Table I.

Location and description of TF radiographic OA in knee joints, with incidence and space joint narrowing by subsets of compartment and radiographic modalities cumulative to 84-month follow-up

Clinic site/Radiographic modality and image resolution	Birmingham, AL (UAB) CR low resolution images 894 knees	Iowa City, IA (UIowa) DF high resolution images 1158 knees
Definition/location
Incident tibiofemoral OA: K–L grade ≥ 2 N (PA view), N (%)	195 (21.8)	303 (26.2)
Medial compartment only	108 (55.4)	164 (54.1)
Lateral compartment only	45 (23.1)	61 (20.1)
Both compartments	2 (1.0)	10 (3.3)
Incident without JSN change	40 (20.5)	68 (22.4)
Medial JSN by ≥0.5 grade (both PA and lateral views), N (%)	137 (15.3)	213 (18.4)
Medial compartment only	134 (97.8)	201 (94.4)
Both compartments	3 (2.2)	12 (5.6)
Lateral JSN by ≥0.5 grade (both PA and lateral views), N (%)	59 (6.6)	86 (7.4)
Lateral compartment only	56 (94.9)	74 (86.0)
Both compartments	3 (5.1)	12 (14.0)