Location of knee pain in medial knee osteoarthritis: patterns and associations with self-reported clinical symptoms

Abstract

To (1) document pain location in medial tibiofemoral osteoarthritis (OA) using the patient-administered Photographic Knee Pain Map (PKPM); (2) compare pain severity, nature and likelihood of neuropathic-like symptoms, physical dysfunction and presence of symptoms at other sites across the most common pain patterns. Baseline data were analysed from 164 participants with medial tibiofemoral OA (TFJOA) participating in a randomised controlled trial (RCT). Participants completed the PKPM indicating all relevant pain zones of their most painful knee. Pain zones were collapsed into regions to determine patterns of pain. Symptoms were quantified using numeric rating scales (NRSs) of pain severity, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Intermittent and Constant Osteoarthritis Pain (ICOAP) and painDETECT questionnaires. Symptoms at other joints were categorised as present/absent. The medial joint line (n=123, 75%), patellar tendon (n=62, 38%) and posterior knee (n=61, 37%) were the most frequently reported pain zones. The most frequent patterns were diffuse (41%), isolated medial (16%), anterior-medial (12%) and medial-posterior (11%) pain. WOMAC and ICOAP scores were higher in the diffuse compared to anterior-medial patterns. Mean PainDETECT scores were higher with both diffuse and medial-posterior pain relative to anterior-medial pain. Only 16% of the cohort indicated isolated medial knee pain, whilst a diffuse pain pattern was most common. People with diffuse knee pain reported more severe pain and physical dysfunction than those with anterior-medial pain. Prevalence of possible/likely neuropathic-like symptoms tended to be more frequent in diffuse and posterior-medial patterns compared to anterior-medial pain.