My daughter is 5.5 months old. She was 5 weeks premature. My concern is how much weight she should be bearing on her legs. Recently if you hold her up she will take just a little weight; her knees will then buckle if you continue to hold her up and she will push down to straighten her legs but she is not stable and will buckle again after a while and then try to straighten and so forth. She also lifts one leg when standing a bit more than on the other. Other than that everything fine – she kicks her legs all the time and has just started trying to put her toes in her mouth. She is one of a twin and so has had a hip scan which was normal – it was routine. I guess I am concerned because the other twin (a boy) is standing really well – almost unsupported for a few seconds. She has rolled but not that keen – likes rolling onto her side though to watch television.
Most babies begin the bear weight fully on their legs between 6-9 months, some even earlier such as your son. We answered a similar question to yours recently, and if you scroll down to the third question at this link you can find some additional suggestions.
At 5 months, it is more important that she spends a lot of time playing on her stomach and learning to actively roll, rather than pushing weight bearing in standing. In fact you can practice weight bearing on her knees first which she’ll need for crawling. Her tummy time will help increase her neck and trunk strength (core) that she needs for later independent sitting, crawling and walking. It will also promote her arm strength when she pushes up to pivot on the floor. You can place her on her knees over your calf and encourage her to place her hands down (your leg is supporting her tummy) and gently rock her back and forth to weight shift her body as you sing to her. You can let her sit straddling your leg facing away from you and give her gentle pressure on her thighs/knees so that she feels the weight bearing under her feet (without shoes), and encourage her to come to stand with your help as a game.
This is a great article that demonstrates other ways to promote tummy time during the day.
Also, keep in mind that spending time in bouncers, walkers and jumpers does not generally promote weight bearing and/or walking. Floor time is the best practice time for babies!