hi u hav not given detailed assesment result.ok then,u say her flexion is restricted.Is it fexion r flexion to extnsion.Becoz in o.a knee mostly in chronic patient like urs develop FFD(fixed flexion deformity)i.e extnsion will be affected. u say the reverse.
Regarding Rx go for waxbath/ IFT,short arc knee exs.try this out