well you can pray sitting down, fold your arms upon your chest, when going into the bowing position just bow half way, when going into the prostration then bow all the way, when in the sitting position place your hands on your knee's.
“So keep your duty to Allaah and fear Him as much as you can”
[al-Taghaabun 64:16]
“Allaah burdens not a person beyond his scope”
[al-Baqarah 2:286]
And the Prophet (peace and blessings of Allaah be upon him) said: “If I command you to do a thing, then do as much of it as you can.” Narrated by al-Bukhaari, 7288; Muslim, 1337.
It was narrated that ‘Imraan ibn Husayn (may Allaah be pleased with him) said: “I was suffering from haemorrhoids and I asked the Prophet (peace and blessings of Allaah be upon him) about praying. He said, ‘Pray standing, and if you cannot, then sitting down, and if you cannot, then lying on your side.’” Narrated by al-Bukhaari, 1117.
Shaykh Ibn ‘Uthaymeen said:
Whoever is not able to bow should lean forward whilst standing, and whoever is not able to prostrate should lean forward whilst sitting.