In vivo serial joint space measurements during dynamic loading in a canine model of osteoarthritis.

OBJECTIVE To devise a reliable, sensitive method to measure joint space in vivo during dynamic loading. Additionally, to determine if dynamic joint space changes were related to the severity of long-term cartilage damage. DESIGN Subjects were 23 adult foxhounds (18 experimental, 5 control). Experimental subjects had surgically transected cranial cruciate ligaments (CCL). Dynamic joint space was serially measured in vivo over 2 years using a unique high speed stereo radiographic system in combination with subject-specific computed tomography reconstructions. RESULTS Dynamic joint space was measured in vivo with a within-day precision of 0.09 mm. Half of the experimental subjects developed minor articular cartilage damage and the other half developed severe articular cartilage damage in the medial knee compartment. Joint space during treadmill running increased significantly in the minor damage group in both the medial (+0.61 mm, P = 0.036) and lateral (+0.84 mm, P = 0.002) compartments of the knee. Dynamic joint space in the severe damage group did not increase significantly on either the medial (+0.27 mm, P = 0.408) or lateral (+0.44 mm, P = 0.199) side. The majority of the change in joint space occurred the first year after CCL transection. Medial meniscus damage was related to severity of medial articular cartilage damage (tau = 0.447, P = 0.003). The minor damage group developed 73% of all osteophytes noted at dissection. CONCLUSIONS This technique is a precise tool for measuring joint space serially in vivo under dynamic loading conditions. The data suggest decreased severity in long-term articular cartilage damage is related to: osteophyte formation, less severe medial meniscus damage and increased joint space the first 12 months after injury.