Patellar tendinitis, also known as jumpers knee, is an overuse injury of the tendon that straightens the knee. Symptoms include pain in the front of the knee. Typically the pain and tenderness is at the lower part of the kneecap, though the upper part may also be affected. Generally there is no pain when the person is at rest. Complications may include patellar tendon rupture.Risk factors include being involved in athletics and being overweight. It is particularly common in athletes who are involved in jumping sports such as basketball and volleyball. The underlying mechanism involves small tears in the tendon connecting the kneecap with the shinbone. Diagnosis is generally based on symptoms and examination. Other conditions that can appear similar include infrapatellar bursitis, chondromalacia patella and patellofemoral syndrome.Treatment often involves resting the knee and physical therapy. Evidence for treatments, including rest, however is poor. Recovery can take between months and persist over years. It is relatively common with about 14% of athletes currently affected; however research reflects that more than half of athletes with this injury end their careers as a result. Males are more commonly affected than females. The term "jumpers knee" was coined in 1973. Signs and symptoms
People report anterior knee pain, often with an aching quality. The symptom onset is insidious. Rarely is a discrete injury described. Usually, the problem is below the kneecap but it may also be above.
Deletions of PLP1 locus (which are rare) cause a milder form of Pelizaeus–Merzbacher disease than is observed with the typical duplication mutations, which demonstrates the critical importance of gene dosage at this locus for normal CNS function. Diagnosis
The diagnosis of Pelizaeus–Merzbacher disease is often first suggested after identification by magnetic resonance imaging of abnormal white matter (high T2 signal intensity, i.e. T2 lengthening) throughout the brain, which is typically evident by about 1 year of age, but more subtle abnormalities should be evident during infancy. Unless a family history consistent with sex-linked inheritance exists, the condition is often misdiagnosed as cerebral palsy. Once a PLP1 mutation is identified, prenatal diagnosis or preimplantation genetic diagnostic testing is possible. Classification
The disease is one in a group of genetic disorders collectively known as leukodystrophies that affect the growth of the myelin sheath, the fatty covering—which acts as an insulator—on nerve fibers in the central nervous system. The several forms of Pelizaeus–Merzbacher disease include classic, congenital, transitional, and adult variants.Milder mutations of the PLP1 gene that mainly cause leg weakness and spasticity, with little or no cerebral involvement, are classified as spastic paraplegia 2 (SPG2). Treatment
No cure for Pelizaeus–Merzbacher disease has been developed. Outcomes are variable: people with the most severe form of the disease do not usually survive to adolescence, although with milder forms, survival into adulthood is possible. Research
In December 2008, StemCells, Inc received clearance in the United States to conduct a phase I clinical trials of human neural stem cell transplantation.