Title: Patient interpretations of the term ‘stiffness’ prior to and following total knee arthroplasty
Authors: Judith Lane, Hamish Simpson, Colin Howie, Fiona MacMillan
Purpose: to gain further understanding of what patients mean when they say that their joint feels
‘stiff’ both prior to and following total knee arthroplasty.
Relevance: Pain, function and joint stiffness are recommended as core outcome measures following
joint replacement surgery although few studies have included stiffness . One study in patients with
rheumatoid arthritis showed that the interpretation of the word ‘stiffness’ was varied. If groups with
osteoarthritis and TKA were to demonstrate a similar variability, doubt could be cast upon the
robustness of currently used measures of stiffness.
Participants: Patients (n = 40) who were due to undergo TKA for osteoarthritis within 6 weeks were
recruited from a pre-admission clinic. TKA patients (n = 76) were recruited from a group who had
undergone primary TKA for osteoarthritis in the previous 10-14 months.
Methods: Participants rated their level of perceived stiffness from 0 -100 using a visual analogue
scale. They were also asked to select words that they felt best described their stiffness from a list of
21. The stiffness descriptors included words that were related to pain, difficulty with movement and
sensation.
Analysis: VAS stiffness was not normally distributed and therefore Mann-Whitney U tests were
used to detect inter-group differences in self reported level of stiffness, number of words used. Chisquare tests were used to explore difference between the groups in the type of words used to
describe stiffness.
Results: The OA group had a higher median VAS stiffness score of 60.0 compared to 40.0 in the TKA
group. These differences were significant (p < 0.001). The median number of words used to describe
stiffness was 4.0 in the OA group compared to 1.0 in the TKA. Overall 49% of participants used words
from the pain category to describe stiffness. A significantly greater proportion (χ2 = 19.65, p < 0.001)
of participants in the OA group (78%) included words from the pain category to describe their
stiffness compared to the TKA group (34%). A similar proportion of participants in the OA group
(75%) included words from the difficulty with movement category compared to the TKA group
(65%). A significantly higher proportion (χ2 = 42.88, p < 0.001) of participants in the OA group (60%)
than the TKA group (5%) used words from the sensation category. The most common combination of
words in the OA group was pain + stiffness+sensation (43%) whereas the largest proportion of TKA
patients (41%) used the difficulty with movement category only.
Conclusions: All participants were likely to use a range of words to describe stiffness but the OA
group were more likely to use pain or sensation related words than the TKA group.
Implications: When a patient reports stiffness either prior to and following TKA, care should be
taken to explore with the patient what they mean. Many patients confused sensations of pain with
sensations of stiffness and this could have implications for provision of adequate pain relief. Further
work is necessary to ensure the validity of patient reported measures of stiffness.
Keywords: TKA, osteoarthritis, stiffness,
Funding acknowledgements: no funding was received in support of this study.