Evaluation of neuropathic-like symptoms and objective signs of neuropathy post-knee replacement in patients with knee osteoarthritis.

Objective: Why persistent pain post-knee replacement occurs is not understood. We examined the association of clinical measures of neuropathy and presence of 'neuropathic-like pain' with pain post-knee replacement.

Design: Participants with a knee replacement from the NIH-funded longitudinal cohort Multicenter Osteoarthritis (MOST) Study were examined ∼12-months post-surgery using clinical assessments of neuropathy (von Frey 2 ​g and 26 ​g monofilaments and pin prick) and the painDETECT questionnaire (PDQ; score ≥13 was considered neuropathic-like pain). We evaluated the relation of the clinical neuropathy assessments and the PDQ to achievement of the patient acceptable symptom state (PASS) post-knee replacement using WOMAC, and of the objective clinical neuropathy assessments to neuropathic-like pain on the PDQ using logistic regression.

Results: This cohort study evaluated 171 participants post-knee replacement (mean age 69, 62 ​% female, mean BMI 32.6). Overall, 57 ​% had any abnormality on ≥1 clinical neuropathy assessment (51 ​% hypoesthesia, 10 ​% allodynia/hyperalgesia), and 7 ​% had neuropathic-like pain. There was no association between presence of any abnormality on clinical assessment and not achieving the PASS (OR 1.4, 95 ​% CI 0.5-4.12). In contrast, higher PDQ scores were significantly associated with not achieving the PASS. There was no association between any abnormality on the clinical assessments of neuropathy with PDQ score ≥13 (OR 0.65 (95 ​% CI 0.14-3.02).

Conclusions: Objective clinical assessments of neuropathy were not associated with worse pain status post-knee replacement, while PDQ scores were. PDQ was not associated with clinical assessments of neuropathy. PDQ may be reflective of pain severity in general, and potentially nociplastic, rather than neuropathic, pain.