http://www.medhelp.org/posts/Multiple-Sclerosis/Can-neuropathy-cause-swelling/show/756145
Extensor Spasticity
Another result of the damage to the motor neurons is increased spasticity of muscles, meaning that muscles tend to spontaneously contract. In some cases, a patient may not be able to consciously relax the contracted muscle. The knees are affect when spasticity occurs in the quadriceps, which are the large muscles on the front of the legs, or the adductor muscles, which are smaller muscles on the inside up the upper legs. When these muscles contract and do not release, the knees are forced to straighten and remain locked in that position, explains the National Multiple Sclerosis Society.
Flexor Spasticity
Patients with multiple sclerosis may alternatively experience the opposite problem of the knees becoming locked in the bent position. This locking of the knees is caused by contraction of the hamstrings, which are the long muscles located on the rear of the upper leg, and the hip flexors, which are the muscles located on the top of the upper thigh, the National Multiple Sclerosis Society explains.
Read more: http://www.livestrong.com/article/214566-multiple-sclerosis-symptoms-in-the-knees/#ixzz1OkognRfL