The correlation of bone scintigraphy and histological findings in patellar tendinitis

Patellar tendinitis is a chronic overuse injury causing pain and tenderness over the proximal insertion of the patellar tendon. Its management is usually conservative, but in intractable cases surgery is effective. Bone scintigraphy has been suggested as a useful investigation in these patients, although we are aware of no large series supporting this. Thirty-four patients with intractable symptoms of patellar tendinitis were treated surgically. The operative specimens were graded histologically and compared with preoperative radionuclide bone scans. The histological findings confirmed tendon and or tendon sheath abnormalities in all the samples. The predominant abnormalities were increased vascularity, fibroblast proliferation, acid mucopolysaccharide and haemosiderin deposition. Bone scintigraphy showed 24 (71%) patients to have abnormalities on the delayed images, 8 with diffusely increased activity in the patella and 16 with increased activity localized to the lower pole. Patients with abnormal bone scans had significantly more severe histological changes in their tendons. These findings support the use of radionuclide bone scans in the pre-operative assessment of patellar tendinitis correlating well with histopathological severity of the disease process. The 10 false-negative cases (29%), however, suggest that bone scans are unhelpful in the routine diagnosis and management of this condition.