Femoral Supracondylar Stress Fractures
An Unusual Cause of Knee Pain
MAJ John E. Glorioso, Jr, MD; CDR Glen Ross, MD;
THE PHYSICIAN AND SPORTSMEDICINE - VOL 30 - NO. 9 - SEPTEMBER 2002
In Brief: Supracondylar stress fractures are rare and can cause anterior knee pain. Persistent, intense pain occurs in the knee and distal thigh and may be mistaken for patellofemoral pain syndrome unless the fracture is identified by radiographic modalities (MRI or bone scan). Two cases of supracondylar femoral stress fractures in female runners highlight the need to seek proximal pathologies when patients report knee pain that cannot be explained by other conditions.
Stress fractures are well-known overuse injuries in active people. Although the tibia and metatarsals are the most common locations, any lower-extremity weight-bearing bone may be affected. The femur is the fourth most common site of stress fractures,1 with injury occurring in the neck, subtrochanteric, shaft, or condylar regions.2
A 19-year-old woman reported left knee pain 1 week after winning an 8K race. Two days after the race, she developed diffuse pain at the knee and distal thigh, especially with knee flexion. She noted the onset of pain with the initiation of any impact activity. Except for an abrupt increase in running mileage—up to 50 miles per week in the weeks prior to the race—her history was unremarkable.
Pertinent physical findings included a slightly antalgic gait and tenderness to palpation at the patellofemoral joint and with patellar compression; however, it was difficult to localize the site of pain. The patient had full range of motion, no joint-line tenderness, a negative McMurray test, no effusion, and no evidence of lower-extremity inflexibility.
Initial radiographs of the knee revealed no abnormalities.
The athlete was diagnosed with patellofemoral pain syndrome and referred to physical therapy.
After 1 month of persistent symptoms, the patient had a magnetic resonance image (MRI) that revealed an incomplete posteromedial supracondylar stress fracture of the distal left femur (figure 1A). Upon further questioning, it was discovered that the patient had a 1-year history of amenorrhea, preceded by 3 years of oligomenorrhea and reduced caloric intake. Dual-energy x-ray absorptiometry (DEXA) revealed that her bone mineral density was within normal limits.
The athlete was treated initially with a knee immobilizer and allowed toe-touch weight bearing with crutches. In addition, the patient underwent medical and gynecologic evaluation and was diagnosed as having amenorrhea secondary to intense activity; she was treated with exercise counseling about the cause of her stress fracture and oral contraceptive therapy.
After 2 weeks, the patient began using a cane for assisted ambulation and performing range-of-motion exercises in a swimming pool. At the 1-month follow-up, she began pool jogging, swimming, and stationary biking. Radiographs revealed progressive healing of the fracture with callus formation and normal anatomic alignment (figure 1B). She returned to light jogging at 4 months postdiagnosis.
A 37-year-old woman had pain for 4 weeks in the posteromedial aspect of her right distal femur. At the onset of symptoms, she switched her activity from jogging on a treadmill to a stationary skiing machine and began using a neoprene knee sleeve. On the day of her appointment, the pain intensified, and she was unable to bear weight on the leg.
The patient, who initially weighed 230 lb, began an exercise program with the fitness goal of weight reduction. Over the past year, she lost 40 lb by exercising on a treadmill. She reported an abrupt increase in her training program just before the onset of symptoms. She had been eumenorrheic during the past year, but she had a history of delayed menarche.
Her physical exam was significant for an antalgic gait and tenderness along the posteromedial aspect of the distal thigh and knee. Range of motion was from 0° to 30°; she resisted further flexion past 30° because of pain.
Plain radiographs of the distal femur and knee were normal. An MRI demonstrated a horizontal stress fracture of the posteromedial aspect of the distal femur (figure 2A).
The patient was placed in a long leg brace locked from 0° to 30°, given crutches, and instructed not to bear weight. Although her increased physical activity was the most likely inciting factor, because of her menstrual history, other metabolic abnormalities were explored. DEXA showed normal bone density.
Two weeks later, her plain films revealed callus formation at the posteromedial aspect of the femoral supracondyle. Partial weight bearing was begun at 4 weeks. Full weight bearing with the brace was begun at 8 weeks when she was pain free, had no point tenderness, had regained full knee range of motion, and had abundant callus formation on radiographs (figure 2B). At 6 months postdiagnosis, the patient was performing low-impact activities without any symptoms.
Stress fractures in the athletic population are not uncommon, but injury to the distal femur is rare. We found only six cases of supracondylar stress fractures noted in the literature.3-5
Schmidt-Brudvig4 studied two men and one woman who experienced distal femoral stress fractures during US Army basic training. All three reported anterior knee discomfort and pain with varus and valgus stress testing. Plain radiographs revealed distal femoral stress fractures in all subjects after 2 to 3 weeks of symptoms. Treatment consisted of a long leg cast for 4 to 6 weeks. The injuries healed uneventfully.
Muralikuttan and Sankarart-Kutty3 described two other military recruits who had supracondylar stress fractures that were diagnosed with plain radiographs. Both patients, who presented with acute anterior knee pain 3 weeks into basic training, were successfully treated with cast immobilization for 8 weeks.
Although both patients in our series were women, 5 of 6 patients described in the literature were men; therefore, no clear sex preference is apparent. Any woman diagnosed with a stress fracture should be evaluated for the female athlete triad (amenorrhea, disordered eating, and osteoporosis). A detailed history with emphasis on menstrual patterns, physical and psychological stressors, and eating disorders should be elicited.
Interestingly, both subjects in this report sustained stress fractures on the posteromedial cortex. This is in agreement with other cases in which 3 occurred medially, 2 were not specified, and 1 was located on the medial and lateral cortex.3-5 The medial cortex is the tension side of the femoral supracondylar region in most individuals who have mild genu valgum. In addition to the valgus alignment, the medial collateral ligament and the adductor muscles may create opposing tensile forces that initiate the stress fracture.
Differential diagnosis. The differential diagnosis of distal thigh pain is extensive and includes patellofemoral pain, quadriceps tendinosis, intra-articular pathology, and femoral condylar stress fractures.6,7 Early diagnosis and cessation of impact activity is essential to prevent complete fracture with displacement. Although no complete fractures have been reported at this site, the sequela of such an injury could be devastating.8
The woman in case 1 in this report and the patients in 5 of the 6 previously reported cases presented with anterior knee pain, which may have led to a delay in diagnosis. What distinguishes femoral supracondylar stress fractures from other conditions is the intensity of pain, especially with weight bearing and knee flexion. As with more common stress fractures, an abrupt increase in the intensity or duration of training is often reported.
Imaging considerations. Standard radiographs have a high specificity but low sensitivity in diagnosing stress fractures and are often normal initially. If the diagnosis of stress fracture is suspected despite normal radiographs, imaging modalities such as scintigraphy, computed tomography, or MRI may provide confirmation.8,9 Bone scans are highly sensitive for detecting stress injuries but lack specificity. MRI has a higher specificity than scintigraphy in distinguishing bone from soft-tissue injury, avoids radiation exposure, and reveals the extent of the stress fracture.
Treatment. Stress fractures of the femoral supracondylar region that extend less than 50% of the width of the bone can be treated with a long leg brace and non-weight-bearing status for 2 to 6 weeks, depending on the severity of symptoms. If the fracture traverses greater than 50% of the width of the bone, we recommend long leg cast immobilization and crutches. Plain films help monitor healing. At 6 to 8 weeks, if callus formation is found on radiographs and no point tenderness is present on examination, the patient may resume low-impact activities.
Uncovering Femoral Stress Fractures
Supracondylar femoral stress fractures can easily be masked by other knee conditions, especially patellofemoral pain. Abrupt increases in training and menstrual irregularities may be early warning signs. In addition to a high index of suspicion, scintigraphy or MRI helps to make an early diagnosis. Immobilization with a brace or cast and non-weight-bearing treatment typically yield good results.
The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Army, the Department of the Navy, the Department of Defense, or the United States government.
Dr Glorioso is a major in the United States Army Medical Corps, military family physician, and primary care sports physician at Madigan Army Medical Center at Ft Lewis, Washington. Dr Ross is a commander in the United States Naval Reserve Medical Corps and an orthopedic surgeon at New England Baptist Hospital in Boston. Dr Leadbetter and Dr Boden are orthopedic surgeons at The Orthopaedic Center in Rockville, Maryland. Address correspondence to MAJ John E. Glorioso, Jr, MD, 318 Marietta Pl, Steilacoom, WA 98388.
Disclosure information: Drs Glorioso, Ross, Leadbetter, and Boden disclose no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.