Tankersley WS, Mont MA, Hungerford DS: In: Rehabilitation Secrets. Young MA, O'Yang B, Steins SA, (eds). Hanley and Belfus, Mosley, Philadelphia, 1997.

1. Define knee arthroplasty.

A knee arthroplasty is a replacement of damaged or arthritic surfaces of the distal femur and proximal tibia and the rest of the knee joint with metal and plastic materials to restore the integrity of the joint.

2. What are the the indications for this procedure?

The main indication is to relieve pain caused by arthritis. Secondary goals are to correct deformity, and to restore function. More specifically, canidates for knee replacements have severe degenerative changes of their knee joint seen on radiographs and have failed multiple methods of nonoperative treatment to relieve their pain. These methods include anti-inflammatory medications, the use of a cane, decreased activity, loss of weight when indicated, as well as interarticular corticosteroid injections. These methods should be tried 3-6 months before a knee arthroplasty.

3. How many knee arthroplasty procedures are performed in the United States annually?

Approximately 150,000.

4. What are the goals of knee arthroplasty?

  1. To restore a painfree joint
  2. To restore range of motion (ROM)
  3. To allow function that approaches normal for a patient

5. How successful are these operations?

About 95-97% of patients can expect a good to excellent clinical result. This clinical result encompasses minimal to no pain, the ability to walk > 1 mile, increased ROM, and patient satisfaction with the procedure. These results generally hold up 5- and 10-year follow-ups, with about a 1% failure rate per year. Thus, one can expect about 90% success with these procedures at 10 years.

6. How long does significant pain last after knee surgery?

Most patients know within 1 or 2 days after surgery that their pain is markedly different than preoperatively. The arthritis pain is typically eliminated immediately. The surgical pain lasts for 2-3 weeks but progressively gets better after the first 1-2 days.

7. When should a knee manipulation be seriously considered?

If you have only 70° flexion by 14 days postoperatively.

8. Since the continuous passive motion machine does not appear to affect long-term ROM, why should one use it in a patient with total knee replacement?

It may be cost effective. It improves knee flexion and may reduce the number of hospital days and frequency of manipulations.

9. Can patients return to playing sports after knee surgery?

Most patients can return to low-impact sports, such as golf, doubles tennis, and bowling, walking, and use such exercise machines as a stationary cycle and cross-country ski simulators. High impact exercises such as running, singles tennis, basketball, volleyball, and football should be avoided as these may lead to undo wear and tear on the prosthesis.

10. Describe a general rehabilitation program in a patient with total knee arthroplasty (TKA).

Day of surgery

  • Deep breathing exercises
  • Active ankle ROM

Postop day 1

  • Lower-limb isometrics including quadriceps, hamstrings, and gluteral sets
  • Wearing a knee immobilizer until the development of active knee enstensionand demonstration of good leg control during ambulation
  • Weight-bearing after TKA may be partial or full, depending on the surgeon’s discretion

Postop day 2

  • Standing at the bedside with knee immobilizer and partial weight-bearing on the operated limb
  • Active assisted ROM                      

Postop day 4

  • Progressive isotonic and isometric knee and hip muscle strengthening
  • Concentrate on terminal knee extension through active knee extension exercises

11. How long will a total knee replacement last?

Although this will vary from patient to patient, many large series in orthopedic literature show continued good to excellent results in > 90% of patients at 10 years

12. When will the patient receive full benefit after knee arthroplasty?

Typically, by 3 months, the patients are doing quite well. Usually, by that time, they have regained most of their strength across the joint as well as ROM. They continue to improve throughout the first year after surgery, and by 1 year, the patient has achieved full benefit from the operation.

13. How should a patient ambulate stairs after knee surgery?

When going up stains, the patient leads with the nonoperative extremity and then follows with crutches and operative extremity, taking one step at a time. When descending, the patient leads crutches and the operative extremity, following with the nonoperative extremity.

14. Is prophylaxis for deep venous needed after knee surgery?


15. List the usual sequence of ambulatory aids given to patients after total knee replacement.

  • For the first day or two, the patient usually works in physical therapy on the parallel bars.
  • He or she is then progressed to crutches or a walker for the first 6 weeks.
  • The patient is then advanced to one crutch or cane, which is continued for an additional 6 weeks.
  • Most patients (70%) are ambulatory without an assistive device by 3 months

16. What are four goals of an occupational therapy after total knee replacement?

  1. To reestablish basic activities of daily living (ADL), with modifications that keep the patient's ROM within restrictions
  2. To teach joint protection
  3. To review for falls risk
  4. To provide equipment with training.

17. Is sex possible after knee replacement?

Provided it does not involve chasing your partner around the room (or other obstacle-laden course) at high speeds.

18. When can patients bear full weight after knee surgery?

Most patients are kept on partial weight-bearing (50%) for 6-8 weeks, with progression to full weight-bearing usually at the end of 6 weeks. For biologic fixed components, full weight-bearing may not be allowed until 12 weeks to ensure bone ingrowth.

19. What muscles should be targeted after knee surgery?

The muscles most affected by surgery are the quadriceps muscles (vastus lateralis, vastus medialis, vastus intermedius,and rectus femoris). Isometric strengthening and active ROM should begin immediately after surgery. For the first 6 weeks, the quadraceps should be strengthened with isometric exercises. Then, progressively resisted isokinetic or isotonic strengthening be added. Other muscles that act at the knee through the open and closed kinetic chains should be strengthened: hamstrings, gastrocsoleus, and ankle dorsiflexors.

20. How should knee range of motion be measured and recorded?

ROM should be measured from the lateral side of the patient's leg with a goniometer. Full extension—i.e., an angle between the femur and the tibial shaft of 0°--should be recorded as 0°. The knee is then brought to full flexion and measured again from the lateral side of the patient's knee, and this is recorded as a positive number, somewhere between 0-135°. If the patient's leg cannot be fully extended, i.e., lacks 10° of complete extension, this should recorded as +10 extension and the flexion recorded as whatever the patient is able to flex past that number. For example, the patient flexing to 100° but lacking complete extension of 10° should be recorded as having an ROM +10-105°. If the patient’s knee comes to hyperextension, then the amount past 0° should be recorded as a negative number. For example, if the subject hyperextended approximately 5° and flexed to 100°. the ROM is recorded as –5--100°.

21. After total knee replacement, what should be the expected range of motion for the patients knee? What are the preliminary goals?

The biggest predictor of postoperative ROM is preoperative ROM. The average postoperative ROM is 105°-110° for most patients. At least 90° of ROM is desirable for a good functional outcome. It is hoped that at least 90° of motion will be obtained within the first 7-10 days after surgery.

22. What is meant by the term "extensor lag"?

With an extensor lag, the patient cannot actively extend to a completely straight position (angle of 0° measured between the femur and tibia). Passive extension is not limited however. This condition occurs because of a lengthening or weakening of the quadriceps after surgery or because of prosthetic component positioning.

23. What is meant by the term "flexion contracture"?

This term is applied to patients who cannot fully extend the leg either actively or passively. This condition is usually caused by a mechanical block, such as retained osteophyte, scarring of the posterior capsule or posterior structures, extremely tight hamstrings or malposition of the prosthetic components. A flexion contructure significantly increases the energy required for ambulation.

24. How do you check stability of the knee after a knee replacement?

Medial/lateral testing (varus or valgus): The knee is checked throughout the ROM starting at full extension and then proceeding to 30°, 60°, and 90°. At each position, the patient's leg should stressed medially and laterally. Any opening or closing of >5° should be considered excessive.

Anterior and posterior testing: Again, the knee is checked throughout the ROM with Lachman's or anterior Drawer test, and the position of the greatest instability is recorded. This displacement is normally 5-8 mm of anterior translation, as the anterior cruciate ligament has been sacrificed in all total knee replacements.

25. Should the physiatrist be made aware of any particular circumstances after knee surgery?

The physiatrist should be aware if the patient has had any surgical procedure performed in addition to the routine surgical exposure. These adjuncts may include a quadriceps muscle turndown, performed by splitting this muscle in an oblique fashion to allow the patella to be retracted distally, for better exposure of the joint. In addition. a tibial tubercle osteotomy sometimes performed to allow exposure of the joint; it is performed by reflecting a portion of the bone underneath the tibial tubercle with the attached patella tendon laterally and then repairing this with some form of internal fixation. In either case, the ROM may be altered after surgery, and the strengthening part of rehabilitation may be delayed allowing the tendon or bone to heal.

26. Are resisted concentric exercises important after knee replacement surgery?

Concentric exercises against resistance should be avoided for the first 6-8 weeks. During that time, the patient can perform isometric and active ROM exercises against gravity. After the first 6-8 weeks, resisted open kinetic chain strengthening can start in the place of joint motion with 1-10 lbs. Exercises performed with heavy weights against resistance cause undue wear and tear on the prosthetic components.


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