29.8.2021].
4. Groen, J.W., Stevens, M., Kersten, R.F., Reininga, I.H. & van den Akker-Scheek I., 2012. After total knee arthroplasty, many people are not active enough to maintain their health and fitnes. J Physiother, 58(2), pp. 113-6.
5. Gstoettner, M., Raschner, C., Dirnberger, E., Leimser, H. & Krismer, M., 2011. Preoperative proprioceptive training in patients with total knee arthroplasty. Knee, 18, pp. 265–270.
6. Jette, D.U., Hunter, S.J., Burkett, L., Langham, B., Logerstedt, D.S:, Piuzzi, N.S., et al, 2020. Physical Therapist Management of Total Knee Arthroplasty. Clinical Practice guidelines. Physical Therapy, 10, pp. 1-29.
7. Levašič, V., Savarin, D. &Milošev, I., 2020. VALDOLTRA KNEE ARTHROPLASTY REGISTRY REPORT 2002-2019. Valdoltra Arthroplasty registry.
8. Liao, C.D., Lin, L.F., Huang, Y.C, Huang, S.W., Chou, L.C. & Liou, T.H., 2015. Functional outcomes of outpatient balance training following total knee replacement in patients with knee osteoarthritis: a randomized controlled trial. Clin Rehabil, 29, pp. 855–867.
9. Mikša, M., 2014. Funkcionalna anatomija kolenskega sklepa – razlike med odraščajočim in odraslim kolenom. Medicina športa, 1, pp. 4-6.
10. Moličnik, A. & Merc, M., 2010. Endoprotetika kolenskega sklepa. In: VI. Mariborsko ortopedstko srečanje. Interdisciplinarno strokovno srečanje in učne delavnice. Artroza in endoprotetika sklepov. Zbornik vabljenih predavanj. Maribor, pp. 81-93.
11. Shadyab, A.H., Eaton, C.B., Li, W. & LaCroix, A.Z., 2018. Association of Physical Activity with late-life mobility limitation among women with total joint replacement for knee or hip osteoarthritis. J Rheumatol, 45, pp. 1180–1187.
12. The stone clinic. Total Knee Replacement Surgery Rehab Protocol & Recovery Time. Available at: https://www.stoneclinic.com/total-knee-replacement-rehab-protocol [29.8.2021].
13. Tungtrongjit, Y., Weingkum, P. & Saunkool, P., 2012. The effect of preoperative quadriceps exercise on functional outcome after total knee arthroplasty. J Med Assoc Thai, 95(10), pp. 58–66.
14. Valtonen, A., Poyhonen, T., Sipila, S. & Heinonen, A., 2010. Effects of aquatic resistance training on mobility limitation and lower-limb impairments after knee replacement. Arch Phys Med Rehabil, 91, pp. 833–839.
15. Vogrin, M. & Naranđa, J., 2010. Osteoartroza: Epidemiologija, patogeneza in dejavniki tveganja. In: VI. Mariborsko ortopedstko srečanje. Interdisciplinarno strokovno srečanje in učne delavnice. Artroza in endoprotetika sklepov. Zbornik vabljenih predavanj. Maribor, pp. 9-21.

A regular, guided and goal-oriented rehabilitation process allows for a better treatment outcome and a life with less limitations after a total knee arthroplasty procedure.

Physical activity has a number of beneficial effects on an individual’s quality of life (6). However, if a certain condition cannot be improved by way of physiotherapy or exercise programs, knee arthroplasty has proven to be a safe and effective procedure. It must be remembered that a knee prosthesis has a certain limited lifespan.

In younger individuals, the decision to opt for a knee arthroplasty is usually taken when due to severe joint impairment no other effective type of treatment is available. It should also be considered that because of the functional complexity of the knee joint it is still not possible to achieve a perfectly »normal« knee, despite all of the newly available techniques and implants (10).

Nevertheless, it has been shown that a regular, guided and goal-oriented rehabilitation process allows for a better treatment outcome, a life with fewer limitations, and promises positive results.

Provided that you decide to continue with a regular exercise regime even after the completed rehabilitation program, you can expect a higher quality of life, which means improved walking function, increased muscle strength and endurance, enhanced balance and mobility, alongside a better ability to care for yourself, as well as a quicker reintegration into your social and recreational life.