Insurance — Uninsured motorist — Coverage — Permanent injury — Directed verdict — Plaintiff seeking coverage from UM insurer for knee injury allegedly caused by automobile accident — Trial court erred in directing verdict on issue of causation and permanency for plaintiff’s knee injury claim — Insurer’s failure to call an expert witness to rebut plaintiff’s expert testimony was not fatal to insurer’s right to have disputed issue decided by a jury — Jury could have found in insurer’s favor where medical records cast doubt on treating physician’s conclusion that injury was caused by the accident; there was a substantial amount of evidence about plaintiff’s prior knee injuries and conflicting testimony about the condition of her knee prior to the accident; and jury could have reasonably questioned treating physician’s credibility, even if only because he was providing services under a letter of protection