Thanks for the information.
The numbness in the knee area and down towards the shin appears to be nerve related -- specificially the peroneal nerve which travels on around the outside of the knee -- goes in this area.
It is fairly common to have numbness the way you describe after an injury that affects the outside of the knee, because this peroneal nerve can be affected by the direct injury, or the swelling which occurs after the injury, or scar tissue pushing on the nerve.
Given that this has been 4 months now, with numbness persisting, there may have been injury to the nerve during the initial trauma, or scar tissue still pressing on this nerve. A diagnosis can be made with a physical exam, and a nerve conduction test to check the function of the nerve.
It is hard to know if this will improve, because if there was a direct injury to the nerve in the trauma, it may not return. If it is scar tissue or something else putting pressure on the nerve, then it may improve.