Performance-Based Test Results Show Quicker Functional Recovery for UKA vs TKA

Researchers from Thailand have found that for selected patients with knee osteoarthritis (OA), unicompartmental knee arthroplasty (UKA) shortens the recovery time for 2 key measures of physical function compared with total knee arthroplasty (TKA).

On performance-based tests of walking speed and mobility, patients who underwent UKA showed better function starting at 6 weeks postoperatively, compared with 3 to 6 months postoperatively for patients who underwent TKA, according to a study published online ahead of print by The Journal of Bone & Joint Surgery. 

Assessing Physical Function

Functional recovery from UKA and TKA is typically measured with by patient-reported outcome measures (PROMs), which provide data regarding patients’ perceptions of their functional activity. “However, recent studies have indicated that actual functional recovery is overestimated by PROMs,” said the researchers from Thammasat University in Pathum Thani, Thailand.

With that in mind, they designed a study that focused on 2 performance-based tests that directly assess physical function:

  • The 2-minute walk test (2MWT), which reflects endurance (walking capacity)
  • The timed up-and-go (TUG) test, which provides information on functional mobility, balance, and risk of falling

Study Findings

In this clinical trial, 99 patients with knee OA isolated to the medial compartment of the knee were randomly assigned to undergo either UKA (n=50) or TKA (n=49). All patients were assessed by the 2MWT and TUG preoperatively and at specified postoperative timepoints. Patient-reported outcomes were evaluated as well.

The patient-reported data suggested that the 2 groups experienced similar outcomes at all postoperative timepoints. The objective data from the 2MWT and TUG test told a different story: The results indicated faster functional recovery in patients who underwent UKA when compared with patients who underwent TKA.

At 6 weeks postoperatively, the 2MWT distance was 96.5 meters in the UKA group versus 81.1 meters in the TKA group. The difference remained significant at 3 months (10.21 vs 87.5 meters, respectively) and at 6 months (102.8 vs 89.6 meters, respectively). At 1 and 2 years postoperatively, 2MWT distances were similar between the 2 groups.

Patients who underwent UKA also had better performance on the TUG test at 6 weeks and 3 months. By 6 months, TUG test times were similar between the groups.

This randomized trial is the first to demonstrate faster recovery of 2MWT and TUG test scores after UKA compared with TKA. The findings are also consistent with prior reports showing that quadriceps muscle strength and knee biomechanics recover more quickly following UKA than following TKA.

Clinical Implications

The researchers aren’t advocating for healthcare professionals to abandon patient-reported data.

“The present study demonstrates that PROMs are not entirely capable of detecting the difference in functional recovery between UKA and TKA,” they said.

“However, PROMs are still important because they can assess some activities of daily living, such as stepping up and down and putting on socks and pants, that are not assessed in performance-based tests.

“Therefore, routine use of the 2MWT and TUG combined with PROMs in standard clinical assessments is recommended to capture the actual improvement in physical status and provide a more comprehensive perspective of functional recovery after UKA and TKA.”


Pongcharoen B, Liengwattanakol P, Boontanapibul K. Comparison of functional recovery between unicompartmental and total knee arthroplasty: a randomized controlled trial. J Bone Joint Surg Am. 2022 Dec 21. doi: 10.2106/JBJS.21.00950. Online ahead of print.PMID: 36542689

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