a 30-year - old woman was presented to our hospital for acute onset of pain in both knees with an inability to extend the knees after a trivial fall following a minor slip . on the physical examination , swelling of the anterior aspect of the distal thigh , bruised skin dimpling at upper pole area ( fig evaluation of range of motion revealed complete loss of active knee extension . on her past medical history , she had been on hemodialysis for the past 8 years due to chronic renal failure secondary to lupus nephritis . but , she had received no treatment for the elevated level of parathyroid hormone due to lack of any symptoms . on plain radiographs , there was no fracture around patella upper pole , but irregular calcific deposits in the supra - patella area where quadriceps tendons insert and patella baja were seen ( fig . sagittal t2-weighted magnetic resonance imaging ( mri ) , quadriceps tendons of both knees appeared ruptured , high signal intensity was observed , and moderate degree knee joint effusion and soft tissue hemorrhage around the ruptured tendons were seen ( fig . the hematochemical analysis revealed the following values ( and their reference values ) : parathyroid hormone ( pth ) 1,701 pg / ml ( normal range , nl 15.0 - 65.0 pg / ml ) , uric acid 6.2 mg / dl ( nl 2.5 - 8 mg / dl ) , creatinine 9.1 mg / dl ( nl 0.5 - 1.3 mg / dl ) , serum alkaline phosphatase 671 iu / l ( nl<130 iu / l ) , calcium 9.2 mg / dl ( nl 8.4 - 10.2 mg / dl ) , and phosphorus 4.4 mg / dl ( nl 2.5 - 5.6 mg / dl ) . on ultrasonography of the neck , multiple well - demarcated homogeneous hypoechoic masses were found ( fig . these findings are compatible with tertiary hyperparathyroidism secondary to chronic renal failure , in which pth secretion occurs independent of blood calcium concentration and autonomous parathyroid function develops . both quadriceps tendons were completely avulsed and ruptured at the tendon insertion sites without bony fragment . the avulsed tendons ' ends were ragged with some dystrophic calcifications and the upper border of patellae was softened due to some degree of bone resorption . around the rupture on superior pole of both patellae , debridement of nonviable surrounding tissues preceded the repair surgery ( fig . we sutured the proximal tear site with a non - absorbable number 5 ethibond suture material by krakow 's method , and subsequently made three vertical tunnels from the supra - patella lesion to distal pole of patella on each knee . the suture ends were passed through the patella tunnels and tied distally to the surrounding soft tissues using pull - out technique ( fig . postoperative rehabilitation protocol included immobilization of both knees in extension for 6 weeks . from the 7th postoperative week , gradual weight - bearing and gait training with braces the braces were removed because the range of motion and strength of both knees increased . during the rehabilitation period the general surgeon recommended medical treatment considering her young age and side effects of parathyroidectomy , such as hypoparathyroidism . the nephro logist prescribed vitamin d analog and recommended close monitoring of the parathyroid hormone level . elevated serum parathyroid hormone level was normalized at 6 months postoperatively . so far we have closely monitored her parathyroid hormone level . at 18 months postoperatively , the patient had minor weakness during knee extension , but did not complain of any disability and returned to previous daily activities . simultaneous bilateral spontaneous rupture of the quadriceps tendon is uncommon , and have been described as a complication of various diseases , such as , secondary hyperparathyroidism , systemic lupus erythematosus , diabetes mellitus , gout , rheumatoid arthritis , obesity , and end stage chronic renal failure4 ) . however , the exact mechanism leading to rupture of tendon is still not entirely understood . some authors pointed out the relationship between the duration of hemodialysis and occurrence of spontaneous tendon rupture , presence of tendinopathy and accumulation of uremic toxin and beta 2-microglobulin amyloid2 ) . the first case of simultaneous bilateral spontaneous rupture of the quadriceps tendon with secondary hyperparathyroidism in a patient on chronic hemodialysis was reported by preston and adicoff5 ) . since then , many authors have described that secondary hyperparathyroidism and its sequel play a major role in the pathogenesis of tendon rupture . in this report we found multiple parathyroid adenoma in ultrasound examination and noticed that autonomous parathyroid function had developed . physiological homeostasis of body calcium and phosphate is regulated by the kidneys , intestines , and parathyroid . in patients with chronic renal failure , a decrease in glomerular filtration rate results in the retention of phosphorus , which leads to hypocalcemia , and decreased serum calcium concentrate causes a proportional increase in the parathyroid hormone level that results in high bone turnover that is caused by osteoclast stimulation to release calcium . as a result , subtendinous bone resorption at the quadriceps tendon insertion site occurs3,4 ) . dystrophic calcification and subperiosteal bone resorption can be observed on plain radiographs as in our patient . in this situation , repeated avulsion injuries can easily occur without major trauma . clinical and physical examination , simple plain x - ray , ultrasonogram , and mri are commonly used for the diagnosis of tendon ruptures7 ) . although extensor mechanism injuries are easily diagnosed by clinical findings , physical examination , plain radiography , and especially mri are necessary for determining the site , extension and pattern of tendon rupture as well as for preoperative planning of repair or tendon reconstruction . conservative management using medication or cast immobilization is not sufficient for complete restoration of the quadriceps tendon function . in some case reports , bunnel suture , krakow stitch and suture - bone tunnel technique were used for quadriceps tendon repair3,8 ) . although several surgical techniques have been introduced in case reports the basic concept of treatment is to attach the ruptured tendons onto the patella by using non - absorbable suture material1,8 ) . in our case , we sutured proximal tendon with using krakow stitch to improve tissue grip , then passed the suture through three predrilled parallel vertical bone tunnels , and tied knots at inferior pole of patella with adequate tension . strict control of hyperphosphatemia , early use of vitamin d analogs , and , in recalcitrant cases , total parathyroidectomy with or without auto transplantation of a part of the parathyroid gland are needed to prevent these ruptures9 ) . clinicians should perform careful clinical assessment of the parathyroid hormone level and strict control of hyperphosphatemia using vitamin - calcium therapy . in summary , bilateral spontaneous rupture of quadriceps tendon is a rare entity , and the role of elevated parathyroid hormone in end - stage renal disease patients seems to play an important role . proper evaluation and management including surgical repair and medical treatment can result in satisfactory clinical and functional outcomes .
simultaneous bilateral spontaneous rupture of the quadriceps tendon is a very rare condition and only a few cases have been reported in the literature . 
 the etiology is not clear yet . 
 but it occurs infrequently in patients with chronic metabolic disorders . a 30-year - old female patient with simultaneous bilateral spontaneous quadriceps tendon rupture visited our hospital . 
 she had chronic renal failure and her parathyroid hormone level was elevated due to parathyroid adenoma . 
 we report a surgical repair of both quadriceps tendons of a patient with chronic renal failure as well as management of hyperparathyroidism .