because of its biomechanical properties , patellofemoral articulation is one of the most complex joints . patella is suspended by tendons and stabilized by ligaments and is prone to dislocate if an imbalance arises . superior dislocation of patella is a rare condition with sixth decade being the peak age of presentation . in ~20 we present a case of spontaneous superior dislocation of patella in a 30-year - old male with no obvious patellofemoral arthrosis . hydrodilatation of his knee was performed using 10 ml of 0.5% chirocaine diluted in 20 ml of 0.9% normal saline . superior patellar dislocation is a rare pathology with patella alta , ligament laxity , neurological diseases and genu recurvatum being risk factors . common mechanism of injury is hyperextension of the knee associated with direct force to patella . voluntary   and spontaneous [ 5 , 6 ] superior patellar dislocations are also reported . a thorough history and careful examination is essential for diagnosis . due to its rarity patient will not be able to do a straight leg raise in both conditions , but for different reasons . it is due to pain in superior patellar dislocation , while loss of extensor mechanism continuity is the cause in patellar tendon rupture . most cases involved trivial or no trauma in superior patellar dislocation , with contraction of quadriceps in extended knee . superior movement of the patella locks its lower articular margin on upper border of trochlea . in contrast , rupture of patellar tendon requires significant force and often is a consequence of eccentric contraction of quadriceps . knee can not be flexed actively or passively in superior patellar dislocation , which is the most important differentiating point . patients with patellar tendon rupture generally have less pain , knee can be passively flexed and often a gap is palpable in patellar tendon area . it should not be forgotten that a tense hematoma in tendon gap is possible . interesting radiographic feature is tilting of patella in lateral view in superior patellar dislocation ( fig . superior end of patella projects forward due to rotation of patella on a horizontal axis . careful history , examination and radiographs are enough to reach diagnosis for prompt treatment . 
 figure 1:lateral radiograph of knee showing dislocated patella . reduction can be attempted with intra - articular local anaesthetic , sedation , femoral nerve block and rarely general anaesthetic . it is advised to immobilize knee in gentle flexion during recovery from general anaesthesia to avoid recurrence in perioperative period . when awake , knee can be left free . intra - articular local anaesthetic diluted in normal saline is recommended , giving analgesic as well as mechanical advantage , by pushing patella away from femur . if other analgesics fail , a general anaesthetic is used as a last resort and spontaneous reduction can happen . in our experience , intra - articular diluted local anaesthetic provided very good pain relief . spontaneous reduction of joint has also been reported after adequate analgesia . the next important step is to hyperextend the knee as much as allowed comfortably by patient ; this releases tension from patella and helps it unlock it from its position . ipsilateral hip flexion with extended knee also helps to relax quadriceps further due to proximal attachment of rectus femoris . two digits should be used under medial and lateral borders of patella to lift it away from surface of femur . medial and lateral rocking movements of patella , while keeping it lifted , helps to relocate patella onto its track on trochlear groove . once free , superior and inferior movement of the patella is felt and the knee can be fully flexed . until the patella is unlocked , it is important not to crank the knee to flexion due to risk of iatrogenic injury to patellar tendon , inferior pole of patella or osteochondral fracture . ability to freely flex knee actively and passively denotes relocation of patella . in all the reported cases , close reduction was successful except one . if digital manipulation was unsuccessful , our plan was to use a pointed reduction clamp , after making small skin incisions to grasp patella , caudal to its equator , to manipulate . effective lifting force can be applied through reduction clamp by eliminating slipping of skin and subcutaneous tissues over patella . the last option is to do arthroscopy . this has an advantage of shaving off the prominent osteophytes from inferior pole of patella and superior margin of femoral trochlea . the examiner should check for full range of movement , to detect the tendency to dislocate and feel for any crepitus . it can be treated by simple manoeuvres in accident and emergency avoiding unnecessary suffering and admission .
abstractsuperior patellar dislocation is a very rare pathology , which happens in middle age . 
 we report a case of spontaneous superior patellar dislocation , which occurred at 30 years of age . 
 differential diagnosis is patellar tendon rupture , which could be reliably excluded by clinical examination and radiographs . 
 reduction manoeuvres should be tried with diluted intra - articular local anaesthetic for hydrodilatation to gain mechanical advantage . splinting the knee in gentle flexion 
 is recommended if general anaesthetic is employed . recurrent dislocation or osteochondral fractures warrants surgical treatment .