18F-fluoride is a positron-emitting bone-seeking agent with favorable pharmacokinetic properties. Its uptake mechanism resembles that of 99mTc-MDP. After IV administration, 18F-fluoride diffuses through the bone capillaries into the bone extracellular fluid (ECF). Its plasma clearance is more rapid than that of 99mTc-MDP and its single-passage extraction efficiency is higher. The fast blood clearance of 18F-fluoride results in a better target- to- background ratio. Bone uptake of 18F-fluoride is two-fold higher than that of 99mTc-MDP. Combining the favorable pharmacokinetic characteristics of 18F-fluoride with the high performance of PET technology, 18F-fluoride is a valuable imaging modality of the skeleton.

There are only few manuscripts on the role of static 18F-fluoride PET for detection of lesions in patients referred for non-oncologic indications The purpose of the study is to prospectively assess the added value of Fluoride PET/CT in the clinical setting of acute knee injury. The findings of Fluoride PET/CT will be correlated with those found on arthroscopy and MRI which the currently used diagnostic techniques with a high, however, not perfect diagnostic accuracy regarding the issue of bone injury which is a critical component on the long term outcome after knee injury.

We intend to inject only 5mCi of Fluoride, as we already did before, thus reducing the radiation exposure to half of that of the routine Tc-MDP bone scintigraphy.

We will refer 50 patients over the age of 18 who had knee trauma, intent to or had MRI assessment and are scheduled for arthroscopy. The compartments of the injured knee will be evaluated on each of the modalities.

Exclusion criterion is pregnancy

Inclusion Criteria:

• patients over the age of 18 who had knee trauma

Exclusion Criteria:

• pregnancy
• age under 18 years

patients over the age of 18 who had knee trauma, intent to or had MRI assessment and are scheduled for arthroscopy