Beyond patient perception: PROMs correlate with objective functional tests following knee cartilage repair

Patient-reported outcome measures (PROMs) are widely used to evaluate subjective knee function after cartilage repair surgery, but their association with objective functional performance is unclear. This study explored correlations between PROMs and functional performance tests in patients after knee cartilage repair.

In this monocentric observational study, 52 patients from the German Cartilage Registry underwent standardized functional testing at a mean follow-up of 66.8 months. PROMs included the subjective IKDC score and KOOS subscales. Functional performance comprised isometric strength testing, single-leg hop tests (SLHD), Timed Up and Go (TUG), Timed 6-Meter Hop (T6H), 30-second Sit-to-Stand, and Single Leg Stance. Spearman correlations were calculated between PROMs and limb symmetry indices or performance categories.

Dynamic unilateral hop tests showed the strongest associations with PROMs, with SLHD symmetry correlating strongly with IKDC (ρ = 0.540) and moderately with all KOOS subscales. T6H performance also correlated strongly with IKDC and KOOS Sport. Knee extension strength showed moderate correlations with IKDC and KOOS Sport, whereas flexion strength and low-demand tests (TUG, Single Leg Stance) showed no significant associations.

PROMs demonstrate moderate, test-dependent correlations with objective functional performance after knee cartilage repair, particularly for dynamic unilateral tasks. PROMs reflect functional impairment but cannot replace objective testing. Therefore, a combined assessment approach is recommended.