TKR: How much motion should we expect?

I'm not sure how this happens, but certain diagnoses seem to come to my clinic in clusters. I see a fair amount of primary TKR in my clinic. For the most part, patients undergoing primary arthroplasty seem to do very well in our clinic subjectively and functionally. Fortunately for all of us, I doubt my outcomes far exceed or lag behind many of you treating the same population.

In spite of the numerous successes we see with primary knee arthroplasty, you may share my frustration with those patients who do not fair so well following this procedure. Although many variables often contribute to a poor functional outcomes, few are as fundamental to a patient's recovery as restoration of adequate ROM. Restoring functional ROM following arthroplasty can often be a routine issue for patients and therapists, but there is an unfortunate minority who are not so fortunate.

Today's research again comes from our colleagues in orthopedic surgery. The article's authors are examine the various factors that contribute to less-than-optional ROM following primary and revision TKR.

Ritter and colleagues recently published an article in The Journal of Arthroplasty retrospectively examined 5622 TKA performed on 3672 patients between 1972 and 2002. The relationships between preoperative and postoperative flexion contracture, pain scores, functional scores, gait speed and stair climbing ability were examined using logistic regression analysis.

Noteworthy findings of this study were:

• The severity of the postoperative flexion contracture strongly correlated with the severity of the preoperative flexion contracture for moderate to severe contractures of 20 degrees or more.
• A mild (5-19 degree) preoperative flexion contracture had only a small effect on pain and functional scores. The authors explain this by the fact that many small knee flexion contractures are corrected intraoperatively.
• A preoperative hyperextension of more than 10 degrees had a negative effect on postoperative pain and functional scores. The authors do not provide explanation for this finding.

An earlier study also performed by Ritter and colleagues attempted to predict postoperative ROM after revision TKA using cluster and log-linear regression analyses. The variables used to predict ROM were preoperative flexion, intraoperative flexion, preoperative alignment, patient demographics, type of posterior soft-tissue release, previous prosthesis type, and revision prosthesis. For this study, 355 revision arthroplasties were examined with the following findings:

• Preoperative and intraoperative flexion were the most important variables predicting postoperative flexion
• Constrained and hinged prostheses had a negative effect on postoperative flexion.

The authors conclude that a patient with high preoperative flexion, middle aged or older, with a nonconstrained prosthesis has the best predicted postoperative flexion. Conversely, low preoperative flexion, younger age, and constrained prostheses had the worst postoperative flexion. Improvements in flexion following a revision were lower than following a primary TKR.

What can these studies tell us?

After wading through the data of these two article, a few important take home messages came to mind. One is the compelling case for preoperative physical therapy for primary and revision TKR. With the right approach, a well-trained therapist should be able to partially address preoperative ROM deficits.

Secondly, these papers lend support to not simply breezing through the history of a patient with a TKR. Factors such as age, preoperative ROM, and even knowing the prosthesis type may provide valuable information for you regarding your patient's rehab potential. I hope you find this summary helpful and as always welcome your questions, comments, and contributions.

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RITTER, M., LUTGRING, J., DAVIS, K., BEREND, M., PIERSON, J., MENEGHINI, R. (2007). The Role of Flexion Contracture on Outcomes in Primary Total Knee Arthroplasty. The Journal of Arthroplasty, 22(8), 1092-1096. DOI: 10.1016/j.arth.2006.11.009

Ritter, M. (2004). Predicting range of motion after revision total knee arthroplasty Clustering and log-linear regression analyses . The Journal of Arthroplasty, 19(3), 338-343. DOI: 10.1016/j.arth.2003.11.001