Hi, thanks for writing to HCM.
Generally, the ligament injuries takes atleast 3 weeks to heal with appropriate management and to return to their pre-injury
If your father is able to perform all activities of daily living without any issues after 3 weeks, then there is nothing to worry about.
If he has still any issues left after that period , then an MRI
scan of the knee joint may be needed to assess the extent of damage to the ligaments.
Consult an orthopedic surgeon and follow his advice.
Hope this information is helpful. Good day