Rafa's injury should not end his career
Tendinitis means inflammation of a tendon. In tennis players whose knees are affected, the commonest type is patellar tendonitis, caused by repetitive overuse.
The condition causes pain at the front of the knee just below the patella (kneecap) and is worst when the knee is flexed, as when bending for a low shot.
Professor Angus Wallace, former chair of the National Institute of Sports Medicine said it could be difficult to predict how long Rafael Nadal might take to recover.
"It will be aggravated by continuing to play. If it is aggravated badly it will set him back for other tournaments. The injury is usually related to over-use combined with small tears of the tendon where it is attached to the bone."
Professor Wallace said the injury would need treatment. Physiotherapy, involving transverse rubbing across the tendon, could help. Ultrasound was also sometimes used. In severe cases surgery can be required but is not often used.
The injury was not career-ending and with rest would probably resolve within a fortnight, Professor Wallace said.
In an older, less fit person it could take months to heal.
Phil Hughes injury: Cricket world reels as Australian opener fights for his life
Phil Hughes: Batsman had one weakness – it has come back to haunt him
Manchester City vs Bayern Munich comment: Frank Lampard's part in City win shows folly of letting him leave
This letter from a reader explains why women can’t play football
Schalke vs Chelsea: Roberto Di Matteo admits thrashing by former side was most painful defeat of his career
- 1 I'm A Celebrity 2014: Jungle security stepped up after murder and 'suspicious death' near to camp
- 2 Black Friday 2014: Opening times for Asda, John Lewis, PC World, GAME and Argos
- 3 To help fuel their propaganda machine against the poor, our government has now decided to redefine the word 'welfare'
- 4 Girl, 7, gets Tesco to remove 'stupid' sign suggesting superheroes are 'for boys'
- 5 Jeremy Hunt: 'I took my children to A&E because I didn't want to wait for GP appointment'
Rochester by-election: Ukip gains second MP as Tory defector Mark Reckless holds seat
'Beast of Bolsover' Dennis Skinner takes Ukip MP Mark Reckless to task moments after he is sworn in
Rochester by-election: Labour MP Emily Thornberry resigns after posting white van and England flags tweet
Ukip says babies born to immigrants in the UK should be classed as migrants – which would include Nigel Farage’s own children
The young are the new poor: Sharp increase in number of under-25s living in poverty, while over-65s are better off than ever
Tamir Rice: 12-year-old boy playing with fake gun dies after being shot by Ohio police