Bone marrow lesions of the knee: longitudinal correlation between lesion size changes and pain before and after conservative treatment by extracorporeal shockwave therapy

BACKGROUND: Bone marrow lesions (BMLs) of the knee have become a common finding on magnetic resonance imaging (MRI), leading to a growing interest in BML, not only for its potential role in the progression of several musculoskeletal conditions, but also for its clinical impact and treatment implications. At present, there is limited and conflicting evidence regarding whether or not pain may be correlated to BML size or not. AIM: To verify the longitudinal correlation between BML size and knee pain. DESIGN: Longitudinal. SETTING: The study was conducted from January to December 2013, at the Galeazzi Institute of Orthopedics in Milan, Italy. POPULATION: The study sample was composed of 72 patients, 27 males and 45 females, with a mean age of 55.9 ± 10.22 years and a mean BMI of 26.1 ± 3.7 kg/m2. All patients presented with BMLs and acute knee pain. METHODS: All 72 patients underwent a knee MRI before and 6 months after a course of high energy ESWT, in order to perform a quantitative measurement of the BML areas. KOOS (Knee Injury and Osteoarthritis Outcome Score) Pain subscale scores were obtained at the same time point. A regression analysis was performed to verify the correlation between knee BML size and KOOS pain subscale score before treatment and the correlation between the reduction of BML size and the improvement of KOOS pain score 6 months after treatment. RESULTS: A statistically significant correlation between the KOOS Pain sub scale and the BML size (beta = -0.362 [CI95%: -0.019/-0.05], p = 0.002) was demonstrated. The clinical score and BML area significantly improved after treatment (p<0.001). The clinical improvement was correlated to the BML size reduction (beta = 0.254 [CI95%: 0.001/0.017], p = 0.031). CONCLUSIONS: This study confirmed a significant correlation between the BML size and the intensity of knee pain. Furthermore, the before and after study using ESWT to treat symptomatic BMLs, revealed a correlation between size reduction of BML and KOOS pain subscale score improvement, demonstrating the utility of BML reduction as a therapeutic goal. Finally, ESWT was validated as a safe and potentially effective treatment of subchondral bone marrow lesions. CLINICAL REHABILITATION IMPACT: Our results confirm that severity of pain is correlated with BML size, and furthermore, demonstrate that increases and decreases in the amount of pain reflect growth or reduction in BML size, respectively. This information may be useful for rehabilitation and decrease the reliance on MRIs for checking the progress of bone lesions. Absence or marked reduction of pain should allow for the resumption of weight-bearing and more strenuous exercises for an adequate musculoskeletal recovery.