This case report was conducted using Dornier Aries
1. Introduction
Due to the rapid growth of the geriatric population, knee pain has become one of the most common signs among older adults in South Korea [1]. Persistent knee pain adversely affects gait dynamics, ultimately leading to impaired mobility. Therefore, accurate diagnosis and timely treatment are needed to improve the quality of life (QOL) of patients.
Osteoarthritis (OA) is the leading cause of knee pain. Other causes, such as ligament or meniscal injuries, are also well known [2]. Unless the condition is amenable to surgery, a conservative approach is chosen to improve pain. Conservative treatments for joint or soft tissue lesions are well established. In particular, water aerobics is often recommended as a safe rehabilitation exercise with a weight-reducing effect [3].
Due to unexplained and vague symptoms, proximal tibial insufficiency fractures can be easily misdiagnosed, often confused with other common knee pathologies, and may not show up with standard screening tools such as x-rays or ultrasounds. When the injury is misdiagnosed or mistreated, the pain persists and can severely reduce the patient's quality of life.
There are relatively limited solutions available for knee pain caused by non-surgical fractures. In this case report, we observed that proximal tibial insufficiency fractures are the leading cause of persistent knee pain after water aerobic exercise. In addition, we report for the first time the application of extracorporeal shock wave therapy (ESWT) for the treatment of painful insufficiency fractures.
2. Case reports
Informed consent has been obtained from the patient to release the patient's data. A 75-year-old woman with diabetes mellitus presents to the hospital with persistent pain in her right knee. She is neither a smoker nor an alcohol, and has no malignant or endocrine disorders other than diabetes and osteoporosis (treated with alendronate medications). She was diagnosed with mild osteoarthritis in both knees 5 years ago and has been attending water aerobics classes regularly twice a week as prescribed. Without any history of trauma, she felt pain in her right knee immediately after water aerobics, which quickly worsened and affected her ability to walk, and her symptoms did not resolve even after 3 weeks of physiotherapy and intra-articular sodium hyaluronate injections at a local clinic.
At the first presentation, she complained of severe pain in a wheelchair (VAS 9). noted severe tenderness and slight swelling in the medial lower part of the right knee; However, further physical examination failed to identify other abnormalities. Thermosensory, motor, and sensory deficits, lateral and medial McMurray tests, Lachman's test, anterior and posterior drawer tests, and valgus and varus stress tests were all negative. Diagnosis of Kellgren-Lawrence grade 1 mild osteoarthritis based on ordinary X-rays (Figure 1). Apart from a small joint effusion, no abnormal ultrasound results were observed. On the day of diagnosis, an intra-articular injection of sodium hyaluronate (20 mg) was administered to the right knee, triamcinolone acetonide trichloroacetate (20 mg) and 0.5% lidocaine (1 ml) was administered to the inner membranous sac of the right knee, and tenderness points were given to the right tenacinal muscle, as we suspect that mild osteoarthritis, inner membranous cystitis, and pain caused by quadriceps myofascial pain syndrome have a mixed etiology. Subsequently, it was given physical therapy and a prescription of pirobuprofen (45 mg) for 7 days. Despite these multimodal treatments, the pain in the right knee did not lessen during this period.
Further plain x-rays showed an old compression fracture of the twelfth thoracic vertebra; Therefore, a bone mineral density (BMD) test and enhanced magnetic resonance imaging (MRI) were performed on the right knee. MRI showed a focal hypointensity on the T1-weighted image of the right proximal medial condyle of the tibia, and a speckled hyperintensity on the T2-weighted, fat-suppressed image with focal enhancement (Fig. 2). Except for a small joint effusion, no other structures were abnormal. Taking into account the diagnosis of osteoporosis using the BMD test (lumbar spine including L1-4 T-score -2.6 and femoral neck T-score -2.5), an incomplete fracture of the proximal medial condyle of the right tibia can be inferred. Despite 3 weeks of physical therapy and intra-articular injections, severe pain (VAS 9) persisted for almost 4 weeks. One ESWT treatment was performed on the lesion site with a single ESWT treatment with an energy density of 0.3-0.9 mJ/mm2, adjusted according to the patient's tolerance, at a frequency of 6 Hz, 2000 shock waves were applied, pain was reduced to VAS 7, in addition to being able to stand with a weight load afterwards. Subsequently, the patient is asked to wear an elastic knee band in their daily life for the next 3 weeks to avoid weight bearing on the right knee and any external trauma. On the basis of patient tolerance, two additional weekly ESWT treatments were performed with an energy density of 2.0 mJ/mm2, and the pain gradually decreased to VAS 4 after the second treatment and finally to VAS 2 after the third treatment. Each treatment lasted approximately 5 minutes without anesthesia, and patients did not report any adverse reactions after the treatment was completed. The final follow-up was performed 5 months after the last ESWT treatment, and we confirmed that symptom improvement was maintained.
3. Discussion
A 75-year-old woman presents with pain in her right knee after being prescribed a water aerobics exercise session for her age. She was diagnosed with degenerative osteoarthritis at a local clinic. Despite a series of treatments, the pain still worsens. MRI of the knee showed an insufficiency fracture of the medial condyle of the proximal tibia on the right side without any signs of concomitant soft tissue injury. After three sessions of ESWT, the pain improved significantly without any adverse effects.
Knee pain is mainly due to osteochondral lesions or ligament injuries. A previous study found that in South Korea, 46.2 percent of patients aged 50 years and older with knee pain were diagnosed with knee degenerative osteoarthritis (32.2 percent in men and 58.0 percent in women) [2]. Severe joint lesions or ligament ruptures may require surgery, however other patients can be treated with a variety of methods, such as injection therapy and physical therapy. Exercise programs for weight control are also often prescribed, as body mass index is strongly associated with knee pain [4].
Inadequate fractures are a stress fracture subtype commonly associated with osteoporosis. It can be related to repeated mechanical stress. Stress fractures of the tibia typically involve the middle and distal third parts of the tibia, but rarely affect the proximal metaphysis [5,6]. To the best of our knowledge, this is the first case report of proximal medial condylar intoxication fracture caused by water aerobic exercise in older adults.
As with other conditions, doctors should consider other possible causes and treatments when dealing with knee pain that doesn't respond to traditional treatments. This case report reveals that proximal tibial insufficiency fractures can cause persistent, severe knee pain in the absence of other soft tissue injuries in older adults. The process of diagnosis and treatment of the above cases hints at three key points.
First, doctors should consider occult fractures when treating patients with pain, even if there are no signs of fracture on plain x-rays. Because it accounts for a small proportion of the cause, minor bone injuries, such as bone contusions or incomplete fractures, are not highlighted as a cause of knee pain. They may be misdiagnosed as soft-tissue injuries or neglected unless a clear history of trauma is noted [7]. The patient presented in this case report had no significant history of trauma, but osteoporosis and consequent lumbar compression fractures suggested the possibility of proximal tibial insufficiency fractures, which were subsequently diagnosed by MRI. In the absence of other soft tissue injuries, a localized inadequate fracture is sufficient to cause such severe pain.
Second, the slight axial loading of the knee during weight-support exercise can likewise lead to traumatic osteochondral lesions. For older people with decreased muscle balance and muscle mass, such as water aerobics, it is widely prescribed to reduce axial load and strengthen lower limb muscles through the resistance of water. On the ground, the knee joint bears about 200-500% of the weight load; In chest-deep water, this load is reduced to about 32-35% [8,9]. However, any type of osteochondral lesion can occur when this reduced force accumulates in a localized part of the bone through repetitive exercises [10]. Since 75 percent of the knee load is transmitted through the tibial plateau when standing on one foot [11], an insufficiency fracture occurs in the anteromedial tibial condyle and causes pain on the first heel landing. This repeated minor trauma is not sufficient to cause lesions of the medial meniscus or ligaments, but sufficient to induce minor fractures of the bone marrow beam (Figure 3).
Third, knee pain responds best to ESWT in this case. Treatment options for nonsurgical bone lesions are typically limited to protective weight-bearing, analgesics, or physical therapy [12]. For older people, pain can become chronic due to its longer natural healing process. In this case, the knee pain did not respond to conventional treatments, yet only three ESWTs almost eliminated the persistent pain. Previous studies have revealed the effectiveness of ESWT in the treatment of various bone disorders, such as tibial nonunion, bone marrow edema, avascular necrosis, and tibial stress syndrome [12-15]. Shock waves are transduced into biochemical signals through mechanical conduction mechanisms, and in addition, they affect endogenous pathways, such as the ATP-triggered ERK1/2 pathway, improve cell proliferation and wound healing, and promote neovascularization, revascularization, recruitment and proliferation of endogenous stem cells, and reduced pain and osteogenesis [13,16]. Previous studies have explored the use of ESWT in the presence of insufficiency fractures in athletes. Taki et al. reported the use of ESWT in five athletes for the treatment of stress fractures at different sites (tibia, descending bone, base of the fifth metatarsal, and medial malleolus) and demonstrated that ESWT is a noninvasive and effective treatment for refractory stress fractures [17]. Morretti et al. described 10 soccer players with fifth metatarsal and tibial stress fractures who received three to four ESWT treatments. At an average follow-up of 8 weeks after treatment, the clinical and radiological results of the athletes were excellent, allowing all athletes to gradually return to physical activity without concurrent ESWT (Extracorporeal Shockwave Therapy) is a treatment that stimulates tissue repair and healing by delivering high-energy shock waves into the patient's body. For skeletal lesions such as fractures in older adults, ESWT is considered a promising treatment option.
In this case, the patient suffers an insufficiency fracture of the knee joint caused by performing water aerobic exercise, and the pain is not relieved by traditional treatments. However, after just three ESWT treatments, the persistent pain almost completely disappeared. ESWT harnesses the mechanical and biochemical effects of shock waves to stimulate cell proliferation, promote wound healing, promote neoangiogenesis and endogenous stem cell proliferation, and reduce pain. Previous studies have demonstrated the effectiveness of ESWT in the treatment of bone diseases such as fractures, bone marrow edema, avascular necrosis, and stress fractures.
For older people, the fracture healing process can be longer, and the pain can become chronic. Therefore, ESWT, as a non-invasive, effective treatment, can help older adults to speed up the fracture repair process, reduce pain, and facilitate their gradual return to normal daily activities and sports.
In conclusion, although water aerobic exercise is safe for knee osteoarthritis by reducing body weight load, we demonstrate that repeated minimally invasive trauma may lead to incomplete fractures. Therefore, we suggest that physicians should consider the possibility of an insufficiency fracture of adjacent bones when the patient has severe and persistent knee pain and no abnormal findings on physical examination and basic imaging studies. In such cases, MRI to localize the lesion and adjuvant ESWT can significantly reduce the duration of pain and improve the patient's quality of life.
To the best of our knowledge, this case study is the first time that ESWT has been reported in the treatment of knee insufficiency fractures in older adults. Therefore, further research is needed to determine the appropriate dose, treatment interval, and number of treatments required to achieve better clinical outcomes.
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