Hi Welcome  to HCM
  Dear , your husband's  problem of  anemia after 
knee replacement surgery  ,  is  very natural , though is a matter of concern .
 When our body undergoes  any process  like surgery  or long term medication  , it imbalances our 
metabolism  and need further sensible treament to  get to absolute health .
Gulping on only meds will not help unless we take care of our life style and food habits to increase our immunity  for flawless heath 
Best is to include  regularly  ,all essestial  nutrients  and supplements full of antixidants in natural form  like veges,fruit, fiber ,vitamins , minerals , protien  in right proportion .
 to increase iron intake , Inclde butter milk , lemon juice, honey , apple , banana , pomegranate dry dates  ,spinach ,carrot , beetroot, tomato juice and soups and lot of water to remove toxin from body  , which  strengthns your immune system and help lead healthy life .
 For proper  blood circulation , i would  like to suggest you to follow ,regular physical activity regime , yoga - pranayam  , 
Meditation , Bhramari ,deep breething, Kapalbhatti .
Avoid processed foods carbs , sugar , fried ,fast foods , Tea , coffee ,alcohol and 
smoking , stress , 
sleeplessness and 
Constipation all will produce biochemical and metabolic conditions in your body that will decrease your immunity.
So avoiding is definitely the first step in the right direction to detoxing the body, boosting the immune system .
 Regular check ups and tests are recommended 
Medical treatment suggested by your doctor can be complemented using a variety of alternative therapies. Most of these therapies or 
home remedies focus on strengthening your immune system so that you may over come the infection and inflammation quicker .
Hope this helps solves your query .Take care .All the best .Get well soon
Don't hesitate to come back in case of any further query .