Osteoarthritis of the knee is an extremely common complaint. In fact, it is the most common joint disorder in the U.S. today. Past the age of 60, symptomatic knee OA affects 10 percent of men and 13 percent of women.

Many factors are usually involved in the development of knee OA. These include but are not limited to:

  • old age
  • obesity
  • previous knee injury
  • female gender
  • bone density
  • muscle weakness
  • biomechanical variations
  • occupation

While OA can be managed, ultimately there is no cure. End-stage knee OA usually results in a total knee replacement (TKR), also sometimes known as a total knee arthroplasty (TKA).

There are currently approximately 600,000 TKR surgeries carried out in America every year, and this number is expected to rise significantly. An aging population and the obesity epidemic will only increase the numbers of people suffering with end-stage OA.

The statistics on TKRs show favorable outcomes. According to the American Academy of Orthopaedic Surgeons, 90 percent of people who undergo a TKR experience a dramatic reduction in knee pain post-operatively. Most of these people are able to return to their normal activities of daily living, including exercise such as walking and golf. Over 90 percent of artificial knees will still be functioning well 15 years after surgery.


The average cost of a TKR in the U.S. is a little over $20,000. Whether this is paid privately or through insurance, that's a hefty sum of money. On top of that, the disruption to daily life, loss of earnings and plenty of other factors mean the decision to undergo TKR should not be taken lightly.

Once that decision has been made and the surgery undertaken, the patient, surgeon and post-operative care providers should all be committed to achieving the best possible result. Thorough rehabilitation post-TKR can speed up recovery times, as well as promote a fuller recovery with a more complete return to activities of daily living and even some forms of physical activity.

In 2014, a review into the variations and delivery of rehabilitation protocols established that there is considerable variation in terms of exercise content, timing and utilization of physical therapy following TKR. The review also highlighted suboptimal use of strengthening exercises.

The authors suggested that further research was necessary to clarify the most suitable protocol to obtain the best results in post-TKR rehab. Over the last couple of months, two studies have been published that start to look at this problem.

Circuit training

In the first of these studies, published online in the Journal of Orthopaedic Surgery and Research, a team from China looked at the effects of circuit training on a group of post-TKR patients.

The study included 34 female patients, with 16 participating in three weekly circuit training classes for a total of 24 weeks. The circuit included stretching, aerobic training and resistance training. The control group followed a routine post-operative rehabilitation protocol, which consisted of quadriceps training and range-of-motion exercises.

Outcomes were assessed using gait analysis, muscle strength testing, knee injury and osteoarthritis outcome score (KOOS) and the short-form health survey, SF-36. Four assessments were carried out for both groups — pre-op, post-op (pre-exercise), 12 weeks post-op, and at the end of the 24-week program.

The results demonstrated that:

  • Circuit training resulted in reduced daily pain compared to the standard protocol.
  • Circuit training enabled patients to return to activities of daily living and social functioning.
  • Circuit training increased stride length, step velocity and knee range of motion during gait.
  • Circuit training promoted an earlier recovery of gait parameters, KOOS and SF-36 scores.
  • No difference was found in muscle strength after the 24-week program.

The authors concluded that circuit training can promote a faster recovery of knee function and reduction of pain compared to conventional TKR rehabilitation.

The lack of increase in muscular strength could not be explained at this point, although it was postulated that it may be due to inadequate loading to strengthen beyond that of daily activities. It is, however, suggested that resistance training played a part in improved ambulation through enhanced muscle coordination.

Maximal strength training

Following on from this, the second study looked at the effect of maximal strength training versus conventional TKR rehab.

The researchers split 41 participants into two groups. The test group undertook supervised maximal strength training three times a week plus one physiotherapy session a week for a total of eight weeks. The control group was provided with standard rehabilitation, which consisted of one physiotherapy session a week and keeping a home exercise log.

Outcomes were measured using maximal leg press and leg extension, a 6-minute walk test and a patient-reported functional outcome and pain score. Assessments took place preoperatively, then seven days, 10 weeks and 12 months post-op.

The results demonstrated that:

  • Maximal strength training resulted in superior increases in muscle strength at seven days and 10 weeks post-operatively.
  • The difference between groups was maintained at the 12-month follow-up.
  • By 12 months, both groups had recovered to "normal" levels in the 6-minute walk test.
  • No differences in functional performance were found at any time.


While both studies used relatively small sample sizes, both demonstrated a positive outcome for more-intense, structured and supervised rehabilitation following TKR. The protocols differed between each study, with one focusing on submaximal mixed circuit training and the other using maximal resistance training, and the results differed in line with this.

In the circuit training study, progress was made in every aspect other than strength. In the maximal strength training program, strength improved but no other differences were recorded between the groups.

This leads me to hypothesize that a rehab program incorporating all the benefits of circuit training, along with more heavily loaded, maximal resistance training may be the most beneficial approach. I also believe the success seen in these studies is at least in part due to the nature of the training environment providing consistent, supervised exercise that addresses the always-present issue of patient compliance and inadequate technique when it comes to home rehab programs.

As usual, further research is required to establish the exact protocol that will provide the most benefits to a patient's recovery, but this is a step in the right direction to demonstrate that more-intense, structured, frequent and supervised rehabilitation is preferable to the standard, limited, self-supervised programs that most TKR patients are prescribed.