the presence of ligamentous instability in some cases this might be a contraindication to the indicated grade of degeneration degeneration is confined to one tf compartment with bone on bone degeneration present osteophytes may be present in the other compartments but these compartments generally retain their integrity the unaffected tf compartment must have a parallel joint extending at least 5 mm deep the meniscus and chondral cartilage must thus be unaffected and intact if a u201c wedge u201d sign is present a pka might not be suitable and case 1 is illustrated in fig2 where contact between medial femoral condyle 34 and medial tibial plateau 24 can be observed in the medial tf compartment it is also clear that lateral joint space 40 remains parallel throughout the lateral tf compartment and that the depth of the lateral joint space 40 remains in excess of 5 mm no subluxation is present on the lateral view indicative of the integrity of the acl the healthy tf compartment is further confirmed by the stress views of fig9 and 10 as discussed above tf compartments are unaffected the unaffected tf compartments will be confirmed by the 15 and 45 degree rosenberg views and stress view similar to that illustrated in fig1 osteophytes may be present in both the affected and healthy compartments but these compartments.