Richard- I agree with Jon-- - all of his points on bike fit are wise--
Also, do not forget to adjust your seat height accordingly - it should go up as your cranks get shorter - as a base point, that is... because if changing crank length is not the solution, then you might want to fiddle with seat height.. and I mean fiddle, as I am sure you know that differences of as little as 1 mm can have an impact on comfort.
Another thought (yup, Off Topic, but still...)- you may want to try using a pedal that gives you a lot of free lateral movement. I have had surgery on both knees and the original speedplay pedals have been terrific. they feel like you are walking on ice when you first use them, but your knees may like it. when you think about how quill pedals lock the ball of your foot in place, and compare that to how most people's foot twists a little on each step - you begin to see the wisdom of a free floating pedal for some of us.
Also, i do not have links, but Lennard Zinn (velo news, maker of KOF frames) has studied and written extensively about crank length and physiology, etc.
What do your physical therapist and orthopedist (preferably of the sports medicine certified variety) say? Have you asked them?
Not being an expert, I would swap out those 175s for 170s ASAP. It is a relatively cheap and easily-accomplished experiment. Ask your sports orthopedist or physical therapist for advice. You will want to modify your seat position, too, I would think...
If they are not bike-fit knowledgeable, ask for a referral to a PT or sports chiropractor who is a bike fit expert. If those avenues fail, check back with your local bike shop(s) and ask their fitting experts.
Locally, I would recommend my friends at Cycle Sports bike shop in Oakland or my buddy, Jessica Graux, DC, who does great bike fitting in Berkeley, CA:
You might call or visit other local CR listers and shop owners in VA or thereabouts:
Wayne Bingham at Velo Classique (540-338-8376; PO Box 2069, Purcellville, VA)
or Dale Brown at Cycles de Oro (1410 Mill Street, Greensboro, North Carolina 27408; 336-274-5959)
(These are the only two references I can think of that are in your "neighborhood," but I'm in Alameda, CA and on the wrong coast to know who else might be closer to you.)
Jon Spangler who has less-than-pristine hips in Alameda, CA
Message: 5 Date: Fri, 23 Jul 2010 05:04:34 -0700 (PDT) From:RICHARD HOWARD <firstname.lastname@example.org> Subject: [CR] Old Age vrs Crank Lengths To: email@example.com Message-ID: <firstname.lastname@example.org> Content-Type: text/plain; charset=us-ascii
I am 65 years old and have been using 175 mm cranks since my first real bike in
1967. I have had a total knee replacement and lost enough range of motion in
the affected knee that it impacts on my ability to ride smoothly. The problem
is mostly at the 12 o'clock position of the affected crank arm. It is a struggle
to power over the top. I am thinking about switching to 170 mm cranks or even
165mm. Considering the skeletal shrinkage that also automatically comes with old
age, I am thinking that 165 may be optimal. Has anyone else had a problem
similar to this? Did you create any new problems for yourself while solving the