Most tibial stress fractures occur posteromedially, along the popliteal-soleal line in the middle and distal third of the tibial diaphysis [1,2]. Although much less common, the proximal medial tibial condyle has been cited as an area subject to stress fracture. Insufficiency fractures of this area have been reported. These fractures are the result of bone that is deficient in strength that is loaded under normal physiologic conditions. Typically, elderly patients with osteoarthritis of the knee and postpartum female patients are at risk for the development of insufficiency fractures [3,4].
The incidence of proximal medial tibial condylar fatigue fractures is unknown. In contrast to the insufficiency fracture, the bone is normal and fails secondary to excessive and repetitive stress . The typical patient is a distance runner . Both intrinsic and extrinsic risk factors have been identified in runners, predis* Corresponding author. E-mail address: [email protected] (P.J. DeMeo).
posing them to fatigue fracture. Intrinsic risk factors include limb malalignment, cavus deformity, and a hyperpronated foot . The primary extrinsic risk factor has been linked to a change in running conditions. Notably, uphill running significantly increases the compressive forces across the knee joint . It is surmised that this sudden increase in load is the cause for the fatigue and failure of the underlying cancellous bone of the medial tibial condyle .
Physical examination reveals tenderness in proximity to the medial joint line. This tenderness, in association with a usually present effusion, may lead the clinician to believe that the patient has sustained an injury to the medial meniscus. In addition, the point of maximal tenderness is often close to the insertion of the pes anserinus. Thus, the diagnosis of pes anserinus bursitis also should be considered . Provocative physical examination tests as well as diagnostic injections should be performed to rule out these other causes of medial tibial pain.
Standard imaging, beginning with plain radiographs, should be obtained. Images should be scrutinized closely for any findings consistent with tumor. However, acute stress fractures illicit no radiographic findings. It has been suggested that interval radiographs will show changes consistent with stress fracture (eg, periosteal bone formation and thickening of the involved cortex). This diagnostic feature is not necessarily true for condylar fractures. Some cases have reported no radiographic evidence of fatigue fracture even after 4 months have elapsed since the onset of symptoms . Although bone scanning has been advocated in the past, new magnetic resonance imaging has been advocated as the most sensitive test for diagnosing stress fracture. Fredericson and colleagues  have proposed an MRI grading system for tibial stress injury. Fat-suppression
MR images often reveal significantly associated marrow edema in the presence of a medial tibial condyle fractures (Fig. 1). MRI not only assists with confirming the diagnosis, it also affords information regarding the extent of bony involvement and severity of the pathology.
Once medial tibial condylar stress fracture has been diagnosed, treatment consists of educating the patient in avoiding the offending activity. Depending on the amount of marrow involvement, cessation of running may be advised for up to 6 months, with the initiation of lower impact training such as swimming or bicycling after 6 weeks . There have been no reports of delayed union, nonunion, or displacement of proximal tibia medial condyle fatigue fractures. An increased awareness by a surgeon, a high level of clinical suspicion, and patient education are requisite for an optimal outcome.
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