There are several causes for a stiff elbow. In general, one can divide stiffness into bony causes or soft tissue causes.
The elbow joint is enclosed by a thin, supple capsular lining. In order for your elbow to be able to bend and straighten, there front capsule of the elbow has spare tissue that folds up when the elbow is bent. After elbow injury, this capsule gets sticky and so the folds of capsule at the front tend to 'fuse together'. This means that it is very common for one's elbow to lose some end-range of straightening after an injury to the elbow. The best way to minimise this stiffness is to avoid immobilizing elbows for a long time and to encourage early therapy. Nevertheless, sometimes the stiffness doesn't resolve with therapy and splinting and an elbow release procedure is required. Depending on your problem, this may be performed by either open or keyhole techniques.
Elbow arthritis usually causes stiffness. The arthritis may have come on without obvious cause, or it may be related to a previous injury or an inflammatory condition, such as rheumatoid arthritis. If the arthritis is not severe enough for an elbow replacement, but nevertheless the stiffness is troubling, then you may benefit from an elbow release procedure. This procedure removes bone spurs, loose bodies and also frees up tightened soft tissues. Sometimes this can performed by keyhole surgery, but for most cases where arthritis is causing stiffness, this is performed via open surgery. If your radial head is arthritic, this may also be removed as part of the elbow release procedure to free up the joint and reduce pain.
Some patients develop loose bodies that float around inside their elbow joint. Sometimes these are part of arthritis, or they may result from a previous injury. Loose bodies can get stuck within the bearing surfaces of the elbow and cause painful locking of the elbow and stiffness. If this is the cause of your symptoms, you may need to have an elbow arthroscopy to remove these loose bodies.