Periarticular heterotopic ossification (HO) is common complication after the injury to joint and central nervous system, which can lead to dysfunction of the involved joints. This article reviewed the literatures and discuss the complex nature of HO, including its pathophysiology, diagnosis, associated risk factors, and medical management. In particularly, an extensive literature review combined with author's clinical practice will serve as a foundation to understand the concepts regarding the management of HO and joints rehabilitation.

Elbow stiffness is a common complication after trauma or surgery to this joint. The soft tissue is a primary factor resulting in stiffness of the elbow. Splints increasing passive range of motion (PROM) with creep or stress relaxation principle play a important role in reconstruction for post-traumatic elbow stiffness. The clinician should follow the basic principle in designing and application of splints. With reasonable resign and appropriate regimen, clinical experience and related research show that splints can improve elbow ROM of post-traumatic elbow stiffness efficiently.

Hoffa's disease is the clinical condition characterized by anterior knee joint pain secondary to inflammation and/or impingement of the infrapatellar fat pad. The substance P positive nerve fibers rich in the infrapatellar fat pad were stimulated by the noxious stimuli,which may associated with the pain of Hoffa's disease. The relationship between Hoffa's disease and substance P positive nerve fibers in the infrapatellar fat pad was reviewed in this paper.

Tissues around the post-traumatic knee, including the capsule, synovial, articular cartilage, meniscus, etc., can produce inflammatory mediators. This suggested that post-traumatic knee pain and stiffness are related with local inflammation and inflammatory cytokines.These inflammatory cytokines included the inflammatory response factor of advancement and acceleration, such as tumor necrosis factor, interleukin-1, interleukin-2, interleukin-6, cyclooxygenase, etc. This article reviewed the researches about some inflammatory cytokines surrounding tissue of post-traumatic knee, analyzed current research shortcomings, and established the foundation for further study.

BACKGROUND:Interleukin-1βand matrix metal oproteinase-13 can promote the metabolism of chondrocytes, inhibit the capacity of synthesizing and repairing, induce the degradation of extracellular matrix, and play a crucial role in the occurrence of osteoarthritis.
OBJECTIVE:To observe the effects of extracorporeal shock wave therapy on the interleukin-1βand matrix metal oproteinase-13 expression in rabbits with experimental knee osteoarthritis.
METHODS:Thirty New Zealand rabbits were randomly and equal y divided into treatment group, model group and control group, with 10 rabbits in each group. Model of knee osteoarthritis was established in both the treatment group and model group, using modified plaster cast in extension position for 6 weeks. Then the rabbits of treatment group were treated with extracorporeal shock wave therapy, each 1 000 impulse, at the energy flux density of 0.1 mJ/mm2. There were no treatments in the control group. The rabbits in each group were sacrificed at 4 weeks after treatment, the knee synovial fluid and articular cartilage were col ected from the rabbits. The pathological changes of knee joint were detected using hematoxylin-eosin staining and toluidine blue staining. The interleukin-1βand matrix metal oproteinase-13 expression in the synovia was detected using ELISA and immunohistochemical staining respectively.
RESULTS AND CONCLUSION:The interleukin-1βconcentration in the synovial fluid was significantly higher in the treatment group and model group than the control group (P<0.01), and the treatment group after treatment showed a lower concentration than the model group (P<0.05). Mankin scores in treatment group and model group were significantly increased compared with the control group (P<0.01), and the treatment group after treatment showed a lower score than the model group (P<0.05). The interleukin-1βand matrix metal oproteinase-13 positive expression rates in the treatment group and model group were significantly increased compared with the control group (P<0.01), and the treatment group after treatment showed a lower rate than the model group (P<0.05). The extracorporeal shock wave therapy can downregulate the expression of interleukin-1βand matrix metal oproteinase-13, promote the synthesis of new col agen.

Objective To explore the effect of extracorporeal shock wave (ESW) on expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in cartilage in rabbits with knee osteoarthritis. Methods 30 rabbits were randomly divided into control group, model group and treatment group, with 10 rabbits in each group. Model of knee osteoarthritis was established with modified plaster cast in extension position for 6 weeks except the control group, and the treatment group was treated with ESW (each 1000 impulse, the energy flux density of 0.1 mJ/mm2). The rabbits were sacrificed respectively 4 weeks after ESW treatment, the general and histological changes of articular cartilage were examined and immunohistochemical staining was used to observe the expression of IL-1β and TNF-α in cartilage. Results The expression of IL-1β and TNF-α were significantly lower in the treatment group than in the model group (P<0.01). Conclusion ESW can down-regulate the expression of IL-1β and TNF-α in chondrocytes with osteoarthritis.

Objective To evaluate prospectively clinical significance and consequence of type Ⅰ bone bruise in acutely sprained knee. Methods 23 outpatients were selected, meeting our criteria from 2005 to 2008. All the injured knees were immobilized with gypsum for 4 to 6 weeks, and the knee complaints and MRI were followed up regularly.Results 18 patients were followed up, averaged 24 months, the bone bruise showed notable resolution in average 3 months and vanished in 6.7 months averagely; the knee pain alleviated obviously in about 4.8 months; 5 out of 9 cases, who were more than 45 years old, still complained knee pain and uncomfortable after 2 years.Conclusion Grade Ⅰ knee sprain can lead to bone bruise in condyles of femur or tibia, and knee immobilization should be given to avoid the further damage; the bone bruise may be a precursor of knee osteoarthritis for people older than 45 years.