US and MR imaging of the postoperative knee

Constantly increasing number of surgical procedures on the soft tissues of and around the knee generates the need for postoperative soft tissue assessment. Sports medicine is constantly seeking new—faster, better, more efficient ways to help patients, especially competitive athletes to come back to their full activity as soon as possible. One of the important factors in that acceleration is postoperative tissue assessment. It helps the clinician making better decisions in terms of the rehabilitation stages, come back to basic and sport-specific training and finally in letting the patient put a full load on the operated structure. The healing of the collagen structure cannot only be guided by patient's pain. Diagnostic imaging methods such as US and MRI, which focus on the soft tissue assessment are best fitted to do the job. They also help in the diagnostics of the reinjuries of operated structures. Often criteria used for basic diagnostics do not fit the need of assessment of the structure which underwent an initial injury, was operated, healed and often reinjured again. Criteria used for regular injury diagnostics are in most cases seriously modified. Moreover the whole matter of structure evaluation after an injury and medical intervention leaves a lot of slippery ground and should be carefully studied before taking the challenge of judging the surgeon and the natural healing processes. Diagnostic judgment has much more impact on the operated patient than the primary injury diagnosis. Depending on the author both MRI and US are pointed out as the best imaging methods in terms of postoperative knee assessment. In fact both methods can be complementarily used in the postoperative follow up. Depending on the operated structure the choice of methods usually depends on local equipment availability and personal doctor's experience. MRI is probably best fitted for evaluation of the internal knee structures such as cruciate ligaments and hyaline cartilage on the tibia and patella. US is my choice always in the evaluation of the superficially located connective tissue structures, femoral cartilage and menisci. In both cases the learning curve is nearly flat, frustrating and dedicated to only those radiologist who know how their surgeon looks like with and without a surgical mask. Tight surgeon-radiologist cooperation and information exchange is essential in this kind of diagnostics.